Reduction of Fuel Tank Flammability in Transport Category Airplanes

Note: EPA no longer updates this information, but it may be useful as a reference or resource.

[Federal Register: November 23, 2005 (Volume 70, Number 225)]
[Proposed Rules]
[Page 70921-70962]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr23no05-45]
[[Page 70922]]

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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Parts 25, 91, 121, 125, and 129
[Docket No. FAA-2005-22997; Notice No. 05-14]
RIN 2120-A123

AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This NPRM proposes new rules that will require operators and
manufacturers of transport-category airplanes to take steps that, in
combination with other required actions, should greatly reduce the
chances of a catastrophic fuel-tank explosion. The proposal follows
seven years of intensive research by the FAA in collaboration with
industry into promising technologies designed to make fuel tanks
effectively inert, thus preventing electrical and other systems from
igniting flammable vapors in the fuel tank ullage (vapor space). The
result of that research is that fuel tank inerting, originally thought
to be prohibitively expensive, can now be accomplished in a reasonably
cost-effective fashion and protect the public from future calamities
which, we have concluded, are otherwise virtually certain to occur. The
new rules, if adopted, would not actually direct the adoption of
specific inerting technology either by manufacturers or operators but
would establish a performance-based set of requirements that do not
specifically direct the use of fuel-inerting but rather set acceptable
levels of flammability exposure in tanks most prone to explosion or
require the installation of an ignition mitigation means in an affected
fuel tank. Technology now provides a variety of commercially feasible
methods to accomplish these vital safety objectives.

DATES: Send your comments on or before March 23, 2006.

ADDRESSES: You may send comments, identified by Docket No. FAA-2005-
22997, using any of the following methods:
DOT Docket Web site: Go to http://dms.dot.gov and follow the
instructions for sending your comments electronically.
Government-wide rulemaking Web site: Go to http://www.regulations.gov
and follow the instructions for sending your comments
electronically.
Mail: Docket Management Facility; U.S. Department of
Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401,
Washington, DC 20590-001.
Fax: 1-202-493-2251.
Hand Delivery: Room PL-401 on the plaza level of the Nassif
Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5
p.m., Monday through Friday, except Federal holidays.
For more information on the rulemaking process, see the
SUPPLEMENTARY INFORMATION section of this document.
Privacy: We will post all comments we receive, without change, to
http://dms.dot.gov, including any personal information you provide. For
more information, see the Privacy Act discussion in the SUPPLEMENTARY
INFORMATION section of this document.
Docket: To read background documents or comments received, go to
http://dms.dot.gov at any time or to Room PL-401 on the plaza level of
the Nassif Building, 400 Seventh Street, SW., Washington, DC between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Michael E. Dostert, FAA, Propulsion/
Mechanical Systems Branch (ANM-112), Transport Airplane Directorate,
Aircraft Certification Service, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2132, facsimile (425) 227-
1320; e-mail: mike.dostert@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites interested persons to participate in this
rulemaking by submitting written comments, data, or views. We also
invite comments relating to the economic, environmental, energy, or
federalism impacts that might result from adopting the proposals in
this document. The most helpful comments reference a specific portion
of the proposal, explain the reason for any recommended change, and
include supporting data. We ask that you send us two copies of written
comments.
We will file in the docket all comments we receive, as well as a
report summarizing each substantive public contact with FAA personnel
concerning this proposed rulemaking. The docket is available for public
inspection before and after the comment closing date. If you wish to
review the docket in person, go to the address in the ADDRESSES section
of this preamble between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. You may also review the docket using the
Internet at the web address in the ADDRESSES section. Comments that you
may consider to be of a sensitive security nature should not be sent to
the docket management system. Send those comments to the FAA, Office of
Rulemaking, ARM-1, 800 Independence Avenue, SW., Washington, DC 20591.
Privacy Act: Using the search function of our docket Web site,
anyone can find and read the comments received into any of our dockets,
including the name of the individual sending the comment (or signing
the comment on behalf of an association, business, labor union, etc.).
You may review DOT's complete Privacy Act Statement in the Federal
Register published on April 11, 2000 (65 FR 19477-78) or you may visit
http://dms.dot.gov. Before acting on this proposal, we will consider
all comments we receive on or before the closing date for comments. We
will consider comments filed late if it is possible to do so without
incurring expense or delay. We may change this proposal in light of the
comments we receive.
If you want the FAA to acknowledge receipt of your comments on this
proposal, include with your comments a pre-addressed, stamped postcard
on which the docket number appears. We will stamp the date on the
postcard and mail it to you.

Availability of Rulemaking Documents

You can get an electronic copy using the Internet by:
(1) Searching the Department of Transportation's electronic Docket
Management System (DMS) web page (http://dms.dot.gov/search);
(2) Visiting the Office of Rulemaking's web page at
http://www.faa.gov/avr/arm/index.cfm; or
(3) Accessing the Government Printing Office's web page at
http://www.access.gpo.gov/su_docs/aces/aces140.html.
You can also get a copy by submitting a request to the Federal
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence
Avenue, SW., Washington, DC 20591, or by calling (202) 267-9680. Make
sure to identify the docket number, notice number, or amendment number
of this rulemaking.

Table of Contents

I. Executive Summary
II. Background
A. The Need for Safety Improvements in Fuel Tank Systems
B. Fuel Properties
C. National Transportation Safety Board (NTSB) Recommendations
D. FAA Response
III. Proposed Requirements Relating to Fuel Tank Flammability

[[Page 70923]]

A. Overview of the Proposal
B. Ongoing Responsibility of Type Certificate Holders for
Continued Airworthiness
C. Applicability
1. Manufacturers and Holders of Type Certificates, Supplemental
Type Certificates and Field Approvals
2. Airplanes
3. Fuel Tanks
4. Airplane Operators
D. Proposed Requirements for Manufacturers and Holders of Type
Certificates, Supplemental Type Certificates and Field Approvals
1. New Airplane Designs
2. Existing Airplane Designs
3. Auxiliary Fuel Tanks
4. Methods of Mitigating the Likelihood of a Fuel Tank Explosion
a. Flammability Analysis Using the Monte Carlo Method
b. Ignition Mitigation Means
c. Flammability Reduction Means
i. Accounting for System Reliability and Performance Issues
ii. Warm Day Fleet Flammability Exposure
iii. Reliability Reporting
iv. Reliability Indication and Maintenance Access
d. Service Instructions and Service Bulletins
e. Critical Design Configuration Control Limitations (CDCCL)
f. Compliance Planning
i. Compliance Plan for Flammability Exposure Analysis
ii. Compliance Plan for Design Changes and Service Instructions
iii. Compliance Plan for Auxiliary Fuel Tanks
g. Compliance Schedule
E. Proposed Requirements for Airplane Operators
1. Requirement to Install and Operate FRM, IMM or FIMM
2. Authority to Operate with an Inoperative FRM, IMM or FIMM
3. Compliance Schedule
F. Additional Provisions
1. Relationship of this Proposal to Aging Airplane Regulatory
Initiatives
2. FAA Advisory Material
3. FAA Oversight Office
4. Workplace Safety Issues
IV. Rulemaking Analyses and Notices
V. The Proposed Amendment

I. Executive Summary

Fuel tank explosions have been a constant threat with serious
aviation safety implications for many years. Since 1960, some 17
airplanes have been destroyed as the result of a fuel tank
explosion.\1\ Four fatal airplane accidents have been caused by fuel
tank explosions just since 1989. Two of the more recent accidents--one
involving a Boeing Model 747 (TWA Flight 800) off Long Island, New York
in 1996 and the other, a Boeing Model 727 accident (Avianca Flight 203)
in Bogot[aacute], Columbia in 1989--occurred during flight and led to
catastrophic losses, including the deaths of 337 individuals. The two
other recent explosions occurred on the ground but led to nine
fatalities.\2\ Although it was determined that a terrorist's bomb had
caused the explosion of the center tank in the Bogot[aacute]
accident,
the NTSB determined the ``bomb explosion did not compromise the
structural integrity of the airplane; however, the explosion punctured
the [center wing tank]
and ignited the fuel-air vapors in the ullage,
resulting in destruction of the airplane.'' Investigations of the other
three accidents failed to identify the ignition source that caused the
explosion. But in each instance the weather was warm, with an outside
air temperature over 80 [deg]F, the incident occurred during the
initial (ground, takeoff or climb) phases of flight, and the explosion
involved empty or nearly empty tanks that had been previously fueled.
Additionally, investigators were able to conclude that the center wing
fuel tank in all four airplanes contained flammable vapors in the
ullage (that portion of the fuel tank not occupied by liquid fuel) when
the fuel tanks exploded. While the proposed requirements are not
intended to address terrorist initiated fuel tank explosions, a system
designed to reduce the likelihood of a fuel tank fire, or mitigate the
effects of a fire should one occur, would have prevented these four
fuel tank explosions.
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\1\ None of the 17 explosions occurred on an airplane
manufactured by Airbus, who, along with Boeing, would be most
affected by this rulemaking. Although Airbus currently delivers more
airplanes worldwide than Boeing, their cumulative fleet hours are
still relatively small, at approximately 65 million (approximately
9% of total fleet hours for all transport category airplanes). Based
on the FAA's projection of the likelihood of an explosion based on
one accident every 60 million hours, there is a 40% chance that no
Airbus accidents would have occurred to date.
\2\ Philippine Airlines 737 accident in 1990 and the Thai
Airlines accident in 2001.
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A statistical evaluation of these accidents has led the FAA to
project that nine more transport category airplanes will likely be
destroyed by a fuel tank explosion in the next 50 years, unless
remedial measures are taken. Although we cannot forecast precisely when
these accidents would occur, computer modeling that has been an
accurate predictor in the past indicates these events are virtually
certain to occur. We believe at least eight of these explosions are
preventable if we adopt a comprehensive safety regime to reduce both
the incidence of ignition and the likelihood of an explosion following
ignition. We have already taken steps through other regulatory actions
to reduce the chances of ignition. Today's proposal attempts to address
the risk of an explosion by reducing the likelihood that fuel tank
vapors cause an explosion when an ignition source is introduced into
the tank.
Since the introduction of turbine powered airplanes, the FAA has
premised its fuel tank rules on the assumption that fuel tanks will
always contain flammable vapors and thus the best way to prevent
explosions is to eliminate ignition sources. Since 2001, we have
imposed airworthiness requirements (including airworthiness directives
or ``ADs'') directed at the elimination of fuel tank ignition sources.
Although these measures--particularly Special Federal Aviation
Regulation 88 of 14 CFR part 21 (SFAR 88), which requires the detection
and correction of potential system failures that can cause ignition--
should prevent some of the nine forecast explosions, review of the
current designs of airplanes in the transport category of all major
manufacturers has shown that unanticipated failures and maintenance
errors will continue to generate unexpected ignition sources. We have
concluded we are unlikely ever to identify and eradicate all possible
sources of ignition.
To ensure safety, therefore, we must also focus on the environment
that permits combustion to occur in the first place. Technology now
exists that can prevent ignition of flammable fuel vapors by reducing
their oxygen concentration below the level that will support
combustion. By thus making the vapors ``inert,'' we can significantly
reduce the likelihood of an explosion when a fire source is introduced
to the fuel tank. Prototype onboard fuel tank inerting systems have
been successfully flight tested on Airbus A320, Boeing Model 747, and
Model 737 airplanes. Boeing applied in 2002 for type certification of
an inerting system for the Model 747 that it plans to install on all
new production 747 aircraft.
Because the chances of a fuel tank explosion naturally correlate
with the exposure of the tank to flammable vapors, the proposed
requirements would mitigate the effects of such exposure or limit such
exposure to acceptable levels by mandating the installation of either a
Flammability Reduction Means (FRM) or an Ignition Mitigation Means
(IMM). In either case, the technology would have to adhere to
performance and reliability standards that would be set by the FAA and
contained in Appendices K and L to Title 14 Code of Federal Regulations
(CFR) part 25.
If adopted, this rulemaking would amend the existing airworthiness

[[Page 70924]]

standards contained in 14 CFR 25.981 so as to require all type
certificate (TC) holders and their licensees to develop FRM or IMM for
many large turbine powered transport category airplanes with high risk
fuel tanks. We would also amend 14 CFR parts 91, 121, 125 and 129 so as
to require operators of these airplanes to incorporate the approved FRM
or IMM and to keep them operational. We estimate that approximately
3,800 Airbus and Boeing airplanes operated in the United States would
be affected. Fuel tank system designs in several pending type-
certification applications, including the Airbus A380 and the Boeing
Model 7E7, would also have to meet the proposed requirements.
We acknowledge that the proposed requirements are costly and
propose these steps only after spending several years, in cooperation
with scientists and other experts from the affected industry,
researching the most cost-effective ways to prevent fuel tank
explosions. Those efforts have resulted in the development of fuel-
inerting technology that is vastly cheaper than originally thought.
The loss of a single, fully loaded large passenger aircraft in
flight, such as a Boeing Model 747 or Airbus A380, moreover, would
result in death and destruction causing societal loss of at least $1.2
billion based on prior calamities, and we project that the new rule
would prevent four accidents of some type (for analytical purposes we
assume the accidents would involve ``average'' aircraft with
``average'' passenger loads) over 50 years. Such estimates of harm do
not account for the intangible costs of a series of in-flight
explosions (such as a loss of confidence in aviation) or the indirect
costs (such as trip cancellations following these incidents).
Our philosophy is to address aviation safety threats whenever
practicable solutions are found, especially when dealing with
intractable and catastrophic risks like fuel tank explosions that are
virtually certain to occur. Thus, now that solutions are reasonably
cost-effective, the Administrator has tentatively determined that it is
necessary for safety and in the public's best interest to adopt the
requirements proposed today. This action is in response to an NTSB
recommendation.

II. Background

A. The Need for Safety Improvements in Fuel Tank Systems

Fuel tank explosions continue to occur despite many safety
improvements over the last 40 years aimed at removing ignition sources
from fuel tanks. Experience tells us that even with the latest and most
comprehensive initiative, SFAR 88, we cannot adequately protect the
public from fuel tank explosions absent measures designed to lessen the
exposure of vulnerable tanks to highly flammable jet fuel vapors.
Fortunately, by taking such steps now to complement ignition-source
reduction measures already taken, we are confident that fuel tank
explosions in affected aircraft will be nearly eliminated.
For a variety of reasons, SFAR 88, though a significant advancement
in safety, will never provide a complete safeguard against fuel tank
explosions; thus our analysis has assumed that SFAR 88 will not reduce
the possibility of a fuel explosion occurring by more than 50 percent.
To be sure, SFAR 88 has resulted in several significant changes in fuel
tank system design and maintenance, including (1) new features to
prevent dry running of fuel pumps within the fuel tanks; (2) use of
ground fault protection of fuel pump power supplies for pumps or wires
exposed to the fuel tank ullage; (3) addition of electrical bonds on
some components; (4) use of electrical energy limiters on wiring
entering fuel tanks that are ``normally emptied'' \3\ and located
within the fuselage contour; (5) electrical bond integrity checks; and
(6) improved maintenance programs. These design improvements, however,
do not and cannot address all sources of ignition (such as external
ignition sources resulting from fire).
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\3\ The phrase ``normally emptied'' refers to fuel tanks that
contain a substantial vapor space during a significant portion of
the airplane operating time. Tanks that are designed to be normally
emptied have been installed in various locations including the
center wing structure, horizontal stabilizers, wings and cargo
compartments. Fuel loading and usage management practices on certain
airplane models use the auxiliary fuel tanks for controlling the
center of gravity.
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Past experience, moreover, shows that it is not possible to
pinpoint and remove every ignition source from a large, complex
transport aircraft. For example, the FAA is aware of one case where a
manufacturer had conducted an exhaustive design review to identify
possible sources of arcing within the fuel tank after a fuel tank
exploded due to lightning. The manufacturer identified several possible
sources of the arcing, and the FAA issued ADs to correct these
deficiencies. The same airplane design was then evaluated as a result
of SFAR 88, and additional sources of lightning-induced ignition were
identified. In another instance, a TC holder submitted a safety
analysis to the FAA claiming that certain airplane models met existing
system safety requirements of Sec. 25.1309 and thus that the
likelihood of an ignition source developing was extremely improbable
(one in a billion flight hours). When the requirements of the SFAR 88
safety review and unsafe condition criteria were applied, however,
approximately 80 new unsafe conditions were found. These conditions
will now be addressed by AD for those airplane models but, in
retrospect, it was clear that the manufacturer's claims were erroneous.
The safety reviews have also identified the potential for system
failures (or ``failure modes'') that cannot be eliminated as possible
ignition sources at reasonable cost. For example, use of ground fault
protection for fuel pump power supplies will protect the fuel pumps
from shorts to ground (such as one might find from lightning), but will
not protect the fuel pumps from shorts between the three power wires to
the pump, commonly referred to as ``phase-to-phase shorts.'' Currently
there is no proven component available to address this failure mode.
Combinations of failure modes are even more problematic. We could
require installation of redundant bond paths to prevent the latent
failure of a critical electrical bond, but doing so would be cost-
prohibitive.
Finally, human error creates continuing risk. Each attempt to fix
an electrical system presents the possibility of an inadvertent
introduction of a new ignition source. Maintenance oversights, such as
the failure to properly install electrical bonds or improper
installation or overhaul of components, compound the possibility of an
ignition source developing.
Carrier fuel carrying practices could impact the possibility of an
explosion as well. If a carrier decides to carry only that fuel
necessary to meet the FAA's fuel reserve requirements, the likelihood
of an explosion is greater than if it carries excess fuel. This
potential exists because more ignition sources within the fuel tank are
exposed to the ullage and because the fuel has insulating properties
which keeps the fuel tank cooler. Thus, ``tankering'', or carrying
excess fuel, could theoretically lower the risk of an explosion.
Current fuel management practices, where excess fuel is carried only
when cost beneficial to the carrier, are largely market driven because
airlines try to minimize their fuel costs to the maximum extent
possible. Both the FAA and industry explored mandatory refueling of
center wing tanks after the NTSB suggested the FAA adopt an interim
flammability reduction measure in 1996. We determined that the reduction in

[[Page 70925]]

flammability exposure would not be significant and would not address
the warm day flammability risk. Thus, while either reducing or
increasing the amount of fuel carried in the center wing tank could
theoretically have some impact on the risk of an explosion, the FAA
does not believe that current fuel carrying practices are likely either
to change significantly or to have a measurable impact on the overall
risk of an explosion. We seek comment on this position.

B. Fuel Properties

Three conditions must be present in a fuel tank to support
combustion and a fuel-tank explosion: Fuel vapor in the right amount,
enough oxygen, and an ignition source. As discussed earlier, our
regulatory efforts since piston-powered aircraft evolved into the jet
age have been focused almost exclusively on the last item, ignition
sources. A basic assumption in this approach has been that the fuel
tank would contain flammable vapors under a wide range of airplane
operating conditions. The question is, what level of exposure is safe?
Jet fuel vapors are flammable only in certain temperature and
pressure ranges. The flammability temperature range of such vapors
varies with the type and properties of the fuel, the ambient pressure
in the tank, and the amount of dissolved oxygen released from the fuel
into the tank. The amount of dissolved oxygen in a tank will also vary
depending on the amount of vibration and sloshing of the fuel that
occurs within the tank. The temperature range in which a flammable fuel
vapor will form can vary with different batches of fuel even for a
specific fuel type, but the threshold temperature for flammability
decreases as the airplane gains altitude because of the corresponding
decrease of internal tank air pressure. Thus, the higher the airplane
is flying, the lower the ambient temperature required for a fuel tank
to explode when an ignition source introduced.
Jet A fuel is the most commonly used commercial jet fuel in the
United States and is widely used in other parts of the world. At sea
level and with no sloshing or vibration present, these fuels have
flammability characteristics that make it unlikely that the fuel
molecules present in the fuel vapor-air mixture will ignite when the
temperature in the fuel tank is below approximately 100 [deg]F. The
vapor will ignite, however, once the fuel temperature reaches
approximately 175 [deg]F, because of the increased concentration of
fuel molecules at higher temperatures. At an altitude of 30,000 feet,
the flammability temperature range drops to approximately 60 to 120
[deg]F.\4\ Use of Jet A or Jet A-1 fuel thus tends to limit the risk of
high flammability to warmer days.
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\4\ Most transport category airplanes used in air carrier
service are approved for operation at altitudes from sea level to
45,000 feet.
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Jet B (JP-4) is another fuel approved for use on most commercial
transport category airplanes, although it is no longer used as a
primary fuel for commercial transports. The flammability range of Jet B
(JP-4) is about 15 to 75 [deg]F at sea level and 20 to 35 [deg]F at
30,000 feet. Because the flammable temperature range of Jet B fuel is
more within the range of typical air temperatures at those altitudes
where the airplane is likely to be operated, airplane fuel tanks with
Jet B fuel are flammable for a much larger portion of the flight.

C. National Transportation Safety Board (NTSB) Recommendations

The NTSB determined that the probable cause of the in-flight
explosion on TWA Flight 800 was the ignition of the flammable fuel/air
mixture in the center wing fuel tank. However, the source of ignition
energy for the explosion could not be determined with certainty. The
Board also faulted, as contributing to the accident, the FAA's design
and certification approach to transport-category airplanes, as it (1)
concentrated solely on precluding all ignition sources, and (2) allowed
heat sources to be located beneath the center wing fuel tank.
In 1996, the NTSB issued recommendations to improve fuel tank
safety. The NTSB recommended both eradicating ignition sources and
reducing fuel tank flammability.\5\ In their accident report, the Board
concluded that ``a fuel tank design and certification philosophy that
relies solely on the elimination of all ignition sources, while
accepting the existence of fuel tank flammability, is fundamentally
flawed because experience has demonstrated that all possible ignition
sources cannot be determined and reliably eliminated.''
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\5\ NTSB recommendations provided on page 309 of NTSB Accident
Report, ``In-flight Breakup Over the Atlantic Ocean, TransWorld
Airlines Flight 800 Boeing 747-131, N93119 Near East Moriches, New
York, July 17, 1996, Report number NTSB/AAR-00/03, DCA96MA070,
Adopted August 23, 2000.
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D. FAA Response

The FAA conducted ignition-prevention safety reviews following the
1996 accident, which revealed many new single-component failure modes
that could ignite fuel tanks. We continue to issue ADs that require
design or maintenance actions to address these deficiencies. These
safety reviews also identified combinations of failures that could
result in an ignition source, but as these combinations were less
likely to occur than single failures, we determined that it was not
practical to address them in existing airplanes. The safety reviews
also confirmed that unforeseen design and maintenance errors could
create ignition sources.
Recognizing the need to focus on flammability rather than just
ignition, on April 3, 1997, the FAA published a notice in the Federal
Register seeking comments on the 1996 NTSB recommendations on
flammability exposure (62 FR 16014). That notice reviewed the service
history of transport category airplane fuel tanks and the challenges
underlying fuel-tank flammability reduction. Public comment indicated
that more information was needed before we could begin a rulemaking on
this safety issue.
Given that control of flammable vapors was a new concept, we
assigned two Aviation Rulemaking Advisory Committee (ARAC) working
groups to study the issues and provide recommendations. (The ARAC
consists of interested parties, including the public, and provides a
process to advise us on the development of new regulations.) The first
working group reviewed the practicality of requiring flammability
reduction, evaluating many different flammability reduction methods.
Upon the recommendation of the first working group, the second working
group then focused exclusively on fuel tank inerting.
On January 23, 1998, we published a notice in the Federal Register
that established the Fuel Tank Harmonization Working Group as part of
ARAC (63 FR 3614). This group was asked to recommend regulations on
fuel tank flammability for both newly certificated and existing
airplanes. The working group looked at fuel tank explosions that
occurred after Jet A fuel had replaced Jet B fuel as the predominant
type used on transport airplanes. The group examined the performance of
two types of fuel tanks: the center wing fuel tanks located within the
fuselage contour, and wing fuel tanks. Fuel tanks located in an
aluminum wing are typically unheated and cool quickly when the wing
surfaces are exposed to colder air during flight. Conversely, the
center wing fuel tanks in certain airplanes have equipment underneath
the tank radiating heat; in addition, with no surfaces exposed to
outside air, the tank

[[Page 70926]]

cools much more slowly than a wing fuel tank.
The working group concluded that the safety records of fuel tanks
located in aluminum wings of airplanes fueled with Jet A type fuel were
satisfactory. These tanks had an average flammability exposure (as
calculated under a methodology contained in proposed Part 25, Appendix
L) of approximately 2 to 6 percent. However, the group found that on
some airplane fleets the center wing fuel tanks had an average
flammability exposure ranging from 7 percent to a high of 30 percent, a
dangerous level.
The working group then evaluated many possible means of reducing or
removing the hazards associated with explosive vapors in fuel tanks,
such as fuel tank inerting, fuel tank cooling, fuel property
alteration, fire suppression systems and polyurethane foam treatments.
The ARAC sent the working group's report to the FAA on July 23, 1998
(Docket No. FAA-1998-4183, viewable on the U.S. Department of
Transportation electronic Document Management System at
http://dms.dot.gov).
The working group report concluded that flammability reduction was
practical for new airplane designs, but impractical for current
production designs or retrofit in the current fleet of transport
category airplanes. The report recommended that the FAA begin
rulemaking to add a requirement to Sec. 25.981, so that fuel tanks in
new airplane designs would have an average flammability exposure of
less than 7 percent. The report also recommended requiring by
regulation that each newly designed airplane incorporate means to
mitigate the effects of an ignition of fuel vapors, such that any
damage caused would not prevent continued safe flight and landing. The
report reviewed various technical solutions, including control of heat
transmission into fuel tanks, use of inerting systems, or ignition
mitigation means like polyurethane foam. The report concluded that the
best solution was likely to be control of heat transmission and
suggested that the most practical means of control were (1) relocation
of the air-conditioning equipment away from the fuel tanks; (2)
ventilation of the air-conditioning bay to limit heating and cool fuel
tanks; or (3) insulation of the tanks from heat. Nevertheless, the ARAC
also recommended that we continue to evaluate the cost-effectiveness of
other means for reducing flammable vapors in the fuel tanks, such as
ground-based inerting of fuel tanks.
Based in part on the ARAC recommendations, we issued a rule
entitled ``Transport Airplane Fuel Tank System Design, and Maintenance
and Inspection Requirements'' in the Federal Register on May 7, 2001
(66 FR 23085). The rule added current Sec. 25.981(c) which requires
minimization of fuel tank flammability exposure in new type designs
without setting a specific safety standard. Section 25.981(c) thus states:

(c) The fuel tank installation must include either--
(1) Means to minimize the development of flammable vapors in the
fuel tanks (in the context of this rule, ``minimize'' means to
incorporate practicable design methods to reduce the likelihood of
flammable vapors); or
(2) Means to mitigate the effects of an ignition of fuel vapors
within fuel tanks such that no damage caused by an ignition will
prevent continued safe flight and landing.

Higher flammability tanks are typically located in the center wing
box, in the horizontal stabilizer where little surface area is exposed
to outside air, or in the cargo compartment. Our intent, as discussed
in that rule's preamble was to ``require that [such] fuel tanks are not
heated, and cool at a rate equivalent to that of a wing tank in the
transport airplane being evaluated.'' We noted that, ``This may require
incorporating design features to reduce flammability, for example
cooling and ventilation means, or inerting for fuel tanks located in
the center wing box, horizontal stabilizer, or auxiliary fuel tanks
located in the cargo compartment.'' (Our reference to a wing tank was
to a conventional subsonic airplane with aluminum wing tanks.) We also
stated, ``At such time as the FAA has completed the necessary research
and identified an appropriate definitive standard to address this
issue, new rulemaking would be considered to revise the standard
proposed in this rulemaking.''
We then issued two Advisory Circulars, AC 25.981-1B, ``Fuel Tank
Ignition Source Prevention Guidelines,'' and AC 25.981-2, ``Fuel Tank
Flammability Minimization.'' These ACs described acceptable means of
showing compliance with Sec. 25.981(c). AC 25.981-2 specifically
discussed the use of fuel tank inerting as a method of compliance with
the flammability exposure requirements. To ``inert'' a fuel tank, as
defined in AC 25.981-2, the percentage of oxygen in a fuel tank's air
should not exceed 10 percent. (Later research, discussed below, showed
that containing oxygen concentrations to 12 percent or less would inert
a fuel tank.)
After revising Sec. 25.981, we began scientific research, hoping
to gain a better understanding of the ignition properties of commercial
aviation jet fuel vapors. We also explored new ideas for removing
flammable fuel air mixtures from fuel tanks, as well as other methods
for improving fuel tank safety. Initially, efforts to develop
commercially viable ways to remove flammable fuel vapors from tanks
failed. For example, to lower the danger of fuel tank explosions after
post-crash ground fires, systems were considered that would ``scrub''
the vapor in the ullage--ventilating the tank with air so as to prevent
the build-up of flammable concentrations of fuel vapor. At the time, we
found these systems to be impractical because of their weight,
complexity, unreliability, and undesirable secondary effects on the
environment.
On the recommendation of the ARAC, we refocused our efforts on
reducing fuel tank flammability through nitrogen inerting. Public
comment on the 1997 notice had suggested inerting was possible through
adoption of a hollow fiber membrane technology, which separates oxygen
from nitrogen in the atmosphere. (Air is made up of about 78 percent
nitrogen and 21 percent oxygen.) The hollow fiber membrane material
uses the absorption difference between the nitrogen and oxygen
molecules to separate nitrogen-enriched air from oxygen. The technology
had been used for many years in non-aerospace applications, such as
obtaining oxygen-enriched air for medical purposes and generating
nitrogen-enriched air to preserve produce in transport. In airplane
applications, nitrogen-enriched air could be produced when pressurized
air is forced through a canister that contains the hollow fibers. The
created nitrogen-enriched air is then directed, at appropriate
concentrations, into the ullage of fuel tanks and displaces the normal
fuel vapor/air mixture in the tank. Use of this technology allows
nitrogen to be separated from the available pressurized air onboard the
airplane, which eliminates the need to carry and store nitrogen in the
airplane.
Initially, we found that airplanes in the current transport
category fleet were not designed with optimized air sources for
creating nitrogen-enriched air. As a result, early designs required
installation of an air compressor, adding significant weight and cost.
Aware of the earlier system's disadvantages, our researchers worked to
address those issues. Earlier fuel tank inerting designs, primarily
produced for military applications to prevent fuel tank

[[Page 70927]]

explosions from battle damage, assumed a fuel tank was ``inert'' with a
maximum of 9 percent oxygen content in the ullage. Achieving this level
of concentration was not needed for transport category airplanes, as
our research determined that a maximum oxygen content of 12 percent
would be sufficient to protect airplanes from less powerful ignition
sources typical of airplane system failures and malfunctions at sea
level. Thus, our testing excluded turbulent flow flame propagation, or
external fuel tank events, such as explosives and hostile fire. (The
FAA test results are available in an FAA Technical Note: ``Limiting
Oxygen Concentrations Required to Inert Jet Fuel Vapors Existing at
Reduced Fuel Tank Pressures'' (DOT/FAA/AR-TN02/79). See:
http://www.fire.tc.faa.gov/pdf/TN02-79.pdf.)
Terrorist initiated accidents were also excluded from consideration
in the earlier ARAC reports and the possible benefits in the regulatory
evaluation within this notice. While the proposed FRM requirements are
not intended to address terrorist initiated explosions, such as the
Bogata 727 accident discussed earlier, inerting fuel tanks may provide
other significant secondary safety benefits by addressing flammability
exposure. Testing conducted by China Lake Naval Weapons Center \6\
showed that inerting a fuel tank to 12 percent oxygen offers a high
degree of protection from a fuel tank explosion when 30-millimeter high
explosive incendiary projectiles shot into fuel tanks. The FAA invites
comments related to the potential additional security benefits that may
be achieved by imposing FRM.
---------------------------------------------------------------------------

\6\ The Effectiveness of Ullage Nitrogen-Inerting Systems
Against 30-mm High-Explosive Incendiary Projectiles, China Lake
Naval Weapons Center, J. Hardy Tyson and John F Barnes, May 1991.
---------------------------------------------------------------------------

Based on our research, we identified a simplified inerting system
that, using existing airplane pressurized air sources, could limit a
fuel tank to the 12 percent oxygen content level. This concept
eliminated the need for an air compressor, thus reducing the size and
complexity of the system. Our research determined that the method of
distributing the nitrogen-enriched air to the fuel tank could also be
simplified, which further reduced the system's weight and installation
cost. We now estimate that a simplified inerting system adequate to
protect the center wing tank on airplanes in the existing fleet should
weigh from 100 to 250 pounds and cost from $140,000 to $225,000 to
procure and install in existing airplanes, depending on fuel tank
capacity. (More information on the costs of these systems is provided
in the Preliminary Regulatory Evaluation.)
The FAA has openly shared with industry information on the
simplified inerting system design ever since it was first developed in
May 2002. This design concept was adopted by Boeing when applying for a
series of type certification and production approvals to incorporate a
fuel inerting system using nitrogen air enrichment in all currently
produced Boeing model airplanes. Thus, on November 15, 2002, Boeing
applied for a change to TC No. A20WE to modify Boeing Model 747 series
airplanes to incorporate the system into its center wing fuel tanks. It
has since applied for similar approvals for the Boeing Model 737
series, Boeing Model 757 series, Boeing Model 767 series, and Boeing
Model 777 series airplanes. We published a request for and received
public comments on a Notice of Proposed Special Conditions for
flammability reduction on the Boeing Model 747 on December 9, 2003 (68
FR 68563). Final Special Conditions No. 25-285-SC was issued on January
24, 2005 (70 FR 7800; February 15, 2005).

III. Proposed Requirements Relating to Fuel Tank Flammability

We are proposing today a performance-based set of requirements that
do not specifically direct the use of fuel inerting, but rather set
acceptable levels of flammability exposure in tanks most prone to
explosion or require the installation of an ignition mitigation means
in an affected fuel tank. We also by separate notice propose to revise
Advisory Circular 25.981-2 so as to describe several means of
compliance with these requirements, including both flammability-
reduction means, such as cooling, inerting using nitrogen or carbon
dioxide, and ignition-mitigation means, such as use of polyurethane
foam or explosion suppression systems. The revised AC sets out detailed
parameters for such systems if used as a means of achieving the
targeted safety standards.
The rule, if adopted, would require a retrofit of much of the
existing fleet of large airplanes but would not necessarily affect all
transport aircraft. We will require retrofit based on safety needs,
using a fleet average flammability exposure limit of seven (7) percent,
the level recommended by ARAC. We know that this level is routinely
exceeded in tanks that are incidentally heated by nearby air
conditioning equipment and in unpressurized auxiliary fuel tanks that
are located in the cargo compartment and that do not significantly
cool. The vast majority of large transport category airplanes operating
in the U.S., including all Airbus models and most Boeing models, have
center wing tanks that are above this level. We estimate that 3,800
airplanes with flammability exposure level above 7 percent would be
retrofitted if this rule is adopted.
As is the case for new production airplanes, all airplanes
currently equipped with a normally emptied or auxiliary fuel tanks that
have a flammability level above 7 percent could not have center wing
tanks that are flammable more than 3 percent on average and 3 percent
on hot days. Lowering the flammability levels of these fuel tanks in
the existing fleet and limiting the permissible level of flammability
on new production airplanes would result in an overall reduction in the
flammability potential of these airplanes of approximately 95 percent.
Some airplane models have center tanks with a fleet average
flammability exposure level that does not exceed 7 percent, including
to the best of our information the Lockheed L-1011, and Boeing MD-11,
DC10, MD80, and Boeing Model 727, and Fokker F28 MK100. At this time we
do not believe that these airplanes would need FRM or IMM for their
center tanks, unless the certificate holder has also installed an
auxiliary fuel tank that is found to be affected.\7\
---------------------------------------------------------------------------

\7\ Auxiliary fuel tanks are installed subject to amended
supplemental type certificates or field approvals. As such they are
``aftermarket'' installations not contemplated by the original
manufacturer of the airplane. Auxiliary fuel tanks are installed to
permit airplanes to fly for longer periods of time by increasing the
amount of available fuel. While all auxiliary fuel tanks are
normally emptied, some ``normally emptied'' tanks are included in
the original type design, such as the center wing tank on the Boeing 747.
---------------------------------------------------------------------------

A. Overview of the Proposal

Our proposal would require manufacturers and operators of most
large transport category airplanes to reduce the average flammability
exposure in affected fleets to tolerable levels of risk. Fleet average
flammability exposure represents the percent of flight time that fuel
vapors in the ullage are flammable, calculated across a fleet of an
airplane type operating over the range of actual or expected flights
and based on a wide range of environmental conditions and fuel
properties.\8\ This

[[Page 70928]]

rulemaking is premised on our finding that fuel tanks whose fleet-wide
average flammability exposure is more than 7 percent have a ``high
flammability exposure,'' which we consider unduly dangerous. This
finding, in turn, is based on the reports and findings of the ARAC and
our own risk assessment of the current transport category airplane fleet.
---------------------------------------------------------------------------

\8\ The airplane flammability exposure evaluation time begins
when the airplane is prepared for flight (which commences upon the
start of preparing the airplane for flight by turning on the
auxiliary power unit/ground power, starting the environmental
control systems, or taking other steps that begin the initial
preparation of the airplane), continues through the actual flight
and landing, and ends when all payload has been unloaded and all
passengers and crew have disembarked.
---------------------------------------------------------------------------

Our proposal would modify current regulations in several important
respects, affecting both manufacturers (TC holders and STC holders) and
operators (air carriers). We would significantly expand the coverage of
part 25 by making manufacturers generally responsible for the
development of service information and safety improvements (including
design changes) where needed to ensure the continued airworthiness of
previously certificated airplanes. This proposal would apply to holders
of existing TCs, holders of STCs, applicants for changes to existing
TCs, and certain other airplane manufacturers. We are proposing to
specify the new requirements for these entities in a new subpart I to
part 25, although we may decide to relocate these requirements at the
time the final rule is issued to simplify harmonization efforts.
As to fuel tank flammability specifically, manufacturers, including
holders of listed airplane TCs and of auxiliary fuel tank STCs, would
be required to conduct a flammability exposure analysis of their fuel
tanks, unless they have already notified the FAA that they will utilize
an ignition mitigation means instead. A new Appendix L to part 25 will
regulate the conduct of these analyses.\9\ As discussed later in this
document, the Appendix contains the method for calculating overall and
warm day fuel tank flammability exposure values needed to show that the
affected aircraft tanks comply with proposed limitations on
flammability exposure levels, described below.
---------------------------------------------------------------------------

\9\ Rather than relying on the analysis already conducted
pursuant to SFAR 88 and then simply regulating those airplanes with
a demonstrated exposure level of 7 percent or greater, today's
proposal contemplates requiring a new exposure analysis. The
existing analyses, while helpful in positing which airplanes are
likely to be affected by a final rule, were derived from incomplete,
and sometimes differing, assumptions. Appendix L would correct such
inconsistencies by establishing a single methodology for calculating
average flammability exposure.
---------------------------------------------------------------------------

Where the required analyses indicate that the fuel tank has an
average flammability exposure level below 7 percent, no changes would
be required. However, for the other fuel tanks, manufacturers would be
required to develop design modifications to support a retrofit of the
airplane. Under today's proposal, the average flammability exposure
level of any affected wing tank would have to be reduced to no more
than 7 percent. In addition, for any normally emptied fuel tank
(including auxiliary fuel tanks) located in whole or in part in the
fuselage, flammability exposure would have to be reduced to 3 percent,
both for the overall fleet average and for operations on warm days.
For long-pending certification projects that have not received a
type certificate from the FAA prior to the date of the final rule
(where application was received by the FAA before June 6, 2001, the
effective date of 14 CFR 25.981(c), applicants would be required to
limit the flammability exposure of any wing tank to no more than 7
percent. Any of those applicants whose proposals include any normally
emptied or auxiliary fuel tank with a flammability exposure level that
exceeds 7 percent would also have to meet the same flammability
exposure requirements proposed for retrofit (i.e., 3 percent), if any
portion of the tank is located within the fuselage contour. Applicants
for more recent certification projects (where application was received
after June 6, 2001), and all applicants for a TC or STC submitted after
the effective date of the final rule would need to meet the new
requirements of that section set forth in today's proposal.
We would set more stringent safety levels for certain critically
located fuel tanks in most new type designs, while maintaining the
current, general standard under Sec. 25.981 for all other fuel tanks.
We expect that as a result of this rule the design of most normally
emptied and auxiliary tanks located, in whole or in part, in the
fuselage of transport-category airplanes would need to incorporate some
form of FRM or IMM. Regulations in a new proposed Appendix K to Part 25
contain detailed specifications for all FRM, if they are used to meet
the flammability exposure limitations. These additional requirements
are designed to ensure the reliability of flammability-reduction means,
reporting of performance metrics and warnings of possible hazards in
and around fuel tanks. Specifications for IMM are detailed in the
current AC-25.981-2 and are not generally discussed in this document.
Type certificate holders for specific airplane models with high
flammability exposure fuel tanks would be required to develop design
changes and service instructions to facilitate the adoption of IMM or
FRM. Manufacturers of these airplanes would have to incorporate these
design changes in airplanes produced in the future. In addition, these
sections would require design approval holders (TC and STC holders) and
applicants to develop airworthiness limitations to ensure that
maintenance actions and future modifications do not increase
flammability exposure above the limits in this proposal. These design
approval holders would have to submit binding certification plans by a
specified date, and these plans would be closely monitored by the
holders' FAA oversight offices to ensure timely progress.
Lastly, the proposal requires affected operators to incorporate FRM
or IMM where required for high-risk fuel tanks in their existing fleet
of affected airplane models. Air carriers would also have to revise
their maintenance and inspection programs to incorporate the
airworthiness limitations developed under the other proposals. We also
intend to establish strict retrofit deadlines, which are premised on
prompt compliance by manufacturers with their certification plans.
Table 1 summarizes the proposed regulatory changes that relate to
fuel tank flammability safety. This table does not summarize the
proposed regulatory changes that are common between this proposal and
other aging airplane initiatives. Those changes are discussed in detail
later.

[[Page 70929]]

Table 1.--Summary of Proposed Rules
------------------------------------------------------------------------
Description of
14 CFR proposal Applies to
------------------------------------------------------------------------
25.1, 25.2.................. Expand applicability Applicants for TCs,
to current holders and changes to
of TCs, STCs, and those TCs for
certain transport category
manufacturers. airplanes.
Amend Sec. 25.2 to Manufacturers of
make reference to certain airplane
the proposed models.
subpart I..
25.981...................... Revise paragraph (b) Applicants for
to specify limits future TCs and
on fuel tank design changes to
flammability. those certificates.
Add paragraph (c) to
restate current
option of providing
ignition mitigation
means (IMM)..
Add paragraph (d) to
include
airworthiness
limitation items
(ALI) for IMM or
Flammability
Reduction Means
(FRM), and move the
existing ignition
prevention ALI
requirements into
this paragraph.
Subpart I 25.1801........... Defines the intent TCs, and design
of the subpart. changes to those
TCs for transport
category airplanes.
Manufacturers of
certain airplane
models.
25.1815..................... Require flammability TC holders.
exposure analysis
of all fuel tanks
within 150 days
after effective
date. If below 7
percent no
flammability
reduction required.
Compliance with
Sec. 25.981(d) to
define ALI required.
If above 7 percent Large transport
and in fuselage and category passenger
normally emptied, airplanes, with
must develop passenger capacity
service of 30 or more or a
instructions to payload of 7500 lbs
meet Sec. or more (original
25.981(b), (c) and TC or later
(d). increase).
If above 7 percent
and other tank
type, must develop
service
instructions to
incorporate IMM
(meet Sec.
25.981(c), or
reduce flammability
to 7 percent)..
Specific compliance
dates for each
Boeing and Airbus
airplane model.
Other models within
24 months.
25.1817..................... Require flammability Auxiliary tank STC
exposure analysis holders for large
of all fuel tanks transport category
installed under STC passenger
within 12 months airplanes, with
after effective passenger capacity
date. of 30 or more or a
Require impact payload of 7500
assessment of fuel lbs. or more
tanks installed by (original TC or
STCs, and (for later increase).
pending and future
applicants) other
STCs affecting fuel
tank flammability,
on IMM or FRM
developed by TC
holder under Sec.
25.1815 to
determine if any
ALI has been
violated 6 months
after FAA approval
of ALI submitted by
TC holders under
Sec. 25.1815 or
before
certification,
whichever is later..
Require development Applicants for
of service future STCs or
instructions to amendments to TCs
correct designs that affect fuel
that compromise ALI tank system or IMM/
defined by TC FRM.
holder under Sec.
25.1815 within 24
months. Require
within 24 months
after TC holder
compliance with
25.1815 development
of service
instructions for a
IMM or FRM for any
tank with
flammability above
7 percent, if
located within the
fuselage and
normally emptied.
25.1819..................... Requires IMM or FRM Pending
for any fuel tank certification
on a passenger projects.
airplane with a Pre Amendment 102.
flammability level
that exceeds 7
percent. Fuel tanks
located in the
fuselage and
normally emptied
must meet Sec.
25.981(b) level.
Other fuel tanks
must not exceed 7
percent.
Requires compliance Post Amendment 102.
with Sec.
25.981(c).
25.1821..................... Requires any Manufacturers of
affected airplanes certain airplane
produced after a models.
certain date to
incorporate IMM or
FRM.
Appendix 25 K............... Establishes Applicants for
performance, approval of
reliability and flammability
reporting reduction means.
requirements for
flammability
reduction means.
Appendix 25 L............... Defines flammability Any person required
analysis method and to perform
input parameters flammability
that must be used analysis.
in the analysis.
91.1509, 121.917, 125.509, Require retrofit of U.S. certificate
129.117. IMM or FRM into holders and foreign
large airplanes persons operating
with high U.S.-registered
flammability fuel large transport
tanks. Require category passenger
large transport airplanes.
category airplanes
manufactured after
specific dates to
have IMM or FRM in
high flammability
fuel tanks. Require
incorporation of
ALI into the
maintenance program.
------------------------------------------------------------------------

B. Ongoing Responsibility of Type Certificate Holders for Continued
Airworthiness

Several recent safety regulations necessitated action by air
carriers and other operators but did not require design approval
holders to develop and provide the necessary data and documents to
facilitate the operators' compliance. Operators are often dependent on
action by a design approval holder before they can implement new safety
rules. Ongoing difficulty reported by operators in attempting to meet
these rules has convinced us that the corresponding design approval
holder responsibilities may be warranted under certain

[[Page 70930]]

circumstances to enable operators to meet regulatory deadlines.
We intend to require type-certificate holders, manufacturers and
others to take actions necessary to support the continued airworthiness
of and to improve the safety of transport-category airplanes. Such
actions include performing assessments, developing design changes,
revising instructions for continued airworthiness (ICA), and making
available necessary documentation to affected persons. We believe this
requirement is necessary to facilitate compliance by air carriers with
operating rules that in effect demand the use of new safety features.
To address this problem, we propose to amend subpart A of part 25
to expand its coverage and to add a new subpart I to establish
requirements for current holders. As discussed in our final rule,
``Fuel Tank Safety Compliance Extension and Aging Airplane Program
Update'' (69 FR 45936, July 30, 2004), this and related proposals would
add provisions to a new subpart I requiring actions by design approval
holders that will allow operators to comply with our rules.
Part 25 currently sets airworthiness standards for the issuance of
TCs, and changes to those certificates, for transport category
airplanes. It does not list the specific responsibilities of
manufacturers to ensure continued airworthiness of these airplanes once
the certificate is issued. Therefore, we propose to revise Sec. 25.1
by adding paragraph (c) to make clear that part 25 creates such
responsibilities for holders of existing and supplemental type
certificates for transport category airplanes, and applicants for
approval of design changes to those certificates; we are also adding
paragraph (d) to require design changes and other service activities by
manufacturers when needed. In order to ensure the effectiveness of
these changes, we would also amend Sec. 25.2 (``Special retroactive
requirements'') so as to require adherence to a new Subpart I which may
require design changes and other activities by type certificate holders.
This proposal would establish a new subpart I, Continued
Airworthiness and Safety Improvements, where we would locate rules
imposing ongoing responsibilities on design approval holders. In the
past, this type of requirement took the form of a Special Federal
Aviation Regulations (SFAR). SFARs are difficult to locate, because
they are scattered throughout Title 14. Placing all these types of
requirements in a single subpart of part 25, which contains the
airworthiness standards for transport category airplanes, would provide
ready access to critical rules.
In preliminary discussions with foreign aviation authorities, with
whom we try to harmonize our safety rules, they have expressed concern
about consolidating parallel requirements in their counterparts to part
25. They have suggested that it may be more appropriate to place them
in part 21 or elsewhere. Therefore, we specifically request comments
from the public, including foreign authorities, on the appropriate
place for these airworthiness requirements for type certificate holders.
We reserve additional sections in this proposal to include other
subparts we would expect to create with future aging airplane rules,
several of which are under development. Some of these proposals include
similar language establishing the general airworthiness
responsibilities of manufacturers and thus include some overlapping
provisions. Once any proposal establishing these broad responsibilities
becomes a final rule, we will delete the duplicative requirements from
the other proposals and retain only that language pertinent to any
specific new safety regulations (such as fuel-tank flammability reduction).
Except in one respect (discussed below), however, the ongoing-
airworthiness requirements in Subpart I would not by their terms reach
applicants for TCs with respect to new projects for which application
is made after the effective date of the proposed rule. This is
unnecessary because, when we adopt a new requirement for TC holders,
there will be a corresponding amendment to part 25 expressly making
compliance with the new, or a similar safety standard a condition for
receiving a TC in the future. For example, in this proposal, the new
requirements of Sec. 25.981(b), (c) and (d) regarding FRM and IMM will
govern future applications.
For safety reasons, however, we are requiring that any application
for a type design change, whenever filed, not degrade the level of
safety already created by the TC holder's presumed compliance with the
subpart I rule. Currently, when reviewing an application for such a
change, we employ the governing standards stated in part 21,
specifically Sec. 21.101. That section generally requires compliance
with standards in effect on the date of application but contains
exceptions that may allow applicants to show compliance with earlier
standards. For example, if a change is not considered ``significant,''
the applicant may be allowed to show compliance by pointing to
standards that applied to the original TC. (See AC 21.101-1,
``Establishing the Certification Basis of Changed Aeronautical
Products,'' a copy of which can be downloaded from
http://www.airweb.faa.gov/rgl).
With the adoption of subpart I rules, we must ensure that safety
improvements that result from TC holder compliance with these
requirements are not undone by later modifications. Therefore, even
when we determine under Sec. 21.101 that an applicant need not comply
with the latest airworthiness standards, it will be required to
demonstrate that the change would not degrade the level of safety
provided by the TC holder's compliance with the subpart I rule. In the
context of today's proposal, for example, this will mean that an
applicant for approval of a design change would have to show that it
would not increase the fuel tank flammability above the limits defined
in this proposal or adversely affect the FRM or IMM established by the
TC holder.

C. Applicability

1. Manufacturers and Holders of Type Certificates, Supplemental Type
Certificates and Field Approvals
Today's proposal, if adopted, will impose requirements on TC
holders for all affected transport category airplanes as well as STC
holders and operators who have field approvals for auxiliary fuel tank
designs. Not all airplanes would require the installation of an FRM or
IMM. Those requirements would be based on the initial average
flammability exposure analysis discussed in detail later in this
document. However, the TC, STC or field approval holder would be
required to develop and provide limitations on the types of alterations
and operations permitted for the airplane in order to retain the
validity of that initial analysis.
Today's proposal, if adopted, would apply not only to domestic TC
holders, but also to foreign TC holders. This rule would be different
from most type certification programs for new TCs, where foreign
applicants typically work with their responsible certification
authority, and the FAA relies, to some degree, upon that authority's
findings of compliance under bilateral airworthiness agreements. No
other certification authority has yet adopted requirements addressing
fuel tank flammability for existing TCs. While some authorities have
indicated an interest in adopting some type of requirements for new
airplane designs, they may not adopt requirements

[[Page 70931]]

applicable to existing TCs. Accordingly, the FAA will retain the
authority to make all the necessary compliance determinations, and
where appropriate may request certain compliance determinations by the
appropriate foreign authorities using procedures developed under the
bilateral agreements. The compliance planning provisions of this
proposed rule are equally important for domestic and foreign TC holders
and applicants, and we will work with the foreign authorities to ensure
that their TC holders and applicants perform the planning necessary to
comply with those requirements.
As discussed briefly above, the proposed rule would require holders
of existing type certificates to incorporate FRM or IMM into all new
production airplanes if the fleet average flammability exposure level
exceeds permissible levels. In past rulemakings where the FAA has
required production cut-in of safety improvements, we have adopted
rules prohibiting operators of airplanes produced after a specified
date from operating those airplanes unless they are equipped with the
improvements. This approach is effective in ensuring that U.S.
operators receive the benefits of these safety improvements. But these
rules do not apply to foreign operators, unless they operate U.S.-
registered airplanes.
By requiring FRM or IMM separately from the operational rules
proposed in this notice, the proposed rule would improve the safety of
the overall fleet of larger transport category airplanes. This
requirement would also facilitate the secondary market for these
airplanes. Even if a manufacturer initially sells an airplane to a
foreign operator who may not be required to have the system, the
operator may later sell or lease it to a U.S. operator. The U.S.
operator would be able to simply place it into service, rather than
having to install a system. Given the frequency of airplane transfers
in today's global economy, we think having these systems installed
during production will provide significant long-term efficiencies since
no retrofit would be required, as well as providing immediate safety
benefits.
2. Airplanes
If adopted, this rule would apply, with some exceptions discussed
below, to transport category turbine-powered airplanes with a maximum
type-certificated capacity of 30 or more passengers, or a maximum
payload capacity of 7500 pounds or more resulting from the original
certification of the airplane or later increase in capacity. This would
result in the coverage of airplanes where the safety benefits and the
public interest are the greatest.
We are proposing to apply this rule to airplanes for which a
passenger capacity of 30 or more has been approved at any time. In the
past, some designers and operators have obtained design change approval
to slightly lower existing capacity to avoid applying requirements
mandated only for airplanes over specified capacities. Today's proposal
would remove this possible means of avoiding compliance. It is also
possible that an airplane design could be originally certificated with
a capacity slightly lower than the minimum specified in this section,
but through later design changes, the capacity could be increased above
this minimum. Today's proposal addresses both of these situations by
proposing to regulate all airplanes that have been approved for
carriage of 30 or more passengers, or 7500-pound or more payload, at
any time.
We considered applying this proposal to all part 25 airplanes. This
would have resulted in modifications to all fuel tanks located in the
fuselage that are normally emptied. However, smaller airplanes
generally do not have a significant number of high flammability
exposure fuel tanks. Few of the smaller transport category airplanes in
the current fleet have center wing tanks that are normally emptied.
While some of the smaller airplanes have auxiliary or normally emptied
fuel tanks located within the fuselage contour, many of these airplane
types use differential fuel pressure to transfer the fuel from the fuel
tanks. The increased pressure results in a reduction in the fuel tank
flammability by keeping the fuel vapors at a level where ignition is
unlikely. We have determined that the benefits of including these
airplane types in this proposal are not sufficient to warrant the cost.
Certain vintage airplanes type certificated before 1958, the
beginning of the jet age, would be excluded from the requirements of
this proposal. They are listed in Sec. 25.1815(j). There are no known
reciprocating-powered transport category airplanes currently in
scheduled passenger service. Compliance would not be required for these
specific older airplanes, because their advanced age and small numbers
would likely make compliance economically impractical. If the public
knows of other airplanes that may present unique compliance challenges,
the FAA is interested in receiving comments. These comments may result
in additional airplane models being excluded from the requirements of
this proposed rule.
The proposal does not extend to airplanes used in all-cargo
operations. Our analysis of the costs of extending the proposal to
include these airplanes does not appear to be justified by the
associated benefits. The potential loss of life in a single accident is
much smaller on all-cargo planes of the size contemplated by today's
proposal than on comparably sized passenger planes. The undiscounted
cargo airplane costs would be about $261 million, with a present value
of $110 million, while the benefits would be less than $1 million.
However, the FAA does believe there is a risk to all-cargo airplanes
because they share the same design features as at-risk passenger
airplanes. We typically do not base our certification standards for
transport category airplanes on use. Rather, our general philosophy is
to address the performance characteristics of these airplanes because
we believe all occupants should be protected against those designs that
present a risk of serious injury or death.
We have not evaluated the risk to all-cargo airplanes because they
are derivatives of passenger airplanes. The risk may be lower for all-
cargo operations than for passenger operations. For example, if the
risk of a fuel tank explosion per operating hour is the same for all-
cargo planes as for passenger airplanes, the projected number of
accidents for these planes is significantly less than one (0.15) in the
next 50 years. This is because the projected number of miles flown by a
cargo plane over the next 50 years is only 23 million miles. The risk
may also be lower for all cargo operations because many cargo
operations are conducted at night when the flammability of the fuel
tanks is lower because of lower ambient temperatures.
The 747 has both a passenger version and a freighter. The Monte
Carlo analysis conducted for the 747 included both types of airplanes,
and was weighted primarily toward the passenger airplane because they
make up the majority of the 747 fleet. Thus, it should be possible to
model the risk of a fuel tank explosion for cargo airplanes separate
from passenger airplanes. We request flammability analyses on all-cargo
airplanes and on the passenger versions of the same airplane model, as
well as any underlying data.
We have provided a breakdown of the estimated costs and benefits
associated with requiring all-cargo airplanes be equipped with a means
of reducing flammability in the preliminary regulatory evaluation. We
believe that

[[Page 70932]]

the cost associated with providing a means of flammability reduction on
newly designed cargo airplanes may be sufficiently low that it could
make sense for all airplanes manufactured under a TC or amended TC
applied for after the effective date of the final to have either an FRM
or IMM. We believe there will be only a minimal cost associated with
equipping newly designed all-cargo airplanes with a means of
flammability reduction since the passenger version of the same model
will be designed with such a system.
We request comment on whether, given the costs involved, the design
rules, the production cut-in rules, or the operating rules, if adopted,
should be applied to all-cargo airplanes.
Even with the categories of airplanes excluded that are discussed
above, we recognize that this proposal is costly. To ensure that this
rule is as cost effective as possible, we specifically request comments
on whether there are other categories of airplanes or ways to
distinguish among airplanes that would focus this rule on those where
the benefits would be greatest. Any comments provided should include
data to support the suggested exclusions or distinctions.
3. Fuel Tanks
The requirements proposed today would apply the proposed new FRM or
IMM requirements to existing fuel tanks with a fleet average
flammability exposure level that exceeds 7 percent. Main fuel tanks on
existing airplanes, i.e., those that are designed both to feed fuel
directly to one or more engines and to hold the required fuel reserves
continually throughout each flight, are unlikely to be affected as they
should have a fleet average flammability exposure level well below 7
percent.
For any fuel tank that is normally emptied and has a fleet average
flammability exposure level that exceeds 7 percent average flammability
exposure, if any portion of the tank is located in the fuselage
contour, the proposal would require TC STC and field approval holders
to develop IMM or FRM that reduces the flammability exposure to 3
percent average flammability exposure and that meets the 3 percent warm
day requirements.
All other tanks with a fleet average flammability exposure level
exceeding 7 percent would need to incorporate IMM, or FRM. If FRM is
installed it would need to provide a fleet average flammability
exposure at one of two levels: Tanks on airplanes manufactured pursuant
to a type certificate applied for prior to June 6, 2001 would have to
have an exposure level no greater than 7 percent; tanks on airplanes
manufactured pursuant to a type certificate applied for after June 6,
2001 would have to have an exposure level either no greater than 3
percent or equivalent to that of a comparable conventional unheated
aluminum tank (which could be either more or less than 3 percent).
The ARAC found fuel tanks that are normally emptied have higher
flammability exposure times than main tanks. Because these tanks
contain a high percentage of ullage during a significant portion of
most flights, a larger number of potential ignition sources are exposed
to fuel vapor space for an extended time. Additionally, when they are
within the fuselage contour, they are not naturally cooled by external
air, which causes the fuel vapor to be flammable for a significant
portion of the airplane operating time.
Auxiliary fuel tanks are developed by TC holders, STC holders and,
occasionally, by operators via field approvals, to increase the fuel
capacity available on a type-certificated airplane. There are 74
different STCs for auxiliary fuel tanks in the airplanes potentially
affected by the proposed rule. There are also field approvals for
auxiliary tanks installed by airplane operators. Data submitted to the
FAA as a result of SFAR 88 shows that fifteen of these auxiliary tanks
have high flammability exposure fuel tanks. Some of these tanks have
been installed in airplanes such as the DC-9 and DC-10 that do not have
any other fuel tanks with high flammability exposure. Production of
these airplane models ended long ago, so many of these airplanes will
be at or near the end of their intended operational life at the end of
the proposed compliance time given to the operators to incorporate FRM
or IMM. Requiring the affected certificate holders to develop service
instructions and the operators to incorporate FRM for these older fuel
tanks increases the cost of the proposed rulemaking with fewer benefits
than incorporation of FRM on newer airplane models. Therefore, the FAA
specifically requests comments on including these auxiliary fuel tanks
in the proposal. Information on the number of fuel tanks installed in
the fleet and the remaining useful life of the affected airplanes
should be provided.
Portions of fuel tanks that are located within the fuselage contour
include those in either the pressurized or unpressurized section of the
fuselage or those whose surfaces make up part of the pressurized
compartment. Fuel tanks located within the cargo compartment and center
wing tanks are considered to be located in the fuselage contour. Many
center tanks have portions that extend from the center wing box to the
wing. The compartments of the tank located within the wing would also
be considered part of the tank located within the fuselage contour and
the same flammability requirements would apply. Fuel tanks located in
the horizontal stabilizer, which also include segments located inside
the fuselage and portions that extend outside the fuselage contour,
would be assessed in the same way. Fuel tanks have also been located
within the vertical stabilizer. If no portion of these tanks is in the
fuselage, these tanks would not be considered as located within the
fuselage boundary.
4. Airplane Operators
The rule proposed today would also apply to operators of the
affected aircraft other than those who operate pursuant to 14 CFR part
135, Operating Requirements: Commuter and On Demand Operations and
Rules Governing Persons On Board Such Aircraft. We are excluding part
135 operators, because we have determined that only a few airplanes
operated under part 135 would be subject to the rule. This is because
part 135 is currently limited to a carrying of capacity of 10 or fewer
passengers and a payload of no more than 7,500 lb. We are in the
process of revising part 135 and may consider increasing the payload
capacity as part of that revision. If an increase in payload capacity
is contemplated, we may also consider requiring FRM or IMM under part 135.
As discussed previously, in an effort to enhance the cost
effectiveness of this rule, we specifically request comments on whether
other categories of operations should be excluded. Any comments
provided should include data to support the suggested exclusions or
distinctions.

D. Proposed Requirements for Manufacturers and Holders of Type
Certificates, Supplemental Type Certificates and Field Approvals

1. New Airplane Designs
Currently, Sec. 25.981(c) establishes a requirement that fuel tank
installation on all airplanes for which the type certificate was
applied for after 2001 must have either a ``means to minimize the
development of flammable vapors in the fuel tanks'' that would ``reduce
the likelihood of flammable vapors, or a ``means to mitigate the
effects of an ignition of fuel vapors * * *.'' We propose amending this
section to address new airplane designs.

[[Page 70933]]

We propose to require those airplanes incorporating FRM to limit
the fleet average flammability exposure to 3 percent, and to limit warm
day exposure to 3 percent, for all normally emptied fuel tanks located,
in whole or in part, in the fuselage. All other fuel tanks could either
meet the 3 percent average flammability exposure limitation or have a
level that is no higher than the exposure level in a conventional
unheated aluminum wing tank that is cooled by exposure to ambient
temperatures during flight. The advantage of the first option is that
manufacturers using unconventional designs would not be required to
conduct the modeling on an equivalent unheated aluminum wing tank that
is a purely theoretical design. The advantage of the second option is
that a manufacturer could increase the level of acceptable exposure
based on the exposure characteristics of this theoretical wing design.
TC Applicants have proposed newer technology airplanes using
composite wing skins or fuel tank designs with little exposed surface
area. These designs may result in average fuel tank flammability
exposure above the levels recommended by the ARAC. We expect future
applicants will propose similar designs. For these airplane types, the
applicant would have the option of demonstrating compliance by
analyzing the fleet average flammability exposure of an equivalently
designed wing made of aluminum for the model under evaluation. The
thermal characteristics of the wing treated as a single fuel tank, as
well as airplane specific parameters such as climb, cruise and descent
profiles and flight length distribution, would be used as inputs to the
flammability exposure analysis defined in Appendix L. This analysis
would establish the maximum allowable flammability for the airplane
model under evaluation.
The safety objective of an ``unheated aluminum wing tank'' that is
proposed as the standard in this notice is consistent with the ARAC
recommendation and 14 CFR 25.981(c). It does not provide a numerical
standard to apply in future type certification programs and the
demonstration of compliance requires the applicant to conduct an
analysis of their design to establish the flammability of a
conventional unheated aluminum wing tank. In certain cases the
compliance demonstration would be simplified if a numerical standard
were provided in the regulation. Therefore we are proposing to
establish a numerical flammability exposure standard of 3 percent that
can be used. This approach may have implementation advantages and
should achieve the safety level intended by the ARAC recommendation and
the current approach of Sec. 25.981(c). We specifically request
comments on which approach would be more workable and effective. If,
based on comments received, we determine that a numerical standard
alone is preferable, we may revise the final rule to adopt this approach.
In addition to designing normally emptied fuel tanks that meet the
proposed requirements, the TC holder would be required to provide
airworthiness limitations designed to prevent exceeding the exposure
limits of this rule or degrading the performance and reliability of FRM
or IMM provided by the TC holder. For example, the manufacturer may
state that any changes to the fuel system may invalidate its exposure
analysis. In such an instance, the party making subsequent changes
would need to conduct its own exposure analysis to ensure that the
affected fuel tanks remain within the applicable limits. Likewise, a
manufacturer may limit the type of jet fuel acceptable for its systems,
as a jet fuel with a lower flash point may invalidate the initial
exposure analysis.
As discussed earlier, today's proposal would not apply to airplanes
designed solely for all-cargo operations. This exclusion applies to
airplanes that, either as a result of initial type certification or
through later design changes, have no passenger carrying capability,
except for carriage of supernumeraries.\10\ Airplanes designed for all-
cargo operations would continue to be subject to the existing
requirements of Sec. 25.981(c), which requires either means to
minimize the development of flammable vapors in the fuel tanks or IMM.
On the other hand, if an airplane that is designed for all-cargo
operations is converted to an airplane equipped to carry passengers,
including a ``combi'' airplane (part cargo, part passenger), this
design change would make the airplane subject to these proposed
requirements.
---------------------------------------------------------------------------

\10\ These are cargo handlers and other persons who are
typically carried on cargo-only airplanes to assist in the cargo
operations.
---------------------------------------------------------------------------

2. Existing Airplane Designs
Holders of existing TCs would be required to first conduct a fleet
average flammability exposure to determine whether the rule proposed
today would apply to their fuel tanks. If the exposure level for
normally emptied fuel tanks within the fuselage exceeds 7 percent,
design changes and instructions for IMM or FRM that limit both overall
and warm day fleet flammability exposure levels (discussed later) to no
more than 3 percent would need to be developed. All other normally
emptied fuel tanks exceeding a 7 percent exposure limit would require
design changes limiting exposure to 7 percent unless manufactured
pursuant to a type certificate applied for after June 6, 2001, in which
case the potentially more stringent requirements of existing Sec.
25.981(c) would continue to apply.\11\ Once design changes are
developed, a second exposure analysis would need to be conducted to
validate the design changes.
---------------------------------------------------------------------------

\11\ If this proposed amendment is not issued until after
affected pending certification projects are completed, the final
rule may revise the retrofit requirements proposed in Sec. 25.1815
to reference Amendment 25-102 as the appropriate standard for fuel
tanks on these airplanes other than those located in the fuselage.
---------------------------------------------------------------------------

Even if no changes to existing fuel tanks are required based on the
fleet average exposure analysis, the manufacturer would be required to
develop the same type of airworthiness limitations as those required
for new airplane designs.
The affected TC holders would also be required to submit compliance
plans for the flammability analysis and the development of service
instructions for an FRM or IMM. The contemplated compliance schedules
and submissions are discussed later in this document.
Finally, today's proposal would require production cut-in for all
airplanes manufactured after the required design changes are available.
This section would apply only if the FAA has jurisdiction over the
organization responsible for final assembly of the airplane. Section
25.1821(a) uses the same terminology as Annex 8 to the Convention on
International Civil Aviation, which defines the limits of the FAA's
authority under international law. In most cases, this refers to final
assembly within the United States; there are limited circumstances
where final assembly may occur in United States, but the responsible
organization is under the jurisdiction of a foreign authority. It is
also possible that final assembly could be done in another country by
an organization over which the FAA has jurisdiction, such as a
production certificate holder.
3. Auxiliary Fuel Tanks
Manufacturers and installers of auxiliary fuel tanks, whether
manufactured under an amended TC, an STC or a field approval, would be
required to conduct both an initial fleet

[[Page 70934]]

average exposure analysis and an impact assessment. The first analysis
would determine the exposure of the tanks for which they are
responsible, while the second would determine whether those tanks
negatively impact the flammability exposure of the tanks originally
installed on the airplane.
Changes to TCs, including installation of auxiliary fuel tanks or
changes in the capacity of fuel tanks, may result in increased fuel
tank flammability exposure or adversely affect FRM or IMM.\12\
Accordingly, the proposed rule would require a flammability exposure
analysis of the auxiliary fuel tank design, an impact assessment to
determine any adverse impact its design may have on the original or
modified type design, and development of a flammability impact mitigation
means (FIMM) to address adverse changes in flammability exposure.
---------------------------------------------------------------------------

\12\ With the adoption of rules requiring the retrofit of fuel
tanks in certain airplanes, we have to consider different issues in
deciding what standards applicants for design change approvals must
meet. Otherwise, the safety improvements that result from TC holder
compliance with these requirements could be undone by later
modifications. Therefore, even if we determine under Sec. 21.101
that it is not necessary to require these applicants to comply with
the latest airworthiness standards, it is still necessary for them
to show that the change would not degrade the level of safety
provided by the TC holder's compliance with the rule proposed today.
---------------------------------------------------------------------------

STC holders or applicants for an amended TC affected by the
proposed rule would need to conduct a flammability analysis using the
``Monte Carlo'' method defined in proposed Appendix L and discussed
later in this document. A number of inputs are required to conduct this
analysis. Airplane specific data, such as fuel management, fuel tank
thermal characteristics, or airplane climb rate may not be readily
available from the original TC holder. We intend the STC holders to
obtain the information by working with the TC holder and operators of
airplanes that have their tanks installed. Applicants would need to
work with prospective customers. Operators have business agreements
with the original TC holders and in many cases access to TC holder
information they obtained when they purchased the airplane.
Conservative assumptions or business agreements with the original TC
holders are other possible methods of gathering airplane type specific
data needed for the analysis.
If an increase in exposure above the allowable limits is
identified, the holder of the STC or field approval would have to
develop a FIMM and demonstrate how it will mitigate the impact of the
increased exposure. One of the easiest methods may be simply
deactivating the auxiliary tank or sealing off the venting to the
affected tank. As another example, if an auxiliary fuel tank vents into
a TC holder's tank for which FRM is provided, the venting may have to
be modified to prevent adversely affecting the FRM's performance.
Finally, a validation analysis would be required for the auxiliary
tanks that demonstrates that the auxiliary tank flammability exposure
levels, as modified with the addition of FRM or IMM, do not exceed the
acceptable limits. Likewise, a validation analysis would be required to
demonstrate that the FIMM is effective in maintaining the level of
exposure in other tanks determined by the manufacturer of the other
tank. As is the case for TC holders of existing airplanes, holders of
STCs and field approvals would need to develop future airworthiness
limitations and meet all mandated compliance schedules should they
decide not to deactivate the fuel tank.
For applicants for STCs and TC amendments, this proposal includes
other design changes that could affect flammability exposure. Because
this rule would require retrofit of airplanes to reduce flammability
exposure, it would be counterproductive to allow future design changes
that might negate the safety benefits of those retrofits.
Any design change to a TC subject to the requirements proposed in
today's document that adds an auxiliary fuel tank, increases fuel tank
capacity, or increases the flammability exposure of the existing fuel
tank would have to meet the requirements of Sec. 25.981 proposed
today. This requirement is intended to apply primarily to future design
changes, but it may also apply to design change projects that are
pending when this rule is issued. For example, in addition to applying
for a new TC for the Airbus Model A380, Airbus has also applied for an
amendment to that TC for the Model A380-800F (freighter derivative).
Among other design changes, this TC amendment would incorporate a new
fuel tank in the fuselage contour that is normally emptied. Under this
proposal, this fuel tank would have to be shown to meet the
requirements of proposed Sec. 25.981. Because of the increased
technical complexity of auxiliary fuel tank installations resulting
from this proposal once this final rule is adopted, field approvals
will no longer be granted for these tanks on airplanes affected by this
rule.
4. Methods of Mitigating the Likelihood of a Fuel Tank Explosion
As noted above, TC and STC holders may need to make design changes
to their fuel tanks located, in whole or in part, within the fuselage
to decrease their level of flammability exposure. The rule proposed
today offers two options, IMM or FRM.
a. Flammability Analysis Using the Monte Carlo Method
For all fuel tanks, an analysis must be performed to determine
whether the fuel tank, as originally designed, meets the fleet average
flammability exposure limits discussed above. By ``average,'' we mean
that the analysis of each fuel tank must be averaged over the entire
flammability exposure evaluation time (FEET) (see footnote 8) of each
airplane in the entire fleet. To determine the flammability exposure of
fuel tanks, the ARAC used a specific methodology referred to as the
Monte Carlo method.\13\ We are proposing that any analysis of a fuel
tank must be performed in accordance with this methodology, as detailed
in proposed Appendix L and in the FAA document, Fuel Tank Flammability
Assessment Method Users Manual.\14\ We considered approving alternative
methodologies in lieu of Appendix L, but we found that no other
alternative considered all factors that influence fuel tank
flammability exposure, which is the safety objective of this proposal.
---------------------------------------------------------------------------

\13\ This methodology determines the fuel tank flammability
exposure for numerous simulated airplane flights during which
various parameters such as ambient temperature, flight length, fuel
flash point are randomly selected. The results of these simulations
are averaged together to determine the fleet average fuel tank
flammability exposure.
\14\ As indicated in Appendix L, we intend to incorporate the
users manual by reference into the final rule.
---------------------------------------------------------------------------

The Monte Carlo method,\15\ as commonly understood by scientists, is

[[Page 70935]]

useful for obtaining numerical solutions to problems which are too
complicated to solve analytically. The method provides approximate
solutions to a variety of mathematical problems by performing
statistical sampling experiments on a computer. The method applies to
problems with no probabilistic content as well as to those with
inherent probabilistic structure.
---------------------------------------------------------------------------

\15\ History of Monte Carlo method
The method is called after the city in the Monaco principality,
because of a roulette, a simple random number generator. The name
and the systematic development of Monte Carlo methods dates from
about 1944.
The real use of Monte Carlo methods as a research tool stems
from work on the atomic bomb during the second world war. This work
involved a direct simulation of the probabilistic problems concerned
with random neutron diffusion in fissile material; but even at an
early stage of these investigations, von Neumann and Ulam refined
this particular `` Russian roulette'' and ``splitting'' methods.
However, the systematic development of these ideas had to await the
work of Harris and Herman Kahn in 1948. About 1948 Fermi,
Metropolis, and Ulam obtained Monte Carlo estimates for the
eigenvalues of Schrodinger equation.
In about 1970, the newly developing theory of computational
complexity began to provide a more precise and persuasive rationale
for employing the Monte Carlo method. The theory identified a class
of problems for which the time to evaluate the exact solution to a
problem within the class grows at least exponentially with M. The
question to be resolved was whether or not the Monte Carlo method
could estimate the solution to a problem in this intractable class
to within a specified statistical accuracy in time bounded above by
a polynomial in M. Numerous examples now support this contention.
Karp (1985) shows this property for estimating reliability in a
planar multiterminal network with randomly failing edges. Dyer
(1989) establish it for estimating the volume of a convex body in M-
dimensional Euclidean space. Broder (1986) and Jerrum and Sinclair
(1988) establish the property for estimating the permanent of a
matrix or, equivalently, the number of perfect matchings in a
bipartite graph. Discussion derived from History of the Monte Carlo
Method, Sabri Pllana,
http://geocities.com/CollegePark/Quad/2435/index.html.
---------------------------------------------------------------------------

Our use of this method to analyze fuel tank flammability exposure
and define acceptable limits is based on the recommendation of the
ARAC, which compared the flammability exposure of conventional unheated
aluminum wing fuel tanks to that of tanks that are located within the
fuselage contour and heated by adjacent equipment. Use of the Monte
Carlo method allows us to consider variables from within defined
distributions that represent possible operating conditions for the
flight. The results of a large number of flights can then be used to
approximate average flammability exposure over a large fleet of airplanes.
Variables include those affecting all airplanes in the transport
category airplane fleet, such as: (1) Ground, overnight, and cruise air
temperatures likely to be experienced worldwide; (2) fuel properties;
and (3) conditions when the tank in question will be considered
flammable. In addition, the analysis factors in specific airplane
models characteristics, such as climb and descent profiles, fuel
management, heat transfer characteristics of fuel tanks, maximum
airplane operating temperature limitations, maximum airplane range for
the airplane model, and the effectiveness of FRM (if installed).
The flammability analysis must include any model variations and
derivatives for which the TC holder has obtained approval that affect
fuel tank flammability exposure. Model variations that may affect fuel
tank flammability could include changes in the fuel tank volume or
usable fuel capacity, changes in the fuel management procedures, and
engine changes that might affect parameters such as airplane climb rate
or bleed air available if needed by an FRM. Other examples of
configuration differences that may affect fuel tank flammability
exposure are provided in the discussion of Sec. 25.1817. The
flammability analysis would also include all modifications and changes
mandated by ADs that affect fuel tank flammability exposure as of the
effective date of the rule. These ADs would only be those issued
against any configurations developed by TC holders. The analysis would
not address any ADs issued against modifications defined by a third
party STC installed on affected airplanes. The result would be a
configuration that is clearly understood by both industry and the FAA.
Mass loading and changes in fuel vapor concentration caused by fuel
condensation and vaporization have been excluded from the flammability
exposure analysis. The method used by the ARAC to establish the
flammability exposure value as the benchmark for fuel tank safety for
wing fuel tanks did not include the effects of cooling of the wing tank
surfaces and the associated condensation of vapors from the tank
ullage. If this effect had been included in the wing tank flammability
exposure calculation, it would have resulted in a significantly lower
wing tank flammability exposure benchmark value. The ARAC analysis also
did not consider the effects of the low fuel condition (or ``mass
loading'') which would lower the calculated flammability exposure value
for fuel tanks that are routinely emptied, such as center wing tanks.
When the amount of fuel is reduced to very low quantities within a fuel
tank, there may be insufficient fuel in the tank to allow vaporization
of fuel to the concentration that would be predicted for any particular
temperature and pressure.
The effect of condensation and vaporization in reducing the
flammability exposure of wing tanks is comparable to the effect of the
low fuel condition in reducing the flammability exposure of center
tanks. Therefore, we consider these effects to be offsetting, so that
by eliminating their consideration, the analysis will produce results
for both types of tanks that are comparable. Accordingly, both factors
have been excluded when establishing the flammability exposure limits
in this proposal. During development of the harmonized special
conditions for the Boeing 747, the FAA and the European Joint Aviation
Authorities (JAA)/EASA agreed that using the ARAC methodology provides
a suitable basis for determining the flammability of a fuel tank and
consideration of these effects should not be permitted.
Using these variables, the Monte Carlo method would then be applied
to a statistically significant number of flights (1,000,000), where
each of the factors described above is randomly selected. The flights
selected are representative of the fleet using the defined
distributions of the variables. For example, flight one may be a short
flight on a cold day with an average flash point fuel. Flight two may
be a long flight on an average day with a low flash point fuel. This
process is repeated until 1,000,000 flights have been defined in this
manner.
For every one of the 1,000,000 flights, the Monte Carlo program
calculates the amount of time the bulk average fuel temperature and
ambient pressure in the fuel tank or compartment of interest would
result in the fuel vapor being within the flammable range. This
calculation is then used, in combination with the oxygen concentration
in the fuel tank (if an FRM is installed), to establish whether the
fuel tank is flammable. Averaging the results for all 1,000,000 flights
provides an average flammability exposure for the fleet of airplanes of
a particular model type.
The determination of whether the fuel tank ullage is flammable is
based on the temperature of the fuel in the tank or the compartment of
interest, determined by the tank thermal model, the atmospheric
pressure in the fuel tank, and properties of the fuel loaded for a
given flight, which is randomly selected from data provided in tables
in this appendix.
The Monte Carlo methodology has previously been recommended by ARAC
and has been used in previous analyses by the affected certificate
holders in evaluating the flammability exposure of fuel tanks conducted
as part of evaluating the findings of SFAR 88. Therefore we expect the
affected type certificate holders already have a good understanding and
can comply with this requirement within the proposed timeframe of 150 days.
b. Ignition Mitigation Means
The proposed rule maintains the option introduced by Amendment 25-
102 for affected manufacturers to use ignition mitigation as a means of
protecting the airplane from the hazards associated with fuel tank
flammability. IMM is a passive system that requires little attention
once installed. IMM does not prevent an ignition in the fuel tank;
rather, material absorbs the heat created by the fire. While a small
fire could occur, an IMM system eliminates the

[[Page 70936]]

possibility of a catastrophic fuel tank explosion.
We acknowledge that IMM presents maintenance challenges. The
mitigation means (such as polyurethane foam, metal foil products and
explosion suppression systems discussed within AC 25.981-2) must be
reinstalled exactly as removed when the fuel tanks are opened up for
maintenance actions. Replacement is particularly difficult because all
voids must be removed. It also appears that the materials used for
mitigation (particularly the polyurethane foams) may be prone to
compression, thus reducing the usable life of the material.
Nevertheless, given the potential effectiveness of IMM, the FAA
believes we should continue to allow installation of IMM as a means of
compliance with the requirements proposed today. A detailed discussion
of acceptable means of compliance for manufacturers choosing to comply
with the IMM option is provided in AC-25.981-2.
c. Flammability Reduction Means
Alternatively, a TC or STC holder could decide to use an FRM that
limits the exposure level of the tanks. For fuel tanks that are
normally emptied and located within the fuselage contour, the exposure
would have to be limited to 3 percent under two sets of conditions,
overall fleet exposure and warm day fleet exposure. Both of these
conditions would be evaluated using the Monte Carlo method described
below. For all other fuel tanks, the 3 percent limit would apply only
to the overall fleet exposure.
The proposed flammability exposure requirements are intended to
provide an additional layer of protection to the existing certification
standards that require designs to preclude fuel tank ignition sources.
This balanced risk management approach of precluding ignition sources
and reducing flammability exposure in certain fuel tanks provides two
independent layers for preventing fuel tank explosions in those tanks.
The proposed requirements could be met by a highly reliable ``single-
string'' (non-redundant) inerting-based FRM, allowing for limited
operation of airplanes with an inoperative FRM until repairs could be
made. These requirements could also be met by a cooling-based FRM.
Compliance with these requirements has been shown to be practical using
existing technology.
i. Accounting for System Reliability and Performance Issues
As discussed in the background section of this document, previous
studies of inerting-based FRM showed that, if inerting systems were
required to be operational for all flights, the system would be
required to have at least some redundant design features and would not
be practical. That is, it would require most components to be
duplicated to provide a back-up function in the event the primary
component failed. A requirement for a redundant FRM that would continue
to operate after component failure would increase the weight and
complexity of an inerting system. This may result in a system that
would not be practical for commercial airplanes at this time. The
overall fleet flammability exposure analysis would assume some periods
of inoperability. However, we would require that the contribution to
average flammability exposure due to either reliability (during periods
when the system is inoperative) or system performance (during periods
when the system does not have the capacity to maintain a non flammable
tank), be limited to 1.8 percent. This gives the designer freedom to
engineer the system, and allows for some operation of airplanes with an
inoperative FRM until repairs can be made at an appropriate maintenance
facility.
ii. Warm Day Fleet Flammability Exposure
The warm day exposure analysis is intended to ensure minimum FRM
system performance levels when there is the greatest risk to safe
flight. Therefore, the 3 percent flammability exposure limit excludes
system reliability related contributions that are included in the
overall fleet flammability exposure assessment. Compliance with this
proposal would require conducting an analysis in accordance with
Appendix L for each of the specific phases of flight during warmer day
conditions defined in the proposal. The flammability exposure of the
tank in question would be determined for the ground, takeoff and climb
phases as separate values, without including the times when the FRM is
not available because of failures of the system or dispatch with the
FRM inoperative. The fleet flammability exposure level of each fuel
tank for ground, takeoff, and climb phases of flight during warm days
must not exceed 3 percent of the flammability exposure evaluation time
in each of the three phases.
iii. Reliability Reporting
Today's proposal, if adopted, would require that the applicant
demonstrate effective means to ensure collection of FRM reliability
data so that the effects of component failures can be assessed on an
on-going basis. The proposed reporting requirement applies to
applicants and holders of the affected TCs, STCs, and field approvals.
The rule would require the TC or STC holder to provide the FAA with
summaries of the FRM reliability data and compliance with Appendix K on
a quarterly basis for the first five years after the FRM is installed
and operational. After that time, continued quarterly reporting
requirements may be replaced with other reliability tracking methods
approved by the FAA oversight office. The requirement for quarterly
reports may be eliminated if the FAA determines that the reliability of
the FRM meets, and will continue to meet, the requirements of the rule.
Operators would not be required to report FRM reliability
information. We intend TC holders to gather the needed data from
operators using existing reporting systems that are currently used for
airplane maintenance, reliability and warranty claims. We anticipate
the operators would provide this information through existing business
arrangements between the TC holders and the airlines.
iv. Reliability Indication and Maintenance Access
The proposed rule would require that indicators be provided to
identify failures of the FRM, so that appropriate actions can be taken
to maintain the reliability of the FRM. The need to provide indication
of the FRM status will depend on the particular FRM design. Various
design methods may be used to make sure an FRM meets the reliability
and performance requirements. These may include a combination of system
integrity monitoring and indication, redundancy of components, and
maintenance actions. A combination of maintenance indication or
maintenance check procedures could be used to limit exposure to latent
failures within the system, or high inherent reliability may be used to
make sure the system will meet the fuel tank flammability exposure
requirements.
The need for FRM indications and the frequency of checking system
performance (maintenance intervals) must be determined as part of the
FRM fuel tank flammability exposure analysis. The determination of a
proper maintenance interval and procedure will follow completion of the
certification testing and demonstration of the system's reliability and
performance prior to certification or as part of the FAA review process
for airplanes manufactured under existing

[[Page 70937]]

TCs or auxiliary fuel tanks under existing STCs.
The rule would also require that sufficient accessibility to FRM
status indications be provided for maintenance personnel. We intend
that maintenance personnel or the flightcrew have access to any
indications that must be accessed at intervals established by the FRM
design approval holder when demonstrating compliance with the
reliability requirements for the FRM. Access doors and panels to the
fuel tanks with FRMs and to any other enclosed areas that could contain
hazardous atmosphere under either normal conditions or failure
conditions would need to be permanently stenciled, marked, or placarded
to warn maintenance personnel of the possible presence of a potentially
hazardous atmosphere. The proposal for markings does not alter the
existing requirements that must be addressed when entering airplane
fuel tanks.
d. Service Instructions and Service Bulletins
If the flammability exposure analysis shows that the average
exposure level for any fuel tank exceeds 7 percent, the TC holder would
be required to develop design changes and service instructions for
either FRM or IMM.
Modifications incorporated into existing airplanes, including
safety related changes (design and/or maintenance) that are mandated by
AD, are typically made by operators using service instructions
developed by the TC holders, commonly referred to as service bulletins.
In this proposal, service instructions must contain sufficient
information for the operator to incorporate the design change and any
associated procedures and airworthiness limitations. They may include
specific step-by-step procedures and information needed by the
operator, such as parts lists and drawings. Therefore, the proposed
rule would require TC holders to develop and submit for approval by the
FAA, not just data defining a proposed design change, but all of the
information necessary to enable an operator to comply with the proposed
operational rules, discussed later.
e. Critical Design Configuration Control Limitations (CDCCL)
If adopted, the rule would require defining airworthiness
limitations, including Critical Design Configuration Control
Limitations (CDCCL), inspections, and other procedures for fuel tanks
to prevent exceeding the applicable flammability exposure limits. For
this proposal, CDCCL include those features of the design that must be
present or maintained for compliance with the requirements of Sec.
25.981(b) and (c) for the operational life of the airplane. For
example, certain fuel tanks may rely on natural cooling to meet the
flammability exposure levels within this proposal. Changes to the
airplane, such as installing a fuel re-circulation system, hydraulic
heat exchanger in the fuel tank, or a heat source adjacent to the fuel
tank, may affect fuel tank flammability. The CDCCL would be necessary
in this example to prohibit the addition of heat to the fuel tank.
Another example of CDCCL might include limits on operation with certain
fuel types such as JP-4. We expect all fuel tanks, even those in
airplanes that do not have high flammability fuel tanks, would need to
have CDCCL defined so that future modifications do not increase the
flammability above the mandatory limit. The proposal applies the same
requirements already applied to fuel tank ignition source prevention in
Sec. 25.981(b) to the FRM or IMM.
The proposal also includes the requirement that visible means
identifying CDCCL are present. Our intent here is to prevent
alterations to critical features of the system. As the visible
identifications are critical to the FRM or IMM system, they are also
considered to be CDCCL. Any tampering or removal would be in violation
of the CDCCL. These CDCCL, inspections, or other procedures would be
documented as airworthiness limitations in the ICA.
Under the proposal, all fuel tanks, regardless of flammability
exposure, must be subject to airworthiness limitations consisting of
CDCCL, inspections, or other procedures. The purpose of these
limitations is to prevent increasing the flammability exposure of the
tanks above that permitted under this section and to prevent
degradation of the performance of any means installed in accordance
with this section. For example, certain fuel tanks may rely on natural
cooling or use of certain fuel types to meet the flammability levels
within this proposal. Therefore, CDCCL may be required that define the
critical features, such as--
? Flammability exposure of the unheated aluminum wing tank,
? Cooling rate,
? Limits on heat input,
? Limits on use of high volatility fuels such as JP-4,
? Quantity of engine bleed air flow that is used for inerting,
? Limits on penetrations of the fuel tank,
? Limits on any changes to fuel management that may affect FRM,
? Limits on changes to any placards or means used to visibly
identify critical design features of the fuel tank system that must not
be compromised for the operational life of the airplane.
As discussed above, airworthiness limitations, such as those
proposed today, are part of the ICA. TC holders would need to make
available to affected parties pertinent changes to the ICAs. (The term
``make available'' is used in the same sense that it is used in Sec.
21.50.) We do not intend by this proposal to alter or interfere with
the existing commercial relationships between TC holders and these
other persons. We anticipate that TC holders would be able to be
reasonably compensated for developing these documents, as they are
under current practice.
The proposed rule would require creation of an Airworthiness
Limitations Section (ALS), unless previously established. The ALS is
required by current part 25 and includes those items that have
mandatory inspection or replacement times related to fuel systems and
structure. The ALS is included in the ICA, approved as part of
certification, and distributed with an airplane on delivery. In this
way the ALS is visible to all who need it and who would be required to
comply with it under Sec. Sec. 91.1509, 121.917, 125.509 and 129.117
of this proposal. The current part 25 ALS and ICA requirements apply
only to airplane types for which the TC application was made after
Amendment 25-54 (adopted in 1981) and were developed for structural
considerations. As a result, they are not applicable to many current
airplanes and do not currently contain information for other systems.
For those TC holders of airplanes that currently do not have an
ALS, the intent of this proposal is to require an ALS only for fuel
tank safety related limits. This proposal would not require that the
ALS for these airplanes include the other requirements for an ALS
established under Amendment 25-54 to part 25, or a later amendment. For
those TC holders or applicants with airplanes certified to Amendment
25-54 or later, the existing ALS would be revised to include the fuel
tank system airworthiness limitation items (ALI).
f. Compliance Planning
Historically, the FAA has worked together with the TC holders when
safety issues arise, in order to identify solutions and actions that
need to be taken. Some of the safety issues that have been addressed by
this process include those involving aging aircraft structure, thrust
reversers, cargo doors,

[[Page 70938]]

and wing icing protection. While some manufacturers have promptly
addressed these safety issues and developed service instructions,
others have not applied the resources necessary to develop service
instructions in a timely manner. This has caused delay in the adoption
of corrective action(s). A more uniform and expeditious response is
necessary to address fuel tank safety issues. Because this proposal
sets a precedent in introducing part 25 requirements for holders of
existing TCs, changes to existing TCs, and manufacturers, it is the
FAA's expectation that they will work closely with the FAA oversight
office in putting together a compliance plan for developing the
required FRM or IMM.
In order to provide TC holders and the FAA with assurance that the
TC holders understand what means of compliance is acceptable and have
taken necessary actions (including assigning sufficient resources) to
achieve compliance with the proposed rule, we are proposing a
compliance planning requirement. This requirement is based
substantially on ``The FAA and Industry Guide to Product
Certification,'' which describes a process for developing project-
specific certification plans for type certification programs. This
Guide may be found in the docket. This planning requirement would not
apply to future applicants for TCs. Since this type of planning
routinely occurs at the beginning of the certification process, no
additional compliance planning is required for future applicants.
The Guide recognizes the importance of ongoing communication and
cooperation between applicants and the FAA. The proposed planning
schedule, while regulatory in nature, is intended to encourage
establishment of the same type of relationship in the process of
complying with this rule, if adopted.
One of the items required in the plan is, ``If the proposed means
of compliance differs from that described in FAA advisory material, a
detailed explanation of how the proposed means will comply with this
section.'' FAA advisory material is never mandatory, because it
describes one means, but not the only means of compliance. In the area
of type certification, applicants frequently propose acceptable
alternatives to the means described in advisory circulars. But when an
applicant chooses to comply by an alternative means, it is important to
identify this as early as possible in the certification process to
provide an opportunity to resolve any issues that may arise that could
lead to delays in the certification schedule.
The same is true for the fuel tank flammability reduction
requirement. As discussed earlier, timely compliance with this section
is necessary to enable operators to comply with the operational
requirements of this proposal. Therefore, this item in the plan would
enable the FAA oversight office to identify and resolve any issues that
may arise with the compliance plan without jeopardizing the TC holders
ability to comply with this section by the compliance time.
i. Compliance Plan for Flammability Exposure Analysis
The proposed rule would require submission of a compliance plan
within 60 days of the effective date of the final rule for the
flammability exposure analysis required by the proposed rule. The
intent of the proposal is to promote early planning and communication
between the certificate holders and the FAA. The exposure analysis
would need to be completed within 150 days of the rule's effective
date. Thus, the 60 day planning submission should provide sufficient
time for the FAA to discuss any concerns that it may have over how the
affected party intends to analyze fleet average flammability exposure.
ii. Compliance Plan for Design Changes and Service Instructions
Under today's proposal, each holder of an existing TC would need to
submit to the FAA oversight office a compliance plan for developing
design changes and service instructions within 210 days of the rule's
effective date.
TC holders and applicants would have to correct a deficient plan,
or deficiencies in implementing those plans, in a manner identified by
the FAA oversight office. Deficiencies in the compliance plan would
need to be corrected within 30 days of notification by the FAA. This
approach differs from the original type approval process. Applicants
for type certificates face commercial pressures, not regulatory
deadlines, so the FAA can permit them to resolve identified
deficiencies on their own schedule. Such leeway is not appropriate here
because operators who are subject to regulatory deadlines are dependent
on TC holders' timely compliance with these requirements. However,
before the FAA formally notifies a TC holder or applicant of
deficiencies, we will contact it to try to understand the deficiencies
and develop a means of correcting them. Therefore, the notification
referred to in this paragraph should document the agreed corrections.
The ability of an operator to comply with the proposed operating
rules will be dependent on TC holders complying with the requirement to
develop design changes and service instructions. The FAA intends to
carefully monitor compliance and take appropriate action if necessary.
Failure to comply by the dates specified in the final rule would
constitute a violation of the requirements and could subject the
violator to certificate action to amend, suspend, or revoke the
affected certificate (49 U.S.C. 44709). It could also subject the
violator to a civil penalty of not more than $25,000 per day per
certificate until Sec. 25.1815 is complied with (49 U.S.C. 46301).
iii. Compliance Plan for Auxiliary Fuel Tanks
The proposed rule would also establish a timeframe in which
affected STC holders, applicants for an amended TC, and operators using
fuel tanks pursuant to a field approval must submit for approval (to
the FAA oversight office) a flammability exposure analysis for their
design changes. The proposal includes a 12-month timeframe to complete
the analysis. Any applicant whose STC or TC amendment is not approved
within the 12-month compliance period would have to complete the
analysis before approval.
The proposed rule would also require submission for approval of an
impact assessment of the fuel tank system, as modified by the STC
holder's design change. The purpose of this proposal is to identify any
features of the modification to the original type design that may
violate the critical design configuration control limitations developed
by the original TC holder. For example, if an FRM that utilized
inerting is incorporated into an airplane, a CDCCL would likely be
developed that would limit venting of air into the fuel tank, because
it could introduce oxygen into the tank, resulting in a flammable vapor
space. In this case the STC holder would need to assess its design and
identify any violation of the CDCCL identified for the FRM. Results
from the analysis would be provided to the FAA in the form of a report
or summary letter.
Supplemental type certificate holders would have to submit the
impact assessment within six months after we approve the TC holder's
CDCCL. Applicants whose design changes are not approved within that
six-month period would have to submit the assessment before approval of
the change. Once the CDCCL is approved, the TC holder would be required
to make them available to other affected persons, including those
subject to this

[[Page 70939]]

section. We consider the six-month period more than enough to perform
the required assessment. The resulting service instructions would be
required to show compliance with the applicable flammability
requirements and to address any adverse effects of the design change on
any IMM or FRM developed by the TC holder.
g. Compliance Schedule
Table 2 contains compliance dates for the required submissions.
This table provides specific dates for each Boeing and Airbus model
airplane that has fuel tanks whose average flammability exposure
exceeds 7 percent. A compliance time of 24 months from the effective
date of the final rule is proposed for all other models subject to this
proposal (if the flammability exposure analysis shows an average
exposure level exceeding 7 percent). We established the compliance
dates proposed in this table after consideration of the time needed by
the TC holders to develop the means to address fuel tank flammability
exposure. We anticipate development of an FRM or IMM would take the
affected TC holder about 2 years. The dates in the proposal were based
on the assumption that it would be adopted well before the end of 2005.
However, the rulemaking process took longer than originally
anticipated. Consequently, given the specific compliance dates I the
proposed rulemaking and the likelihood that finalization of the rules
will be later than expected, there may not be as much time allowed for
compliance as originally planned. We recognize that compliance
intervals may need to be adjusted and will consider your comments on
this condition.
On February 17, 2004, the FAA Administrator announced that the
agency is developing a proposal for new rules that would require
reducing the flammability exposure of new production transport category
airplanes and existing transport category airplanes with high-
flammability fuel tanks. Since then, Boeing has announced plans to
incorporate FRM in newly produced airplanes and to make service
instructions available for the airplane models listed in this notice.
Boeing has also submitted applications for type certification of
flammability reduction systems. On February 15, 2005, we published a
Special Conditions No. 25-285-SC for flammability reduction means on
the Boeing Model 747 (70 FR 780068563). Airbus flew an A320 \16\ in
August 2003 with the prototype FAA inerting system, but has not
committed to production incorporation or development of service
instructions for any flammability reduction means on its airplane models.
---------------------------------------------------------------------------

\16\ Flight-Testing of the FAA Onboard Inert Gas Generation
System on an Airbus A320, DOT/FAA/AR-03/58, dated June 2004.
---------------------------------------------------------------------------

While Airbus and Boeing may have less than 2 years from the
effective date of the final rule to develop an FRM or IMM for some of
their models, we know that both companies have been considering these
improvements well in advance of this rulemaking. The proposed
compliance dates are thus staggered to allow the engineering resources
of the TC holders to develop design means for all of their models. The
proposed dates are established based on both our assessment of when it
is feasible for TC holders to comply and the risks associated with
particular airplane models, due to the flammability of the fuel tanks
and numbers of airplanes in the fleet. For example, the Boeing Model
747 is first, followed by the Boeing Model 737. The first Airbus model
affected is the A320. The proposed dates will support the retrofit of
airplanes at the earliest reasonable time to achieve the safety
benefits intended by this rulemaking.
The compliance times proposed for airplane and fuel tank
manufacturers are also used as the basis for the proposed compliance
dates for introduction of these systems into the operators' fleets
under parts 91, 121, 125, and 129. Extension of the compliance dates
for development of the service instructions by the certificate holders
would either reduce the amount of time available to operators or delay
full deployment of these safety improvements. As discussed later in
this proposal for the operational requirements, incorporation of FRM or
IMM will likely require access inside the fuel tanks.

Table 2
------------------------------------------------------------------------
Service instruction submittal
Model date
------------------------------------------------------------------------
Boeing
747 Series.............................. December 31, 2005.
737 Series.............................. March 31, 2006.
777 Series.............................. March 31, 2006.
767 Series.............................. September 30, 2006.
757 Series.............................. March 31, 2007.
707/720 Series.......................... December 31, 2007.
Airbus
A319, A320, A321 Series................. December 31, 2006.
A300, A321 Series....................... June 30, 2007.
A330, A340 Series....................... December 31, 2007.
All other affected models............... Within 24 months of effective
date of this amendment.
------------------------------------------------------------------------

E. Proposed Requirements for Airplane Operators

The proposed operating rules would prohibit the operation of
certain transport category airplanes operated under parts 91, 121, 125,
and 129 beyond specified compliance dates, unless the operator of those
airplanes has incorporated approved IMM, FRM or FIMM modifications and
associated airworthiness limitations for the affected fuel tanks. The
proposed rules would not apply to airplanes used only in all-cargo
operations.
This rulemaking also includes a proposal to create new subparts
that pertain to the support of continued airworthiness and safety
improvements in the following parts of Title 14 Code of Federal
Regulations:
? Part 91, General Operating and Flight Rules;
? Part 121, Operating Requirements: Domestic Flag and
Supplemental Operation;
? Part 125, Certification and Operation: Airplanes Having a
Seating Capacity of 20 or More Passengers or a Maximum Payload Capacity
of 6,000 Pounds or More; and Rules Governing Persons On Board Such
Aircraft; and
? Part 129, Operations: Foreign Air Carriers and Foreign
Operators of U.S.-registered Aircraft Engaged in Common Carriage.
As discussed earlier, this proposal does not include part 135,
since the number of airplanes in part 135 operation that would be
affected by these proposals is relatively small. In the event changes
to part 135 result in a greater number of affected airplanes operating
under that part, the FAA will reassess the need to apply these proposed
requirements to that part.
The FAA believes that inclusion of certain rules under the new
subparts will enhance the reader's ability to readily identify rules
pertinent to continued airworthiness. Unless stated otherwise, our
purpose in moving requirements to the new subparts is to ensure easy
visibility of those requirements applicable to the continued
airworthiness of the airplane. We do not intend to change their legal
effect in any other way. The new subparts are substantially the same
and accordingly are not discussed separately here. Table 3 illustrates
what proposed and existing requirements will be included in the new
subparts. Each new subpart is titled ``Continued Airworthiness and
Safety Improvements.'' The proposed new subparts consist of relocated,
revised, and new regulations pertaining to continued airworthiness of
the airplane.

[[Page 70940]]

Table 3.--New Subparts for Parts 91, 121, 125, and 129
----------------------------------------------------------------------------------------------------------------
Part 121 new/relocated Part 125 new/relocated Part 129 new/relocated
Part 91 new/relocated rules within rules within proposed rules within proposed rules within proposed
proposed subpart K subpart Y subpart M subpart B
----------------------------------------------------------------------------------------------------------------
Sec. 91.1501, Applicability (new).. Sec. 121.901, Sec. 125.501, Sec. 129.101,
Applicability. Applicability. Applicability.
Sec. 91.1503, Reserved............. Sec. 121.903, Sec. 125.503, Sec. 129.103,
Reserved. Reserved. Reserved.
Sec. 91.1505, fuel tank system Sec. 121.905, Sec. 125.505, Fuel Sec. 129.105,
maintenance program. Electrical wiring tank system inspection Electrical wiring
interconnection program. interconnection
systems (EWIS) systems (EWIS)
maintenance program. maintenance program.
Sec. 91.1507, Repairs assessment Sec. 121.907, Fuel Sec. 125.507, Repairs Sec. 129.107, Fuel
for pressurized fuselages (formerly tank system assessment for tank system
Sec. 91.401(a)). maintenance program. pressurized fuselages maintenance program.
(formerly Sec.
125.248(a)).
Sec. 91.1509, Reserved............. Sec. 121.909, Sec. 125.509, Sec. 129.109,
Reserved. Reserved. Reserved.
Sec. 91.1511, Reserved............. Sec. 121.911, Sec. 125.511, Sec. 129.111,
Reserved. Reserved. Reserved.
Sec. 121.913, Aging ....................... Sec. 129.113,
airplane inspections Supplemental
and records reviews inspections for U.S.-
(formerly Sec. registered aircraft
121.368). (formerly Sec.
129.16).
Sec. 121.915, Repairs ....................... Sec. 129.115, Repairs
assessment for assessment for
pressurized fuselages pressurized fuselages
(formerly Sec. (formerly Sec.
121.370(a)). 129.32(a)).
Sec. 91.1513, Reserved............. Sec. 121.917, ....................... Sec. 129.117, Aging
Supplemental airplane inspections
inspections (formerly and records reviews
Sec. 121.370(a). for U.S.-registered
aircraft (formerly
Sec. 129.33).
----------------------------------------------------------------------------------------------------------------

1. Requirement to Install and Operate FRM, IMM or FIMM
The proposed rules would prohibit certificate holders from
operating any affected airplane after dates specified, unless IMM, FRM
or FIMM, as applicable, are installed and operational for any fuel tank
for which they are required. The safety objective of these proposed
rules is to have the required modifications installed and operational
at the earliest opportunity.
The proposed rule would require that operators of the affected
airplanes incorporate applicable maintenance program changes before
returning an airplane to service after accomplishing any required
modifications.
For some of the affected airplanes, manufacturer compliance with
the proposed requirements may not result in any design changes, but
would result in development of airworthiness limitations in the form of
maintenance actions, operational procedures, or CDCCL, as previously
discussed. In these cases the affected operators would be required to
incorporate these limitations within one year after their approval by
the FAA oversight office. The FAA will inform the affected operators
and principal inspectors of the availability of the approved information.
Once an operator revises its maintenance or inspection program, it
is important to make sure that later alterations to the airplane do not
degrade the level of safety provided by these revisions. The proposed
rules would require future applicants for approval of design changes to
develop new airworthiness limitations for new auxiliary fuel tanks and
other design changes affecting fuel tank flammability. To ensure that
these airworthiness limitations are implemented, operators who
incorporate these design changes into their airplanes would be required
to revise their maintenance and inspection programs to incorporate the
corresponding airworthiness limitations.
Today's proposal would require operators to submit the proposed
maintenance and inspection program changes to their FAA Principal
Inspector for review and approval.\17\ This review would include the
integration of the applicable airworthiness limitations for the TC and
any STC and field approved auxiliary fuel tank to ensure their
consistency and compatibility in the maintenance or inspection program.
Guidance will be provided to operators and principal inspectors
regarding how to address any deviations that may be proposed by the
affected operators from the information approved by the FAA oversight
office. As airworthiness limitations, these cannot be changed without
FAA approval, nor are they subject to maintenance review board or other
maintenance program development processes.
---------------------------------------------------------------------------

\17\ A part 91 operator would send the relevant information to
either their principal inspector or Flight Standards District
Office, as applicable.
---------------------------------------------------------------------------

2. Authority To Operate With an Inoperative FRM, IMM or FIMM
Generally, the FAA does not require operators to use or maintain
equipment installed on airplanes prior to a uniform compliance date. In
this proposal, we take a different approach. The safety advantages
associated with a fuel tank system equipped with an FRM or IMM design,
as modified by any FIMM, are so compelling that we propose requiring
that operators use these systems as soon as they are available. We have
accommodated the difficulties faced by operators in making the required
design changes by providing a phased-in compliance schedule that
extends up to seven years after the manufacturer's compliance date for
each model. Accordingly, an operator may not operate any airplane with
fuel tanks equipped with FRM, IMM or FIMM, unless those systems are
fully operational. The sole exception is when the systems are
inoperative and the conditions and limitations specified in the
operator's Minimum Equipment List (MEL) are met.
The method used to allow operation of an airplane when an FRM is
inoperative would be to include the FRM dispatch relief in the FAA-
approved MEL. The MEL contains a list of equipment that may be
inoperative for a defined period of time. Under Sec. 91.213 and
similar regulations, the airplane may be dispatched with inoperative
equipment in accordance with the Master Minimum Equipment List (MMEL).

[[Page 70941]]

The FAA Flight Operations Evaluation Board (FOEB) would establish
the MMEL dispatch relief interval for an FRM based on data submitted by
the applicant to the FAA. The expected MMEL dispatch relief interval is
one of the contributing factors affecting the overall system
reliability analyses that must be established early in the design of
the FRM. The proposed requirements of Appendix K allow the designer to
choose to design a highly reliable FRM and then request longer MMEL
dispatch relief intervals when submitting their data to the FOEB.
This proposal does not recommend the adoption of a specific MMEL
dispatch inoperative interval at this time. However, the comments
received from the NTSB on to the proposed special conditions for the
Boeing 747 indicate that the FRM should be treated like other non-
redundant safety equipment, such as the flight data recorder. The
recorders are allowed a 3-day MMEL inoperative interval. We
specifically request public comment on the proposal to allow the
current FOEB process to establish the MMEL interval rather than
requiring a specific maximum interval.
3. Compliance Schedule
To achieve the safety benefits of this initiative, we believe it is
necessary to have a mandatory schedule for phasing in the design
changes rather than to rely solely on market forces to drive the
production and availability of parts and normal maintenance scheduling
for the installation of the FRM, IMM, or FIMM. Accordingly, this rule,
if adopted, would require at least 50 percent of the affected airplanes
be outfitted within four years after the relevant TC holder is required
to comply with the proposed requirements. The remainder of the
operator's fleet would have to comply with the final rule within seven
years after the specified date. The affected fleet would include those
airplanes that have field or STC approved auxiliary fuel tanks.
Certificate holders that operate only one airplane of an affected model
would have to modify that airplane within the seven-year compliance period.
The proposed compliance schedule of 7 years after TC holders to
develop service instructions, while long, should allow for the approval
of the service instructions for IMM, FRM, or FIMM, manufacture of
modification parts for a large fleet of airplanes, and accomplishment
of the modifications with minimum disruption of normal maintenance
schedules. Typically, fuel tanks are only accessed during heavy
maintenance checks that are done on a schedule that is established
during development of the maintenance program. The compliance dates
proposed for the operational rules were developed to allow for the
majority of the modifications to be done during these heavy maintenance
checks. Introduction of FRM, IMM or FIMM outside of normally scheduled
maintenance would increase the cost to the operators, because extra
tank entry and airplane down time would be needed.
Some airplane types or specific airplanes within an operator's
fleet may not be scheduled for normally scheduled maintenance, where
the fuel tanks would be opened, during the 7-year compliance time after
service instructions become available. These airplanes would require
incorporation of modifications outside of the normally scheduled
maintenance. We have determined the number of airplanes that would be
affected is small and that further lengthening the compliance period
would not achieve the safety benefits of this proposal in a timely way.
Also, we anticipate that some of the upcoming ADs to address ignition
source issues will occur in this time period and in some cases will
require fuel tank entry. Compliance with the AD may provide additional
opportunities for incorporating approved FRM, IMM or FIMM if not
occurring during normal scheduled maintenance. These issues are further
discussed in the regulatory evaluation.

F. Additional Provisions

1. Relationship of This Proposal to Aging Airplane Regulatory Initiatives
As part of our broader review of several important initiatives
comprising the Aging Airplane Program, we have revised certain
compliance dates in existing rules and pending proposals so that
operators can make required modifications during scheduled maintenance.
Changing compliance dates affects our ability to expedite some aspects
of this program but reduces the costs of the rules and proposals in
place to deal with aging airplanes. Notice of these changes and a
description of our Aging Airplane Program review appeared in the
Federal Register on July 30, 2004 (69 FR 45936). In addition to this
Fuel Tank Flammability Reduction proposal, the actions affected by
these revisions include:
? Aging Aircraft Program (Widespread Fatigue Damage (proposal),
? Aging Airplane Safety (interim final rule), and
? Enhanced Airworthiness Program for Airplane Systems/Fuel
Tank Safety (proposal).
Today's proposal, if adopted, would also affect compliance with
SFAR 88 and potentially make it less costly. The safety reviews
following the TWA 800 accident led us to require that the fuel quantity
indication system wiring entering high flammability tanks incorporate
either adequate separation or energy limiting devices, known as
transient suppression devices, on the Boeing 737 and 747 to protect the
tank from ignition sources. As part of the safety reviews of SFAR 88,
we have identified other models that likewise would need a transient
suppression device. We have determined that if FRM are incorporated in
high flammability fuel tanks, ADs requiring installation of devices to
protect the fuel quantity system wiring will no longer be needed. We
have not yet estimated the potential savings and have not included
these savings in the current regulatory evaluation. We specifically
request comments regarding the savings that would be achieved if
electrical energy limiting devices were not required on wiring entering
high flammability fuel tanks affected by this proposal.
2. FAA Advisory Material
We are developing extensive guidance material to supplement the
proposed rule, including a revised AC 25.981-2 to include guidelines on
conducting a fuel tank flammability exposure assessment using the Monte
Carlo methodology and developing IMM and FRM. It will also include
guidance on development of the airworthiness limitations section,
confined space hazards and markings, documentation required by the FAA,
and reporting methods. We have incorporated some comments on these
topics from a group of specialists at the Aerospace Industries
Association, which included airplane manufacturers, airline operators
and manufacturers of inert gas generating equipment.\18\ The group
provided advice on fuel tank inerting and use of the Monte Carlo
methodology. We will invite public comments on the proposed ACs (which
references the Monte Carlo User's Manual) by separate notice published
in the issue of the Federal Register.
---------------------------------------------------------------------------

\18\ A copy of the AIA report is included in the docket for this
rulemaking.
---------------------------------------------------------------------------

3. FAA Oversight Office
We are also requiring affected persons to submit various compliance
materials to the FAA Oversight Office, defined in proposed Sec.
25.1803(c). The FAA Oversight Office is the aircraft

[[Page 70942]]

certification office or office within the Transport Airplane
Directorate having oversight responsibility for the relevant TC or STC,
as delegated by the Administrator. For example, with respect to fuel-
tank flammability issues, TC and STC holders must obtain approvals from
the responsible office in the FAA's Aircraft Certification Service. In
other contexts, we have described the FAA office performing these
functions as the ``cognizant FAA office.''
Table 4 lists the FAA offices that currently oversee issuance of
TCs and amended TCs for manufacturers of large transport category
airplanes.

Table 4.--FAA Offices That Oversee Type Certificates
------------------------------------------------------------------------
Airplane manufacturer FAA Oversight Office
------------------------------------------------------------------------
Aerospatiale........................... Transport Airplane Directorate,
International Branch.
Airbus................................. Transport Airplane Directorate,
International Branch.
BAE.................................... Transport Airplane Directorate,
International Branch.
Boeing................................. Seattle Aircraft Certification
Office.
Bombardier............................. New York Aircraft Certification
Office.
Embraer................................ Transport Airplane Directorate,
International Branch.
Fokker................................. Transport Airplane Directorate,
International Branch.
Gulfstream............................. Atlanta Aircraft Certification
Office.
Lockheed............................... Atlanta Aircraft Certification
Office.
Boeing/McDonnell-Douglas Corp.......... Los Angeles Aircraft
Certification Office.
------------------------------------------------------------------------

4. Workplace Safety Issues
Because we would require that maintenance personnel be given access
to FRM installations, the proposal could increase occupational safety
risks for these personnel. A large percentage of the work involved in
properly inspecting and modifying airplane fuel tanks and their
associated systems must be done in the interior of the tanks.
Performing the necessary tasks requires inspection and maintenance
personnel to physically enter the tank, where environmental hazards
exist. These hazards exist in any fuel tank (regardless of whether a
nitrogen inerting system is installed) and include fire and explosion,
toxic and irritating chemicals, oxygen deficiency, and the confinement
to the fuel tank itself. To prevent related injuries, operator and
repair station maintenance organizations have developed specific
procedures for identifying, controlling, or eliminating the hazards of
fuel-tank entry. In addition, government agencies have adopted safety
requirements for use when entering fuel tanks and other confined
spaces. These same procedures would be applied to the reduced oxygen
environment likely to be present in an inerted fuel tank.
Introduction of nitrogen enriched air within the fuel tanks and the
possibility of nitrogen enriched air in compartments adjacent to the
fuel tanks if leakage occurs creates additional risk. Lack of oxygen in
these areas could be hazardous to maintenance personnel, the
passengers, or flight crew. Existing certification requirements address
these hazards. This proposal requires markings to emphasize the
potential hazards associated with confined spaces and areas where a
hazardous atmosphere could be present as a result specifically of the
addition of FRM. We would require that the access doors and panels to
the fuel tanks with FRMs and to any other enclosed areas that could
contain hazardous atmosphere under either normal conditions or failure
conditions be permanently stenciled, marked, or placarded to warn of
hazards.
Fuel tanks are confined spaces \19\ and contain high concentrations
of fuel vapors that must be exhausted from the fuel tank before entry.
Other precautions such as measurement of oxygen concentrations before
entering a fuel tank are already required. Addition of the FRM that
utilizes inerting may result in reduced oxygen concentrations due to
leakage of the system in locations in the airplane where service
personnel would not expect it. These gases may be under pressure
because of the FRM design, and any hazards associated with working in
adjacent spaces near the opening should be identified in the marking of
the opening to the confined space.
---------------------------------------------------------------------------

\19\ Our worker safety requirements apply to confined spaces,
which are partly or fully enclosed areas big enough for a worker to
enter and perform assigned work and with limited or restricted means
of entry or exit. Such areas are not designed for someone to work in
regularly but for tasks such as inspection, cleaning, maintenance,
and repair. (Reference U.S. Department of Labor Occupational Safety
& Health Administration (OSHA), 29 CFR Sec. 1910.146(b).) This
proposal would not significantly change the procedures used by
maintenance personnel to enter fuel tanks and is not intended to
conflict with existing government agency requirements (e.g., OSHA).
---------------------------------------------------------------------------

Designs currently under consideration locate the FRM in the fairing
below the center wing fuel tank. Access to these areas is obtained by
opening doors or removing panels, which could allow some ventilation of
the spaces adjacent to the FRM. But this may not be enough to avoid
creating a hazard. Therefore, unless the design eliminates this hazard,
we intend that marking be provided to warn service personnel of
possible hazards associated with the reduced oxygen concentrations in
the areas adjacent to the FRM. Appropriate markings would be required
for all inerted fuel tanks, tanks adjacent to inerted fuel tanks and
all fuel tanks communicating with the inerted tanks via plumbing. The
plumbing includes, but is not limited to, plumbing for the vent system,
fuel feed system, refuel system, transfer system and cross-feed system.
The markings should also be stenciled on the external upper and lower
surfaces of the inerted tank adjacent to any openings, to ensure
maintenance personnel understand the possible contents of the fuel tank.
Advisory Circular 25.981-2 will provide additional guidance
regarding markings and placards.

IV. Rulemaking Analyses and Notices

Authority for This Rulemaking

The FAA's authority to issue rules regarding aviation safety is
found in Title 49 of the United States Code. Subtitle I, Section 106,
describes the authority of the FAA Administrator. Subtitle VII,
Aviation Programs, describes in more detail the scope of the agency's
authority. This rulemaking is promulgated under the authority described
in Subtitle VII, Part A, Subpart III, Section 44701, ``General
requirements.'' Under that section, the FAA is charged with promoting
safe flight of civil aircraft in air commerce by prescribing.
? Minimum standards required in the interest of safety for
the design and performance of aircraft;

[[Page 70943]]

? Regulations and minimum standards in the interest of
safety for inspecting, servicing, and overhauling aircraft; and
? Regulations for other practices, methods, and procedures
the Administrator finds necessary for safety in air commerce.
This regulation is within the scope of that authority because it
prescribes--
? New safety standards for the design of transport category
airplanes, and
? New requirements necessary for safety for the design,
production, operation, and maintenance of those airplanes, and for
other practices, methods and procedures relating to those airplanes.

Paperwork Reduction Act

This proposal contains the following new information collection
requirements. As required by the Paperwork Reduction Act of 1955 (44
U.S.C. 3507(d)), the Department of Transportation has sent the
information requirements associated with this proposal to the Office of
Management and Budget for its review.
Title: Transport Category Airplane Fuel Tank Flammability Reduction
Safety Improvements.
Summary: This proposal would require certain certificate holders to
develop means to reduce the flammability of high flammability exposure
fuel tanks on certain large turbine-powered transport category
airplanes. In addition, this proposal requires operators of the
affected airplanes with high flammability exposure fuel tanks to
incorporate FRM. The current requirements for fuel tank flammability
exposure for new designs would be revised to add requirements for
inerting systems if inerting is used to minimize flammability exposure.
This proposal also proposes to expand the coverage of part 25 to
include requirements that must be complied with by current holders of
these certificates. Certificate holders would be required to provide a
quarterly report to the FAA that contains reliability data for the FRM.
There is no specific reporting requirement for operators. Data
collected by the certificate holders from operators would be obtained
through normal business agreements.
Proposed subpart I would also require that TC holders submit to the
FAA a plan detailing how they intend to comply with its requirements.
This information would be used by the FAA to assist the TC holder in
complying with requirements. The compliance plan would be necessary to
ensure that TC holders fully understand the requirements, correct any
deficiencies in planning in a timely manner, and are able to provide
the information needed by the operators for the operators' timely
compliance with the rule.
Reporting: When scheduled or unscheduled maintenance and
inspections are performed, including tasks that are not identified as
ALI or Certification Maintenance Requirements, the operators are only
required to report specific discrepancies and corrective actions in
accordance with Sec. 121.703. This proposal would not mandate any
additional reporting above the current requirements for ALI by the
operators. We do not intend that operators report to the FAA the
results of routine inerting system operational checks, or discrepancies
found .
The proposed reporting requirement applies to applicants and
holders of the affected certificates. There is no proposed additional
requirement within this rulemaking for operators to report FRM
reliability information. We intend for certificate holders to gather
the needed data from operators using existing reporting systems that
are currently used for airplane maintenance, reliability and warranty
claims. The operators would provide this information through existing
or new business arrangements between the certificate holders and the
airlines.
Use of: This proposal would support the information needs of the
FAA in approving design approval holder and operator compliance with
the proposed rule.
Respondents (including number of): The likely respondents to this
proposed information requirement are the affected type certificate
holders such as Boeing, Airbus and several auxiliary fuel tank
manufacturers.
Frequency: The proposal would require the certificate holders to
submit a report to the FAA once each quarter for a period up to 5 years.
Average Annual Burden Estimate: The burden would consist of the
work necessary to:
? Develop the design and the data for STCs to install fuel
tank inerting systems,
? Develop and incorporate a maintenance plan into the
existing maintenance programs,
? Record the results of the installation and maintenance activities.
The largest paperwork burden would be a one-time effort (spread over 3
years) associated with the STC applications. This one-time total burden
would be as follows:

------------------------------------------------------------------------
Present value
Documents required to show discounted cost
compliance with the proposed rule One-time pages (in millions of
$2005)
------------------------------------------------------------------------
Specifications for Fuel Tank STC.... 8,000 2.7
Manuals (Flight Manuals, Operations, 12,000 2.7
and Maintenance) for Fuel Tank STC.
Production for Fuel Tank STC........ 500 0.4
Documentation for FAA/EASA 1,000 13.4
Certification......................
-------------------
Total........................... 21,500 19.2
------------------------------------------------------------------------

The yearly burden for each of the 3 years would have a present
value of about $6.4 million and involve 7,167 pages.
This proposed rulemaking would result in a minimal annual
recordkeeping and reporting burden. All records that would be generated
to verify the installation, to record any fuel tank system inerting
failures, and to record any maintenance would use forms currently
required by the FAA.
The FAA computed the annual recordkeeping (Total Pages) burden by
analyzing the necessary paperwork requirements needed to satisfy each
process of the proposed rulemaking.
The agency is seeking comments to--
? Evaluate whether the proposed information requirement is
necessary for the proper performance of the roles of the agency,
including whether the information will have practical utility;
? Evaluate the accuracy of the agency's estimate of the burden;
? Improve the quality, utility, and clarity of the
information to be collected; and
? Minimize the burden of the collection of information on
those who are to respond using appropriate automated, electronic,
mechanical, or

[[Page 70944]]

other technological collection techniques or other forms of information
technology.
Individuals and organizations may submit comments to the FAA on the
information collection requirement by February 21, 2006. You should
send your comments to the address listed in the ADDRESSES section of
this document.
Under the Paperwork Reduction Act of 1995, (5 CFR
1320.8(b)(2)(vi)), an agency may not conduct or sponsor, and a person
is not required to respond to, a collection of information unless it
displays a currently valid OMB control number. The OMB control number
for this information collection will be published in the Federal
Register, after the Office of Management and Budget approves it.

International Compatibility

In keeping with U.S. obligations under the Convention on
International Civil Aviation, it is FAA policy to comply with
International Civil Aviation Organization (ICAO) Standards and
Recommended Practices to the maximum extent practicable. The FAA has
determined that there are no ICAO Standards and Recommended Practices
that correspond to these proposed regulations.

Regulatory Evaluation, Regulatory Flexibility Determination,
International Trade Assessment, and Unfunded Mandates Assessment

Regulatory Evaluation
This portion of the preamble summarizes our analysis of the
economic impacts of this NPRM. It also includes summaries of the
initial regulatory flexibility determination. We suggest readers
seeking greater detail read the full regulatory evaluation, a copy of
which we have placed in the docket for this rulemaking.
Changes to Federal regulations must undergo several economic
analyses. First, Executive Order 12866 directs that each Federal agency
shall propose or adopt a regulation only upon a reasoned determination
that the benefits of the intended regulation justify its costs. Second,
the Regulatory Flexibility Act of 1980 requires agencies to analyze the
economic impact of regulatory changes on small entities. Third, the
Trade Agreements Act (19 U.S.C. 2531-2533) prohibits agencies from
setting standards that create unnecessary obstacles to the foreign
commerce of the United States. In developing U.S. standards, this Trade
Act requires agencies to consider international standards and, where
appropriate, to be the basis of U.S. standards. Fourth, the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4) requires agencies to
prepare a written assessment of the costs, benefits, and other effects
of proposed or final rules that include a Federal mandate likely to
result in the expenditure by State, local, or tribal governments, in
the aggregate, or by the private sector, of $100 million or more
annually (adjusted for inflation).
In conducting these analyses, we determined this rule: (1) Is a
``significant regulatory action'' as defined in section 3(f) of
Executive Order 12866, and is ``significant'' as defined in DOT's
Regulatory Policies and Procedures; (2) would have a significant
economic impact on a substantial number of small entities; (3) has a
neutral international trade impact; and (4) does not impose an unfunded
mandate on state, local, or tribal governments, or on the private
sector. These analyses, available in the docket, are summarized as follows.
Total Benefits and Costs of This Rulemaking
We estimated that the proposed rule would prevent an expected 4
catastrophic passenger accidents over the analysis period. If all
accidents happened in-flight, the present value total benefit would be
of $490 million. The model of fuel tank flammability risk suggests an 8
percent probability that the explosion may occur on the ground.
Assuming this rate of ground explosions, the present value of the total
benefit would be about $460 million. This estimate is based on an
average number of occupants per airplane. If the first of the prevented
accidents would occur on a large passenger capacity airplane, like the
Airbus A380 or TWA-800 Boeing Model 747, the quantified benefit of
preventing one accident could exceed the present value costs. In
addition, another fuel tank explosion would have a negative impact on
public confidence in air travel safety, and, on the subsequent demand
for air travel.
Table 1 displays the present value compliance costs by major
element for the existing air carrier fleet and for airplanes
manufactured over the next 25 years and operated over the next 50 years
to be $919 million.

Table 1.--Present Value Costs of Compliance (2006-2055)
[In millions 2005 $]
------------------------------------------------------------------------
Present value
of the
Source of cost compliance
costs
------------------------------------------------------------------------
Engineering Redesign................................... $64
Retrofitting Costs..................................... 377
Production Costs....................................... 133
Operational Costs...................................... 345
----------------
Total.............................................. 919
------------------------------------------------------------------------

Who is Potentially Affected By This Rulemaking
Boeing, Airbus, all operators flying U.S.-registered Boeing and
Airbus airplanes, and holders of fuel tank supplemental type
certificates (STCs).
Cost Assumptions and Sources of Information
Period of analysis is 2006-2055.
For 2008-2030, we evaluated the costs and benefits for all
airplanes that would have fuel tank inerting systems. This includes
airplanes that would be retrofitted between 2008 and 2015 and
production airplanes manufactured between 2008 and 2030.
For 2031-2055, we evaluated the costs and benefits for all
airplanes that had fuel tank inerting systems and are expected to be in
service in 2030. No airplanes are added after that date. This time
allows for all of the airplanes in this evaluation to complete their
productive lives in U.S. aviation and be retired.
Based on Boeing's assertion that their production airplanes will
have fuel tank inerting installed by 2008, we do not include Boeing
production airplanes built during and after 2008 in either the cost or
the benefits estimates.
? Final rule would be effective January 1, 2006.
? Discount rate is 7 percent.
? Fully burdened labor rate for an aviation engineer is $125 an hour.
? Fully burdened labor rate for an aviation mechanic is $85 an hour.
? 3,804 airplanes would be retrofitted between 2008 and 2016.
? No airplane scheduled to be retired before 2016 would be retrofitted.
? Cost of aviation fuel is $1.00 per gallon.\20\
---------------------------------------------------------------------------

\20\ The estimated cost for aviation fuel is based on both the
FAA's 2005 forecast and the Department of Energy Information
Administration's forecast ``Annual Energy Outlook with Projections
to 2025'' (2005). Should these forecasts change prior to the
publication of the final rule, if any, we will use the updated
number. However, we do not expect changes in the forecast cost of
aviation fuel to have a large impact on the overall cost of this
rulemaking.
---------------------------------------------------------------------------

? The type of accident that would be prevented is a
catastrophic accident in

[[Page 70945]]

which all die and the airplane is destroyed.
? Special Federal Air Regulation (SFAR) 88 would prevent 50
percent of the future fuel tank explosions. (See ``History of Industry
and Government Actions in Response to Fuel Tank Explosions'' in the
full regulatory evaluation located within the docket file for this
proposal)
? Boeing and Airbus airplanes have equal risk of an explosion.
? The explosion rate calculation does not include explosions
caused by terrorist activity.
? An explosion is estimated to occur every 60 million hours
of flight by heated center wing tank airplanes.
? The value of a statistical fatality averted is $3 million.
? An average of 140 passengers and crew are on a Boeing or
Airbus airplane.
? The cost to investigate a catastrophic accident is $8 million.
? The average value of property loss and fatalities located
on the ground is $500,000 to $1 million.
We obtained data from two Aviation Rulemaking Advisory Committee
(ARAC) working groups, Boeing, and Airbus.
Finally, we request comments and information about all of our
assumptions, values, and results. In particular, we request information
concerning the potential cost savings from not requiring airplanes to
install transient suppression devices. We also request that you provide
documentation for the comments.
Estimated Benefits
We estimated the proposed rule would prevent four fuel tank
explosions over the next 50 years, for a present value total benefit of
$490 million.\21\ The undiscounted benefits from preventing one
average-sized airplane catastrophic accident are about $500 million,
assuming $3 million for the value of a prevented fatality. If the value
of prevented fatality is $5.5 million, the undiscounted benefits are
about $890 million.
---------------------------------------------------------------------------

\21\ These four accidents represent the expected average. Based
on the Poisson distribution and a past average of one accident every
60 million flight hours for airplanes with a heated center wing fuel
tank there is a 37 percent chance that there would be 5 or more such
accidents.
---------------------------------------------------------------------------

The model of fuel tank flammability risk suggests an 8 percent
probability that an airplane would explode on the runway, with an
average of four fatalities. Under this scenario, the average benefit
would be about $60 million. Assuming an 8 percent chance on an accident
while the airplane is still on the ground would reduce the total
benefit, in present value, by $30 million to be about $460 million.
Costs of This Rulemaking
The undiscounted total costs for the analysis period 2006-2055 for
all airplanes would be about $2.279 billion, with a present value of
$919 million. The undiscounted passenger airplane costs would be about
$2.018 billion with a present value of $809 million.
However, there is a potential cost reduction factor. If we enact a
fuel tank flammability reduction rule, we would not require transient
suppression devices and we would allow airlines that have installed
them to remove them. We request information on potential cost savings
from this action.
Analysis of the Proposed Rule and Alternatives, All Airplanes (2006-2055)
In all of the tables that follow, the results for the base case are
found in the first row. As shown in Table 2, using a discount rate of 7
percent, $3 million for a prevented fatality, and an SFAR 88
effectiveness rate of 50 percent, the proposed rule benefits would be
about $424 million less (54 percent) than the costs. Increasing the
value of a prevented fatality to $5.5 million would make the benefits
about 94 percent of the costs. At an SFAR effectiveness rate of 25
percent, the benefits would be 80 percent of the costs for a $3 million
value of a prevented fatality, but would be 41 percent greater than the
costs for a $5.5 million value of a prevented fatality.
For a 3 percent discount rate, the proposed rule benefits would be
greater than the costs at an SFAR effectiveness rate of 25 percent. At
50 percent, the value of a fatality would need to be $5.5 million for
the benefits to be greater than the costs--a $3 million value would
result in the benefits being about three quarters of the costs.
At an SFAR 88 effectiveness rate of 75 percent, the proposed rule
benefits would be less than the compliance costs under any combination
of discount rate and value of a prevented fatality.

Table 2.--Present Values of the Estimated Benefits and Costs for All Airplanes by Discount Rate, Value of a Prevented Fatality, and SFAR 88
Effectiveness Rate
[Values in million of 2005 dollars]
--------------------------------------------------------------------------------------------------------------------------------------------------------
SFAR 88 Present values Benefit/cost
Discount rate (percent) Value of effectiveness ---------------------------------- ratio
fatality (percent) Benefits Costs (percent)
--------------------------------------------------------------------------------------------------------------------------------------------------------
7................................................................. $3 50 $495 $919 54
7................................................................. 5.5 50 861 919 94
7................................................................. 3 25 743 919 81
7................................................................. 5.5 25 1,292 919 141
7................................................................. 3 75 248 919 27
7................................................................. 5.5 75 431 919 47
3................................................................. 3 50 1,011 1,312 77
3................................................................. 5.5 50 1,774 1,312 135
3................................................................. 3 25 1,517 1,312 116
3................................................................. 5.5 25 2,662 1,312 203
3................................................................. 3 75 506 1,312 39
3................................................................. 5.5 75 888 1,312 68
--------------------------------------------------------------------------------------------------------------------------------------------------------

Passenger Airplanes (2006-2055)
As shown in Table 3, using a discount rate of 7 percent, a $3
million value for a prevented fatality, and an SFAR 88 effectiveness
rate of 50 percent, we estimated that the proposed rule benefits for
passenger airplanes would be about $313 million less than the costs.
Increasing the value of a prevented fatality to $5.5 million indicates
the proposed rule benefits would be greater than the costs by about 6
percent for passenger airplanes. At an SFAR effectiveness rate of 25
percent,

[[Page 70946]]

the proposed rule benefits would be less than the costs for a $3
million value of a prevented fatality (benefits would be 92 percent of
costs), but would be greater than the costs for a $5.5 million value of
a prevented fatality (benefits would be 60 percent greater than the
costs) for passenger airplanes.
For a 3 percent discount rate, the proposed rule benefits for
passenger airplanes would be greater than their costs at an SFAR
effectiveness rate of 25 percent. At 50 percent, the value of a
fatality would need to be $5.5 million for the benefits to be greater
than the costs--a $3 million value would result in the benefits would
be about 87 percent of the costs.
At an SFAR 88 effectiveness rate of 75 percent, the proposed rule
benefits would be less than the costs for passenger airplanes under any
combination of discount rate and value of a prevented fatality.

Table 3.--Present Values of the Estimated Benefits and Costs for All Passenger Airplanes by Discount Rate, Value of a Prevented Fatality, and SFAR 88
Effectiveness Rate
[Values in million of 2005 dollars]
--------------------------------------------------------------------------------------------------------------------------------------------------------
SFAR 88 Present values Benefit/cost
Discount rate (percent) Value of effectiveness ---------------------------------- ratio
fatality (percent) Benefits Costs (percent)
--------------------------------------------------------------------------------------------------------------------------------------------------------
7................................................................. $3 50 $495 $808 61
7................................................................. 5.5 50 861 808 106
7................................................................. 3 25 743 808 92
7................................................................. 5.5 25 1,292 808 160
7................................................................. 3 75 248 808 31
7................................................................. 5.5 75 431 808 53
3................................................................. 3 50 1,011 1,157 87
3................................................................. 5.5 50 1,774 1,157 153
3................................................................. 3 25 1,517 1,157 131
3................................................................. 5.5 25 2,662 1,157 230
3................................................................. 3 75 506 1,157 44
3................................................................. 5.5 75 888 1,157 77
--------------------------------------------------------------------------------------------------------------------------------------------------------

Retrofitted Passenger Airplanes (2006-2037)
As shown in Table 4, if the SFAR 88 effectiveness rate is 75
percent, the proposed rule benefits would not be greater than the costs
for retrofitted passenger airplanes under any combination of discount
rate and value of a prevented fatality.
Using a discount rate of 7 percent, a $3 million value for a
prevented fatality, and an SFAR 88 effectiveness rate of 50 percent,
the proposed rule benefits for retrofitted passenger airplanes would be
about $217 million less than the costs. Increasing the value of a
prevented fatality to $5.5 million indicates the proposed rule benefits
would be greater than the costs by about 4 percent for retrofitted
passenger airplanes. At an SFAR effectiveness rate of 25 percent, the
proposed rule benefits would be less than the costs for a $3 million
value of a prevented fatality (benefits would be 88 percent of costs),
but would be greater than the costs for a $5.5 million value of a
prevented fatality (benefits would be 55 percent greater than the
costs) for retrofitted passenger airplanes.
For a 3 percent discount rate, the proposed rule benefits for
retrofitted passenger airplanes would be greater than their costs at an
SFAR effectiveness rate of 25 percent.
At 50 percent, the value of a fatality would need to be $5.5
million for the benefits to be greater than the costs--a $3 million
value would result in the benefits would be about three quarters
percent of the costs.
At an SFAR 88 effectiveness rate of 75 percent, the proposed rule
benefits would be less than the costs for retrofitted passenger
airplanes under any combination of discount rate and value of a
prevented fatality.

Table 4.--Present Values of the Estimated Benefits and Costs for All Retrofitted Passenger Airplanes by Discount Rate, Value of a Prevented Fatality,
and SFAR 88 Effectiveness Rate
[Values in million of 2005 dollars]
--------------------------------------------------------------------------------------------------------------------------------------------------------
SFAR 88 Present values Benefit/cost
Discount rate (percent) Value of effectiveness ---------------------------------- ratio
fatality (percent) Benefits Costs (percent)
--------------------------------------------------------------------------------------------------------------------------------------------------------
7................................................................. $3 50 $313 $530 59
7................................................................. 5.5 50 549 530 104
7................................................................. 3 25 469 530 88
7................................................................. 5.5 25 824 530 155
7................................................................. 3 75 156 530 29
7................................................................. 5.5 75 275 530 52
3................................................................. 3 50 557 750 74
3................................................................. 5.5 50 992 750 132
3................................................................. 3 25 836 750 111
3................................................................. 5.5 25 1,488 750 198
3................................................................. 3 75 279 750 37
3................................................................. 5.5 75 496 750 66
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 70947]]

Production Passenger Airplanes (2006-2055)
We determined that all of the retrofitted airplanes would have been
retired from U.S. service by 2038. As shown in Table 5, using a
discount rate of 7 percent, a $3 million value for a prevented
fatality, and an SFAR 88 effectiveness rate of 50 percent, the proposed
rule benefits for production passenger airplanes would be about $196
million less than the costs--about 65 percent of the costs. Increasing
the value of a prevented fatality to $5.5 million indicates that the
proposed rule benefits would be greater than the costs by about 12
percent for production passenger airplanes.
At an SFAR effectiveness rate of 25 percent, the proposed rule
benefits for production airplanes would be greater than their costs for
both combinations of discount rates and values of a prevented fatality.
At a 3 percent discount rate, the proposed rule benefits for
production airplanes would be greater than their costs at an SFAR
effectiveness rate of either 25 percent or 50 percent.
At an SFAR 88 effectiveness rate of 75 percent, the proposed rule
benefits would be less than the costs for production passenger
airplanes under any combination of discount rate and value of a
prevented fatality--although they would be 96 percent of the costs if a
3 percent discount rate and a $5.5 million value of a prevented
fatality were used.

Table 5.--Present Values of the Estimated Benefits and Costs for All Production Passenger Airplanes by Discount Rate, Value of a Prevented Fatality, and
SFAR 88 Effectiveness Rate
[Values in million of 2005 dollars]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Present values
Value of SFAR 88 --------------------------------------------------
Discount rate (percent) fatality effectiveness Benefit/cost
(percent) Benefits Costs ratio (percent)
--------------------------------------------------------------------------------------------------------------------------------------------------------
7................................................................. $3 50 $182 $278 65
7................................................................. 5.5 50 312 278 112
7................................................................. 3 25 273 278 98
7................................................................. 5.5 25 468 278 168
7................................................................. 3 75 91 278 33
7................................................................. 5.5 75 156 278 56
3................................................................. 3 50 454 407 112
3................................................................. 5.5 50 783 407 192
3................................................................. 3 25 681 407 167
3................................................................. 5.5 25 1,175 407 289
3................................................................. 3 75 227 407 56
3................................................................. 5.5 75 392 407 96
--------------------------------------------------------------------------------------------------------------------------------------------------------

Alternative One: Apply the Proposed Rule Only to Production Airplanes--
Exclude Retrofitting Requirements
As shown in Table 6, the benefit-cost ratios of the present values
are lower for retrofitted airplanes than they are for production
airplanes. However, at a 7 percent discount rate, the ratios are very
close. Using the standard values, there is only a 6-percentage point
difference (about 10 percent) between the 59 percent ratio for
retrofitted passenger airplanes and the 65 percent ratio for production
passenger airplanes. This same result is observed for all benefit/cost
ratios calculated using a 7 percent discount rate. The difference
becomes more pronounced (about 30 percent to 40 percent) when a 3
percent discount rate is used. This apparent conflict is resolved by
noting that a far greater percentage of the total benefits for
retrofitted airplanes would occur in the more immediate future than it
would for production airplanes that have more of its benefits occurring
farther out in time. Thus, a lower discount rate has a greater positive
impact (relatively) on present value calculations for longer-term
benefits than for shorter-term benefits. That is, retrofitted airplanes
would incur the vast bulk of these airplanes flight hours and the
relatively greater overall risk until about 2030.

Table 6.--Benefit-Cost Present Values Ratios for Passenger Airplanes by Discount Rate, Value of a Prevented Fatality, SFAR 88 Effectiveness Rate, and
Type of Fuel Tank Inerting Installation
[Values in million of 2005 dollars]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Benefit/cost ratios
SFAR 88 --------------------------------------------------
Discount rate (percent) Value of effectiveness Production-
fatality (percent) Retrofitted Production retrofitted
(percent) (percent) (percent)
--------------------------------------------------------------------------------------------------------------------------------------------------------
7................................................................. $3 50 59 65 6
7................................................................. 5.5 50 104 112 8
7................................................................. 3 25 88 98 10
7................................................................. 5.5 25 155 168 13
7................................................................. 3 75 29 33 4
7................................................................. 5.5 75 52 56 4
3................................................................. 3 50 74 112 38
3................................................................. 5.5 50 132 192 60
3................................................................. 3 25 111 167 56
3................................................................. 5.5 25 198 289 91
3................................................................. 3 75 37 56 19

[[Page 70948]]

3................................................................. 5.5 75 66 96 30
--------------------------------------------------------------------------------------------------------------------------------------------------------

In light of these results, we determined that the benefit-cost
analysis does not justify requiring production airplanes to have fuel
tank inerting systems while not requiring these systems on retrofitted
airplanes. Both airplanes need these systems.
Alternative Two: Include Cargo Airplanes in the Proposed Rule
As shown by Tables 2 and 3, including cargo airplanes in the
proposed rule would have no affect on the present value of the proposed
rule's quantified benefits and it would increase the cost by $111
million (a 12 percent increase). Using a discount rate of 7 percent, a
$3 million value for a prevented fatality and an SFAR 88 effectiveness
rate of 50 percent, the benefit-cost ratio would decrease from 61
percent to 53 percent.
Cost Benefit Summary
We believe the benefits of preventing four expected fuel tank
explosions over fifty years justify the compliance cost. While our
model predicts one accident every 60 million flight hours of fleet
operation and a total of four prevented accidents within the analysis
period, there is a nearly 40 percent probability of five or more
accidents. In addition, these accidents could occur on airplanes with
larger passenger capacity than the average assumed in this analysis,
and they could occur sooner than we forecast. If this rule prevents two
accidents comparable to the TWA accident with 230 fatalities, then
preventing two of these accidents would produce estimated undiscounted
benefits of $2.5 billion and would justify the undiscounted compliance
cost of this proposed rule. Finally, we did not include the potential
losses associated with the likely disruption to commercial aviation
resulting from an in-flight explosion. Such an explosion could
immediately raise a terrorism concern. In the preliminary regulatory
evaluation, we estimate that the costs associated with a potential
disruption could cost approximately $5 billion per accident.
Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980 (RFA) establishes ``as a
principle of regulatory issuance that agencies shall endeavor,
consistent with the objective of the rule and of applicable statutes,
to fit regulatory and informational requirements to the scale of the
business, organizations, and governmental jurisdictions subject to
regulation.'' To achieve that principle, the RFA requires agencies to
solicit and consider flexible regulatory proposals and to explain the
rationale for their actions. The RFA covers a wide-range of small
entities, including small businesses, not-for-profit organizations and
small governmental jurisdictions.
Agencies must perform a review to determine whether a proposed or
final rule will have a significant economic impact on a substantial
number of small entities. If the agency determines that it will, the
agency must prepare a regulatory flexibility analysis as described in
the Act.
The proposed rule would require all Boeing and Airbus airplane
operators, including about 18 small business operators, to retrofit
their airplanes. We believe that this proposed rule would have a
significant impact on a substantial number of small entities.
Accordingly, an initial regulatory flexibility analysis, as required by
the RFA, is included as part of the Initial Regulatory Analysis that is
in the docket.
International Trade Impact Assessment
This proposed rule would impose the same costs on Boeing and Airbus
N-registered airplanes operated by domestic entities. It would also
impose costs on the airplanes and the operations of domestic entities
flying internationally. However, foreign entities flying into the
United States would not be affected by the proposed rule and would have
a competitive advantage in competing for international business with
U.S. domestic carriers. Based on the safety issues involved, we
determined that these costs are acceptable to obtain the required level
of air travel safety.
Unfunded Mandates Reform Act
The Unfunded Mandates Reform Act of 1995 (the Act) is intended,
among other things, to curb the practice of imposing unfunded Federal
mandates on State, local, and tribal governments. Title II of the Act
requires each Federal agency to prepare a written statement assessing
the effects of any Federal mandate in a proposed or final agency rule
that may result in an expenditure of $100 million or more (adjusted
annually for inflation) in any one year by State, local, and tribal
governments, in the aggregate, or by the private sector; such a mandate
is deemed to be a ``significant regulatory action.'' We currently use
an inflation-adjusted value of $120.7 million in lieu of $100 million.
We note that the rule would impose a significant private sector
cost in 2014 and 2015, as the estimated undiscounted retrofitting cost
would be about $110 million, which has a present value of about $70
million. Thus, this proposed rule does not contain such a mandate and
the requirements of Title II of the Unfunded Mandates Reform Act of
1995 do not apply.
Executive Order 13132, Federalism
The FAA has analyzed this proposed rule under the principles and
criteria of Executive Order 13132, Federalism. We determined that this
action would not have a substantial direct effect on the States, on the
relationship between the national Government and the States, or on the
distribution of power and responsibilities among the various levels of
government, and therefore would not have federalism implications.
Regulations Affecting Intrastate Aviation in Alaska
Section 1205 of the FAA Reauthorization Act of 1996 (110 Stat.
3213) requires the Administrator, when modifying regulations in title
14 of the CFR in manner affecting intrastate aviation in Alaska, to
consider the extent to which Alaska is not served by transportation
modes other than aviation, and to establish such regulatory
distinctions, as he or she

[[Page 70949]]

considers appropriate. Because this proposed rule would apply to the
certification of future designs of transport category airplanes and
their subsequent operation, it could, if adopted, affect intrastate
aviation in Alaska. The FAA therefore specifically requests comments on
whether there is justification for applying the proposed rule
differently in intrastate operations in Alaska.
Plain English
Executive Order 12866 (58 FR 51735, Oct. 4, 1993) requires each
agency to write regulations that are simple and easy to understand. We
invite your comments on how to make these proposed regulations easier
to understand, including answers to questions such as the following:
? Are the requirements in the proposed regulations clearly stated?
? Do the proposed regulations contain unnecessary technical
language or jargon that interferes with their clarity?
? Would the regulations be easier to understand if they were
divided into more (but shorter) sections?
? Is the description in the preamble helpful in
understanding the proposed regulations?
Please send your comments to the address specified in the ADDRESSES
section.
Environmental Analysis
FAA Order 1050.1E identifies FAA actions that are categorically
excluded from preparation of an environmental assessment or
environmental impact statement under the National Environmental Policy
Act in the absence of extraordinary circumstances. The FAA has
determined this proposed rulemaking action qualifies for the
categorical exclusion identified in paragraph 312f and involves no
extraordinary circumstances.
Regulations That Significantly Affect Energy Supply, Distribution, or Use
We have determined that it is not a ``significant energy action''
under the executive order. The FAA has analyzed this NPRM under
Executive Order 13211, Actions Concerning Regulations that
Significantly Affect Energy Supply, Distribution, or Use (May 18,
2001). We have determined that it is not a ``significant energy
action'' under the executive order because the proposed rule is not
likely to have a significant adverse effect on the supply,
distribution, or use of energy.

List of Subjects

14 CFR Part 25

Aircraft, Aviation safety, Reporting and recordkeeping requirements.

14 CFR Part 91

Aircraft, Aviation safety, Reporting and recordkeeping requirements.

14 CFR Part 121

Air carriers, Aircraft, Aviation safety, Reporting and
recordkeeping requirements, Safety, Transportation.

14 CFR Part 125

Aircraft, Aviation safety, Reporting and recordkeeping requirements.

14 CFR Part 129

Air carriers, Aircraft, Aviation safety, Reporting and
recordkeeping requirements, Security measures.

V. The Proposed Amendment

In consideration of the foregoing, the Federal Aviation
Administration proposes to amend Chapter 1 of Title 14, Code of Federal
Regulations (CFR) parts 25, 91, 121, 125, and 129, as follows:

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

1. The authority citation for part 25 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701, 44702 and 44704.

2. Amend Sec. 25.1 by adding new paragraphs (c) and (d) to read as
follows:

Sec. 25.1 Applicability.

* * * * *
(c) This part also establishes requirements for holders of type
certificates, supplemental type certificates, and field approvals to
take specific actions necessary to support the continued airworthiness
of transport category airplanes.
(d) This part also establishes requirements for holders or
licensees of type certificates for transport category airplanes to
introduce design changes necessary for safety into newly produced
airplanes.
3. Amend Sec. 25.2 by adding a new paragraph (d) to read as follows:

Sec. 25.2 Special retroactive requirements.

* * * * *
(d) In addition to the requirements of this section, subpart I of
this part contains requirements that apply to:
(1) Holders of type certificates, and supplemental type certificates;
(2) Applicants for type certificates, amendments to type
certificates (including service bulletins describing design changes),
and supplemental type certificates;
(3) [Reserved];
(4) Licensees of type certificates.
4. Amend Sec. 25.981 by revising paragraphs (b) and (c) and adding
paragraphs (d) and (e) to read as follows:

Sec. 25.981 Fuel tank ignition prevention.

* * * * *
(b) Except as provided in paragraph (c) of this section, no fuel
tank Fleet Average Flammability Exposure level on an airplane other
than one designed solely for all-cargo operations may exceed three
percent, or a fuel tank within the wing of the airplane model being
evaluated. If the wing is not a conventional unheated aluminum wing,
the analysis must be based on an assumed Equivalent Conventional
Unheated Aluminum Wing.
(1) Fleet Average Flammability Exposure is determined in accordance
with Appendix L of this part.
(2) Any fuel tank other than a main tank on an airplane other than
one designed solely for all-cargo operations must meet the flammability
exposure criteria of Appendix K to this part if any portion of the tank
is located within the fuselage contour.
(3) As used in this paragraph,
(i) Equivalent Conventional Unheated Aluminum Wing is a semi-
monocoque aluminum wing of a subsonic airplane that is equivalent in
aerodynamic performance, structural capability, fuel tank capacity and
tank configuration to the designed wing.
(ii) Fleet Average Flammability Exposure is defined in Appendix L
to this part and means the percentage of time the fuel tank ullage is
flammable for a fleet of an airplane type operating over the range of
flight lengths.
(iii) Main Fuel Tank means a fuel tank that feeds fuel directly
into one or more engines and holds required fuel reserves continually
throughout each flight.
(c) Paragraphs (b) and (e) of this section do not apply to a fuel
tank if means are provided to mitigate the effects of an ignition of
fuel vapors within that fuel tank such that no damage caused by an
ignition will prevent continued safe flight and landing.
(d) Critical design configuration control limitations (CDCCL),
inspections, or other procedures must be established, as necessary, to
prevent development of ignition sources within the fuel tank system
pursuant to paragraph (a) of this section, to prevent increasing the
flammability exposure of the tanks above that permitted under paragraph
(b) of this section, and to prevent degradation of the performance

[[Page 70950]]

and reliability of any means provided according to paragraphs (a), (b)
or (c). These CDCCL, inspections, and procedures must be included in
the Airworthiness Limitations section of the instructions for continued
airworthiness required by Sec. 25.1529. Visible means of identifying
critical features of the design must be placed in areas of the airplane
where foreseeable maintenance actions, repairs, or alterations may
compromise the critical design configuration limitations (e.g., color-
coding of wire to identify separation limitation). These visible means
must also be identified as CDCCL.
(e) For airplanes designed solely for all-cargo operations, except
as provided in paragraph (c) of this section, the fuel tank
installation must include means to minimize the development of
flammable vapors in the fuel tanks (in the context of this rule,
``minimize'' means to incorporate practicable design methods to reduce
the likelihood of flammable vapors).
5. Amend part 25 by adding a new subpart I to read as follows:
Subpart I--Continued Airworthiness and Safety Improvements

General

Sec.
25.1801 Purpose and Scope.
25.1803 Definitions.
25.1805-25.1813 [Reserved]

Fuel Tank Flammability

25.1815 Holders of type certificates: Fuel tank flammability safety.
25.1817 Changes to type certificates affecting fuel tank flammability.
25.1819 Pending type certification projects: Fuel tank flammability safety.
25.1821 Newly produced airplanes: Fuel tank flammability safety.

Subpart I--Continued Airworthiness and Safety Improvements

General

Sec. 25.1801 Purpose and scope.

(a) This subpart establishes requirements for support of the
continued airworthiness of and safety improvements for transport
category airplanes. These requirements may include performing
assessments, developing design changes, developing revisions to
Instructions for Continued Airworthiness, and making necessary
documentation available to affected persons.
(b) This subpart applies to the following persons, as specified in
each section of this subpart:
(1) Holders of type certificates and supplemental type certificates.
(2) Applicants for type certificates and changes to type
certificates (including service bulletins describing design changes).
Applicants for changes to type certificates must comply with the
requirements of this subpart in addition to the airworthiness
requirements determined applicable under Sec. 21.101 of this subchapter.
(3) [Reserved]
(4) Holders of type certificates and their licensees producing new
airplanes.

Sec. 25.1803 Definitions.

(a) Auxiliary Fuel Tank is a Normally Emptied fuel tank that has
been installed pursuant to a supplemental type certificate or field
approval to make additional fuel available.
(b) Fleet Average Flammability Exposure has the meaning defined in
Appendix L of this part.
(c) FAA Oversight Office is the aircraft certification office or
office of the Transport Airplane Directorate with oversight
responsibility for the relevant type certificate, supplemental type
certificate, or manufacturer, as determined by the Administrator.
(d) Normally Emptied means a fuel tank other than a Main Fuel Tank
as defined in 14 CFR 25.981(b).

Sec. 25.1805-25.1813 [Reserved]

Fuel Tank Flammability

Sec. 25.1815 Holders of type certificates: Fuel tank flammability safety.

(a) Applicability. Except as provided in paragraph (j) of this
section, this section applies to transport category, turbine-powered
airplanes with a type certificate issued after January 1, 1958, other
than those designed solely for all-cargo operations, that, as a result
of original type certification or later increase in capacity have:
(1) A maximum type-certificated passenger capacity of 30 or more,
or
(2) A maximum payload capacity of 7,500 pounds or more.
(b) Flammability Exposure Analysis--(1) General. Within 150 days
after [effective date of final rule], holders of type certificates must
submit for approval to the FAA Oversight Office a flammability exposure
analysis of all fuel tanks defined in the type design, as well as all
design variations approved under the type certificate that affect
flammability exposure. This analysis must be conducted in accordance
with appendix L of this part.
(2) Exception. This paragraph does not apply to fuel tanks for
which the type certificate holder has notified the FAA under paragraph
(g) of this section that it will provide design changes and service
instructions for an Ignition Mitigation Means (IMM) meeting the
requirements of paragraph (c)(2) of this section.
(c) Design modifications. For fuel tanks with a Fleet Average
Flammability Exposure level exceeding 7 percent, one of the following
design modifications must be made.
(1) Flammability Reduction Means (FRM). A means must be provided to
reduce the fuel tank flammability.
(i) Fuel tanks that are designed to be Normally Emptied must meet
the flammability exposure criteria of Appendix K of this part if any
portion of the tank is located within the fuselage contour.
(ii) For all other fuel tanks, the FRM must meet all of the
requirements of Appendix K of this part, except, instead of complying
with paragraph K25.1, the Fleet Average Flammability Exposure level
must not exceed 7 percent.
(2) IMM. A means must be provided to mitigate the effects of an
ignition of fuel vapors within the fuel tank such that no damage caused
by an ignition will prevent continued safe flight and landing.
(d) Design Changes and Service Instructions. No later than the
applicable date stated in Table 1 of this section, holders of type
certificates affected by this section must meet one of the following
requirements:
(1) FRM. The type certificate holder must submit for approval by
the FAA Oversight Office design changes and service instructions for
installation of fuel tank flammability reduction means (FRM) meeting
the criteria of paragraph (c) of this section.
(2) IMM. The type certificate holder must submit for approval by
the FAA Oversight Office design changes and service instructions for
installation of fuel tank IMM that comply with 14 CFR 25.981(c) in
effect on [effective date of final rule].

Table 1
------------------------------------------------------------------------
Service instruction submittal
Model-- date
------------------------------------------------------------------------
Boeing
------------------------------------------------------------------------
747 Series.............................. December 31, 2005.
737 Series.............................. March 31, 2006.
777 Series.............................. March 31, 2006.
767 Series.............................. September 30, 2006.
757 Series.............................. March 31, 2007.
707/720 Series.......................... December 31, 2007.
-----------------------------------------
Airbus
------------------------------------------------------------------------
A319, A320, A321 Series................. December 31, 2006.
A300, A310 Series....................... June 30, 2007.
A330, A340 Series....................... December 31, 2007.
All other affected models............... Within 24 months of effective
date of this amendment.
------------------------------------------------------------------------

[[Page 70951]]

(e) Instructions for Continued Airworthiness (ICA). For all fuel
tanks, regardless of flammability exposure, no later than the
applicable date specified in Table 1 of this section, holders of type
certificates affected by this section must submit for approval by the
FAA Oversight Office, critical design configuration control limitations
(CDCCL), inspections, or other procedures to prevent increasing the
flammability exposure of the tanks above that permitted under this
section and to prevent degradation of the performance of any means
provided under paragraph (c)(1) or (c)(2) of this section. These CDCCL,
inspections, and procedures must be included in the Airworthiness
Limitations section of the ICA required by 14 CFR 25.1529 or paragraph
(f) of this section. Visible means to identify critical features of the
design must be placed in areas of the airplane where foreseeable
maintenance actions, repairs, or alterations may compromise the
critical design configuration limitations. These visible means must
also be identified as a CDCCL.
(f) Airworthiness Limitations. Unless previously accomplished, no
later than the applicable date specified in Table 1 of this section,
holders of type certificates affected by this section must establish an
Airworthiness Limitations Section (ALS) of the maintenance manual or
ICA for each airplane configuration evaluated under paragraph (b)(1)
and submit it to the FAA oversight office for approval. The ALS must
include a section that contains the (CDCCL), inspections, or other
procedures developed under paragraph (e) of this section.
(g) Compliance Plan for Flammability Exposure Analysis. Within 60
days after [effective date of final rule], each holder of a type
certificate identified in paragraph (a) of this section must submit to
the FAA Oversight Office a compliance plan consisting of the following:
(1) A proposed project schedule for submitting the required
analysis, or a determination that compliance with paragraph (b) of this
section is not required as design changes and service instructions for
IMM will be made available.
(2) A proposed means of compliance with paragraph (b) of this
section, if applicable.
(3) If the affected holder proposes a means of compliance that
differs from that described in FAA advisory material, a detailed
explanation of how the proposed means will comply with this section.
(h) Compliance Plan for Design Changes and Service Instructions.
Within 210 days after [effective date of final rule], each holder of a
type certificate required to comply with paragraph (d) of this section
must submit to the FAA Oversight Office a compliance plan consisting of
the following:
(1) A proposed project schedule, identifying all major milestones,
for meeting the compliance dates specified in paragraph (d) of this
section.
(2) A proposed means of compliance with paragraph (d) of this section.
(3) If the affected holder proposes a means of compliance that
differs from that described in FAA advisory material, a detailed
explanation of how the proposed means will comply with this section.
(4) A proposal for submitting a draft of all compliance items
required by paragraph (d) of this section for review by the FAA
Oversight Office not less than 60 days before the compliance time
specified in paragraph (d) of this section.
(5) A proposal for how the approved service information and any
necessary modification parts will be made available to affected persons.
(i) Deficiencies in Compliance Plans. Each affected type
certificate holder must implement the compliance plans as approved
under paragraph (g) and (h) of this section. The FAA Oversight Office
will notify the affected holder of deficiencies in the proposed
compliance plan, or in the type certificate holder's implementation of
the plan, and provide the means for correcting those deficiencies. The
type certificate holder must submit a corrected plan to the FAA
Oversight Office within 30 days after such notification and implement
the corrected plan.
(j) Exceptions. The requirements of this section do not apply to
the following airplane models:
(1) Convair CV-240, 340, 440, including turbine powered conversions.
(2) Lockheed L-188.
(3) Vickers Armstrong Viscount.
(4) Douglas DC-3, including turbine powered conversions.
(5) Bombardier CL-44.
(6) Mitsubishi YS-11.
(7) BAC 1-11.
(8) Concorde.
(9) deHavilland D.H. 106 Comet 4C.
(10) VFW-Vereinigte Flugtechnische VFW-614.
(11) Illyushin Aviation IL 96T.
(12) Bristol Aircraft Britannia 305.
(13) Handley Page Handley Page Herald Type 300.
(14) Avions Marcel Dassault--Breguet Aviation Mercure 100C.
(15) Airbus Caravelle.
(16) Fokker F27.
(17) Maryland Air Service V-27/FH-227.

Sec. 25.1817 Changes to type certificates affecting fuel tank
flammability.

(a) Applicability. This section applies to the following design
changes to any airplane subject to 14 CFR 25.1815(a) unless the design
change converts the airplane to one designed solely for all-cargo
operations:
(1) Any fuel tank designed to be Normally Emptied if any of the
following occurred before [effective date of final rule]:
(i) The fuel tank was installed on an airplane pursuant to a
supplemental type certificate or a field approval;
(ii) An application for a supplemental type certificate or an
amendment to a type certificate was made, or
(iii) A field approval was granted.
(2) Installation of a fuel tank designed to be Normally Emptied,
including Auxiliary Fuel Tanks, changes to existing fuel tank capacity,
and changes that may increase the flammability exposure of an existing
fuel tank on airplanes for which an application for a supplemental type
certificate or an amendment to a type certificate is made on or after
[effective date of final rule].
(b) Flammability Exposure Analysis--(1) General. By the times
specified in paragraphs (b)(1)(i) and (b)(1)(ii) of this section, each
person subject to this section must submit for approval to the FAA
Oversight Office a flammability exposure analysis of the Auxiliary Fuel
Tanks or other affected fuel tanks, as defined in the type design. This
analysis must be conducted in accordance with appendix L of this part.
(i) Holders of supplemental type certificates and field approvals:
Within 12 months of [effective date of final rule],
(ii) Applicants for supplemental type certificates and for
amendments to type certificates: Within 12 months of [effective date of
final rule], or before the certificate is issued, whichever occurs later.
(2) Exception. This paragraph does not apply to fuel tanks for
which the type certificate holder, supplemental type certificate
holder, and field approval holder has notified the FAA under paragraph
(f) of this section that it will provide design changes and service
instructions for an IMM meeting the requirements of Sec. 25.981(c) of
this part in effect on [effective date of final rule].
(c) Impact Assessment. By the times specified in paragraphs (c)(1)
and (c)(2) of this section, each person subject to

[[Page 70952]]

this section must submit for approval to the FAA Oversight Office an
assessment of the fuel tank system, as modified by their design change.
The assessment must identify any features of the design change that
compromise any critical design configuration control limitation (CDCCL)
applicable to any airplane on which the design change is eligible for
installation.
(1) Holders of supplemental type certificates and field approvals:
Within 6 months of the date of FAA approval of the submission
identified in Sec. 25.1815(d) for the applicable airplane model.
(2) Applicants for supplemental type certificates and for
amendments to type certificates: Within 6 months of the date of FAA
approval of the submission identified in 14 CFR 25.1815(d) for the
applicable airplane model or before the certificate is issued,
whichever occurs later.
(d) Design Changes and Service Instructions. By the times specified
in paragraph (e) of this section, each person subject to this section
must meet the requirements of paragraphs (d)(1), (d)(2), (d)(3), and
(d)(4) of this section, as applicable.
(1) If the application was submitted before June 6, 2001, for any
fuel tank exceeding a Fleet Average Flammability Exposure level of 7
percent, submit for approval by the FAA oversight office design changes
and service instructions for installation of either:
(i) IMM. Fuel tank IMM that comply with 14 CFR 25.981(c) of this
part in effect on [effective date of final rule]; or
(ii) FRM. Any fuel tank that is designed to be Normally Emptied,
including Auxiliary Fuel tanks, must meet the flammability exposure
criteria of Appendix K if any portion of the tank is located within the
fuselage contour. For all other fuel tanks, the FRM must meet all of
the requirements of Appendix K of this part, except, instead of
complying with paragraph K25.1, the Fleet Average Flammability Exposure
level must not exceed 7 percent.
(2) If the application was made on or after June 6, 2001, comply
with the requirements of 14 CFR 25.981, in effect on [effective date of
final rule], for all fuel tanks subject to this section.
(3) For design changes adding a fuel tank designed to be Normally
Emptied, including Auxiliary Fuel Tanks, or changing fuel tank
capacity, establish critical design configuration control limitations
(CDCCL), inspections, or other procedures to prevent increasing the
flammability exposure of the tanks above that permitted under this
section and to prevent degradation of the performance of any means
provided according to paragraphs (d)(1)(i) or (d)(1)(ii) of this
section. These CDCCL, inspections, and procedures must be included in
the Airworthiness Limitations section of the ICA required by 14 CFR
25.1529 of this part. Visible means to identify critical features of
the design must be placed in areas of the airplane where foreseeable
maintenance actions, repairs, or alterations may compromise the
critical design configuration limitations. These visible means must
also be identified as CDCCL.
(4) If the assessment required by paragraph (c) of this section
identifies any features of the design change that compromise any CDCCL
applicable to any airplane on which the design change is eligible for
installation, the holder or applicant must submit for approval by the
FAA Oversight Office design changes and service instructions for
Flammability Impact Mitigation Means (FIMM) that would bring the design
change into compliance with the CDCCL. Any fuel tank modified as
required by this paragraph must also be evaluated as required by
paragraph (b) of this section and comply with paragraphs (d)(1),
(d)(2), and (d)(3) of this section, as applicable.
(e) Compliance Times for Design Changes and Service Instructions.
The following persons subject to this section must comply with the
requirements of paragraph (d) of this section at the specified times.
(1) Holders of supplemental type certificates and field approvals:
Within 24 months of the date identified in 14 CFR 25.1815(d) for the
applicable airplane model.
(2) Applicants for supplemental type certificates and for
amendments to type certificates: Within 24 months of the date
identified in 14 CFR 25.1815(d) for the applicable airplane model or
before the certificate is issued, whichever occurs later.
(f) Compliance Planning. By the applicable times specified in Table
2 of this section, each person subject to this section must submit for
approval by the FAA Oversight Office compliance plans for the
flammability exposure analysis required by paragraph (b) of this
section, the impact assessment required by paragraph (c) of this
section, and the design changes and service instructions required by
paragraph (d) of this section. Each person's compliance plans must
include the following:
(1) A proposed project schedule for submitting the required
analysis or impact assessment.
(2) A proposed means of compliance with paragraph (d) of this section.
(3) If the affected holder proposes a means of compliance that
differs from that described in FAA advisory material, a detailed
explanation of how the proposed means will be shown to comply with this
section.
(4) For the requirements of paragraph (d) of this section, a
proposal for submitting a draft of all design changes, if any are
required, and CDCCLs for review by the FAA Oversight Office not less
than 60 days before the compliance time specified in paragraph (e) of
this section.
(5) For the requirements of paragraph (d) of this section, a
proposal for how the approved service information and any necessary
modification parts will be made available to affected persons.

Table 2.--Compliance Planning Dates
----------------------------------------------------------------------------------------------------------------
Design changes and
Flammability exposure Impact assessment plan service instructions
analysis plan plan
----------------------------------------------------------------------------------------------------------------
STC and Field Approval Holders....... 60 days after 60 days after the date 240 days after the date
[effective date of identified in Sec. identified in Sec.
final rule]. 25.1815(d) for the 25.1815(d) for the
applicable airplane applicable airplane
model. model.
STC and ATC Applicants............... 60 days after 60 days after the date 240 days after the date
[effective date of identified in Sec. identified in Sec.
final rule]
or before 25.1815(d) for the 25.1815(d) for the
the certificate is applicable airplane applicable airplane
issued, whichever model or before the model or before the
occurs later. certificate is issued, certificate is issued,
whichever occurs later. whichever occurs
later.
----------------------------------------------------------------------------------------------------------------

[[Page 70953]]

(g) Deficiencies in Compliance Plans. Each person subject to this
section must implement the compliance plans as approved under paragraph
(f) of this section. The FAA Oversight Office will notify the affected
person of deficiencies in the proposed compliance plan, or in the
person's implementation of the plan, and of the means for correcting
those deficiencies. The person must submit a corrected plan to the FAA
oversight office within 30 days after such notification, and implement
the corrected plan.

Sec. 25.1819 Pending type certification projects: Fuel tank
flammability safety.

(a) Applicability. This section applies to any new type certificate
for a transport category airplane, other than one designed solely for
all-cargo operations, if the application was made before [effective
date of final rule and if the certificate was not issued before
[effective date of final rule]. This section applies only if the
airplane would have--
(1) A maximum type-certificated passenger capacity of 30 or more,
or
(2) A maximum payload capacity of 7,500 pounds or more.
(b) Flammability Exposure Analysis. Before issuance of the type
certificate, the applicant must submit for approval to the FAA
Oversight Office a flammability exposure analysis of all fuel tanks
defined in the type design. This analysis must be conducted in
accordance with Appendix L of this part.
(c) If the application was made before June 6, 2001, the
requirements of paragraphs (c)(1) and (c)(2) of this section apply.
(1) Any fuel tank meeting all of the criteria stated in paragraphs
(c)(1)(i), (c)(1)(ii) and (c)(1)(iii) of this section must have FRM or
IMM that meet the requirements of 14 CFR 25.981 of this part in effect
on [effective date of final rule].
(i) The fuel tank is a fuel tank designed to be Normally Emptied.
(ii) Any portion of the fuel tank is located within the fuselage
contour.
(iii) The fuel tank exceeds a Fleet Average Flammability Exposure
level of this part, of 7 percent.
(2) All other fuel tanks that exceed a Fleet Average Flammability
Exposure level of 7 percent must have either an IMM meeting 14 CFR
25.981(c) of this part in effect on [effective date of final rule]
or
an FRM meeting the requirements of Appendix K of this part, except,
instead of complying with paragraph K25.1, the Fleet Average
Flammability Exposure level must not exceed 7 percent.
(d) If the application was made on or after June 6, 2001, the
requirements of 14 CFR 25.981 in effect on [effective date of final
rule]
apply.
(e) Any design change to a type certificate subject to this section
that adds an Auxiliary Fuel Tank or fuel tank designed to be Normally
Emptied, that increases fuel tank capacity, or that may increase the
flammability exposure of an existing fuel tank, must meet the
requirements of 14 CFR 25.981 in effect on [effective date of final rule].
(f) For all fuel tanks, regardless of flammability exposure, no
later than the applicable date specified in Table 1 of this subpart,
holders of type certificates affected by this section must submit for
approval by the FAA Oversight Office, critical design configuration
control limitations (CDCCL), inspections, or other procedures to
prevent increasing the flammability exposure of the tanks above that
permitted under paragraph (c) or (d) of this section and to prevent
degradation of the performance of any means provided under paragraph
(c) or (d) of this section. These CDCCL, inspections, and procedures
must be included in the Airworthiness Limitations section of the ICA
required by 14 CFR 25.1529. Visible means to identify critical features
of the design must be placed in areas of the airplane where foreseeable
maintenance actions, repairs, or alterations may compromise the
critical design configuration limitations. These visible means must
also be identified as CDCCL.

Sec. 25.1821 Newly produced airplanes: Fuel tank flammability safety.

(a) Applicability: This section applies to holders of type
certificates for airplanes, other than those designed or produced
solely for all-cargo operations, subject to 14 CFR 25.1815(c) of this
part when application is made for original certificates of
airworthiness or export airworthiness approvals after the applicable
dates shown in 14 CFR 25.1815(d) of this part. This section only
applies if the FAA has jurisdiction over the organization responsible
for final assembly of the airplane.
(b) Any fuel tank meeting all of the criteria stated in paragraphs
(b)(1), (b)(2) and (b)(3) of this section must have flammability
reduction means (FRM) or ignition mitigation means (IMM) that meet the
requirements of 14 CFR 25.981 in effect on [effective date of final rule].
(1) The fuel tank is Normally Emptied.
(2) Any portion of the fuel tank is located within the fuselage
contour.
(3) The fuel tank exceeds a Fleet Average Flammability Exposure
level of 7 percent.
(c) All other fuel tanks that exceed an Fleet Average Flammability
Exposure level of 7 percent must have an IMM that meets 14 CFR
25.981(c) in effect on [effective date of final rule]
or an FRM that
meets all of the requirements of Appendix K to this part, except
instead of complying with paragraph K25.1, the Fleet Average
Flammability Exposure level must not exceed 7 percent.
6. Part 25 is amended by adding a new appendix K to read as follows:

Appendix K to Part 25--Fuel Tank System Flammability Reduction Means

K25.1 Fuel tank flammability exposure requirements

(a) The Fleet Average Flammability Exposure level of each fuel
tank, as determined in accordance with Appendix L of this part, must
not exceed 3 percent of the Flammability Exposure Evaluation Time
(FEET), as defined in Appendix L of this part. If flammability
reduction means (FRM) are used, neither time periods when any FRM is
operational but the fuel tank is not inert, nor time periods when
any FRM is inoperative may contribute more than 1.8 percent to the 3
percent average fleet flammability exposure of a tank.
(b) The Fleet Average Flammability Exposure, as defined in
Appendix L of this part, of each fuel tank for ground, takeoff and
climb phases of flight during warm days must not exceed 3 percent of
FEET in each of these phases. The analysis must consider the
following conditions.
(1) The analysis must use the subset of flights starting with a
sea level ground ambient temperature of 80[deg]F (standard day plus
21[deg]F atmosphere) or more, from the flammability exposure
analysis done for overall performance.
(2) For the ground, takeoff, and climb phases of flight, the
average flammability exposure must be calculated by dividing the
time during the specific flight phase the fuel tank is flammable by
the total time of the specific flight phase.
(3) Compliance with this paragraph may be shown using only those
flights for which the airplane is dispatched with the flammability
reduction means operational.

K25.2 Showing compliance

(a) The applicant must provide data from analysis, ground
testing, and flight testing, or any combination of these, that:
(1) Validate the parameters used in the analysis required by
paragraph K25.1;
(2) Substantiate that the FRM is effective at limiting
flammability exposure in all compartments of each tank for which the
FRM is used to show compliance with paragraph K25.1; and
(3) Describe the circumstances under which the FRM would not be
operated during each phase of flight.
(b) The applicant must validate that the FRM meets the
requirements of paragraph K25.1 with any combination of engine
model, engine thrust rating, fuel type, and relevant pneumatic
system configuration for which approval is sought.

[[Page 70954]]

K25.3 Reliability indications and maintenance access

(a) Reliability indications must be provided to identify latent
failures of the FRM.
(b) Sufficient accessibility to FRM reliability indications must
be provided for maintenance personnel or the flightcrew.
(c) The access doors and panels to the fuel tanks with FRMs
(including any tanks that communicate with a tank via a vent
system), and to any other confined spaces or enclosed areas that
could contain hazardous atmosphere under normal conditions or
failure conditions must be permanently stenciled, marked, or
placarded to warn maintenance personnel of the possible presence of
a potentially hazardous atmosphere.

K25.4 Airworthiness limitations and procedures

(a) If FRM is used to comply with paragraph K25.1, Airworthiness
Limitations must be identified for all maintenance or inspection
tasks required to identify failures of components within the FRM
that are needed to meet paragraph K25.1.
(b) Maintenance procedures must be developed to identify any
hazards to be considered during maintenance of the FRM. These
procedures must be included in the instructions for continued
airworthiness (ICA).

K25.5 Reliability reporting

The effects of airplane component failures on FRM reliability
must be assessed on an on-going basis. The applicant must do the following:
(a) Demonstrate effective means to ensure collection of FRM
reliability data. The means must provide data affecting FRM
reliability, such as component failures.
(b) Provide a report to the FAA on a quarterly basis for the
first five years after service introduction. After that period,
continued quarterly reporting may be replaced with other reliability
tracking methods found acceptable to the FAA or eliminated if it is
established that the reliability of the FRM meets, and will continue
to meet, the exposure requirements of paragraph K25.1.
(c) Develop service instructions or revise the applicable
airplane manual, according to a schedule approved by the FAA
Oversight Office, as defined in Subpart I of this part, to correct
any failures of the FRM that occur in service that could increase
any fuel tank's Fleet Average Flammability Exposure to more than
that required by paragraph K25.1.

7. Part 25 is amended by adding a new appendix L to read as follows:

Appendix L to Part 25--Fuel Tank Flammability Exposure and Reliability
Analysis

L25.1 General

(a) This appendix specifies the requirements for conducting fuel
tank fleet average flammability exposure analyses required to meet
Sec. 25.981(b) and Appendix K of this part. This appendix defines
parameters affecting fuel tank flammability that must be used in
performing the analysis. These include parameters that affect all
airplanes within the fleet, such as a statistical distribution of
ambient temperature, fuel flash point, flight lengths, and airplane
descent rate. Demonstration of compliance also requires application
of factors specific to the airplane model being evaluated. Factors
that need to be included are maximum range, cruise mach number,
typical altitude where the airplane begins initial cruise phase of
flight fuel temperature during both ground and flight times, and the
performance of a flammability reduction means (FRM) if installed.
(b) The FAA program defined in FAA document, Fuel Tank
Flammability Assessment Method Users Manual, must be used as the
means of compliance with Sec. 25.981(b) and appendix K. [You must
proceed in accordance with FAA document, Fuel Tank Flammability
Assessment Method Users Manual. The Director of the Federal Register
approves this incorporation by reference in accordance with 5 U.S.C.
552(a) and 1 CFR part 51. You may obtain a copy from the following
Web site: http://www.fire.tc.faa.gov/systems/fueltank/FTFAM.stm_.
You may inspect a copy at the Transport Airplane Directorate,
Aircraft Certification Service, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056 or at the Office of the Federal Register, 800
North Capitol Street, NW., Suite 700, Washington, DC. The following
definitions, input variables, and data tables must be used in the
program to determine fleet average flammability exposure for a
specific airplane model.

L25.2 Definitions

(a) Bulk Average Fuel Temperature means the average fuel
temperature within the fuel tank or different sections of the tank
if the tank is subdivided by baffles or compartments.
(b) Flammability Exposure Evaluation Time (FEET). The time from
the start of preparing the airplane for flight, through the flight
and landing, until all payload is unloaded, and all passengers and
crew have disembarked. In the Monte Carlo program, the flight time
is randomly selected from the Flight Length Distribution (Table 3),
the pre-flight times are provided as a function of the flight time,
and the post-flight time is a constant 30 minutes.
(c) Flammable. With respect to a fluid or gas, flammable means
susceptible to igniting readily or to exploding (14 CFR Part 1,
Definitions). A non-flammable ullage is one where the fuel-air vapor
is too lean or too rich to burn or is inert as defined below. For
the purposes of this appendix, a fuel tank that is not inert is
considered flammable when the bulk average fuel temperature within
the tank is within the flammable range for the fuel type being used.
For any fuel tank that is subdivided into sections by baffles or
compartments, the tank is considered flammable when the bulk average
fuel temperature within any section of the tank, that is not inert,
is within the flammable range for the fuel type being used.
(d) Flash Point. The flash point of a flammable fluid means the
lowest temperature at which the application of a flame to a heated
sample causes the vapor to ignite momentarily, or ``flash.'' Table 1
of this appendix provides the flash point for the standard fuel to
be used in the analysis.
(e) Fleet average flammability exposure is the percentage of the
flammability exposure evaluation time (FEET) the fuel tank ullage is
flammable for a fleet of an airplane type operating over the range
of flight lengths in a world-wide range of environmental conditions
and fuel properties as defined in this appendix.
(f) Gaussian Distribution is another name for the normal
distribution, a symmetrical frequency distribution having a precise
mathematical formula relating the mean and standard deviation of the
samples. Gaussian distributions yield bell shaped frequency curves
having a preponderance of values around the mean with progressively
fewer observations as the curve extends outward.
(g) Hazardous atmosphere. An atmosphere that may expose
maintenance personnel, passengers or flight crew to the risk of
death, incapacitation, impairment of ability to self-rescue (that
is, escape unaided from a confined space), injury, or acute illness.
(h) Inert. For the purpose of this appendix, the tank is
considered inert when the bulk average oxygen concentration within
each compartment of the tank is 12 percent or less from sea level up
to 10,000 feet altitude, then linearly increasing from 12 percent at
10,000 feet to 14.5 percent at 40,000 feet altitude, and
extrapolated linearly above that altitude.
(i) Inerting. A process where a noncombustible gas is introduced
into the ullage of a fuel tank so that the ullage becomes non-flammable.
(j) Monte Carlo Analysis. The analytical method that is
specified in this appendix as the compliance means for assessing the
fleet average flammability exposure time for a fuel tank.
(k) Standard deviation is a statistical measure of the
dispersion or variation in a distribution, equal to the square root
of the arithmetic mean of the squares of the deviations from the
arithmetic means.
(l) Transport Effects. For purposes of this appendix, transport
effects are the change in fuel vapor concentration in a fuel tank
caused by low fuel conditions and fuel condensation and vaporization.
(m) Ullage. The volume within the fuel tank not occupied by
liquid fuel.

L25.3 Fuel tank flammability exposure analysis

(a) A flammability exposure analysis must be conducted for the
fuel tank under evaluation to determine fleet average flammability
exposure for the airplane and fuel types under evaluation. For fuel
tanks that are subdivided by baffles or compartments, an analysis
must be performed either for each section of the tank, or for the
section of the tank having the highest flammability exposure.
Consideration of transport effects is not allowed in the analysis.
The Monte Carlo program is contained in FAA document, Fuel Tank
Flammability Assessment Method Users Manual. The parameters
specified in sections L25.3(b) and (c) must be used in the fuel tank
flammability exposure ``Monte Carlo'' analysis.

[[Page 70955]]

(b) The following parameters are defined in the Monte Carlo
analysis and provided in paragraph L25.4:
(1) Cruise Ambient Temperature--as defined in this appendix.
(2) Ground Temperature--as defined in this appendix.
(3) Fuel Flash Point--as defined in this appendix.
(4) Flight Length Distribution--that must be used is defined in
Table 2 of this appendix.
(5) Airplane Climb and Descent Profiles--the applicant must use
the climb and descent profiles defined in the users manual.
(c) Parameters that are specific to the particular airplane
model under evaluation that must be provided as inputs to the Monte
Carlo analysis are:
(1) Airplane Cruise Altitude.
(2) Fuel Tank Quantities. If fuel quantity affects fuel tank
flammability, inputs to the Monte Carlo analysis must be provided
that represent the actual fuel quantity within the fuel tank or
compartment of the fuel tank throughout each of the flights being
evaluated. Input values for this data must be obtained from ground
and flight test data or the approved FAA fuel management procedures.
(3) Airplane Cruise Mach Number.
(4) Airplane Maximum Range.
(5) Fuel Tank Thermal Characteristics. If fuel temperature
affects fuel tank flammability, inputs to the Monte Carlo analysis
must be provided that represent the actual bulk average fuel
temperature within the fuel tank throughout each of the flights
being evaluated. For fuel tanks that are subdivided by baffles or
compartments, bulk average fuel temperature inputs must be provided
either for each section of the tank or for the section of the tank
having the highest flammability exposure. Input values for these
data must be obtained from ground and flight test data or a thermal
model of the tank that has been validated by ground and flight test data.
(6) Maximum airplane operating temperature limit as defined by
any limitations in the airplane flight manual.
(d) Fuel Tank FRM Model. If FRM is used, an FAA approved Monte
Carlo program must be used to show compliance with the flammability
requirements of Sec. 25.981 and Appendix K of this part. The
program must determine the time periods during each flight phase
when the fuel tank or compartment with the FRM would be flammable.
The following factors must be considered in establishing these time
periods:
(1) Any time periods throughout the flammability exposure
evaluation time and under the full range of expected operating
conditions, when the FRM is operating properly but fails to maintain
a non-flammable fuel tank because of the effects of the fuel tank
vent system or other causes,
(2) If dispatch with the system inoperative under the Master
Minimum Equipment List (MMEL) is requested, the time period assumed
in the reliability analysis, (60 flight hours must be used for a 10-
day MMEL dispatch limit unless an alternative period has been
approved by the Administrator),
(3) Frequency and duration of time periods of FRM inoperability,
substantiated by test or analysis acceptable to the FAA, caused by
latent or known failures, including airplane system shut-downs and
failures that could cause the FRM to shut down or become inoperative,
(4) Effects of failures of the FRM that could increase the
flammability exposure of the fuel tank,
(5) Oxygen Evolution: If an FRM is used that is affected by
oxygen concentrations in the fuel tank, the time periods when oxygen
evolution from the fuel results in the fuel tank or compartment
exceeding the inert level. The applicant must include any times when
oxygen evolution from the fuel in the tank or compartment under
evaluation would result in a flammable fuel tank. The oxygen
evolution rate that must be used is defined in the user's manual.
(6) If an inerting system FRM is used, the effects of any air
that may enter the fuel tank following the last flight of the day
due to changes in ambient temperature, as defined in Table 4, during
a 12-hour overnight period.
(e) The applicant must submit to the FAA oversight office for
approval the fuel tank flammability analysis, including the
airplane-specific parameters identified under paragraph L25.3(c) of
this appendix and any deviations from the parameters identified in
paragraph L25.3(b), that affect flammability exposure,
substantiating data, and any airworthiness limitations and other
conditions assumed in the analysis, must be submitted.

L25.4 Variables and data tables

The following data must be used when conducting a flammability
exposure analysis to determine the fleet average flammability
exposure. Variables used to calculate fleet flammability exposure
must include atmospheric ambient temperatures, flight length,
flammability exposure evaluation time, fuel flash point, thermal
characteristics of the fuel tank, overnight temperature drop, and
oxygen evolution from the fuel into the ullage.
(a) Atmospheric Ambient Temperatures and Fuel Properties.
(1) In order to predict flammability exposure during a given
flight, the variation of ground ambient temperatures, cruise ambient
temperatures, and a method to compute the transition from ground to
cruise and back again must be used. The variation of the ground and
cruise ambient temperatures and the flash point of the fuel is
defined by a Gaussian curve, given by the 50 percent value and a
± 1-standard deviation value.
(2) Ambient Temperature: Under the program, the ground and
cruise ambient temperatures are linked by a set of assumptions on
the atmosphere. The temperature varies with altitude following the
International Standard Atmosphere (ISA) rate of change from the
ground ambient temperature until the cruise temperature for the
flight is reached. Above this altitude, the ambient temperature is
fixed at the cruise ambient temperature. This results in a variation
in the upper atmospheric temperature. For cold days, an inversion is
applied up to 10,000 feet, and then the ISA rate of change is used.
(3) Fuel properties:
(A) For Jet A fuel, the variation of flash point of the fuel is
defined by a Gaussian curve, given by the 50 percent value and a
± 1-standard deviation, as shown in Table 1.
(B) The flammability envelope of the fuel that must be used for
the flammability exposure analysis is a function of the flash point
of the fuel selected by the Monte Carlo for a given flight. The
flammability envelope for the fuel is defined by the upper
flammability limit (UFL) and lower flammability limit (LFL) as follows:
(i) LFL at sea level = flash point temperature of the fuel at
sea level minus 10 [deg]F. LFL decreases from sea level value with
increasing altitude at a rate of 1 [deg]F per 808 feet.
(ii) UFL at sea level = flash point temperature of the fuel at
sea level plus 63.5 [deg]F. UFL decreases from the sea level value
with increasing altitude at a rate of 1 [deg]F per 512 feet.
(4) For each flight analyzed, a separate random number must be
generated for each of the three parameters (ground ambient
temperature, cruise ambient temperature, and fuel flash point) using
the Gaussian distribution defined in Table 1.

Table 1.--Gaussian Distribution for Ground Ambient Temperature, Cruise Ambient Temperature, and Fuel Flash Point
----------------------------------------------------------------------------------------------------------------
Temperature in deg F
-----------------------------------------------------
Parameter Ground ambient Cruise ambient Fuel flash point
temperature temperature (FP)
----------------------------------------------------------------------------------------------------------------
Mean Temp................................................. 59.95 -70 120
Neg 1 std dev............................................. 20.14 8 8
Pos 1 std dev............................................. 17.28 8 8
----------------------------------------------------------------------------------------------------------------

[[Page 70956]]

(b) The Flight Length Distribution defined in Table 2 must be
used in the Monte Carlo analysis.

Table 2.--Flight Length Distribution
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Flight length (NM) Airplane maximum range--nautical miles (NM)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
From To 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Distribution of flight lengths (percentage of total)
-----------------------------------------------------------------------------------
0.............................................. 200.............................. 11.7 7.5 6.2 5.5 4.7 4.0 3.4 3.0 2.6 2.3
200............................................ 400.............................. 27.3 19.9 17.0 15.2 13.2 11.4 9.7 8.5 7.5 6.7
400............................................ 600.............................. 46.3 40.0 35.7 32.6 28.5 24.9 21.2 18.7 16.4 14.8
600............................................ 800.............................. 10.3 11.6 11.0 10.2 9.1 8.0 6.9 6.1 5.4 4.8
800............................................ 1000............................. 4.4 8.5 8.6 8.2 7.4 6.6 5.7 5.0 4.5 4.0
1000........................................... 1200............................. 0.0 4.8 5.3 5.3 4.8 4.3 3.8 3.3 3.0 2.7
1200........................................... 1400............................. 0.0 3.6 4.4 4.5 4.2 3.8 3.3 3.0 2.7 2.4
1400........................................... 1600............................. 0.0 2.2 3.3 3.5 3.3 3.1 2.7 2.4 2.2 2.0
1600........................................... 1800............................. 0.0 1.2 2.3 2.6 2.5 2.4 2.1 1.9 1.7 1.6
1800........................................... 2000............................. 0.0 0.7 2.2 2.6 2.6 2.5 2.2 2.0 1.8 1.7
2000........................................... 2200............................. 0.0 0.0 1.6 2.1 2.2 2.1 1.9 1.7 1.6 1.4
2200........................................... 2400............................. 0.0 0.0 1.1 1.6 1.7 1.7 1.6 1.4 1.3 1.2
2400........................................... 2600............................. 0.0 0.0 0.7 1.2 1.4 1.4 1.3 1.2 1.1 1.0
2600........................................... 2800............................. 0.0 0.0 0.4 0.9 1.0 1.1 1.0 0.9 0.9 0.8
2800........................................... 3000............................. 0.0 0.0 0.2 0.6 0.7 0.8 0.7 0.7 0.6 0.6
3000........................................... 3200............................. 0.0 0.0 0.0 0.6 0.8 0.8 0.8 0.8 0.7 0.7
3200........................................... 3400............................. 0.0 0.0 0.0 0.7 1.1 1.2 1.2 1.1 1.1 1.0
3400........................................... 3600............................. 0.0 0.0 0.0 0.7 1.3 1.6 1.6 1.5 1.5 1.4
3600........................................... 3800............................. 0.0 0.0 0.0 0.9 2.2 2.7 2.8 2.7 2.6 2.5
3800........................................... 4000............................. 0.0 0.0 0.0 0.5 2.0 2.6 2.8 2.8 2.7 2.6
4000........................................... 4200............................. 0.0 0.0 0.0 0.0 2.1 3.0 3.2 3.3 3.2 3.1
4200........................................... 4400............................. 0.0 0.0 0.0 0.0 1.4 2.2 2.5 2.6 2.6 2.5
4400........................................... 4600............................. 0.0 0.0 0.0 0.0 1.0 2.0 2.3 2.5 2.5 2.4
4600........................................... 4800............................. 0.0 0.0 0.0 0.0 0.6 1.5 1.8 2.0 2.0 2.0
4800........................................... 5000............................. 0.0 0.0 0.0 0.0 0.2 1.0 1.4 1.5 1.6 1.5
5000........................................... 5200............................. 0.0 0.0 0.0 0.0 0.0 0.8 1.1 1.3 1.3 1.3
5200........................................... 5400............................. 0.0 0.0 0.0 0.0 0.0 0.8 1.2 1.5 1.6 1.6
5400........................................... 5600............................. 0.0 0.0 0.0 0.0 0.0 0.9 1.7 2.1 2.2 2.3
5600........................................... 5800............................. 0.0 0.0 0.0 0.0 0.0 0.6 1.6 2.2 2.4 2.5
5800........................................... 6000............................. 0.0 0.0 0.0 0.0 0.0 0.2 1.8 2.4 2.8 2.9
6000........................................... 6200............................. 0.0 0.0 0.0 0.0 0.0 0.0 1.7 2.6 3.1 3.3
6200........................................... 6400............................. 0.0 0.0 0.0 0.0 0.0 0.0 1.4 2.4 2.9 3.1
6400........................................... 6600............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.9 1.8 2.2 2.5
6600........................................... 6800............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.5 1.2 1.6 1.9
6800........................................... 7000............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.8 1.1 1.3
7000........................................... 7200............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.7 0.8
7200........................................... 7400............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.5 0.7
7400........................................... 7600............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.5 0.6
7600........................................... 7800............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.5 0.7
7800........................................... 8000............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.6 0.8
8000........................................... 8200............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.8
8200........................................... 8400............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 1.0
8400........................................... 8600............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 1.3
8600........................................... 8800............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 1.1
8800........................................... 9000............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.8
9000........................................... 9200............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5
9200........................................... 9400............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2
9400........................................... 9600............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1
9600........................................... 9800............................. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1
9800........................................... 10000............................ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

(c) Overnight Temperature Drop. For airplanes on which FRM is
installed, the overnight temperature drop for this appendix is
defined using:
(1) A temperature at the beginning of the overnight period that
equals the landing temperature of the previous flight that is a
random value based on a Gaussian distribution; and
(2) An overnight temperature drop that is a random value based
on a Gaussian distribution.
(3) For any flight that will end with an overnight ground period
(one flight per day out of an average of number of flights per day,
depending on utilization of the particular airplane model being
evaluated), the landing outside air temperature (OAT) is

[[Page 70957]]

to be chosen as a random value from the following Gaussian curve:

Table 3.--Landing Outside Air Temperature
------------------------------------------------------------------------
Landing outside
Parameter air temperature
[deg]F
------------------------------------------------------------------------
Mean Temperature.................................... 58.68
negative 1 std dev.................................. 20.55
positive 1 std dev.................................. 13.21
------------------------------------------------------------------------

(4) The outside ambient air temperature (OAT) overnight
temperature drop is to be chosen as a random value from the
following Gaussian curve:

Table 4.--Outside Air Temperature (OAT) Drop
------------------------------------------------------------------------
OAT drop
Parameter temperature [deg]F
------------------------------------------------------------------------
Mean Temp........................................... 12.0
1 std dev........................................... 6.0
------------------------------------------------------------------------

(d) Number of Simulated Flights Required in Analysis. In order
for the Monte Carlo analysis to be valid for showing compliance with
the fleet average and warm day flammability exposure requirements,
the applicant must run the analysis for a minimum number of flights
to ensure that the fleet average and warm day flammability exposure
for the fuel tank under evaluation meets the applicable flammability
limits defined in Table 5.

Table 5.--Flammability Exposure Limit
------------------------------------------------------------------------
Maximum acceptable Maximum acceptable
Monte Carlo Monte Carlo
average fuel tank average fuel tank
Minimum number of flights in flammability flammability
Monte Carlo analysis exposure (%) to exposure (%) to
meet 3% meet 7%
requirements requirements
------------------------------------------------------------------------
10,000.......................... 2.91 6.79
100,000......................... 2.98 6.96
1,000,000....................... 3.00 7.00
------------------------------------------------------------------------

PART 91--GENERAL OPERATING AND FLIGHT RULES

8. The authority citation for part 91 continues to read as follows:

Authority: 49 U.S.C. 1155, 40103, 40113, 40120, 44101, 44111,
44701, 44709, 44711, 44715, 44716, 11417, 44722, 46306, 36315,
46316, 46504, 46506-46507, 47122, 47508, 47528-47531, articles 12
and 20 of the Convention on International Civil Aviation (61 stat. 1180).

9. Amend Sec. 91.1 by adding a new paragraph (d) to read as follows:

Sec. 91.1 Applicability.

* * * * *
(d) This part also establishes requirements for operators to take
actions to support the continued airworthiness of each airplane.
10. Amend part 91 by adding a new subpart L to read as follows:
Subpart L--Continued Airworthiness and Safety Improvements
Sec.
91.1501 Purpose and definition.
91.1503-91.1507 [Reserved]
91.1509 Flammability reduction means.

Subpart L--Continued Airworthiness and Safety Improvements

Sec. 91.1501 Purpose and definition.

(a) This subpart establishes requirements for operators to take
actions necessary to support the continued airworthiness of each
airplane. Such actions may include, but are not limited to, revising
the inspection program, incorporating design changes, and incorporating
revisions to Instructions for Continued Airworthiness (ICA).
(b) For purposes of this subpart, the ``FAA Oversight Office'' is
the aircraft certification office or office of the Transport Airplane
Directorate with oversight responsibility for the relevant type
certificate or supplemental type certificate, as determined by the
Administrator.

Sec. Sec. 91.1503-91.1507 [Reserved]

Sec. 91.1509 Flammability reduction means.

(a) Applicability. This section applies to persons operating
transport category, turbine-powered airplanes for which development of
an ignition mitigation means (IMM), flammability reduction means (FRM),
or Flammability Impact Mitigation Means (FIMM) is required under
Sec. Sec. 25.1815, 25.1817, or 25.1819 of this chapter.
(b) New Production Airplanes. Except in accordance with Sec.
91.213 of this part, no person may operate an airplane on which IMM or
FRM has been installed by the type certificate holder or licensee under
14 CFR 25.1821 unless the IMM or FRM is operational.
(c) Auxiliary Fuel Tanks. After the applicable date stated in
paragraphs (e)(1) and (e)(2), no person may operate any airplane
subject to this section that has an Auxiliary fuel tank installed
pursuant to a field approval, unless the following requirements are met:
(1) The person complies with 14 CFR 25.1817 by the applicable date
stated in that section.
(2) The person installs IMM, FRM, or FIMM, as applicable, that is
approved by the FAA Oversight Office.
(3) Except in accordance with Sec. 91.213 of this part, the IMM,
FRM, or FIMM, as applicable, are operational.
(d) Retrofit. After the dates specified in paragraph (e) of this
section, no person may operate an airplane to which this section
applies unless the requirements of paragraphs (d)(1) and (d)(2) of this
section are met.
(1) IMM, FRM, and FIMM, if required by Sec. Sec. 25.1815, 25.1817,
or 25.1819 of this chapter, that are approved by the FAA Oversight
Office, are installed in at least the percentage of the operator's
fleet of each airplane model indicated in the applicable column of
Table 1 of this section.
(2) Except in accordance with Sec. 91.213 of this part, the IMM,
FRM, and FIMM, as applicable, are operational.
(e) Compliance Times. The installations required by paragraph (d)
of this section must be accomplished no later than the applicable dates
specified in paragraph (e)(1) or (e)(2) of this section.
(1) The applicable dates specified in Table 1.

[[Page 70958]]

Table 1
----------------------------------------------------------------------------------------------------------------
Compliance date for 50%
Model of fleet Compliance date for 100% of fleet
----------------------------------------------------------------------------------------------------------------
Boeing
----------------------------------------------------------------------------------------------------------------
747 Series........................... December 31, 2009...... December 31, 2012.
737 Series........................... March 31, 2010......... March 31, 2013.
777 Series........................... March 31, 2010......... March 31, 2013.
767 Series........................... September 30, 2010..... September 30, 2013.
757 Series........................... March 31, 2011......... March 31, 2014.
707/720 Series....................... December 31, 2011...... December 31, 2014.
--------------------------------------
Airbus
----------------------------------------------------------------------------------------------------------------
A319, A320, A321 Series.............. December 31, 2010...... December 31, 2013.
A300, A310 Series.................... June 30, 2011.......... June 30, 2014.
A330, A340 Series.................... December 31, 2011...... December 31, 2014.
All other affected models............ Within 4 years after Within 7 years after the effective date of this
the effective date of amendment.
this amendment.
----------------------------------------------------------------------------------------------------------------

(2) For those persons that have only one airplane of a model
identified in Table 1, the compliance date is that stated for 100% of
Fleet in Table 1 of this section.
(f) Early Compliance. Notwithstanding paragraphs (c) and (d) of
this section, no person may operate an airplane on which IMM, FRM or
FIMM has been installed unless the IMM, FRM or FIMM is operational,
except in accordance with Sec. 91.213 of this part.
(g) Inspection Program Revisions. No person may operate an airplane
to which this section applies after the date specified in paragraph
(g)(1) or (g)(2) of this section, as applicable, unless the inspection
program for that airplane is revised to include applicable
airworthiness limitations that are approved by the FAA Oversight Office
under Sec. Sec. 25.1815, 25.1817 or 25.1819 of this chapter.
(1) For any airplane that must be modified in accordance with
paragraph (d) of this section, the date of return to service after
those modifications are accomplished.
(2) For any airplane that is not required to be modified in
accordance with paragraph (d) of this section, the date one year after
the date of approval of the airworthiness limitations by the FAA
Oversight Office.
(h) After the inspection program is revised as required by
paragraph (g) of this section, before returning an airplane to service
after any alteration for which airworthiness limitations are required
by Sec. Sec. 25.1817, or 25.1819 of this chapter, the person must
revise the inspection program for the airplane to include those
airworthiness limitations.
(i) The inspection program changes identified in paragraphs (g) and
(h) of this section must be submitted to the operator's Principal
Inspector or the Flight Standards District Office (FSDO) responsible
for review and approval prior to incorporation.

Sec. 91.410 [Redesignated as Sec. 91.1505]

11. Redesignate Sec. 91.410 as new Sec. 91.1505.

Sec. 91.410 [Added and Reserved]

12. A new Sec. 91.410 is added and reserved.

PART 121--OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL
OPERATIONS

13. The authority citation for part 121 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 40119, 41706, 44101, 44701-
44702, 44705, 44709-44711, 44713, 44716-44717, 44722, 44901, 44903-
44904, 44012, 46105, 46105, 46301.

14. Amend Sec. 121.1 by adding a new paragraph (g) to read as follows:

Sec. 121.1 Applicability.

* * * * *
(g) This part also establishes requirements for operators to take
actions to support the continued airworthiness of each airplane.
15. Amend part 121 by adding a new Subpart AA to read as follows:
Subpart AA--Continued Airworthiness and Safety Improvements
Sec.
121.1101 Purpose and definition.
121.1103-121.1115 [Reserved]
121.1117 Flammability reduction means.

Subpart AA--Continued Airworthiness and Safety Improvements

Sec. 121.1101 Purpose and definition.

(a) This subpart requires persons holding an air carrier or
operating certificate under part 119 of this chapter to support the
continued airworthiness of each airplane. These requirements may
include, but are not limited to, revising the maintenance program,
incorporating design changes, and incorporating revisions to
Instructions for Continued Airworthiness.
(b) For purposes of this subpart, the ``FAA Oversight Office'' is
the aircraft certification office or office of the Transport Airplane
Directorate with oversight responsibility for the relevant type
certificate or supplemental type certificate, as determined by the
Administrator.

Sec. 121.1103-121.1115 [Reserved]

Sec. 121.1117 Flammability reduction means.

[[Page 70959]]

is approved by the FAA Oversight Office.
(3) Except in accordance with Sec. 121.628 of this part, the IMM,
FRM or FIMM, as applicable, are operational.
(d) Retrofit. After the dates specified in paragraph (e) of this
section, no certificate holder may operate an airplane to which this
section applies unless the requirements of paragraphs (d)(1) and (d)(2)
of this section are met.
(1) IMM, FRM or FIMM, if required by Sec. Sec. 25.1815, 25.1817,
or 25.1819 of this chapter, that are approved by the FAA Oversight
Office, are installed in at least the percentage of the operator's
fleet of each airplane model indicated in the applicable column of
Table 1 of this section.
(2) Except in accordance with Sec. 121.628 of this part, the IMM,
FRM or FIMM, as applicable, are operational.
(e) Compliance Times. The installations required by paragraph (d)
of this section must be accomplished no later than the applicable dates
specified in paragraph (e)(1) or (e)(2) of this section.
(1) The applicable dates specified in Table 1.

(2) For those certificate holders that have only one airplane of a
model identified in Table 1, the compliance date is that stated for 100
percent of Fleet in Table 1 of this section.
(f) Early Compliance. Notwithstanding paragraphs (c) and (d) of
this section, no person may operate an airplane on which IMM or FRM has
been installed unless the IMM or FRM is operational, except in
accordance with Sec. 121.628 of this part.
(g) Maintenance Program Revisions. No certificate holder may
operate an airplane to which this section applies after the date
specified in paragraph (g)(1) or (g)(2) of this section, as applicable,
unless the maintenance program for that airplane is revised to include
applicable airworthiness limitations that are approved by the FAA
Oversight Office under Sec. Sec. 25.1815, 25.1817 or 25.1819 of this
chapter.
(1) For any airplane that must be modified in accordance with
paragraph (d) of this section, the date of return to service after
those modifications are accomplished.
(2) For any airplane that is not required to be modified in
accordance with paragraph (d) of this section, the date one year after
the date approval of the airworthiness limitations by the FAA Oversight
Office.
(h) After the maintenance program is revised as required by
paragraph (g) of this section, before returning an airplane to service
after any alteration for which airworthiness limitations are required
by Sec. Sec. 25.1817, or 25.1819 of this chapter, the certificate
holder must revise the maintenance program for the airplane to include
those airworthiness limitations.
(i) The maintenance program changes identified in paragraphs (g)
and (h) of this section must be submitted to the operator's Principal
Inspector responsible for review and approval prior to incorporation

Sec. 121.368 [Redesignated as Sec. 121.1105]

16. Redesignate 121.368 as new Sec. 121.1105.

Sec. 121.368 [Added and Reserved]

17. A new Sec. 121.368 is added and reserved.

Sec. 121.370 [Redesignated as Sec. 121.1107]

18. Redesignate Sec. 121.370 as new Sec. 121.1107.

Sec. 121.370 [Added and Reserved]

19. A new Sec. 121.370 is added and reserved.

Sec. 121.370a [Redesignated as Sec. 121.1109]

20-21. Redesignate Sec. 121.370a as new Sec. 121.1109.

Sec. 121.370a [Added and Reserved]

PART 125--CERTIFICATION AND OPERATIONS; AIRPLANES HAVING A SEATING
CAPCITY OF 20 OR MORE PASSENGERS OR A MAXIMUM PAYLOAD CAPACITY OF
6,000 POUNDS OR MORE; AND RULES GOVERNING PERSONS ON BOARD SUCH AIRCRAFT

22. The authority citation for part 125 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44705, 44710-
44711, 44713, 44716-44717, 44722

23. Amend Sec. 125.1 by adding a new paragraph (e) to read as follows:

Sec. 125.1 Applicability.

* * * * *
(e) This part also establishes requirements for operators to take
actions to support the continued airworthiness of each airplane.
24. Amend part 125 by adding a new subpart M to read as follows:
Subpart M--Continued Airworthiness and Safety Improvements
Sec.
125.501 Purpose and definition.
125.503-125.507 [Reserved]
125.509 Flammability reduction means.

[[Page 70960]]

Subpart M--Continued Airworthiness and Safety Improvements

Sec. 125.501 Purpose and definition.

(a) This subpart establishes requirements for operators to take
actions necessary to report the continued airworthiness of each
airplane. Such actions may include, but are not limited to, revising
the inspection program, incorporating design changes, and incorporating
revisions to Instructions for Continued Airworthiness.
(b) For purposes of this subpart, the ``FAA Oversight Office'' is
the aircraft certification office or office of the Transport Airplane
Directorate with oversight responsibility for the relevant type
certification or supplemental type certificate, as determined by the
Administrator.

Sec. Sec. 125.503-125.507 [Reserved]

Sec. 125.509 Flammability reduction means.

(a) Applicability. This section applies to certificate holders
operating transport category, turbine-powered airplanes for which
development of an ignition mitigation means (IMM), flammability
reduction means (FRM), or Flammability Impact Mitigation Means (FIMM)
is required under Sec. Sec. 25.1815, 25.1817, or 25.1819 of this chapter.
(b) New Production Airplanes. Except in accordance with Sec.
125.201 of this part, no person may operate an airplane on which IMM or
FRM has been installed by the type certificate holder or licensee under
14 CFR 25.1821 unless the IMM or FRM is operational.
(c) Auxiliary Fuel Tanks. After the applicable date stated in
paragraphs (e)(1) and (e)(2) of this section, no certificate holder may
operate any airplane subject to this section that has an Auxiliary Fuel
Tank installed pursuant to a field approval, unless the following
requirements are met--
(1) The certificate holder complies with 14 CFR 25.1817 by the
applicable date stated in that section.
(2) The certificate holder installs IMM, FRM or FIMM, as
applicable, that is approved by the FAA Oversight Office.
(3) Except in accordance with Sec. 125.201 of this part, the IMM,
FRM or FIMM, as applicable, are operational.
(d) Retrofit. After the dates specified in paragraph (e) of this
section, no certificate holder may operate an airplane to which this
section applies unless the requirements of paragraphs (d)(1) and (d)(2)
of this section are met.
(1) IMM, FRM or FIMM, if required by Sec. Sec. 25.1815, 25.1817,
or 25.1819 of this chapter, that are approved by the FAA Oversight
Office, are installed in at least the percentage of the operator's
fleet of each airplane model indicated in the applicable column of
Table 1 of this section.
(2) Except in accordance with Sec. 125.201 of this part, the IMM,
FRM or FIMM, as applicable, are operational.
(e) Compliance Times. The installations required by paragraph (d)
of this section must be accomplished no later than the applicable dates
specified in paragraph (e)(1) or (e)(2) of this section.
(1) The applicable dates specified in Table 1.

(2) For those certificate holders that have only one airplane of a
model identified in Table 1, the compliance date is that stated for 100
percent of Fleet in Table 1 of this section.
(f) Early Compliance. Notwithstanding paragraphs (c) and (d) of
this section, no person may operate an airplane on which IMM or FRM has
been installed unless the IMM or FRM is operational, except in
accordance with Sec. 125.201 of this part.
(g) Maintenance Program Revisions. No certificate holder may
operate an airplane to which this section applies after the date
specified in paragraph (g)(1) or (g)(2) of this section, as applicable,
unless the maintenance program for that airplane is revised to include
applicable airworthiness limitations that are approved by the FAA
Oversight Office under Sec. Sec. 25.1815, 25.1817 or 25.1819 of this
chapter.
(1) For any airplane that must be modified in accordance with
paragraph (d) of this section, the date of return to service after
those modifications are accomplished.
(2) For any airplane that is not required to be modified in
accordance with paragraph (d) of this section, the date one year after
the date approval of the airworthiness limitations by the FAA Oversight
Office.
(h) After the maintenance program is revised as required by
paragraph (g) of this section, before returning an airplane to service
after any alteration for which airworthiness limitations are required
by Sec. Sec. 25.1817, or 25.1819 of this chapter, the certificate
holder must revise the maintenance program for the airplane to include
those airworthiness limitations.
(i) The maintenance program changes identified in paragraphs (g)
and (h) of this section must be submitted to the operator's Principal
Inspector responsible for review and approval prior to incorporation.

Sec. 125.248 [Redesignated as Sec. 125.505]

25. Redesignate Sec. 125.248 as new Sec. 125.505.

[[Page 70961]]

Sec. 125.248 [Added and Reserved]

26. A new Sec. 125.248 is added and reserved.

PART 129--OPERATIONS: FOREIGN AIR CARRIERS AND FOREIGN OPERATORS OF
U.S.-REGISTERED AIRCRAFT ENGAGED IN COMMON CARRIAGE

27. The authority citation for part 129 continues to read as follows:

Authority: 49 U.S.C. 1372, 49113, 440119, 44101, 44701-44702,
447-5, 44709-44711, 44713, 44716-44717, 44722, 44901-44904, 44906,
44912, 44105, 107-71 sec. 104.

28. Amend Sec. 129.1 by revising paragraph (b), and adding a new
paragraph (d) to read as follows:

Sec. 129.1 Applicability and definition.

* * * * *
(b) Operations of U.S.-registered aircraft solely outside the
United States. In addition to the operations specified under paragraph
(a) of this section, Sec. Sec. 129.14 and 129.20 and subpart B of this
part also apply to U.S.-registered aircraft operated solely outside the
United States in common carriage by a foreign person or foreign air
carrier.
* * * * *
(d) This part also establishes requirements for an operator to take
actions to support the continued airworthiness of each airplane.
29. Amend part 129 by adding subpart A and designating Sec. 129.1
through Sec. 129.15 and Sec. 129.17 through Sec. 129.29 into subpart
A to read as follows:
Subpart A--General
Sec.
129.1 Applicability and definitions.
129.11 Operations specifications.
129.13 Airworthiness and registration certificates.
129.14 Maintenance program and minimum equipment list requirements
for U.S. registered aircraft.
129.15 Flight crewmember certificates.
129.17 Radio equipment.
129.18 Collision avoidance system.
129.19 Air traffic rules and procedures.
129.20 Digital flight data recorders.
129.21 Control of traffic.
129.23 Transport category cargo service airplanes: Increased zero
fuel and landing weights.
129.25 Airplane security.
129.28 Flightdeck security.
129.29 Smoking prohibitions.

30. Amend part 129 by adding subpart B to read as follows:
Subpart B--Continued Airworthiness and Safety Improvements
Sec.
129.101 Purpose and definition.
129.103-129.115 [Reserved]
129.117 Flammability reduction means.

Subpart B--Continued Airworthiness and Safety Improvements

Sec. 129.101 Purpose and definition.

(a) This subpart requires a foreign person or foreign air carrier
operating a U.S.-registered airplane in common carriage to support the
continued airworthiness of each airplane. These requirements may
include, but are not limited to, revising the maintenance program,
incorporating design changes, and incorporating revisions to
Instructions for Continued Airworthiness.
(b) For purposes of this subpart, the ``FAA Oversight Office'' is
the aircraft certification office or office of the Transport Airplane
Directorate with oversight responsibility for the relevant type
certificate or supplemental type certificate, as determined by the
Administrator.

Sec. Sec. 129.103-129.115 [Reserved]

Sec. 129.117 Flammability reduction means.

(a) Applicability. This section applies to foreign persons and
foreign air carriers operating transport category, turbine-powered
airplanes for which development of an ignition mitigation means (IMM),
flammability reduction means (FRM), or Flammability Impact Mitigation
Means (FIMM) is required under Sec. Sec. 25.1815, 25.1817, or 25.1819
of this chapter.
(b) New Production Airplanes. Except in accordance with Sec.
129.14 of this part, no foreign person or foreign air carrier may
operate an airplane on which IMM or FRM has been installed by the type
certificate holder or licensee under 14 CFR 25.1821 unless the IMM or
FRM is operational.
(c) Auxiliary Fuel Tanks. After the applicable date stated in
paragraphs (e)(1) and (e)(2), no foreign person or foreign air carrier
may operate any airplane subject to this section that has an Auxiliary
Fuel Tank installed pursuant to a field approval, unless the following
requirements are met:
(1) The foreign person or foreign air carrier complies with 14 CFR
25.1817 by the applicable date stated in that section.
(2) The foreign person or foreign air carrier installs IMM, FRM or
FIMM, as applicable, that are approved by the FAA Oversight Office.
(3) Except in accordance with Sec. 129.14 of this part, the IMM,
FRM or FIMM, as applicable, are operational.
(d) Retrofit. After the dates specified in paragraph (e) of this
section, no foreign person or foreign air carrier may operate an
airplane to which this section applies unless the requirements of
paragraphs (d)(1) and (d)(2) of this section are met.
(1) IMM, FRM or FIMM, if required by Sec. Sec. 25.1815, 25.1817,
or 25.1819 of this chapter, that are approved by the FAA Oversight
Office, are installed in at least the percentage of the operator's
fleet of each airplane model indicated in the applicable column of
Table 1 of this section.
(2) Except in accordance with Sec. 129.14 of this part, the IMM,
FRM or FIMM, as applicable, are operational.
(e) Compliance Times. The installations required by paragraph (d)
of this section must be accomplished no later than the applicable dates
specified in paragraph (e)(1) or (e)(2) of this section.
(1) The applicable dates specified in Table 1.

[[Page 70962]]

A300, A310 Series.................... June 30, 2011.......... June 30, 2014.
A330, A340 Series.................... December 31, 2011...... December 31, 2014.
All other affected models............ Within 4 years after Within 7 years after the effective date of this
the effective date of amendment.
this amendment.
----------------------------------------------------------------------------------------------------------------

(2) For those foreign persons or foreign air carriers that have
only one airplane of a model identified in Table 1, the compliance date
is that stated for 100 percent of Fleet in Table 1 of this section.
(f) Early Compliance. Notwithstanding paragraphs (c) and (d) of
this section, no person may operate an airplane on which IMM or FRM has
been installed unless the IMM or FRM is operational, except in
accordance with Sec. 129.14 of this part.
(g) Maintenance Program Revisions. No foreign person or foreign air
carrier may operate an airplane to which this section applies after the
date specified in paragraph (g)(1) or (g)(2) of this section, as
applicable, unless the maintenance program for that airplane is revised
to include applicable airworthiness limitations that are approved by
the FAA Oversight Office under Sec. Sec. 25.1815, 25.1817 or 25.1819
of this chapter.
(1) For any airplane that must be modified in accordance with
paragraph (d) of this section, the date of return to service after
those modifications are accomplished.
(2) For any airplane that is not required to be modified in
accordance with paragraph (d) of this section, the date one year after
the date approval of the airworthiness limitations by the FAA Oversight
Office.
(h) After the maintenance program is revised as required by
paragraph (g) of this section, before returning an airplane to service
after any alteration for which airworthiness limitations are required
by Sec. Sec. 25.1817, or 25.1819 of this chapter, the foreign person
or foreign air carrier must revise the maintenance program for the
airplane to include those airworthiness limitations.
(i) The maintenance program changes identified in paragraphs (g)
and (h) of this section must be submitted to the operator's Principal
Inspector for review and approval prior to incorporation.

Sec. 129.16 [Redesignated as Sec. 129.109]

31. Redesignate Sec. 129.16 as new Sec. 129.109.

Sec. 129.16 [Added and Reserved]

32. A new Sec. 129.16 is added and reserved.

Sec. 129.32 [Redesignated as Sec. 129.107]

33. Redesignate Sec. 129.32 as new Sec. 129.107.

Sec. 129.32 [Added and Reserved]

34. A new Sec. 129.32 is added and reserved.

Sec. 129.33 [Redesignated as Sec. 129.105]

35. Redesignate Sec. 129.33 as new Sec. 129.105.

Sec. 129.33 [Added and Reserved]

36. A new Sec. 129.33 is added and reserved.

Issued in Washington, DC, on November 17, 2005.
Dorenda D. Baker,
Acting Director, Aircraft Certification Service.
[FR Doc. 05-23109 Filed 11-17-05; 4:06 pm]
BILLING CODE 4910-13-P

Notices For
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Reduction of Fuel Tank Flammability in Transport Category Airplanes

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