Special Conditions: Boeing Model 787-8 Airplane; Tire Debris Penetration of Fuel Tank Structure, 32023-32025 [E7-11150]
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Federal Register / Vol. 72, No. 111 / Monday, June 11, 2007 / Proposed Rules
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airplane vertical descent velocities up to
30 ft/sec.
The FAA is proposing this special
condition to maintain the level of safety
envisioned in the existing airworthiness
standards under foreseeable survivable
impact events.
Discussion of Proposed Special
Condition
In order to provide the same level of
safety as exists with conventional
airplane construction, Boeing must
demonstrate that the 787 has sufficient
crashworthiness capabilities under
foreseeable survivable impact events. To
demonstrate this, Boeing would have to
evaluate the impact response
characteristics of the 787 to ensure that
its crashworthiness characteristics are
not significantly different from those of
a similarly sized airplane fabricated
from traditionally used metals. If the
evaluation shows that the 787 impact
response characteristics are significantly
different, Boeing would have to make
design changes to bring the different
impact response characteristics in line
with those of a similarly sized metal
construction airplane, or incorporate
mitigating design features.
Factors in crash survivability are
retention of items of mass, maintenance
of occupant emergency egress paths,
maintenance of acceptable acceleration
and loads experienced by the occupants,
and maintenance of a survivable
volume. In reviewing available data
from accidents, tests simulating crash
conditions, and analytical modeling of a
range of crash conditions, the FAA has
concluded that the airplane
performance should be evaluated over a
range of airplane level vertical impact
velocities up to 30 ft/sec.
If the 787 impact characteristics differ
significantly from those of a previously
certificated wide body transport, this
would result in a need to meet load
factors higher than those defined in 14
CFR 25.561 in order to maintain the
same level of safety for the occupants,
in terms of retention of items of mass.
In the cases of acceleration and loads
experienced by the occupants, means
would have to be incorporated to reduce
load levels experienced by those
occupants to the injury criteria levels of
§ 25.562, or load levels of a previously
certificated comparable airplane, in
order to maintain the same level of
safety for the occupants.
Applicability
As discussed above, these proposed
special conditions are applicable to the
787 airplane. Should Boeing apply at a
later date for a change to the type
certificate to include another model
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Jkt 223001
incorporating the same novel or unusual
design features, these proposed special
conditions would apply to that model as
well under the provisions of § 21.101.
Conclusion
This action affects only certain novel
or unusual design features of the 787
airplane. It is not a rule of general
applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting
and recordkeeping requirements.
The authority citation for these
Special Conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701,
44702, 44704.
The Proposed Special Conditions
Accordingly, the Administrator of the
Federal Aviation Administration (FAA)
proposes the following special
conditions as part of the type
certification basis for the Boeing Model
787–8 airplane.
The Boeing Model 787–8 must
provide an equivalent level of occupant
safety and survivability to that provided
by previously certificated wide-body
transports of similar size under
foreseeable survivable impact events for
the following four criteria. In order to
demonstrate an equivalent level of
occupant safety and survivability, the
applicant must demonstrate that the
Model 787–8 meets the following
criteria for a range of airplane vertical
descent velocities up to 30 ft/sec.
1. Retention of items of mass. The
occupants, i.e., passengers, flight
attendants and flightcrew, must be
protected during the impact event from
release of seats, overhead bins, and
other items of mass due to the impact
loads and resultant structural
deformation of the supporting airframe
and floor structures. The applicant must
show that loads due to the impact event
and resultant structural deformation of
the supporting airframe and floor
structure at the interface of the airplane
structure to seats, overhead bins, and
other items of mass are comparable to
those of previously certificated widebody transports of similar size for the
range of descent velocities stated above.
The attachments of these items need not
be designed for static emergency
landing loads in excess of those defined
in § 25.561 if impact response
characteristics of the Boeing Model 787–
8 yield load factors at the attach points
that are comparable to those for a
previously certificated wide-body
transport category airplane.
2. Maintenance of acceptable
acceleration and loads experienced by
the occupants. The applicant must show
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Fmt 4702
Sfmt 4702
32023
that the impact response characteristics
of the 787, specifically the vertical
acceleration levels experienced at the
seat/floor interface and loads
experienced by the occupants during
the impact events, are consistent with
those found in § 25.562(b) or with levels
expected for a previously certificated
wide-body transport category airplane
for the conditions stated above.
3. Maintenance of a survivable
volume. For the conditions stated above,
the applicant must show that all areas
of the airplane occupied for takeoff and
landing provide a survivable volume
comparable to that of previously
certificated wide-body transports of
similar size during and after the impact
event. This means that structural
deformation will not result in
infringement of the occupants’ normal
living space so that passenger
survivability will not be significantly
affected.
4. Maintenance of occupant
emergency egress paths. The evacuation
of occupants must be comparable to that
from a previously certificated widebody transport of similar size. To show
this, the applicant must show that the
suitability of the egress paths, as
determined following the vertical
impact events, is comparable to the
suitability of the egress paths of a
comparable, certificated wide-body
transport, as determined following the
same vertical impact events.
Issued in Renton, Washington, on May 31,
2007.
Ali Bahrami,
Manager, Transport Airplane Directorate,
Aircraft Certification Service.
[FR Doc. E7–11153 Filed 6–8–07; 8:45 am]
BILLING CODE 4910–13–P
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM367 Special Conditions No.
25–07–04–SC]
Special Conditions: Boeing Model 787–
8 Airplane; Tire Debris Penetration of
Fuel Tank Structure
Federal Aviation
Administration (FAA), DOT.
ACTION: Notice of proposed special
conditions.
AGENCY:
SUMMARY: This notice proposes special
conditions for the Boeing Model 787–8
airplane. This airplane will have novel
or unusual design features when
compared to the state of technology
envisioned in the airworthiness
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Federal Register / Vol. 72, No. 111 / Monday, June 11, 2007 / Proposed Rules
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standards for transport category
airplanes. These design features include
wing fuel tanks constructed of carbon
fiber composite materials. These
proposed special conditions contain the
additional safety standards that the
Administrator considers necessary to
establish a level of safety equivalent to
that established by the existing
airworthiness standards. Additional
special conditions will be issued for
other novel or unusual design features
of the Boeing Model 787–8 airplanes.
DATES: Comments must be received on
or before July 26, 2007.
ADDRESSES: Comments on this proposal
may be mailed in duplicate to: Federal
Aviation Administration, Transport
Airplane Directorate, Attention: Rules
Docket (ANM–113), Docket No. NM367,
1601 Lind Avenue, SW., Renton,
Washington 98057–3356; or delivered in
duplicate to the Transport Airplane
Directorate at the above address. All
comments must be marked Docket No.
NM367. Comments may be inspected in
the Rules Docket weekdays, except
Federal holidays, between 7:30 a.m. and
4 p.m.
FOR FURTHER INFORMATION CONTACT:
Mike Dostert, FAA, Propulsion/
Mechanical Systems, ANM–112,
Transport Airplane Directorate, Aircraft
Certification Service, 1601 Lind
Avenue, SW., Renton, Washington
98057–3356; telephone (425) 227–2132;
facsimile (425) 227–1320.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites interested persons to
participate in this rulemaking by
submitting written comments, data, or
views. The most helpful comments
reference a specific portion of the
special conditions, 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
these proposed special conditions. 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 notice
between 7:30 a.m. and 4 p.m., Monday
through Friday, except Federal holidays.
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 the proposed special
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12:18 Mar 07, 2011
Jkt 223001
conditions based on 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 back to you.
Background
On March 28, 2003, Boeing applied
for an FAA type certificate for its new
Boeing Model 787–8 passenger airplane.
The Boeing Model 787–8 airplane will
be an all-new, two-engine jet transport
airplane with a two-aisle cabin. The
maximum takeoff weight will be
476,000 pounds, with a maximum
passenger count of 381 passengers.
Type Certification Basis
Under provisions of 14 CFR 21.17,
Boeing must show that Boeing Model
787–8 airplanes (hereafter referred to as
‘‘the 787’’) meet the applicable
provisions of 14 CFR part 25, as
amended by Amendments 25–1 through
25–117, except §§ 25.809(a) and 25.812,
which will remain at Amendment 25–
115. If the Administrator finds that the
applicable airworthiness regulations do
not contain adequate or appropriate
safety standards for the 787 because of
a novel or unusual design feature,
special conditions are prescribed under
provisions of 14 CFR 21.16.
In addition to the applicable
airworthiness regulations and special
conditions, the 787 must comply with
the fuel vent and exhaust emission
requirements of 14 CFR part 34 and the
noise certification requirements of part
36. In addition, the FAA must issue a
finding of regulatory adequacy pursuant
to section 611 of Public Law 92–574, the
‘‘Noise Control Act of 1972.’’
Special conditions, as defined in
§ 11.19, are issued in accordance with
§ 11.38 and become part of the type
certification basis in accordance with
§ 21.17(a)(2).
Special conditions are initially
applicable to the model for which they
are issued. Should the type certificate
for that model be amended later to
include any other model that
incorporates the same or similar novel
or unusual design feature, the special
conditions would also apply to the other
model under the provisions of § 21.101.
Novel or Unusual Design Features
The 787 will incorporate a number of
novel or unusual design features.
Because of rapid improvements in
airplane technology, the applicable
airworthiness regulations do not contain
adequate or appropriate safety standards
PO 00000
Frm 00007
Fmt 4702
Sfmt 4702
for these design features. These
proposed special conditions for the 787
contain the additional safety standards
that the Administrator considers
necessary to establish a level of safety
equivalent to that established by the
existing airworthiness standards.
The 787 will use carbon fiber
composite materials for most of the
wing fuel tank structure. The ability of
aluminum wing skins, as has been
conventionally used, to resist
penetration or rupture when impacted
by tire debris is understood from
extensive experience. The ability of
carbon fiber composite material
construction to resist these hazards has
not been established, and thus there are
no current airworthiness standards
specifically addressing this hazard for
all the exposed wing surfaces.
The FAA is proposing these special
conditions to maintain the level of
safety envisioned in the existing
airworthiness standards by proposing a
standard for resistance to potential tire
debris impacts to the 787 contiguous
wing surfaces.
Discussion
Historically, accidents have resulted
from uncontrolled fires caused by fuel
leaks following penetration or rupture of
the lower wing by fragments of tires or
from uncontained engine failure.
In one incident, in Honolulu, Hawaii,
a tire on a Boeing Model 747 burst and
tire debris penetrated a fuel tank access
cover, causing a substantial fuel leak.
Takeoff was aborted and passengers
were evacuated down the emergency
chutes into pools of fuel which
fortunately had not ignited.
This accident highlighted deficiencies
in the then-existing title 14 CFR part 25
regulations pertaining to fuel retention
following impact to fuel tanks by tire
fragments. After a subsequent Boeing
Model 737 accident in Manchester,
England, in which a fuel tank access
panel was penetrated by engine debris,
the FAA amended § 25.963 to require
that fuel tank access panels be resistant
to both tire and engine debris. An
amendment to title 14 CFR part 121
required operators to modify their
existing fleets of airplanes with impact
resistant access panels. The amendment
only addressed fuel tank access covers
since service experience at the time
indicated that the lower wing skin of a
conventional, subsonic airplane
provided adequate, inherent capability
to resist tire and engine debris threats.
Section 25.963(e) requires showing by
analysis or tests that fuel tank access
covers, ‘‘* * * minimize penetration
and deformation by tire fragments, low
energy engine debris, or other likely
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Federal Register / Vol. 72, No. 111 / Monday, June 11, 2007 / Proposed Rules
debris.’’ Advisory Circular (AC) 25.963–
1 defines the region of the wing that is
vulnerable to impact damage from these
sources and provides a method to
substantiate that the rule has been met
for tire fragments. No specific
requirements were established for the
contiguous wing areas into which the
access covers are installed because of
the inherent ability of conventional
aluminum wing skins to resist
penetration by tire debris. AC 25.963–1
specifically notes, ‘‘The access covers,
however, need not be more impact
resistant than the contiguous tank
structure,’’ highlighting the assumption
that wing basic structures meet some
higher standard.
However, in another event in 2000, on
the Concorde airplane, an unanticipated
failure mode occurred when tire debris
impacted the fuel tank. The skin on the
unique delta wing design of this
supersonic airplane is made of titanium,
with a thickness much less than that of
the skin on a conventional subsonic
airplane. The initial impact of the tire
debris did not penetrate the fuel tank,
but a pressure wave caused by the tire
impact caused the fuel tank to rupture.
Regulatory authorities subsequently
required modifications to Concorde
airplanes to add a means to retain fuel
if the primary fuel retention means was
damaged.
In order to maintain the level of safety
envisioned by 14 CFR 25.963(e), these
special conditions propose a standard
for resistance to potential tire debris
impacts to the contiguous wing surfaces
and require consideration of possible
secondary effects of a tire impact, such
as the induced pressure wave that was
a factor in the Concorde accident. It
takes into account that new construction
methods and materials will not
necessarily yield debris resistance that
has historically been shown as
adequate. The proposed standard is
based on the defined tire impact areas
and tire fragment characteristics
described in AC 25.963–1.
In addition, despite practical design
considerations, some exceptional debris
larger than that defined in paragraph (b)
may cause a fuel leak within the defined
area, so paragraph (c) of these proposed
special conditions also takes into
consideration possible leakage paths.
Fuel tank surfaces of typical transport
airplanes have thick aluminum
construction in the tire debris impact
areas that is tolerant to tire debris larger
than that defined in paragraph (b) of
these special conditions. Consideration
of leaks caused by larger tire fragments
is needed to ensure that an adequate
level of safety is provided.
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12:18 Mar 07, 2011
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Note: While § 25.963 includes
consideration of uncontained engine debris,
the effects of engine debris are not included
in these special conditions because this
hazard will be addressed on the 787 under
the existing requirements of § 25.903(d).
Section 25.903(d) requires minimizing the
hazards from uncontained engine debris.
Applicability
As discussed above, these proposed
special conditions are applicable to the
787. Should Boeing apply at a later date
for a change to the type certificate to
include another model incorporating the
same novel or unusual design features,
these proposed special conditions
would apply to that model as well
under the provisions of § 21.101.
Conclusion
This action affects only certain novel
or unusual design features of the 787. It
is not a rule of general applicability, and
it affects only the applicant that applied
to the FAA for approval of these features
on the airplane.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting
and recordkeeping requirements.
The authority citation for these
Special Conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701,
44702, 44704.
The Proposed Special Conditions
Accordingly, the Administrator of the
Federal Aviation Administration (FAA)
proposes the following special
conditions as part of the type
certification basis for the Boeing Model
787–8 airplane.
Debris Impacts to Fuel Tanks
(a) Impacts by tire debris to any fuel
tank or fuel system component located
within 30 degrees to either side of wheel
rotational planes may not result in
penetration or otherwise induce fuel
tank deformation, rupture (for example,
through propagation of pressure waves),
or cracking sufficient to allow a
hazardous fuel leak. A hazardous fuel
leak results if debris impact to a fuel
tank surface causes—
1. a running leak,
2. a dripping leak, or
3. a leak that, 15 minutes after wiping
dry, results in a wetted airplane surface
exceeding 6 inches.
The leak must be evaluated under
maximum fuel head pressure.
(b) Compliance with paragraph (a)
must be shown by analysis or tests
assuming all of the following.
1. The tire debris fragment size is 1
percent of the tire mass.
2. The tire debris fragment is
propelled at a tangential speed that
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Fmt 4702
Sfmt 4702
32025
could be attained by a tire tread at the
airplane flight manual airplane
rotational speed (VR at maximum gross
weight).
3. The tire debris fragment load is
distributed over an area on the fuel tank
surface equal to 11⁄2 percent of the total
tire tread area.
(c) Fuel leaks caused by impact from
tire debris larger than that specified in
paragraph (b), from any portion of a fuel
tank located within the tire debris
impact area, may not result in
hazardous quantities of fuel entering
any of the following areas of the
airplane.
1. Engine inlet,
2. APU inlet, or
3. Cabin air inlet.
This must be shown by test or
analysis, or a combination of both, for
each approved engine forward thrust
condition and each approved reverse
thrust condition.
Issued in Renton, Washington, on May 31,
2007.
Ali Bahrami,
Manager, Transport Airplane Directorate,
Aircraft Certification Service.
[FR Doc. E7–11150 Filed 6–8–07; 8:45 am]
BILLING CODE 4910–13–P
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA–2007–28372; Directorate
Identifier 2007–NM–080–AD]
RIN 2120–AA64
Airworthiness Directives; Airbus Model
A300F4–605R and A300F4–622R
Airplanes
Federal Aviation
Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking
(NPRM).
AGENCY:
SUMMARY: We propose to adopt a new
airworthiness directive (AD) for the
products listed above. This proposed
AD results from mandatory continuing
airworthiness information (MCAI)
originated by an aviation authority of
another country to identify and correct
an unsafe condition on an aviation
product. The MCAI describes the unsafe
condition as:
Further to cases of parking brake loss at the
gate, a pressure switch system had been
introduced on some A300–600 aircraft. The
aim of this modification was to recover
pedals braking authority if parking brake is
not efficient, without having to set the
parking brake handle to OFF.
E:\ERIC\11JNP1.SGM
11JNP1
]]>Agencies
[Federal Register Volume 72, Number 111 (Monday, June 11, 2007)]
[Proposed Rules]
[Pages 32023-32025]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E7-11150]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM367 Special Conditions No. 25-07-04-SC]
Special Conditions: Boeing Model 787-8 Airplane; Tire Debris
Penetration of Fuel Tank Structure
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
-----------------------------------------------------------------------
SUMMARY: This notice proposes special conditions for the Boeing Model
787-8 airplane. This airplane will have novel or unusual design
features when compared to the state of technology envisioned in the
airworthiness
[[Page 32024]]
standards for transport category airplanes. These design features
include wing fuel tanks constructed of carbon fiber composite
materials. These proposed special conditions contain the additional
safety standards that the Administrator considers necessary to
establish a level of safety equivalent to that established by the
existing airworthiness standards. Additional special conditions will be
issued for other novel or unusual design features of the Boeing Model
787-8 airplanes.
DATES: Comments must be received on or before July 26, 2007.
ADDRESSES: Comments on this proposal may be mailed in duplicate to:
Federal Aviation Administration, Transport Airplane Directorate,
Attention: Rules Docket (ANM-113), Docket No. NM367, 1601 Lind Avenue,
SW., Renton, Washington 98057-3356; or delivered in duplicate to the
Transport Airplane Directorate at the above address. All comments must
be marked Docket No. NM367. Comments may be inspected in the Rules
Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.
FOR FURTHER INFORMATION CONTACT: Mike Dostert, FAA, Propulsion/
Mechanical Systems, ANM-112, Transport Airplane Directorate, Aircraft
Certification Service, 1601 Lind Avenue, SW., Renton, Washington 98057-
3356; telephone (425) 227-2132; facsimile (425) 227-1320.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites interested persons to participate in this
rulemaking by submitting written comments, data, or views. The most
helpful comments reference a specific portion of the special
conditions, 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 these proposed special conditions. 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 notice between 7:30 a.m. and 4 p.m., Monday through
Friday, except Federal holidays.
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 the
proposed special conditions based on 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 back to you.
Background
On March 28, 2003, Boeing applied for an FAA type certificate for
its new Boeing Model 787-8 passenger airplane. The Boeing Model 787-8
airplane will be an all-new, two-engine jet transport airplane with a
two-aisle cabin. The maximum takeoff weight will be 476,000 pounds,
with a maximum passenger count of 381 passengers.
Type Certification Basis
Under provisions of 14 CFR 21.17, Boeing must show that Boeing
Model 787-8 airplanes (hereafter referred to as ``the 787'') meet the
applicable provisions of 14 CFR part 25, as amended by Amendments 25-1
through 25-117, except Sec. Sec. 25.809(a) and 25.812, which will
remain at Amendment 25-115. If the Administrator finds that the
applicable airworthiness regulations do not contain adequate or
appropriate safety standards for the 787 because of a novel or unusual
design feature, special conditions are prescribed under provisions of
14 CFR 21.16.
In addition to the applicable airworthiness regulations and special
conditions, the 787 must comply with the fuel vent and exhaust emission
requirements of 14 CFR part 34 and the noise certification requirements
of part 36. In addition, the FAA must issue a finding of regulatory
adequacy pursuant to section 611 of Public Law 92-574, the ``Noise
Control Act of 1972.''
Special conditions, as defined in Sec. 11.19, are issued in
accordance with Sec. 11.38 and become part of the type certification
basis in accordance with Sec. 21.17(a)(2).
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same or similar
novel or unusual design feature, the special conditions would also
apply to the other model under the provisions of Sec. 21.101.
Novel or Unusual Design Features
The 787 will incorporate a number of novel or unusual design
features. Because of rapid improvements in airplane technology, the
applicable airworthiness regulations do not contain adequate or
appropriate safety standards for these design features. These proposed
special conditions for the 787 contain the additional safety standards
that the Administrator considers necessary to establish a level of
safety equivalent to that established by the existing airworthiness
standards.
The 787 will use carbon fiber composite materials for most of the
wing fuel tank structure. The ability of aluminum wing skins, as has
been conventionally used, to resist penetration or rupture when
impacted by tire debris is understood from extensive experience. The
ability of carbon fiber composite material construction to resist these
hazards has not been established, and thus there are no current
airworthiness standards specifically addressing this hazard for all the
exposed wing surfaces.
The FAA is proposing these special conditions to maintain the level
of safety envisioned in the existing airworthiness standards by
proposing a standard for resistance to potential tire debris impacts to
the 787 contiguous wing surfaces.
Discussion
Historically, accidents have resulted from uncontrolled fires
caused by fuel leaks following penetration or rupture of the lower wing
by fragments of tires or from uncontained engine failure.
In one incident, in Honolulu, Hawaii, a tire on a Boeing Model 747
burst and tire debris penetrated a fuel tank access cover, causing a
substantial fuel leak. Takeoff was aborted and passengers were
evacuated down the emergency chutes into pools of fuel which
fortunately had not ignited.
This accident highlighted deficiencies in the then-existing title
14 CFR part 25 regulations pertaining to fuel retention following
impact to fuel tanks by tire fragments. After a subsequent Boeing Model
737 accident in Manchester, England, in which a fuel tank access panel
was penetrated by engine debris, the FAA amended Sec. 25.963 to
require that fuel tank access panels be resistant to both tire and
engine debris. An amendment to title 14 CFR part 121 required operators
to modify their existing fleets of airplanes with impact resistant
access panels. The amendment only addressed fuel tank access covers
since service experience at the time indicated that the lower wing skin
of a conventional, subsonic airplane provided adequate, inherent
capability to resist tire and engine debris threats. Section 25.963(e)
requires showing by analysis or tests that fuel tank access covers, ``*
* * minimize penetration and deformation by tire fragments, low energy
engine debris, or other likely
[[Page 32025]]
debris.'' Advisory Circular (AC) 25.963-1 defines the region of the
wing that is vulnerable to impact damage from these sources and
provides a method to substantiate that the rule has been met for tire
fragments. No specific requirements were established for the contiguous
wing areas into which the access covers are installed because of the
inherent ability of conventional aluminum wing skins to resist
penetration by tire debris. AC 25.963-1 specifically notes, ``The
access covers, however, need not be more impact resistant than the
contiguous tank structure,'' highlighting the assumption that wing
basic structures meet some higher standard.
However, in another event in 2000, on the Concorde airplane, an
unanticipated failure mode occurred when tire debris impacted the fuel
tank. The skin on the unique delta wing design of this supersonic
airplane is made of titanium, with a thickness much less than that of
the skin on a conventional subsonic airplane. The initial impact of the
tire debris did not penetrate the fuel tank, but a pressure wave caused
by the tire impact caused the fuel tank to rupture. Regulatory
authorities subsequently required modifications to Concorde airplanes
to add a means to retain fuel if the primary fuel retention means was
damaged.
In order to maintain the level of safety envisioned by 14 CFR
25.963(e), these special conditions propose a standard for resistance
to potential tire debris impacts to the contiguous wing surfaces and
require consideration of possible secondary effects of a tire impact,
such as the induced pressure wave that was a factor in the Concorde
accident. It takes into account that new construction methods and
materials will not necessarily yield debris resistance that has
historically been shown as adequate. The proposed standard is based on
the defined tire impact areas and tire fragment characteristics
described in AC 25.963-1.
In addition, despite practical design considerations, some
exceptional debris larger than that defined in paragraph (b) may cause
a fuel leak within the defined area, so paragraph (c) of these proposed
special conditions also takes into consideration possible leakage
paths. Fuel tank surfaces of typical transport airplanes have thick
aluminum construction in the tire debris impact areas that is tolerant
to tire debris larger than that defined in paragraph (b) of these
special conditions. Consideration of leaks caused by larger tire
fragments is needed to ensure that an adequate level of safety is
provided.
Note: While Sec. 25.963 includes consideration of uncontained
engine debris, the effects of engine debris are not included in
these special conditions because this hazard will be addressed on
the 787 under the existing requirements of Sec. 25.903(d). Section
25.903(d) requires minimizing the hazards from uncontained engine
debris.
Applicability
As discussed above, these proposed special conditions are
applicable to the 787. Should Boeing apply at a later date for a change
to the type certificate to include another model incorporating the same
novel or unusual design features, these proposed special conditions
would apply to that model as well under the provisions of Sec. 21.101.
Conclusion
This action affects only certain novel or unusual design features
of the 787. It is not a rule of general applicability, and it affects
only the applicant that applied to the FAA for approval of these
features on the airplane.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The authority citation for these Special Conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.
The Proposed Special Conditions
Accordingly, the Administrator of the Federal Aviation
Administration (FAA) proposes the following special conditions as part
of the type certification basis for the Boeing Model 787-8 airplane.
Debris Impacts to Fuel Tanks
(a) Impacts by tire debris to any fuel tank or fuel system
component located within 30 degrees to either side of wheel rotational
planes may not result in penetration or otherwise induce fuel tank
deformation, rupture (for example, through propagation of pressure
waves), or cracking sufficient to allow a hazardous fuel leak. A
hazardous fuel leak results if debris impact to a fuel tank surface
causes--
1. a running leak,
2. a dripping leak, or
3. a leak that, 15 minutes after wiping dry, results in a wetted
airplane surface exceeding 6 inches.
The leak must be evaluated under maximum fuel head pressure.
(b) Compliance with paragraph (a) must be shown by analysis or
tests assuming all of the following.
1. The tire debris fragment size is 1 percent of the tire mass.
2. The tire debris fragment is propelled at a tangential speed that
could be attained by a tire tread at the airplane flight manual
airplane rotational speed (VR at maximum gross weight).
3. The tire debris fragment load is distributed over an area on the
fuel tank surface equal to 1\1/2\ percent of the total tire tread area.
(c) Fuel leaks caused by impact from tire debris larger than that
specified in paragraph (b), from any portion of a fuel tank located
within the tire debris impact area, may not result in hazardous
quantities of fuel entering any of the following areas of the airplane.
1. Engine inlet,
2. APU inlet, or
3. Cabin air inlet.
This must be shown by test or analysis, or a combination of both,
for each approved engine forward thrust condition and each approved
reverse thrust condition.
Issued in Renton, Washington, on May 31, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E7-11150 Filed 6-8-07; 8:45 am]
BILLING CODE 4910-13-P
