[Federal Register: September 26, 2007 (Volume 72, Number 186)]
[Rules and Regulations]
[Page 54531-54533]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr26se07-5]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM368 Special Conditions No. 25-362-SC]
Special Conditions: Boeing Model 787-8 Airplane; Crashworthiness
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: The FAA issues these 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 standards for transport category airplanes. These novel
or unusual design features are associated with carbon fiber reinforced
plastic used in the construction of the fuselage. For these design
features, the applicable airworthiness regulations do not contain
adequate or appropriate safety standards for impact response
characteristics to ensure survivable crashworthiness. These 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 standards. We will issue
additional special conditions for other novel or unusual design
features of the Boeing Model 787-8 airplanes.
DATES: Effective Date: October 26, 2007.
FOR FURTHER INFORMATION CONTACT: Ian Won, FAA, Airframe/Cabin Safety,
ANM-115, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue, SW., Renton, Washington 98057-3356;
telephone (425) 227-2145; facsimile (425) 227-1320.
SUPPLEMENTARY INFORMATION:
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 Title 14 Code of Federal Regulations (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 14 CFR part 36. The FAA must also issue a finding of regulatory
adequacy under section 611 of Public Law 92-574, the ``Noise Control
Act of 1972.''
The FAA issues special conditions, as defined in 14 CFR 11.19,
under Sec. 11.38, and they become part of the type certification basis
under 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 Sec. 21.101.
Novel or Unusual Design Features
The 787 airplane will incorporate several 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 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 fuselage will be fabricated with carbon fiber reinforced
plastic (CFRP) semi-monocoque construction, consisting of skins with
co-cured longitudinal stringers and mechanically fastened
circumferential frames. This is a novel and unusual design feature for
a large transport category airplane certificated under 14 CFR part 25.
Structure fabricated from CFRP may behave differently than metallic
structure because of differences in material ductility, stiffness,
failure modes, and energy absorption characteristics. Therefore, Boeing
must evaluate impact response characteristics of the 787 to ensure that
its survivable crashworthiness characteristics provide approximately
the same level of safety as those of a similarly sized airplane
fabricated from traditionally used metallic materials.
The FAA and industry have been working together for many years to
understand how to improve transport airplane occupant safety for what
are considered survivable accidents. This work has involved examining
airplane accidents, conducting tests to simulate crash conditions, and
performing analytical modeling of a range of crash conditions, all with
the purpose of providing further insight into factors that can
influence occupant safety. Results of this continuing effort have
enabled specific changes to regulatory standards and design practices
to improve occupant safety. This evolution is reflected in changes to
the part 25 Emergency Landing Conditions regulations. For example,
airplane emergency load factors in Sec. 25.561, General, have been
increased. We have added passenger seat dynamic load conditions in
Sec. 25.562, Emergency Landing Dynamic Conditions.
The seat dynamic conditions were added to the regulations based on
FAA and industry tests and a review of accidents. These seat dynamic
conditions reflect the environment for passengers and the airframe
during a crash event. They are based on data gathered from accidents of
previously certificated airplanes given conditions that were
survivable. Tests of previously certificated airplanes showed that
performance of the airframe was acceptable in a survivable crash event.
We continually update our requirements as such new information becomes
available. In the context of this evolution of the regulations, there
is at present no specific dynamic regulatory requirement for airplane-
level crashworthiness. However, the FAA reviews the design of each new
airplane model to determine if it incorporates novel or unusual design
features that may have a significant influence on the crash dynamics of
the airframe. The Administrator prescribes special conditions for the
airplane model if the applicable airworthiness regulations do not
contain adequate or appropriate safety standards because of the novel
or unusual design feature.
Because of the novel design features of the 787, Boeing must
conduct an assessment to ensure that the 787 will not have dynamic
characteristics that differ significantly from those found in
previously certificated designs. The nature of this design assessment
is largely dependent on the similarities and differences between the
new type design and previously certificated airplanes. Such an
assessment ensures that the level of safety of the new type
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design is commensurate with that implicitly assumed in the existing
regulations, and achieved by airplane designs previously certificated.
If significant trends in industry warrant change to the existing
regulations, the FAA may use its rulemaking process in collaboration
with industry to develop an appropriate dynamic regulatory requirement
for airplane level crashworthiness.
The FAA and industry have collected a significant amount of
experimental data as well as data from crashes of transport category
airplanes that shows a high occupant survival rate at vertical descent
velocities up to 30 ft/sec. Most of this data was collected on narrow-
body (single aisle) transport category airplanes. Based on this
information, the FAA finds it appropriate and necessary for an
assessment of the 787 to span a range of airplane vertical descent
speeds up to 30 ft/sec.
The FAA is imposing these special conditions to maintain the level
of safety envisioned in the existing airworthiness standards under
foreseeable survivable impact events.
Discussion of Final Special Conditions
To provide the same level of safety as exists with conventional
airplane construction, Boeing must show that the 787 has sufficient
crashworthiness capabilities under foreseeable survivable impact
events. To show this, Boeing will 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 built from traditionally used metals. If the
evaluation shows that the 787 impact response characteristics are
significantly different, Boeing will 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. The FAA has reviewed available data
from accidents, tests simulating crash conditions, and analytical
modeling of a range of crash conditions. From this information we have
concluded that airplane performance should be evaluated over a range of
airplane level vertical impact speeds up to 30 ft/sec.
If the 787 impact characteristics differ significantly from those
of a previously certificated wide body transport, this will result in a
need to meet load factors higher than those defined in 14 CFR 25.561.
The higher load factors will be necessary in order to maintain the same
level of safety for the occupants, in terms of retention of items of
mass. In the case 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 Sec.
25.562, or load levels of a previously certificated comparable
airplane, in order to maintain the same level of safety for the
occupants.
Discussion of Comments
Notice of Proposed Special Conditions No. 25-07-05-SC for the 787
was published in the Federal Register on June 11, 2007 (72 FR 32021).
Several comments were received from two commenters.
First Commenter: The commenter, a member of the public, provided
suggestions and comments related to the subject of crash simulation
structural analysis as it pertains to the applicant's demonstration of
compliance to these special conditions. This commenter agreed with the
intent of the special conditions. However, he suggested that they be
expanded or new special conditions developed to require a full fuselage
fuel fed fire test to address possible fire, smoke, and toxicity (FST)
hazards that may be associated with use of carbon fiber epoxy structure
on the 787.
The commenter recommended that the special conditions include a
requirement for a full scale drop test with a forward velocity vector
to simulate a condition representative of a wheels-up landing, with the
resultant vector sum of the vertical and longitudinal velocity
components being included to assess the loads on the passengers and
crew.
FAA Response: We agree that fuselage post-crash fire survivability
of the 787, including FST hazards that may be associated with use of
carbon fiber epoxy structure, is an important issue. This issue is
outside the scope of these special conditions, however. It is being
addressed in conjunction with the requirements for Sec. 25.856(b)
relating to fuselage fire penetration protection.
The FAA considered longitudinal loading conditions as well as
combined longitudinal and vertical loading conditions of the 787
airframe under survivable crash conditions and emergency landing
conditions with various landing gear configurations (wheels up
configurations). The factors (principally deformation, mass, and
friction) that govern impact response characteristics in the
longitudinal direction are not significantly altered with the change
from metallic to composite fuselage structure. Given the similarity of
the 787 to the current fleet with respect to these conditions, the FAA
has determined that these special conditions will be limited to an
assessment of the 787 for the vertical impact direction.
With respect to the commenter's suggestions on the specific method
of compliance, the FAA does not mandate a specific method of compliance
for the requirements specified. The applicant is responsible for
demonstrating compliance with these special conditions.
Second Commenter: This commenter, also a member of the public,
suggested that the FAA conduct the crash impact testing necessary to
show that the 787 meets these special conditions. He suggested that
requirements for demonstrating compliance with the crashworthiness
special conditions should consist of a drop test of a fuselage section
of the 787 from a height of 14 feet onto concrete with an impact
velocity of approximately 30 feet per second. The commenter suggested
that the criteria of these special conditions should be that the 787
demonstrate the same level of vertical impact shock-absorption
capability as demonstrated by an FAA-sponsored drop test of a Boeing
737 fuselage section conducted in 2000. This commenter also suggested
that the special conditions be expanded to address post-crash fire
survivability of the 787 in the post-impact damaged state. He provided
suggestions and comments related to means of compliance to these
special conditions, and also some comments on issues outside the scope
of these special conditions.
FAA Response: The Administrator prescribes special conditions
necessary to establish a level of safety equivalent to that established
by the existing airworthiness standards. The requirements of these
special conditions were prescribed to ensure that the 787 provides an
equivalent level of occupant safety and survivability under foreseeable
survivable impact events to that provided by previously certificated
wide-body transports of similar size.
These special conditions do not mandate a specific method of
compliance for the requirements specified. The applicant is responsible
for demonstrating compliance with these special conditions. The FAA's
role is to verify that the special conditions have been complied with,
rather than to develop a method for compliance. While there are merits
in conducting a
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full-scale test, there are other approaches using tests and analysis
that can actually yield more data than would a single test. Thus, we
consider it more effective to establish the standards and encourage the
applicant to develop the most effective method of compliance.
The FAA agrees that fuselage post-crash fire survivability of the
787, including FST hazards that may be associated with use of carbon
fiber epoxy structure, is an important issue. This issue is outside the
scope of these special conditions, however. It is being addressed in
conjunction with the requirements for Sec. 25.856(b) relating to
fuselage fire penetration protection.
These special conditions are adopted as proposed.
Applicability
As discussed above, these 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 on the same type certificate
incorporating the same novel or unusual design features, these special
conditions would apply to that model as well.
Conclusion
This action affects only certain novel or unusual design features
of the 787. 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 Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued 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 wide-body 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 Sec. 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 that the impact response
characteristics of the Boeing Model 787-8, 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 Sec. 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
wide-body 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 September 14, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E7-18942 Filed 9-25-07; 8:45 am]
BILLING CODE 4910-13-P