787, novel design features

[Federal Register: August 15, 2007 (Volume 72, Number 157)]
[Rules and Regulations]
[Page 45626-45628]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr15au07-3]

-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM373; Special Conditions No. 25-360-SC]


Special Conditions: Boeing Model 787-8 Airplane; Composite
Fuselage In-Flight Fire/Flammability Resistance

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

-----------------------------------------------------------------------

SUMMARY: These special conditions are issued 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. The fuselage of the Boeing
Model 787-8 series airplane will be made of composite materials rather
than conventional aluminum. While the regulations include flame
propagation standards for some materials commonly found in inaccessible
areas of the airplane, they do not yet incorporate standards for
materials used to construct the fuselage. Therefore, special conditions
are needed to address this design feature. 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. Additional special conditions
will be issued for other novel or unusual design features of the Boeing
Model 787-8 airplanes.

[[Page 45627]]


DATES: Effective Date: September 14, 2007.

FOR FURTHER INFORMATION CONTACT: Jeff Gardlin, FAA, Airframe/Cabin
Safety, ANM-115, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue, SW., Renton, Washington 98057-3356;
telephone (425) 227-2136; 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 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 part 36. The FAA must also issue a finding of regulatory adequacy
pursuant to section 611 of Public Law 92-574, the ``Noise Control Act
of 1972.''
The FAA issues special conditions, as defined in Sec. 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

In-flight fires have originated in inaccessible areas of aircraft
where thermal/acoustic insulation located adjacent to the aluminum
aircraft skin has been the path for flame propagation and fire growth.
Although these insulation materials were required to comply with the
basic ``Bunsen burner'' requirements of 14 CFR 25.853(a) and 25.855(d),
these incidents revealed unexpected flame spread along the insulation
film covering material of the thermal/acoustic insulation. In all
cases, the ignition source was relatively modest and, in most cases,
was electrical in origin (for example an electrical short circuit,
arcing caused by chafed wiring, or a ruptured ballast case).
In September 2003, in an effort to limit use of materials that
sustain or propagate a fire in inaccessible areas, the FAA promulgated
14 CFR 25.856(a), which requires that thermal/acoustic insulation
material installed in the fuselage meet newly developed flame
propagation test requirements. That rule was Amendment 25-111. These
requirements were developed to address a realistic fire threat. We
consider that threat generally applicable to the 787.
Conventional aluminum fuselage material does not contribute to in-
flight fire propagation. As a result, there are no standards that
address in-flight fire safety of the fuselage structure itself. The 787
will make extensive use of composite materials in the fabrication of
the majority of the
Wing,
Fuselage skin,
Stringers,
Spars, and
Most other structural elements of all major sub-assemblies
of the airplane.
As a result of this extensive use of a new construction material,
the fuselage cannot be assumed to have the fire resistance previously
afforded by aluminum during the in-flight fire scenario mentioned
above. These special conditions require that the 787 provide the same
level of in-flight survivability as a conventional aluminum fuselage
airplane. This includes its thermal/acoustic insulation meeting the
requirements of Sec. 25.856(a). Resistance to flame propagation must
be shown, and all products of combustion that may result must be
evaluated for toxicity and found acceptable.

Discussion of Comments

Notice of Proposed Special Conditions No. 25-07-09-SC for the 787
was published in the Federal Register on April 26, 2007 (72 FR 20774).
Two commenters, the Air Line Pilots Association (ALPA) and an
individual member of the public, responded to the notice. Both
commenters concur with the proposed special conditions but have
additional concerns about composite structures that they feel should be
addressed.
Comment 1. A member of the public commented that a post-crash, fuel
fed fire is a significant hazard that is not addressed in these special
conditions. This commenter cites research conducted on behalf of the
Australian Government that documents potential fire hazards associated
with composite materials--in particular toxicity and smoke. The
commenter noted that the fire penetration resistance of a composite
material alone is not sufficient to determine its overall contribution
to fire safety.
FAA Response: We agree with the commenter that consideration of
post-crash fire safety must include all the factors that influence
survivability, and not just focus on one characteristic. These special
conditions focus on in-flight fire safety, so any issues related to
post-crash fire safety go beyond the scope of these special conditions.
Nonetheless, the FAA is equally concerned with post-crash survivability
and is addressing this issue through separate criteria. In this case,
because there are requirements related to post-crash fire safety in
Sec. 25.856(b), the approach will be via an equivalent level of safety
finding in accordance with Sec. 21.21(b)(1). A summary of this finding
will be available in the FAA Regulatory and Guidance Library at http://rgl.faa.gov/
.

Comment 2. ALPA commented that the effects of moisture ingress must
be addressed for all aspects of composite material integrity.
FAA Response: From the standpoint of flammability, moisture ingress
is not an issue, because moisture will tend to reduce the flammability
of the material. Since these special conditions only concern
flammability resulting from an in-flight fire, the remainder of the
issues go beyond the scope of these special conditions. Moisture is
known to influence properties of composite materials and this concern
is a well documented environmental condition that Boeing will have to
address. In fact, the use of composite materials in aviation is not new
and there is a significant amount of experience with the behavior of
composites over time in service. Advisory Circular 20-107A, Composite
Aircraft Structure, also discusses factors that need to be addressed
when using composite structure.
Comment 3. ALPA also commented that aluminum structure can
dissipate heat using the airflow over the skin, but this may not be the
case for a composite structure because of its different thermal

[[Page 45628]]

conductivity. ALPA believes that this difference must be taken into
account with any in-flight fire safety assessment.
FAA Response: We agree that the heat transfer characteristics of
aluminum influence its response to an in-flight fire, and that a
composite structure will doubtless behave differently. The goal of
these special conditions is to enable continued safe flight and landing
in the event of an in-flight fire that directly impinges on the
fuselage structure. Since these special conditions require Boeing to
show that the composite structure is resistant to flame propagation
resulting from in-flight fire, all the relevant material properties and
performance characteristics of the composite structure will need to be
addressed. This requirement is not a comparison with aluminum
structure. It is a new requirement for composite structure. Since this
is so, the special conditions as written cover the ALPA concern, and
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

0
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.
0
In addition to the requirements of 14 CFR 25.853(a) governing material
flammability, the following special conditions apply:

The 787-8 composite fuselage structure must be shown to be
resistant to flame propagation under the fire threat used to develop
14 CFR 25.856(a). If products of combustion are observed beyond the
test heat source, they must be evaluated and found acceptable.

Issued in Renton, Washington, on August 6, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E7-16020 Filed 8-14-07; 8:45 am]

BILLING CODE 4910-13-P