### 49429 Federal Register / Vol. 79, No. 162 / Thursday, August 21, 2014 / Rules and Regulations

VD /MD that is consistent with showing compliance to § 25.335(b), without the benefit of the high-speed protection
system.

5. Dispatch of the airplane with the high-speed protection system inoperative is prohibited except under an approved MEL that requires AFM
instructions to indicate reduced maximum operating speeds, as described in special condition (4), above. In addition, the cockpit display of the reduced operating speeds, as well as the overspeed warning for exceeding those speeds, must be equivalent to thatof the normal airplane with the highspeed protection system operative. Also,
it must be shown that no additionalhazards are introduced with the highspeed protection system inoperative.

Issued in Renton, Washington, on July 30,

2014. Jeffrey E. Duven,
Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 2014–19824 Filed 8–20–14; 8:45 am]

**BILLING CODE 4910–13–P**

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Part 25**

**[Docket No. FAA–2013–0908; Special Conditions No. 25–538–SC]** 

**Special Conditions: Airbus Model A350–900 Series Airplane; Airplane**  **Level of Safety Provided by Composite**
**Fuel-Tank Structure: Post-Crash Fire Survivability** 

**AGENCY :**  Federal Aviation Administration (FAA), DOT.

**ACTION :**  Final special conditions.

**SUMMARY :**  These special conditions are
issued for Airbus Model A350–900 series airplanes. These airplanes will have a novel or unusual design feature associated with the post-crash fire survivability of composite fuel tanks. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for 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 airworthiness standards.

**DATES :**  Effective date: September 22,

2014.

**FOR FURTHER INFORMATION CONTACT :**  Doug Bryant, Propulsion and Mechanical Systems, ANM–112, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, Washington 98057–3356; telephone (425) 227–2384; facsimile (425) 227–1320.

**SUPPLEMENTARY INFORMATION :** 
Background

On August 25, 2008, Airbus applied for a type certificate for their new Model A350–900 series airplane. Later, Airbus requested, and the FAA approved, an extension to the application for FAA type certification to November 15, 2009. The Model A350–900 series airplane has a conventional layout with twin wing-mounted Rolls-Royce Trent XWB engines. It features a twin-aisle, 9- abreast, economy-class layout, and accommodates side-by-side placement of LD–3 containers in the cargo compartment. The basic Model A350– 900 series airplane configuration accommodates 315 passengers in a standard two-class arrangement. The design cruise speed is Mach 0.85 with a maximum take-off weight of 602,000
lbs.

The Model A350–900 series airplanewill be the second large, transportcategory airplane certificated with composite wing and fuel-tank structure that may be exposed to the direct effects of post-crash ground, or under-wing, fuel-fed fires. Although the FAA has previously approved fuel tanks made of composite materials located in the horizontal stabilizer of some airplanes, the composite wing structure of the Model A350–900 series airplane will incorporate a new fuel-tank

construction into service.

Advisory Circular (AC) 20–107A, Composite Aircraft Structure, under the topic of flammability, states:

The existing requirements for flammability and fire protection of aircraft structure attempt to minimize the hazard to the occupants in the event ignition of flammable fluids or vapors occurs. The use of composite structure should not decrease this existing level of safety.

Pertinent to the wing structure, postcrash-fire passenger survivability is dependent on the time available for passenger evacuation prior to fuel-tank
breach or structural failure. Structural failure can be a result of degradation in load-carrying capability in the upper or lower wing surface caused by a fuel-fed ground fire. Structural failure can also be a result of over-pressurization caused by ignition of fuel vapors inside the fuel
tank.

The inherent capability of aluminum to resist fire has been considered by the FAA in development of the current regulations. Title 14, Code of Federal Regulations (14 CFR) part 25 Chapter 1, Section 1.1, General Definitions, defines ‘‘fire resistant’’ to mean, with respect to sheet or structural members, the capacity to withstand heat associated
with fire at least as well as aluminum alloy does in dimensions appropriate for the purpose for which those materials
are used.

Note that aluminum alloy is identified as the performance standard for fire resistance, although no thickness or heat
intensities are defined. Based on the performance of aluminum alloy, the
definition of ‘‘fire resistance’’ was later defined, for testing of other materials in AC 20–135, as the capability to
withstand a 2000 ° F flame for five

minutes.

The FAA has historically issued rules with the assumption that the material of construction for wing and fuselage would be aluminum. As a representative case, 14 CFR 25.963 was issued as a result of a large, fuel-fed fire following
the failures of fuel-tank access doors caused by uncontained engine failures. During the subsequent Aviation Rulemaking Advisory Committee (ARAC) harmonization process, the structures group attempted to harmonize § 25.963 regarding theimpact-and-fire resistance of the fueltank access panels. Discussions between the FAA and the European Aviation Safety Agency (EASA), formerly the European Joint Aviation Authorities (JAA), ensued regarding the need for fire resistance of the fuel-tank access panels. The EASA position was that the FAA requirement for the access panels to be fire resistant, when the surrounding wing structure was not required to be fire resistant, was inconsistent, and that the access panels only needed to be as fire resistant as the surrounding tank structure. The FAA position stated that the fuel-tank access-panel fire-resistance requirement should be retained, and that, long-term, a minimum requirement should be created for the wing skin itself. Both authorities recognized that existing aluminum wing structure provided an acceptable level of safety. Further rulemaking has not yet been pursued.

As with previous Airbus airplane designs with under-wing-mounted engines, the wing tanks and center tanks are located in proximity to the passengers and near the engines. Past experience indicates that post-crash survivability is greatly influenced by the size and intensity of any fire that occurs. The ability of aluminum wing surfaces, wetted by fuel on their interior surface, to withstand post-crash fire conditions, has been demonstrated by tests conducted at the FAA William J.


### 49430 Federal Register / Vol. 79, No. 162 / Thursday, August 21, 2014 / Rules and Regulations

1 Hill, R., and Johnson, G.R., ‘‘Investigation of Aircraft Fuel Tank Explosions and Nitrogen Inerting Requirements During Ground Fires,’’ FAA Report DOT/FAA/RD–75–119, October 1975. Available via the FAA Technical Center Web site for Fire Safety

at http://www.fire.tc.faa.gov/. 2 Cherry, R. and Warren, K. ‘‘Fuselage Burnthrough Protection for Increased Postcrash Occupant Survivability: Safety Benefit Analysis Based on Past Accidents, ‘‘FAA Report DOT/FAA/ AR–99/57, September 1999 and R G W Cherry & Associates Limited, ‘‘A Benefit Analysis for Cabin Water Spray Systems and Enhanced Fuselage Burnthrough Protection,’’ FAA Report DOT/FAA/ AR–02/49, April 7, 2003. Hughes Technical Center. 1 Results of these tests have verified adequate dissipation of heat across wetted
aluminum fuel-tank surfaces so that localized hot spots do not occur, thus minimizing the threat of explosion. This inherent capability of aluminum to dissipate heat also allows the wing lower surface to retain its load-carrying characteristics during a fuel-fed ground fire, and significantly delay wing collapse or burn-through for a time interval that usually exceeds evacuation times. In addition, as an aluminum fuel tank is heated with significant quantities of fuel inside, fuel vapor accumulates in the ullage space, exceeding the upper flammability limit relatively quickly and thus reducing the threat of a fuel-tank explosion prior to fuel-tank burn-through. Service history of conventional aluminum airplanes has shown that fuel-tank explosions caused by ground fires have been rare on airplanes configured with flame
arrestors in the fuel-tank vent lines. Fuel tanks constructed with composite materials may or may not have equivalent capability.

Due to the inherent properties provided by aluminum skin and structure, current regulations may not be adequate as they were developed, and have evolved under the assumption that wing construction would be of aluminum materials. Inherent properties of aluminum, with respect to fuel tanks and fuel-fed fires, are as follows:

• Aluminum is highly thermally conductive and readily transmits the
heat of a fuel-fed external fire to fuel in the tank. This has the benefit of rapidly driving the fuel-tank ullage to exceed the upper flammability limit prior to burn-through of the fuel-tank skin, or heating of the wing upper surface above the auto-ignition temperature, thus greatly reducing the threat of fuel-tank explosion.

• Aluminum panels at thicknesses previously used in wing lower surfaces of large, transport-category airplanes
have been fire resistant as defined in 14
CFR 1.1 and AC 20–135.

• Heat capacity of aluminum and fuel prevents burn-through or wing collapse for a time interval that generally exceeds the passenger evacuation time.

Type Certification Basis

Under 14 CFR 21.17, Airbus must
show that the Model A350–900 series airplane meets the applicable provisions of 14 CFR part 25, as amended by Amendments 25–1 through 25–129.

If the Administrator finds that the applicable airworthiness regulations (i.e., 14 CFR part 25) do not contain adequate or appropriate safety standards for the Model A350–900 series airplane because of a novel or unusual design feature, special conditions are prescribed under § 21.16.

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 § 21.101.

The FAA issues special conditions, as defined in 14 CFR 11.19, under § 11.38,and they become part of the typecertification basis under § 21.17(a)(2).

In addition to the applicable airworthiness regulations and special conditions, the Model A350–900 series airplane must comply with the fuel-vent and exhaust-emission requirements of14 CFR part 34, and the noisecertification requirements of 14 CFR part 36. The FAA must issue a finding of regulatory adequacy under section 611 of Public Law 92–574, the ‘‘Noise
Control Act of 1972.’’

Novel or Unusual Design Features

The Airbus Model A350–900 series airplane will incorporate the following novel or unusual design feature: Composite fuel tanks.

Discussion

The extensive use of composite materials in the design of the A350–900 airplane wing and fuel-tank structure is considered a major change from
conventional and traditional methods of construction, as this will be only the second large, transport-category airplane design to be certificated with this level of composite material for these purposes. The applicable airworthiness regulations do not contain specific standards for post-crash fire-safety performance of wing and fuel-tank skin

or structure.

To provide the same level of safety as exists with conventional airplane construction, Airbus must demonstrate that the Model A350–900 series airplane has sufficient post-crash survivability to enable occupants to safely evacuate in the event that the wings are exposed to a large, fuel-fed fire. Factors in fuel-tank survivability are the structural integrity of the wing and tank; flammability of the tank; burn-through resistance of thewing skin; and the presence of autoignition threats during exposure to a fire. The FAA assessed post-crash survival time during the adoption ofAmendment 25–111 for fuselage burnthrough protection. Studies conducted by, and on behalf of, the FAA indicated that, following a survivable accident, prevention of fuselage burn-through for approximately 5 minutes can significantly enhance survivability. 2

There is little benefit in requiring thedesign to prevent wing-skin burnthrough beyond five minutes, due to the
effects of the fuel fire itself on the rest of the airplane. That assessment was carried out based on accidents involving airplanes with conventional fuel tanks, and considering the ability of ground personnel to rescue occupants. In addition, AC 20–135 indicates that, when aluminum is used for fuel tanks,
the tank should withstand the effects of
fire for 5 minutes without failure. Therefore, to be consistent with existing capability and related requirements, the Model A350–900 series airplane fuel tanks must be capable of resisting a post-crash fire for at least 5 minutes. In demonstrating compliance, Airbus must address a range of fuel loads from minimum to maximum, as well as any
other critical fuel load.

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
airworthiness standards.

Discussion of Comments

Notice of Proposed Special
Conditions No. 25–13–24–SC for Airbus Model A350–900 series airplanes was published in the Federal Register on January 8, 2014 (79 FR 1334). No comments were received, and the special conditions are adopted as proposed.

Applicability

As discussed above, these special conditions apply to Airbus Model A350–900 series airplanes. Should Airbus apply later for a change to the type certificate to include another model incorporating the same novel or unusual design feature, the special conditions would apply to that model as well under the provisions of § 21.101.


### 49431 Federal Register / Vol. 79, No. 162 / Thursday, August 21, 2014 / Rules and Regulations

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 and 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 Airbus Model A350–900 series airplanes.

In addition to complying with 14 CFRpart 25 regulations governing the firesafety performance of the fuel tanks, wings, and nacelle, the Airbus Model A350–900 series airplane must demonstrate acceptable post-crash survivability in the event the wings are exposed to a large fuel-fed ground fire. Airbus must demonstrate that the wing and fuel-tank design can endure an external fuel-fed pool fire for at least
five minutes. This must be
demonstrated for minimum fuel loads (not less than reserve fuel levels) and maximum fuel loads (maximum-range fuel quantities), and other identified
critical fuel loads. Considerations mustinclude fuel-tank flammability, burnthrough resistance, wing structuralstrength retention properties, and autoignition threats during a ground-fire event for the required time duration.

Issued in Renton, Washington, on August

1, 2014. Jeffrey E. Duven,
Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 2014–19823 Filed 8–20–14; 8:45 am]

**BILLING CODE 4910–13–P**

**DEPARTMENT OF TRANSPORTATION**

**Federal Aviation Administration**

**14 CFR Part 39**

**[Docket No. FAA–2014–0124; Directorate Identifier 2012–NM–197–AD; Amendment**  **39–17944; AD 2014–16–20]**

**RIN 2120–AA64**

**Airworthiness Directives; Airbus Airplanes** 

**AGENCY :**  Federal Aviation Administration (FAA), Department of Transportation (DOT).

**ACTION :**  Final rule.

**SUMMARY :**  We are adopting a new airworthiness directive (AD) for all Airbus Model A300 series airplanes. This AD was prompted by an analysis of the impacts of extended service goal
activities on Airbus Model A300 series airplanes. This AD requires revising the maintenance or inspection program. We are issuing this AD to prevent failure of flight critical systems.

**DATES :**  This AD becomes effective September 25, 2014.

**ADDRESSES :**  You may examine the AD
docket on the Internet at http:// www.regulations.gov/ #!docketDetail;D=FAA-2014-0124; or in person at the Docket Management Facility, U.S. Department of Transportation, Docket Operations, M– 30, West Building Ground Floor, Room W12–140, 1200 New Jersey Avenue SE., Washington, DC.

**FOR FURTHER INFORMATION CONTACT :**  Dan Rodina, Aerospace Engineer, International Branch, ANM–116, Transport Airplane Directorate, FAA, 1601 Lind Avenue SW., Renton, WA 98057–3356; telephone 425–227–2125;
fax 425–227–1149.

**SUPPLEMENTARY INFORMATION :** 

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Airbus Model A300 series airplanes. The NPRM published in the Federal Register on February 28, 2014 (79 FR 11358). The NPRM was prompted by an analysis of the impacts of extended service goal activities on Airbus Model A300 series airplanes. The NPRM proposed to require revising the maintenance program. We are issuing this AD to prevent failure of flight critical systems.

The European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, has issued EASA Airworthiness Directive 2012–0233, dated November 7, 2012 (referred to after this as the Mandatory Continuing Airworthiness Information, or ‘‘the MCAI’’), to correct an unsafe condition
on all Airbus Model A300 series airplanes. The MCAI states:

The results of the Extended Service Goal (ESG) exercise for A300 series aeroplanes (75,000 flight hours (FH) or 48,000 flight cycles (FC), whichever occurs first) identified certain operational tests as Airworthiness Limitation Items (ALI), necessary to ensure the safety objectives for aeroplanes which have accumulated or exceeded 60,000 FH.

These ALI are not fully new, since all nine tasks derive from existing Maintenance Planning Document (MPD) tasks. Consequently, the intervals of those nine tasks can no longer be escalated or retained at an interval higher than that specified in this [EASA] AD for each task. Failure to comply with these tasks within
the established maximum intervals could be detrimental to the safety of the affected aeroplanes.

For the reasons described above, this [EASA] AD requires the implementation of nine specific operational ALI test for aeroplanes which have accumulated or exceeded 60,000 FH.

In addition, Airbus performed an analysis of the impacts of ESG activities on A300 series aeroplanes and, based on the results, this [EASA] AD publishes an operational life of 75,000 FH or 48,000 FC, whichever occurs first, applicable to A300 system installations.

You may examine the MCAI in the
AD docket on the Internet at http:// www.regulations.gov/ #!documentDetail;D=FAA-2014-0124-

0002.

Comments

We gave the public the opportunity to participate in developing this AD. We received no comments on the NPRM (79 FR 11358, February 28, 2014) or on the determination of the cost to the public.

‘‘Contacting the Manufacturer’’ Paragraph in This AD

Since late 2006, we have included a standard paragraph titled ‘‘Airworthy
Product’’ in all MCAI ADs in which the FAA develops an AD based on a foreign authority’s AD.

The MCAI or referenced service
information in an FAA AD often directs the owner/operator to contact the manufacturer for corrective actions, such as a repair. Briefly, the Airworthy Product paragraph allowed owners/ operators to use corrective actions provided by the manufacturer if those actions were FAA-approved. In addition, the paragraph stated that any actions approved by the State of Design Authority (or its delegated agent) are considered to be FAA-approved.

In the NPRM (79 FR 11358, February 28, 2014), we proposed to prevent the use of repairs that were not specifically developed to correct the unsafe condition, by requiring that the repair approval provided by the State of Design Authority or its delegated agent specifically refer to this FAA AD. This change was intended to clarify the method of compliance and to provide operators with better visibility of repairs that are specifically developed and approved to correct the unsafe condition. In addition, we proposed to change the phrase ‘‘its delegated agent’’ to include a design approval holder (DAH) with State of Design Authority design organization approval (DOA), as applicable, to refer to a DAH authorized to approve required repairs for the proposed AD.