2388 Federal Register / Vol. 79, No. 9 / Tuesday, January 14, 2014 / Proposed Rules 

the cargo compartment. The basic 

Model A350–900 series configuration 

will accommodate 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. Airbus proposes the Model A350– 

900 series to be certified for extended 

operations (ETOPS) beyond 180 minutes 

at entry into service for up to a 420- 

minute maximum diversion time. 

Flight envelope protection is the 

subject of several proposed special 

conditions for the A350. Each specific 

type of envelope protection is addressed 

individually, but some requirements are 

common to all limiting systems and are 

therefore put forth as general limiting 

requirements. 

Type Certification Basis 

Under Title 14, Code of Federal 

Regulations (14 CFR) 21.17, Airbus must 

show that the Model A350–900 series 

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 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 proposed 

special conditions would also apply to 

the other model under § 21.101. 

In addition to the applicable 

airworthiness regulations and proposed 

special conditions, the Model A350–900 

series 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 and the FAA must 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 § 11.38, 

and they become part of the typecertification basis under § 21.17(a)(2). 

Novel or Unusual Design Features 

The Airbus Model A350–900 series 

will incorporate the following novel or 

unusual design features: General 

Limiting Requirements for the flight 

envelope protection system. 

Discussion 

This proposed special condition and 

the following ones which pertain to 

flight envelope protection present 

general limiting requirements for all the 

unique flight envelope protection 

features of the basic A350 Electronic 

Flight Control System (EFCS) design. 

Current regulations do not address these 

types of protection features. The general 

limiting requirements are necessary to 

ensure a smooth transition from normal 

flight to the protection mode and 

adequate maneuver capability. The 

general limiting requirements also 

ensure that the structural limits of the 

airplane are not exceeded. Furthermore, 

failure of the protection feature must not 

create hazardous flight conditions. 

Envelope protection parameters include 

angle of attack, normal load factor, bank 

angle, pitch angle, and speed. To 

accomplish these envelope protections, 

one or more significant changes occur in 

the EFCS control laws as the normal 

flight envelope limit is approached or 

exceeded. 

Applicability 

As discussed above, these proposed 

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 proposed 

special conditions would apply to that 

model as well. 

Conclusion 

This action affects only certain novel 

or unusual design features on the Airbus 

Model A350–900 series airplanes. 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 Federal Aviation 

Administration (FAA) proposes the 

following special conditions as part of 

the type certification basis for Airbus 

Model A350–900 series airplanes. 

1. General Limiting Requirements. 

a. Onset characteristics of each 

envelope protection feature must be 

smooth, appropriate to the phase of 

flight and type of maneuver, and not in 

conflict with the ability of the pilot to 

satisfactorily change airplane flight 

path, speed, or attitude as needed. 

b. Limit values of protected flight 

parameters (and if applicable, associated 

warning thresholds) must be compatible 

with the following: 

(1) Airplane structural limits, 

(2) Required safe and controllable 

maneuvering of the airplane, and 

(3) Margins to critical conditions. 

Unsafe flight characteristics/conditions 

must not result if dynamic 

maneuvering, airframe and system 

tolerances (both manufacturing and inservice), and non-steady atmospheric 

conditions, in any appropriate 

combination and phase of flight, can 

produce a limited flight parameter 

beyond the nominal design limit value. 

c. The airplane must be responsive to 

intentional dynamic maneuvering to 

within a suitable range of the parameter 

limit. Dynamic characteristics such as 

damping and overshoot must also be 

appropriate for the flight maneuver and 

limit parameter in question. 

d. When simultaneous envelope 

limiting is engaged, adverse coupling or 

adverse priority must not result. 

2. Failure States 

EFCS failures (including sensor) must 

not result in a condition where a 

parameter is limited to such a reduced 

value that safe and controllable 

maneuvering is no longer available. The 

crew must be alerted by suitable means 

if any change in envelope limiting or 

maneuverability is produced by single 

or multiple failures of the EFCS not 

shown to be extremely improbable. 

Issued in Renton, Washington, on October 

22, 2013. 

Stephen P. Boyd, 

Acting Manager, Transport Airplane 

Directorate, Aircraft Certification Service. 

[FR Doc. 2014–00448 Filed 1–13–14; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA–2013–0907; Notice No. 25– 

13–19–SC] 

Special Conditions: Airbus, Model 

A350–900 series airplane; Tire 

Failure—Debris Penetration or Rupture 

of Fuel Tank Structure 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed special 

conditions. 

SUMMARY: This action proposes special 

conditions for the Airbus Model A350– 

900 series airplane. These airplanes will 

have a novel or unusual design feature 


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Federal Register / Vol. 79, No. 9 / Tuesday, January 14, 2014 / Proposed Rules 2389 

associated with fuel tanks constructed 

of carbon fiber reinforced plastic (CFRP) 

materials located within the tire impact 

zone, including the wing fuel tanks. 

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 to 

resist these hazards has not been 

established. There are no current 

airworthiness standards specifically 

addressing this hazard for all exposed 

wing surfaces. 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. 

DATES: Send your comments on or 

before February 28, 2014. 

ADDRESSES: Send comments identified 

by docket number FAA–2013–0907 

using any of the following methods: 

• Federal eRegulations Portal: Go to 

http://www.regulations.gov/ and follow 

the online instructions for sending your 

comments electronically. 

• Mail: Send comments to Docket 

Operations, M–30, U.S. Department of 

Transportation (DOT), 1200 New Jersey 

Avenue SE., Room W12–140, West 

Building Ground Floor, Washington, 

DC, 20590–0001. 

• Hand Delivery or Courier: Take 

comments to Docket Operations in 

Room W12–140 of the West Building 

Ground Floor at 1200 New Jersey 

Avenue SE., Washington, DC, between 9 

a.m. and 5 p.m., Monday through 

Friday, except federal holidays. 

• Fax: Fax comments to Docket 

Operations at 202–493–2251. 

Privacy: The FAA will post all 

comments it receives, without change, 

to http://www.regulations.gov/, 

including any personal information the 

commenter provides. Using the search 

function of the docket Web site, anyone 

can find and read the electronic form of 

all comments received into any FAA 

docket, including the name of the 

individual sending the comment (or 

signing the comment for an association, 

business, labor union, etc.). DOT’s 

complete Privacy Act Statement can be 

found in the Federal Register published 

on April 11, 2000 (65 FR 19477–19478), 

as well as at 

http://DocketsInfo.dot.gov/. 

Docket: Background documents or 

comments received may be read at 

http://www.regulations.gov/ at any time. 

Follow the online instructions for 

accessing the docket or go to the Docket 

Operations in Room W12–140 of the 

West Building Ground Floor at 1200 

New Jersey Avenue SE., Washington, 

DC, between 9 a.m. and 5 p.m., Monday 

through Friday, except federal holidays. 

FOR FURTHER INFORMATION CONTACT: 

Doug Bryant, Propulsion/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: 

Comments Invited 

We invite interested people to take 

part in this rulemaking by sending 

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 will consider all comments we 

receive on or before the closing date for 

comments. We may change these 

proposed special conditions based on 

the comments we receive. 

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 June 28, 2009. The 

Model A350–900 series has a 

conventional layout with twin wingmounted Rolls-Royce Trent engines. It 

features a twin aisle 9-abreast economy 

class layout, and accommodates side-byside placement of LD–3 containers in 

the cargo compartment. The basic 

Model A350–900 series configuration 

will accommodate 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. Airbus proposes the Model A350– 

900 series to be certified for extended 

operations (ETOPS) beyond 180 minutes 

at entry into service for up to a 420 

minute maximum diversion time. 

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 a 

November 1984 accident, a Boeing 

Model 747 tire burst during an aborted 

takeoff from Honolulu, Hawaii. That tire 

debris penetrated a fuel tank access 

cover causing substantial fuel leakage. 

Passengers were evacuated down the 

emergency slides into pools of fuel that 

fortunately had not ignited. 

After an August 1985 Boeing Model 

737 accident in Manchester, England, in 

which a fuel tank access panel was 

penetrated by engine debris creating a 

fire, the FAA amended Title 14, Code of 

Federal Regulations (14 CFR) 25.963 to 

require fuel tank access panels that are 

resistant to both tire and engine debris 

(engine debris is addressed outside of 

this proposed special condition). 

Modifications to the access covers were 

required of the existing fleet by an 

amendment to part 121. This regulation, 

§ 25.963(e), only addressed the fuel tank 

access covers since service experience at 

the time showed that the lower wing 

skin of a conventional, subsonic 

airplane provided adequate inherent 

capability to resist tire and engine 

debris threats. More specifically, this 

regulation requires showing by analysis 

or tests that the access covers ‘‘. . . 

minimize penetration and deformation 

by tire fragments, low energy engine 

debris, or other likely 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. 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 the 

wing was adequately addressed. 

The Concorde accident in July 2000 is 

the most notable example. That accident 

demonstrated an unanticipated failure 

mode in an airplane with an unusual 

transport airplane configuration. Impact 

to the thin aluminum wing surface by 

tire debris induced pressure waves 

within the fuel tank that resulted in fuel 

leakage and fire. The skin on the 

Concorde delta wing, supersonic 

airplane is made of aluminum having a 

thickness that is much less than that of 

a conventional subsonic airplane. 

There were several previous accidents 

from burst tires that damaged the fuel 

tank and wings in the Concorde. In 1979 

a burst main gear tire put a hole through 

the wing and caused both fuel and 

hydraulic leaks. In 1980 a burst tire 

damaged the engine and airframe. In 

July 1993 a main gear tire burst, 

damaging the wing and causing 

hydraulic problems. In October 1993 a 

main gear tire burst, broke the water 

deflector, and caused some holes in the 

fuel tank. Fortunately the fuel did not 

catch fire during any of these events 

before the July 2000 accident involving 

the Concorde airplane. 

Following the accident in 2000, 

regulatory authorities required 

modifications to the Concorde aircraft to 

improve impact resistance of the lower 


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2390 Federal Register / Vol. 79, No. 9 / Tuesday, January 14, 2014 / Proposed Rules 

wing, or means to retain fuel if the 

primary fuel retention means is 

damaged. 

These accidents and incidents 

highlight the need to establish standards 

for fuel tank designs and configurations 

that were not envisioned when the 

existing standards in 14 CFR part 25 

were issued. 

Type Certification Basis 

Under 14 CFR 21.17, Airbus must 

show that the Model A350–900 series 

meets the applicable provisions of 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 Model A350–900 series airplanes 

because of a novel or unusual design 

feature, special conditions are 

prescribed under the provisions of 

§ 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 proposed 

special conditions would also apply to 

the other model under § 21.101. 

In addition to the applicable 

airworthiness regulations and proposed 

special conditions, the Model A350–900 

series 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 and the FAA must issue a 

finding of regulatory adequacy under 

§ 611 of Public Law 92–574, the ‘‘Noise 

Control Act of 1972.’’ 

The FAA issues special conditions, as 

defined in 14 CFR 11.19, in accordance 

with § 11.38, and they become part of 

the type-certification basis under 

§ 21.17(a)(2). 

Novel or Unusual Design Features 

The Airbus Model A350–900 series 

will incorporate the following novel or 

unusual design features: CFRP materials 

for most of the wing fuel tank structure. 

Discussion 

In order to maintain the level of safety 

prescribed by § 25.963(e) for fuel tank 

access covers, these special conditions 

establish 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 may not necessarily 

provide the resistance to debris impact 

that has historically been shown as 

adequate. These proposed special 

conditions are based on the defined tire 

impact areas and tire fragment 

characteristics described in AC 25.963– 

1. 

In addition, despite practical design 

considerations, some uncommon 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 proposed special conditions. 

Consideration of leaks caused by larger 

tire fragments is needed to ensure that 

an adequate level of safety is provided. 

Note: While § 25.963 includes 

consideration of uncontained engine debris, 

the effects of engine debris are not included 

in these proposed special conditions because 

these related potential hazards will be 

addressed on the Model A350–900 series 

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 

Airbus Model A350–900 series 

airplanes. Should Airbus apply at a later 

date for a change to the type certificate 

to include another model incorporating 

the same novel or unusual design 

feature, the proposed special conditions 

would apply to that model as well. 

Conclusion 

This action affects only certain novel 

or unusual design features on Airbus 

Model A350–900 series airplanes. 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 Federal Aviation 

Administration (FAA) proposes the 

following special conditions as part of 

the type certification basis for Airbus 

Model A350–900 series airplanes. 

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 in length or 

diameter. 

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 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 or fuel system component located 

within the tire debris impact area 

defined in paragraph (a), 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 October 

22, 2013. 

Stephen P. Boyd, 

Acting Manager, Transport Airplane 

Directorate, Aircraft Certification Service. 

[FR Doc. 2014–00450 Filed 1–13–14; 8:45 am] 

BILLING CODE 4910–13–P 


tkelley on DSK3SPTVN1PROD with PROPOSALS