[491 0-13] 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA-2014-0303; Special Conditions No. 25-561-SC] 

Special Conditions: Airbus Model A350-900 airplane; operation without normal electrical 

power. 

AGENCY: Federal Aviation Administration (FAA), DOT. 

ACTION: Final special condition; request for comments. 

SUMMARY: These special conditions are issued for the Airbus Model A350-900 airplane. This 

airplane will have a novel or unusual design feature associated with operation without normal 

electrical power. 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: The effective date of these special conditions is August 7, 2014. We must receive your 

comments by September 22, 2014. 

ADDRESSES: Send comments identified by docket number FAA-2014-0303 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, D.C., 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, D.C., 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 ofthe 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://Docketslnfo.dot.gov/. 

Docket: Background documents or comments received may be read at 

http://www.rcgulations.gov/ at any time. Follow the online instructions for accessing the docket 

or go to the Docket Operations in Room Wl2-140 of the West Building Ground Floor at 1200 

New Jersey Avenue, SE, Washington, D.C., between 9 a.m. and 5 p.m., Monday through Friday, 

except federal holidays. 

FOR FURTHER INFORMATION CONTACT: Nazih Khaouly, FAA, Airframe and 

Flightcrew Interface Branch, ANM-111 , Transport Airplane Directorate, Aircraft Cetiification 

Service, 1601 Lind Avenue SW., Renton, Washington, 98057-3356; telephone (425) 227-2432; 

facsimile (425) 227-1320. 

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SUPPLEMENTARY INFORMATION: 

The FAA has determined that notice of, and opportunity for prior public comment on, 

these special conditions is impracticable because these procedures would significantly delay 

issuance of the design approval and thus delivery of the affected aircraft. In addition, the 

substance of these special conditions has been subject to the public-comment process in several 

prior instances with no substantive comments received. The FAA therefore finds that good cause 

exists for making these special conditions effective upon publication in the Federal Register. 

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 supp011ing data. 

We will consider all comments we receive by the closing date for comments. We may 

change these 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 

1e FAA approved, an extension to the application for 

. The Model A350-900 airplane has a conventional 

e 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 Airbus Model A350-900 airplane 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. 

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The Airbus Model A350-900 airplane fly-by-wire control system requires a continuous 

source of electrical power to maintain an operable flight-control system. The current rule, Title 

14, Code ofFederal Regulations (14 CFR) 25.135l(d), Amendment 25-72, requires safe 

operation under visual flight rules (VFR) conditions for at least five minutes after loss of all 

normal electrical power. This rule was structured around a traditional design utilizing mechanical 

control cables for flight control while the crew took time to sort out the electrical failure, start 

engine(s) if necessary, and re-establish some ofthe electrical-power-generation capability. 

To maintain the same level of safety associated with traditional designs, Airbus Model 

A350-900 airplanes must be designed for operation with the normal sources of engine- or 

Auxiliary Power Unit (APU)-generated electrical power inoperative. Service experience has 

shown that loss of all electrical power from the airplane's engine and APU-driven generators is 

not extremely improbable. Therefore, it must be shown that the airplane is capable of recovering 

adequate primary electrical-power generation for safe flight and landing with the use of its 

emergency electrical-power systems. These emergency electrical-power systems must be able to 

power loads that are essential for continued safe flight and landing. 

Type Certification Basis 

Under 14 CFR 21.17, Airbus must show that the Airbus Model A350-900 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 Airbus Model A350-900 

airplane because of a novel or unusual design feature, special conditions are prescribed under 

§ 21.16. These special conditions are an extension of part 25 due to the inadequacies of the 

existing part 25 requirements to address loss of all normal electrical power. 

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SUPPLEMENTARY INFORMATION: 

The FAA has determined that notice of, and opportunity for prior public comment on, 

these special conditions is impracticable because these procedures would significantly delay 

issuance of the design approval and thus delivery of the affected aircraft. In addition, the 

substance of these special conditions has been subject to the public-comment process in several 

prior instances with no substantive comments received. The FAA therefore finds that good cause 

exists for making these special conditions effective upon publication in the Federal Register. 

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 by the closing date for comments. We may 

change these 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 

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 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 Airbus Model A350-900 airplane 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. 

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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 novel or unusual design feature , the special conditions would also apply to the other 

model under § 21. 1 01 . 

In addition to the applicable airworthiness regulations and special conditions, the Airbus 

Model A350-900 airplane must be shown to 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 issue a finding ofregulatory 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, under§ 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 airplane incorporates the following novel or unusual design 

features: the capability of continued safe flight and landing that are dependent on one or more 

continuous sources of electrical power. 

Due to 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 Airbus Model A350-900 airplane 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. 

In addition to an electronic f1ight-control system, a number of systems that have 

traditionally been mechanically operated have been implemented as electrically powered systems 

on the Model A350-900 airplane. The criticality of some of these systems is such that their 

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failure will either reduce the capability of the airplane or the ability of the crew to cope with 

adverse operating conditions, or prevent continued safe flight and landing of the airplane. 

Discussion 

The cunent rule, 14 CFR 25.1351 (d), Amendment 25-72, requires safe operation under 

VFR conditions for at least five minutes after loss of all normal electrical power. This rule was 

structured around traditional airplane designs that use mechanical control cables and linkages for 

flight control. These manual controls allow the tlightcrew to maintain aerodynamic control of the 

airplane for an indefinite time after loss of all electrical power. Under these conditions, the 

mechanical flight-control system provides the flightcrew with the ability to fly the airplane while 

attempting to identify the cause of the electrical failure, start the engine(s) if necessary, and 

reestablish some of the electrical-power-generation capability, if possible. 

To maintain the same level of safety associated with traditional designs, the Airbus 

Model A350-900 airplane must be designed for operation with the normal sources of engine- and 

APU-generated electrical power inoperative. The FAA has identified electrically powered 

functions required to safely complete a maximum ETOPS diversion as another potential 

catastrophic effect from the loss of all normal electrical power. Service history has shown that 

analytical means have not been accurate at anticipating common-cause failures, nor have such 

means been accurate at predicting that loss of all normal sources of electrical power is extremely 

improbable. 

Airbus must demonstrate that the airplane is capable of recovering adequate primary 

electrical-power generation during ETOPS, and for continued safe flight and landing. An 

alternative source of electrical power would have to be provided for the time necessary to restore 

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the minimum power-generation capability necessary during ETOPS, and for continued safe flight 

and landing. 

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. 

Applicability 

As discussed above, these special conditions are applicable to the Airbus Model A350-

900. 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 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 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 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 airplanes. 

In lieu ofthe requirements of 14 CFR 25.1351(d) the following special conditions apply: 

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1. The applicant must show by test, or a combination of test and analysis, that the 

airplane is capable of continued safe flight and landing with all normal sources of 

engine- and APU-generated electrical power inoperative as prescribed by 

paragraphs l.a. and l.b. below. For purposes of these special conditions, normal 

sources of electrical power generation do not include any alternate power sources 

such as batteries, ram-air turbine (RAT), or independent power systems such as 

the flight-control permanent magnet generating system. In showing capability for 

continued safe flight and landing, consideration must be given to systems 

capability, effects on flightcrew workload and operating conditions, and the 

physiological needs of the flightcrew and passengers for the longest diversion 

time for which approval is sought. 

a. Common mode failures, cascading failures, and zonal physical threats 

must be considered in ,showing compliance with this requirement. 

b. In showing compliance with this requirement, the ability to restore 

operation of portions of the electrical-power generation and distribution 

system may be considered if it can be shown that unrecoverable loss of 

those portions of the system is extremely improbable. An alternative 

source of electrical power must be provided for the time required to 

restore the minimum electrical-power generation capability required for 

continued safe flight and landing. Unrecoverable loss of all engines may 

be excluded when showing that unrecoverable loss of critical portions of 

the electrical system is extremely improbable. 

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2. Regardless of any electrical generation-and-distribution system-recovery 

capability shown under paragraph 1, above, sufficient electrical-system capability 

must be provided toa. allow time to descend, with all engines inoperative, at the speed that 

provides the best glide distance, from the maximum operating altitude to 

the top of the engine-restart envelope, and 

b. subsequently allow multiple start attempts of the engines and APU. This 

capability must be provided in addition to the electrical capability required 

by existing part 25 requirements related to operation with all engines 

inoperative. 

3. The electrical energy the airplane uses in descending with engines inoperative, 

from the maximum operating altitude at the best glide speed, and in making 

multiple attempts to start the engines and APU, must be considered when showing 

compliance with paragraphs I and 2 of these special conditions, and with existing 

14 CFR part 25 requirements related to continued safe flight and landing. 

Issued in Renton, Washington, on JUL 2 3 2014 

~~}-

John P. Piccola, Jr. 

Acting Manager, Transport Airplane Directorate 

Aircraft Certification Service 

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