43236 Federal Register / Vol. 79, No. 143 / Friday, July 25, 2014 / Rules and Regulations 

(e) In straight, steady sideslips over 

the range of sideslip angles appropriate 

to the operation of the airplane, but not 

less than those obtained with one-half of 

the available rudder-control movement 

(but not exceeding a rudder-control 

force of 180 pounds), rudder-control 

movements and forces must be 

substantially proportional to the angle 

of sideslip in a stable sense; and the 

factor of proportionality must lie 

between limits found necessary for safe 

operation. This requirement must be 

met for the configurations and speeds 

specified in paragraph (c) of this 

section. 

(f) For sideslip angles greater than 

those prescribed by paragraph (e) of this 

section, up to the angle at which full 

rudder control is used or a ruddercontrol force of 180 pounds is obtained, 

the rudder-control forces may not 

reverse, and increased rudder deflection 

must be needed for increased angles of 

sideslip. Compliance with this 

requirement must be shown using 

straight, steady sideslips, unless full 

lateral-control input is achieved before 

reaching either full rudder-control input 

or a rudder-control force of 180 pounds; 

a straight, steady sideslip need not be 

maintained after achieving full lateralcontrol input. 

This requirement must be met at all 

approved landing-gear and wing-flap 

positions for the range of operating 

speeds and power conditions 

appropriate to each landing-gear and 

wing-flap position with all engines 

operating. 

Issued in Renton, Washington, on July 9, 

2014. 

Jeffrey E. Duven, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2014–17575 Filed 7–24–14; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA–2013–0911; Special 

Conditions No. 25–539–SC] 

Special Conditions: Airbus Model 

A350–900 Airplanes; Lateral-Trim 

Function Through Differential Flap 

Setting 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final special conditions. 

SUMMARY: These special conditions are 

issued for Airbus Model A350–900 

airplanes. These airplanes will have a 

novel or unusual design feature 

associated with a lateral-trim function 

that deploys flaps asymmetrically for 

airplane lateral-trim control. This 

function replaces the traditional method 

of providing airplane lateral trim over a 

small range through flap and aileron 

mechanical rigging. 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: August 25, 2014. 

FOR FURTHER INFORMATION CONTACT: 

Robert C. Jones, FAA, Propulsion and 

Mechanical Systems, ANM–112, 

Transport Airplane Directorate, Aircraft 

Certification Service, 1601 Lind Avenue 

SW., Renton, Washington 98057–3356; 

telephone (425) 227–1234; facsimile 

(425) 227–1320. 

SUPPLEMENTARY INFORMATION: 

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 wingmounted 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 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. 

On conventional airplanes, small, 

lateral, airplane asymmetries typically 

have been addressed through flap and 

aileron rigging (e.g., using shims). On 

Model A350–900 airplanes, an order for 

asymmetric flap deployment will be 

computed by the primary flight-control 

system as a function of the aileron 

position. The current airworthiness 

standards do not contain adequate 

safety standards for asymmetric use of 

the flaps for Airbus Model A350–900 

airplanes. Special conditions are needed 

to account for the aspects of a function 

used to command an intended flap 

asymmetry. The lateral-trim function is 

intended to be performed once during 

climb and once during cruise to 

compensate for airplane small lateral 

asymmetries. 

The lateral-trim function is not a trimcontrol system in the conventional 

sense as it has no pilot interface and is 

not governed by Title 14, Code of 

Federal Regulations (14 CFR) 25.677. 

Some fly-by-wire airplanes have no 

pilot-operated lateral trim at all. The 

lateral-trim function is simply an 

additional fly-by-wire flight-control 

function that nulls small roll 

asymmetries in certain flight phases 

with small, asymmetric flap 

deployments. Although the function 

operates under normal conditions 

within the small range of the traditional 

rigging, failure cases may result in a 

significant out-of-range asymmetric flap 

condition. An asymmetry threshold 

protects the system against excessive 

flap asymmetry. 

Type Certification Basis 

Under 14 CFR 21.17, Airbus must 

show that the 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 Model A350–900 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 novel or unusual 

design feature, the special conditions 

would also apply to the other model 

under § 21.101. 

In addition to the applicable 

airworthiness regulations and special 

conditions, the Model A350–900 

airplane must comply with the fuel-vent 

and exhaust-emission requirements of 

14 CFR part 34, and the noisecertification requirements of 14 CFR 

part 36. 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, 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 airplane 

incorporates the following novel or 

unusual design features: The 

asymmetric use of flaps to address 

lateral trim, which is not adequately 

addressed by § 25.701. 


rmajette on DSK2TPTVN1PROD with RULES
Federal Register / Vol. 79, No. 143 / Friday, July 25, 2014 / Rules and Regulations 43237 

Discussion 

Section 25.701(a) requires that, unless 

the airplane has safe-flight 

characteristics with the flaps or slats 

retracted on one side and extended on 

the other, flap and slat surfaces must be 

synchronized by either a mechanical 

interconnection or any equivalent 

means that has the same integrity. 

Synchronization is interpreted to mean 

that flap movement is symmetrical 

throughout the full range of flap motion. 

Because the lateral-trim function 

intentionally creates asymmetric flap 

motions, the flap-system installation of 

the Model A350–900 airplane does not 

meet the requirement of § 25.701(a) and 

(d). 

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. 25–13–22–SC for Airbus Model 

A350–900 airplanes was published in 

the Federal Register on January 8, 2014 

(79 FR 1339). 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 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. 

Conclusion 

This action affects only certain novel 

or unusual design features on the Airbus 

Model A350–900 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 Special Conditions 

Accordingly, pursuant to the 

authority delegated to me by the 

Administrator, the following special 

conditions are issued as part of the typecertification basis for Airbus Model 

A350–900 airplanes: 

Lateral-Trim Function Through 

Differential Flap Setting 

Current airworthiness standards, 

specifically § 25.701, do not contain 

adequate safety standards for this 

airplane design. In lieu of the 

requirements of § 25.701(a) and (d) for 

the lateral-trim function, the following 

special condition are issued: 

1. Airbus must demonstrate that an 

unsafe condition is not created by using 

the flaps asymmetrically. 

2. The degree of acceptable 

asymmetry must be defined and 

justified for all flight phases with 

respect to: 

a. Section 25.701(b) and (c), with the 

worst-case asymmetric flap 

configurations, and 

b. Providing equivalent protection 

against excess asymmetry in the same 

manner as § 25.701 provides to systems 

that are synchronized, or use another 

equivalent means to prevent asymmetry. 

3. This lateral-trim function is a flightcontrol system and therefore must be 

shown to comply with both general 

system requirements as well as general 

flight-control requirements. Therefore, 

the function must be demonstrated not 

to have significant latent failures, where 

practicable. 

Issued in Renton, Washington, on July 9, 

2014. 

Jeffrey E. Duven, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2014–17578 Filed 7–24–14; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA–2013–0892; Special 

Conditions No. 25–537–SC] 

Special Conditions: Airbus A350–900 

Airplane; Crashworthiness, Emergency 

Landing Conditions 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final special conditions. 

SUMMARY: These special conditions are 

issued for Airbus Model A350–900 

airplanes. These airplanes have a novel 

or unusual design feature associated 

with crashworthiness of carbon-fiberreinforced plastic used in the 

construction of the fuselage. 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: August 25, 2014. 

FOR FURTHER INFORMATION CONTACT: 

Todd Martin, FAA, Airframe/Cabin 

Safety, ANM–115, Transport Airplane 

Directorate, Aircraft Certification 

Service, 1601 Lind Avenue SW., 

Renton, Washington 98057–3356; 

telephone (425) 227–1178; facsimile 

(425) 227–1320. 

SUPPLEMENTARY INFORMATION: 

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 wingmounted 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 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. 

Changes in the structural behavior of 

the Airbus Model A350–900 airplane, 

compared to currently certificated 

designs, could degrade the survivability 

of the Model A350–900 airplane 

occupants in crash conditions that are 

within the limits of survivability for 

other designs. 

The airworthiness regulations specify 

no aircraft-level survivable crash 

condition, and metallic aircraft have not 

been designed specifically against 

survivable impact conditions. However, 

the structural behavior of previously 

certificated aircraft in a survivable crash 

event, and the associated limits, are 

considered generally acceptable. It is 

therefore reasonable to expect that a 

design using new materials, such as the 

Model A350–900 airplanes use, should 

be assessed to ensure that the material 

meets the currently accepted level of 

safety. 

The FAA and industry have collected 

a significant amount of experimental 

data, as well as data from crashes of 

transport-category airplanes, that show a 

high occupant-survival rate at verticaldescent velocities up to 30 ft/sec. Based 

on this information, the FAA finds it 

appropriate and necessary for an 


rmajette on DSK2TPTVN1PROD with RULES