### 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 bemaintained 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 aconventional 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 of14 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.


### 43237 Federal Register / Vol. 79, No. 143 / Friday, July 25, 2014 / Rules and Regulations

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 specialconditions 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 aconventional 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 ahigh occupant-survival rate at verticaldescent velocities up to 30 ft/sec. Based on this information, the FAA finds it appropriate and necessary for an