Document ID: FAA-2013-0901-0003
Agency: faa
Document Type: Rule
Title: Special Conditions: Airbus Model A350-900 Airplanes; Flight-Envelope Protection - High-Speed Limiting
Posted Date: 2014-08-21T04:00Z

[Federal Register Volume 79, Number 162 (Thursday, August 21, 2014)]
[Rules and Regulations]
[Pages 49426-49427]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-19822]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-0901; Special Conditions No. 25-536-SC]

Special Conditions: Airbus Model A350-900 Airplanes; Flight-
Envelope Protection: High-Speed Limiting

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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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 high speed limiting. 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: Joe Jacobsen, FAA, Airplane and 
Flightcrew Interface Branch, ANM-111, Transport Airplane Directorate, 
Aircraft Certification Service, 1601 Lind Avenue SW., Renton, 
Washington 98057-3356; telephone (425) 227-2011; 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 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 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 longitudinal-control law design of the Airbus Model A350-900 
airplane incorporates an overspeed protection system in the normal 
mode, which prevents the pilot from inadvertently or intentionally 
exceeding a speed approximately equivalent to VFC or 
attaining VDF. Current Title 14 Code of Federal Regulations 
(14 CFR) part 25 sections do not relate to a high-speed-limiting 
protection system that might preclude or modify flying-qualities 
assessments in the overspeed region. However, the requirements of Sec.  
25.253 (high-speed characteristics) and its related policy are 
applicable to the Model A350-900 airplane and are not affected by this 
special condition.

Type Certification Basis

    Under 14 CFR 21.17, Airbus must show that the Model A350-900 
airplane 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 the Airbus Model A350-900 airplane 
because of a novel or unusual design feature, special conditions are 
prescribed under Sec.  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 Sec.  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 noise-
certification 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.''
    The FAA issues special conditions, as defined in 14 CFR 11.19, 
under Sec.  11.38, and they become part of the type-certification basis 
under Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The Model A350-900 airplane incorporates the following novel or 
unusual design features: an overspeed protection system that prevents 
the pilot from inadvertently or intentionally exceeding a speed 
approximately equivalent to VFC, or attaining 
VDF.
    At VMO + 10 knots or MMO + 0.02 knots, an 
automatic nose-up pitch is applied with phase advance in the event of 
high acceleration. The speed stabilizes at VD-10kts/
MD-0.02 if the stick is full forward, or the speed will 
return below VMO/MMO if the stick is released.

Discussion

    This special condition establishes requirements to ensure that 
operation of the high-speed-limiting protection system does not impede 
normal attainment of speeds up to the overspeed warning. Its main 
features are:
    1. It protects the airplane against high-speed/high Mach-number 
flight conditions beyond VMO/MMO.
    2. It does not interfere with flight at VMO/
MMO, even in turbulent air.
    3. It still provides load-factor limitation through the ``pitch 
limiting'' function described below.
    4. It restores positive static stability beyond VMO/
MMO.
    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. 25-13-23-SC for the 
Airbus Model A350-900 airplane was published in the Federal Register on 
January 8, 2014 (79 FR 1336). An anonymous comment was received January 
16, 2014. The commenter was concerned about high-level windshears, and 
the potential violation of Reduced Vertical Separation Minimums (RVSM) 
airspace restrictions that might accompany a nose-up input of a high-
speed protection system. In addition, the commenter was concerned about 
system failures or malfunctions leading to unintended control 
consequences and the pilot's ability to appropriately counteract those 
control anomalies.
    The FAA would like to clarify that this special condition only 
addresses one aspect of high-speed limiting designs. Many other 
regulations, such as 14 CFR 25.1301 and 25.1309, address the proper 
intended function and failure scenarios of such a system. Therefore,

[[Page 49427]]

the anonymous comment is beyond the scope of this special condition, 
and is already accounted for and considered in the basic regulatory-
compliance process.

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 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 Special Conditions

0
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 Sec.  25.143, the following requirements apply: 
Operation of the high-speed limiter during all routine and descent-
procedure flight must not impede normal attainment of speeds up to 
overspeed warning.

    Issued in Renton, Washington, on August 15, 2014.
Jeffrey E. Duven,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2014-19822 Filed 8-20-14; 8:45 am]
BILLING CODE 4910-13-P