[Federal Register Volume 79, Number 162 (Thursday, August 21, 2014)]
[Rules and Regulations]
[Pages 49426-49427]
From the Federal Register Online via the Government Publishing 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]
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