[Federal Register Volume 79, Number 5 (Wednesday, January 8, 2014)]
[Proposed Rules]
[Pages 1339-1341]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-00105]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2013-0911; Notice No. 25-13-22-SC]
Special Conditions: Airbus, Model A350-900 Series Airplane;
Lateral Trim Function Through Differential Flap Setting
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This action proposes special conditions for the Airbus Model
A350-900 series 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 proposed
special conditions contain the additional safety standards that the
Administrator considers necessary to establish a level of safety
[[Page 1340]]
equivalent to that established by the existing airworthiness standards.
DATES: Send your comments on or before February 24, 2014.
ADDRESSES: Send comments identified by docket number FAA-2013-0911
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, DC 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, DC, 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 of the
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://DocketsInfo.dot.gov/.
Docket: Background documents or comments received may be read at
http://www.regulations.gov/ at any time. Follow the online instructions
for accessing the docket or go to the Docket Operations in Room W12-140
of the West Building Ground Floor at 1200 New Jersey Avenue SE.,
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday,
except federal holidays.
FOR FURTHER INFORMATION CONTACT: Robert C. Jones, FAA, Propulsion/
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:
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 on or before the closing
date for comments. We may change these proposed 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 series airplane. Later, Airbus requested and the FAA
approved an extension to the application for FAA type certification to
June 28, 2009. The Model A350-900 series 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 series 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. Airbus proposes the
Model A350-900 series to be certified for extended operations (ETOPS)
beyond 180 minutes at entry into service for up to a 420-minute maximum
diversion time.
On conventional airplanes, small lateral airplane asymmetries have
typically been addressed through flap and aileron rigging (e.g., using
shims). On Model A350-900 series 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 as proposed for Airbus Model A350-900 series 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 small airplane lateral asymmetries.
The lateral trim function is not a trim control system in the
conventional sense as it has no pilot interface and is not governed by
Sec. 25.677. In fact 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, there may be failure cases leading to
a significant out of range asymmetric flap condition. An asymmetry
threshold will protect the system against excessive flap asymmetry.
Type Certification Basis
Under Title 14, Code of Federal Regulations (14 CFR) 21.17, Airbus
must show that the Model A350-900 series 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 series 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 novel or
unusual design feature, the proposed special conditions would also
apply to the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and
proposed special conditions, the Model A350-900 series 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 and the FAA must
issue a finding of regulatory adequacy under Sec. 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 Airbus Model A350-900 series will incorporate the following
novel or unusual design features: the asymmetric use of flaps to
address lateral trim which is not adequately addressed by Sec. 25.701.
Discussion
Title 14 Code of Federal Regulations (14 CFR) part 25 Sec.
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
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intentionally creates asymmetric flap motions, the flap system
installation of the Model A350-900 series does not meet the requirement
of Sec. 25.701(a) and (d).
Applicability
As discussed above, these proposed special conditions apply to
Airbus Model A350-900 series 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 proposed 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 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 Proposed Special Conditions
Accordingly, the Federal Aviation Administration (FAA) proposes the
following special conditions as part of the type certification basis
for Airbus Model A350-900 series airplanes.
1. Lateral Trim Function through Differential Flap Setting.
Current airworthiness standards, specifically Sec. 25.701, do not
contain adequate safety standards for the proposed design. In lieu of
the requirements of Sec. 25.701(a) and (d) for the lateral trim
function, the following special condition is proposed:
a. Airbus must demonstrate that an unsafe condition is not created
by using the flaps asymmetrically,
b. The degree of acceptable asymmetry must be defined and justified
for all flight phases with respect to:
Sec. 25.701(b) and (c), with the worst case asymmetric
flap configurations, and
providing equivalent protection against excess asymmetry
in the same manner as Sec. 25.701 provides to systems that are
synchronized or use another equivalent means to prevent asymmetry.
c. This lateral trim function is a flight control system and
therefore must show compliance to both general system requirements as
well as general flight control requirements. Therefore, the function
must be demonstrated not to embody, where practicable, significant
latent failures.
Issued in Renton, Washington, on October 22, 2013.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2014-00105 Filed 1-7-14; 8:45 am]
BILLING CODE 4910-13-P