Document ID: FAA-2013-0902-0003
Agency: faa
Document Type: Rule
Title: Special Conditions: Airbus Model A350-900 Series Airplane; Electronic Flight-Control System to Limit Pitch and Roll
Posted Date: 2014-08-01T04:00Z

[Federal Register Volume 79, Number 148 (Friday, August 1, 2014)]
[Rules and Regulations]
[Pages 44658-44660]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-18176]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-0902; Special Conditions No. 25-521-SC]

Special Conditions: Airbus Model A350-900 Series Airplane; 
Electronic Flight-Control System (EFCS) To Limit Pitch and Roll

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Airbus Model A350-
900 airplane. This airplane will have a novel or unusual design feature 
associated with the electronic flight-control system (EFCS) that limits 
pitch- and roll-attitude functions. The applicable airworthiness 
regulations do not contain adequate or appropriate safety standards

[[Page 44659]]

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 2, 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 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.
    A special condition to supplement Sec.  25.143 concerning pitch and 
roll limits was developed for the Airbus Model A320, A330, A340, and 
A380 airplanes wherein performance of the limiting functions was 
monitored throughout the flight-test program. The FAA expects similar 
monitoring to take place during the A350 flight-test program to 
substantiate the pitch- and roll-attitude limiting functions, and the 
appropriateness of the chosen limits.

Type Certification Basis

    Under Title 14, Code of Federal Regulations (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 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 final 
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 Airbus Model A350-900 series will incorporate the following 
novel or unusual design features: an EFCS that, when operating in its 
normal mode, will prevent airplane pitch attitudes greater than +30 
degrees and less than -15 degrees, and roll angles greater than plus or 
minus 67 degrees. In addition, positive spiral stability is introduced 
for roll angles greater than 33 degrees at speeds below VMO/
MMO. At speeds greater than VMO and up to 
VDF, maximum aileron-control force is limited to only 45 
degrees maximum bank angle.

Discussion

    It is expected that high thrust-to-weight ratios provide the most 
critical cases for the positive-pitch limit. A margin in pitch control 
must be available to enable speed control in maneuvers such as climb 
after takeoff, and balked landing climb. The pitch limit must not 
impede likely maneuvering made necessary by collision avoidance 
efforts. A negative-pitch limit must similarly not interfere with 
collision-avoidance capability, or with attaining and maintaining 
speeds near VMO/MMO for emergency descent.
    Spiral stability, which is introduced above 33 degrees roll angle, 
and the roll limit must not restrict attaining roll angles up to 66 
degrees (approximately 2.5g level turn) with flaps up and 60 degrees 
(approximately 2.0g level turn) with flaps down. The implementation of 
this spiral stability requires a steady aileron-control force to 
maintain a constant bank angle above 33 degrees. This force must not 
require excessive pilot strength as stated in Sec.  25.143(f).
    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. 25-13-25-SC for the 
Airbus Model A350-900 airplane was published in the Federal Register on 
November 12, 2013 (78 FR 67320). One comment supporting the special 
conditions was received. These 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 type certification basis for Airbus Model A350-900 airplanes. In 
addition to Sec.  25.143, the following requirements apply:
    1. The pitch-limiting function must not impede normal maneuvering 
for pitch angles up to the maximum required for normal maneuvering, 
including a normal all-engines-operating takeoff, plus a suitable 
margin to allow for satisfactory speed control.
    2. The pitch and roll limiting functions must not restrict or 
prevent attaining pitch attitudes necessary for emergency maneuvering, 
or roll angles up to 66 degrees with flaps up or 60 degrees with flaps 
down. Spiral stability, which is introduced above 33 degrees roll 
angle, must not require excessive pilot strength to achieve these roll-
limit angles. Other protections, which further limit the roll 
capability under certain extreme angle-of-attack,

[[Page 44660]]

attitude, or high-speed conditions, are acceptable as long as they 
allow at least 45 degrees of roll capability.

    Issued in Renton, Washington, on July 11, 2014.
Michael Kaszycki,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2014-18176 Filed 7-31-14; 8:45 am]
BILLING CODE 4910-13-P