Special Conditions: Airbus, Model A350-900 Series Airplane; Flight Envelope Protection: Normal Load Factor (g) Limiting, 76249-76251 [2013-29941]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 78, Number 242 (Tuesday, December 17, 2013)]
[Proposed Rules]
[Pages 76249-76251]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-29941]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-0905; Notice No. 25-13-28-SC]


Special Conditions: Airbus, Model A350-900 Series Airplane; 
Flight Envelope Protection: Normal Load Factor (g) Limiting

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for Airbus Model A350-
900 series airplanes. These airplanes will have a novel or unusual 
design feature(s) associated with a flight control system that prevents 
the pilot from inadvertently or intentionally exceeding the positive or 
negative airplane limit load factor. 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 equivalent to that established by the 
existing airworthiness standards.

DATES: Send your comments on or before January 31, 2014.

ADDRESSES: Send comments identified by docket number FAA-2013-0905 
using any of the following methods:
     Federal eRegulations Portal: Go to https://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 https://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 https://DocketsInfo.dot.gov/.
    Docket: Background documents or comments received may be read at 
https://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: 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:

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 will consider comments filed late if it is 
possible to do so without incurring expense or delay. We may change 
these proposed special conditions based on the comments we receive.

[[Page 76250]]

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 Airbus 
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.
    The normal load factor limit on Airbus Model A350-900 series 
airplanes is unique in that traditional airplanes with conventional 
flight control systems (mechanical linkages) are limited in the pitch 
axis only by the elevator surface area and deflection limit. The 
elevator control power is normally derived for adequate controllability 
and maneuverability at the most critical longitudinal pitching moment. 
The result is that traditional airplanes have a significant portion of 
the flight envelope wherein maneuverability in excess of limit 
structural design values is possible.
    Title 14 Code of Federal Regulations (14 CFR) part 25 sections do 
not specify requirements or policy for demonstrating maneuver control 
that impose any handling qualities requirements beyond the design limit 
structural loads. Nevertheless, some pilots have become accustomed to 
the availability of this excess maneuver capacity in case of extreme 
emergency such as upset recoveries or collision avoidance.
    These proposed special conditions are needed to ensure adequate 
maneuverability and controllability for the Model A350-900 series using 
the Airbus flight control system.
    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-
128.
    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 or similar 
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 Airbus 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: a flight control system that prevents 
the pilot from inadvertently or intentionally exceeding the positive or 
negative airplane limit load factor.

Discussion

    Flight envelope protection that limits normal load factor (g) 
limiting is considered novel and unusual because the current 
regulations do not provide standards for maneuverability and 
controllability evaluations for such systems. Special conditions are 
needed to ensure adequate maneuverability and controllability when 
using this design feature.
    As with the previous fly-by-wire airplanes, the FAA has no 
regulatory or safety reason to inhibit the design concept of the Airbus 
A350 flight control system with load factor limiting. Pilots accustomed 
to this control feature may feel more freedom in commanding full stick 
displacement maneuvers because of the following:
    (1) Knowledge that the limit system will protect the structure,
    (2) Low stick force/displacement gradients, and
    (3) Smooth transition from pilot elevator control to limit control.

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.
    To meet the intent of adequate maneuverability and controllability 
required by Sec.  25.143(a), and in the absence of other limiting 
factors, the following special condition is proposed:
    1. The positive limiting load factor must not be less than:
    (a) 2.5g for the EFCS normal state with the high lift devices 
retracted up to VMO/MMO. The positive limiting 
load factor may be gradually reduced down to 2.25g above 
VMO/MMO.
    (b) 2.0g for the EFCS normal state with the high lift devices 
extended.
    2. The negative limiting load factor must be equal to or more 
negative than:
    (a) Minus 1.0g for the EFCS normal state with the high lift devices 
retracted.
    (b) 0.0g for the EFCS normal state with high lift devices extended.
    3. Maximum reachable positive load factor wings level may be 
limited by flight control system characteristics or flight envelope 
protections (other than load factor protection) provided:
    (a) That the required values are readily achievable in turns and
    (b) that wings level pitch up responsiveness is satisfactory.
    4. Maximum achievable negative load factor may be limited by flight 
control system characteristics or flight envelope protections (other 
than load factor protection) provided:
    (a) pitch down responsiveness is satisfactory
    (b) from level flight, 0g is readily achievable or alternatively, a 
satisfactory* trajectory change is readily achievable at operational 
speeds (from VLS to max speed -10kts). VLS is the 
lowest speed that the crew may fly with

[[Page 76251]]

auto thrust or auto pilot engaged. It is displayed on primary flight 
displays as the top of the low speed amber band, and is the lower end 
of the normal flight envelope. Max speed - 10kts is proposed to cover 
typical margin from VMO/MMO to cruise speeds and 
typical margin from VFE to standard speed in high lift 
configurations.

* For the FAA to consider a trajectory change as satisfactory, the 
applicant should propose and justify a pitch rate that provides 
sufficient maneuvering capability in the most critical scenarios.

Compliance demonstration with the above requirements may be performed 
without ice accretion on the airframe.

    Issued in Renton, Washington, on October 22, 2013.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2013-29941 Filed 12-16-13; 8:45 am]
BILLING CODE 4910-13-P