Document ID: FAA-2013-1001-0001
Agency: faa
Document Type: Proposed Rule
Title: Special Conditions: Airbus, A350-900 Series Airplane; High Speed Protection System
Posted Date: 2013-12-24T05:00Z

[Federal Register Volume 78, Number 247 (Tuesday, December 24, 2013)]
[Proposed Rules]
[Pages 77611-77613]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-29938]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2013-1001; Notice No. 25-13-35-SC]

Special Conditions: Airbus, A350-900 Series Airplane; High Speed 
Protection System

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for Airbus A350-900 
series airplanes. These airplanes will have a novel or unusual design 
feature when compared to the state of technology envisioned in the 
airworthiness standards for transport category airplanes. These design 
features include a high-speed protection system. 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: We must receive your comments by February 7, 2014.

ADDRESSES: Send comments identified by docket number FAA-2013-1001 
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 8 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: Todd Martin, FAA, Airframe/Cabin 
Safety, ANM-115, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone 
(425) 227-1178; facsimile (425) 227-1322.

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 ask 
that you send us two copies of written comments.

[[Page 77612]]

    We will file in the docket all comments we receive, as well as a 
report summarizing each substantive public contact with FAA personnel 
concerning these special conditions. You can inspect the docket before 
and after the comment closing date. If you wish to review the docket in 
person, go to the address in the ADDRESSES section of this preamble 
between 7:30 a.m. and 4:00 p.m., Monday through Friday, except Federal 
holidays.
    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 special conditions based on the comments we receive.
    If you want us to acknowledge receipt of your comments on this 
proposal, include with your comments a self-addressed, stamped postcard 
on which you have written the docket number. We will stamp the date on 
the postcard and mail it back to you.

Background

    On August 25, 2008, Airbus applied for a type certificate for their 
new 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 A350-900 series has a conventional layout with twin 
wing-mounted Rolls Royce Trent 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 A350-900 series 
configuration accommodates 315 passengers in a standard two-class 
arrangement. The design cruise speed is Mach 0.89 with a Maximum Take-
Off Weight of 591,000 lbs. Airbus proposes the 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 A350-900, like Airbus A320, A330, A340 and A380 series 
aircraft, has a high speed protection system that limits nose down 
pilot authority at speeds above VC/MC, and 
prevents the airplane from actually performing the maneuver required 
under Sec.  25.335(b)(1). Special conditions are necessary to address 
the Airbus A350-900 series high speed protection system. The proposed 
special conditions identify various symmetric and non-symmetric 
maneuvers that will ensure that an appropriate design dive speed, 
VD/MD, is established.

Type Certification Basis

    Under Title 14, Code of Federal Regulations (14 CFR) 21.17, Airbus 
must show that the A350-900 series 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 A350-900 series because of a novel 
or unusual design feature, special conditions are prescribed under the 
provisions of 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 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 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 A350-900 series will incorporate the following novel or 
unusual design features:
    A high speed protection system that limits nose down pilot 
authority at speeds above VC/MC, and prevents the 
airplane from actually performing the maneuver required under Sec.  
25.335(b)(1). The proposed special conditions identify various 
symmetric and non-symmetric maneuvers that will ensure that an 
appropriate design dive speed, VD/MD, is 
established.

Discussion

    Section 25.335(b)(1) is an analytical envelope condition which was 
originally adopted in Part 4b of the Civil Air Regulations in order to 
provide an acceptable speed margin between design cruise speed and 
design dive speed. Flutter clearance design speeds and airframe design 
loads are impacted by the design dive speed. While the initial 
condition for the upset specified in the rule is 1g level flight, 
protection is afforded for other inadvertent overspeed conditions as 
well. Section 25.335(b)(1) is intended as a conservative enveloping 
condition for potential overspeed conditions, including non-symmetric 
ones.
    To establish that potential overspeed conditions are enveloped, the 
applicant should demonstrate that any reduced speed margin, based on 
the high speed protection system in the A350-900 series, will not be 
exceeded in inadvertent, or gust induced, upsets resulting in 
initiation of the dive from non-symmetric attitudes; or that the 
airplane is protected by the flight control laws from getting into non-
symmetric upset conditions. The proposed special conditions identify 
various symmetric and non-symmetric maneuvers that will ensure than an 
appropriate design dive speed, VD/MD, is 
established.
    These special conditions are proposed in lieu of Sec.  
25.335(b)(1). Section 25.335(b)(2), which also addresses the design 
dive speed, is applied separately (Advisory Circular (AC) 25.335-1A 
provides an acceptable means of compliance to Sec.  25.335(b)(2)). The 
applicant should conduct a demonstration that includes a comprehensive 
set of conditions, as described below.
    Paragraph (2) of the proposed special condition references AC 25-
7C, section 32.c.(3), included here for information.
    ``(3) Gust Upset. In the following three upset tests, the values of 
displacement should be appropriate to the airplane type and should 
depend upon airplane stability and inertia characteristics. The lower 
and upper limits should be used for airplanes with low and high 
maneuverability, respectively.
    (a) With the airplane trimmed in wings-level flight, simulate a 
transient gust by rapidly rolling to the maximum bank angle appropriate 
for the airplane, but not less than 45 degrees nor more than 60 
degrees. The rudder and longitudinal control should be held fixed 
during the time that the required bank is being attained. The rolling 
velocity should be arrested at this bank angle. Following this, the 
controls should be abandoned for a minimum of 3 seconds after 
VMO/MMO or 10 seconds, whichever occurs first.
    (b) Perform a longitudinal upset from normal cruise. Airplane trim 
is determined at VMO/MMO using power/thrust 
required for level flight but with not more than maximum continuous 
power/thrust. (If VMO/MMO cannot be reached in 
level flight with maximum continuous power or thrust, then the airplane 
should be trimmed at VMO/MMO in a descent.) This 
is followed by a decrease in speed, after which a pitch

[[Page 77613]]

attitude of 6-12 degrees nose down, as appropriate for the airplane 
type, is attained using the same power/thrust and trim. The airplane is 
permitted to accelerate until 3 seconds after VMO/
MMO. The force limits of Sec.  25.143(d) for short term 
application apply.
    (c) Perform a two-axis upset, consisting of combined longitudinal 
and lateral upsets. Perform the longitudinal upset, as in paragraph (b) 
above, and when the pitch attitude is set, but before reaching 
VMO/MMO, roll the airplane 15-25 degrees. The 
established attitude should be maintained until 3 seconds after 
VMO/MMO.''
    Paragraphs (3) and (4) of the proposed special condition indicate 
that failures of the high speed protection system must be improbable 
and must be annunciated to the pilots. If these two criteria are not 
met, then the probability that the established dive speed will be 
exceeded, and the resulting risk to the airplane, is too great. On the 
other hand, if the high speed protection system is known to be 
inoperative, then dispatch of the airplane could be acceptable under an 
approved Minimum Equipment List (MEL) containing language similar to 
paragraph (5). Dispatch under an MEL would require that appropriate 
reduced operating speeds, VMO/MMO, are provided 
in the airplane flight manual, and the cockpit display of those reduced 
speeds, as well as the overspeed warning for exceeding those speeds, 
are equivalent to that of the normal airplane with the high speed 
protection system operative.
    We do not believe that application of the Interaction of Systems 
and Structures special condition (reference A350 issue paper A-3) or 
the European Aviation Safety Agency (EASA) Certification Specification 
(CS) 25.302, is appropriate in this case, because design dive speed is, 
in and of itself, part of the design criteria. Stability and control, 
flight loads, and flutter evaluations all depend on the design dive 
speed. Therefore, a single design dive speed should be established that 
will not be exceeded taking into account the performance of the high 
speed protection system, as well as its failure modes, failure 
indications and accompanying flight manual instructions.

Applicability

    As discussed above, these special conditions apply to A350-900 
series airplanes. Should Airbus apply at a later date for a change to 
the type certificate to include another series incorporating the same 
novel or unusual design feature, the special conditions would apply to 
that series as well.

Conclusion

    This action affects only certain novel or unusual design features 
on the Airbus 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 A350-900 series airplanes.
    (1) In lieu of compliance with Sec.  25.335(b)(1), if the flight 
control system includes functions that act automatically to initiate 
recovery before the end of the 20 second period specified in Sec.  
25.335(b)(1), VD/MD must be determined from the 
greater of the speeds resulting from conditions (a) and (b) below. The 
speed increase occurring in these maneuvers may be calculated, if 
reliable or conservative aerodynamic data are used.
    (a) From an initial condition of stabilized flight at 
VC/MC, the airplane is upset so as to take up a 
new flight path 7.5 degrees below the initial path. Control 
application, up to full authority, is made to try and maintain this new 
flight path. Twenty seconds after initiating the upset, manual recovery 
is made at a load factor of 1.5 g (0.5 acceleration increment), or such 
greater load factor that is automatically applied by the system with 
the pilot's pitch control set to neutral. Power, as specified in Sec.  
25.175(b)(1)(iv), is assumed until recovery is initiated, at which time 
power reduction and the use of pilot controlled drag devices may be 
used.
    (b) From a speed below VC/MC, with power to 
maintain stabilized level flight at this speed, the airplane is upset 
so as to accelerate through VC/MC at a flight 
path 15 degrees below the initial path (or at the steepest nose down 
attitude that the system will permit with full control authority if 
less than 15 degrees). The pilot's controls may be in the neutral 
position after reaching VC/MC and before recovery 
is initiated. Recovery may be initiated three seconds after operation 
of the high speed warning system by application of a load of 1.5g (0.5 
acceleration increment), or such greater load factor that is 
automatically applied by the system with the pilot's pitch control 
neutral. Power may be reduced simultaneously. All other means of 
decelerating the airplane, the use of which is authorized up to the 
highest speed reached in the maneuver, may be used. The interval 
between successive pilot actions must not be less than one second.
    (2) The applicant must also demonstrate that the speed margin, 
established as above, will not be exceeded in inadvertent, or gust 
induced, upsets resulting in initiation of the dive from non-symmetric 
attitudes, unless the airplane is protected by the flight control laws 
from getting into non-symmetric upset conditions. The upset maneuvers 
described in AC 25-7C, Chapter 2, Section 8, Paragraph 32c.(3)(a) and 
(c), may be used to comply with this requirement.
    (3) Detected loss of the high speed protection function must be 
less than 10-3 per flight hour.
    (4) Failures of the system must be annunciated to the pilots. The 
Operating Limitations Section of the Airplane Flight Manual must 
contain instructions that reduce the maximum operating speeds, 
Vmax/Mmax, to a value that maintains a speed 
margin between these speeds and VD/MD that is 
consistent with showing compliance to Sec.  25.335(b) without the 
benefit of the high speed protection system.
    (5) Dispatch of the airplane with the high speed protection system 
inoperative is prohibited except under an approved Minimum Equipment 
List (MEL) that requires Airplane Flight Manual instructions to 
indicate reduced maximum operating speeds, as described in paragraph 
(4). In addition, the cockpit display of the reduced operating speeds, 
as well as the overspeed warning for exceeding those speeds, must be 
equivalent to that of the normal airplane with the high speed 
protection system operative. Also, it must be shown that no additional 
hazards are introduced with the high speed protection system 
inoperative.

    Issued in Renton, Washington, on November 16, 2013.
Jeffrey E. Duven,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2013-29938 Filed 12-23-13; 8:45 am]
BILLING CODE 4910-13-P