[Federal Register Volume 67, Number 54 (Wednesday, March 20, 2002)]
[Proposed Rules]
[Pages 12903-12907]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-5876]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM211; Notice No. 25-02-03-SC]


Special Conditions: Airbus Industrie, Model A340-500/-600 
Airplanes; Ground Loads and Conditions for Center Landing Gear With 
Four Wheels and Braking Capability

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for Airbus Industrie 
Model A340-500 and -600 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. This design feature is associated with the landing gear, in 
the form of a four-wheeled center landing gear, installed under the 
fuselage, which functions like a main landing gear in all respects, 
including the ability to brake. 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: Comments must be received on or before April 19, 2002.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Transport Airplane Directorate, Attn: 
Rules Docket (ANM-113), Docket No. NM211, 1601 Lind Avenue SW., Renton, 
Washington, 98055-4056; or delivered in duplicate to the Transport 
Airplane Directorate at the above address. Comments must be marked: 
Docket No. NM211. Comments may be inspected in the Rules Docket 
weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Tim Backman, FAA, ANM-116, Transport 
Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue 
SW., Renton, Washington, 98055-4056; telephone (425) 227-2797; 
facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites interested persons to participate in this 
rulemaking by submitting written comments, data, or views. The most 
helpful comments reference a specific portion of the proposal, explain 
the reason for any recommended change, and include supporting data. We 
ask that you send us two copies of written comments.
    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 proposed special conditions. The docket is available 
for public inspection 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 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 
this proposal for special conditions in light of the comments we 
receive.
    If you want the FAA to acknowledge receipt of your comments on this 
proposal, include with your comments a pre-addressed, stamped postcard 
on which the docket number appears. We will stamp the date on the 
postcard and mail it back to you.

Background

    On November 14, 1996, Airbus Industrie applied for an amendment to 
U.S. type certificate (TC) A43NM to include the new models A340-500 and 
-600. These models are derivatives of the A340-300, which is approved 
under the same TC.
    The Model A340-500 fuselage is a 6-frame stretch of the Model A340-
300 and is powered by 4 Rolls Royce Trent 553 engines, each rated at 
53,000 pounds of thrust. The airplane has interior seating arrangements 
for up to 375 passengers, with a maximum takeoff weight (MTOW) of 
820,000 pounds. The Model 340-500 is intended for long-range operations 
and has additional fuel capacity over that of the model A340-600.
    The Model A340-600 fuselage is a 20-frame stretch of the Model 
A340-300 and is powered by 4 Rolls Royce Trent 556 engines, each rated 
at 56,000 pounds of thrust. The airplane has interior seating 
arrangements for up to 440 passengers, with a MTOW of 804,500 pounds.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Airbus Industrie must show 
that the Model A340-500 and -600 airplanes

[[Page 12904]]

meet the applicable provisions of the regulations incorporated by 
reference in TC A43NM or the applicable regulations in effect on the 
date of application for the change to the type certificate. The 
regulations incorporated by reference in the type certificate are 
commonly referred to as the ``original type certification basis.'' The 
regulations incorporated by reference in TC A43NM are 14 CFR part 25, 
effective February 1, 1965, including Amendments 25-1 through 25-63, 
and Amendments 25-64, 25-65, 25-66, and 25-77, with certain exceptions 
that are not relevant to these proposed special conditions.
    In addition, if the regulations incorporated by reference do not 
provide adequate standards with respect to the change, the applicant 
must comply with certain regulations in effect on the date of 
application for the change. The FAA has determined that the Model A340-
500 and -600 airplanes must be shown to comply with Amendments 25-1 
through 25-91 to part 25, with certain FAA-allowed reversions for 
specific part 25 regulations to the part 25 amendment levels of the 
original type certification basis.
    Airbus has also chosen to comply with part 25 as amended by 
Amendments 25-92, -93, -94, -95, -97, -98, and -104.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25 as amended) do not contain adequate or 
appropriate safety standards for the Airbus Industrie Model A340-500 
and -600 because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of 14 CFR 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Airbus Industrie Model A340-500 and -600 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.
    Special conditions, as defined in 14 CFR 11.19, are issued in 
accordance with Sec. 11.38 and become part of the type certification 
basis in accordance with Sec. 21.101(b)(2).
    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, or should any other model already included on 
the same type certificate be modified to incorporate the same novel or 
unusual design feature, the special conditions would also apply to the 
other model under the provisions of Sec. 21.101(a)(1).

Novel or Unusual Design Features

    The Airbus Models A340-500 and -600 will incorporate the following 
novel or unusual design feature: a four-wheel center landing gear with 
braking ability.

Discussion

    The basic A340 included a two-wheel center landing gear which did 
not have brakes. The purpose of the center landing gear was to assist 
the main landing gear during ground handling conditions for heavy 
airplane weights. This center landing gear was not intended for energy 
absorption during landing, even if it could participate in the impact 
under certain conditions. Therefore, to provide additional taxi, 
takeoff, and landing criteria for this arrangement, Special Conditions 
25-ANM-69 was issued.
    The Model A340-500 and -600 airplanes have a four-wheel center 
landing gear which functions in all respects like a main landing gear, 
including braking capabilities. Because the speeds and weights of the 
Models A340-500 and -600 are greater than that of the basic A340, 
redesign of the center landing gear was necessary. As a result, the 
current rules, applying to the original two-wheel center landing gear, 
are inadequate.

Applicability

    As discussed above, these special conditions are applicable to the 
Airbus Models A340-500 and -600. Should Airbus Industries apply at a 
later date 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 under the 
provisions of Sec. 21.101(a)(1).

Conclusion

    This action affects only certain novel or unusual design features 
of the center landing gear on the Model A340-500 and A340-600 
airplanes. It is not a rule of general applicability, and it affects 
only the applicant who applied to the FAA for approval of these 
features on the airplane.

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 A340-500 and A340-600 airplanes.
    The following special conditions are proposed in lieu of the 
previously issued special conditions, ``Ground Load Conditions for 
Center Landing Gear,'' recorded as item 10 of Special Conditions: 
Airbus Industrie Model A340 Series Airplanes [Docket No. NM-75, Special 
Conditions No. 25-ANM-69]:
    1. Ground Load Conditions for Center Landing Gear. Notwithstanding 
Sec. 25.477, the requirements of Sec. 25.473 and Secs. 25.479 through 
25.485 apply, except as noted:
    (a) In addition to the requirements of Sec. 25.473, ``Landing load 
conditions and assumptions,'' and Sec. 25.479, ``Level landing 
conditions,'' landing should be considered on a level runway and on a 
runway having a convex upward shape that may be approximated by a slope 
of 1.5 percent at main landing gear stations. The maximum loads 
determined from these two conditions must be applied to each main 
landing gear and to the center landing gear.
    (b) In addition to the requirements of Sec. 25.483, ``One gear 
landing conditions,'' the condition represented by Figure 1 also 
applies:
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[[Page 12905]]

[GRAPHIC] [TIFF OMITTED] TP20MR02.005

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[[Page 12906]]

    (c) In lieu of the requirements of Sec. 25.485, ``Side load 
conditions,'' the following apply:
    (1) The airplane is considered to be in the level attitude with 
only the main and center wheels contacting the ground.
    (2) Vertical reactions of one-half of the maximum vertical reaction 
obtained at each main and center gear in the level landing conditions 
should be considered. The vertical loads must be combined with side 
loads as follows: for the main gear, 0.8 of the vertical reaction (on 
one side) acting inward and 0.6 of the vertical reaction (on the other 
side) acting outward; for the center gear, 0.7 of the vertical reaction 
acting in the same direction as main gear side loads. These loads are 
assumed to be applied at the ground contact point and to be resisted by 
the inertia of the airplane. The drag loads may be assumed to be zero.
    (d) In addition to Sec. 25.489, ``Ground handling conditions,'' the 
airplane should be considered to be on a level runway and on a runway 
having a convex upward shape that may be approximated by a slope of 1.5 
percent at main landing gear stations. The ground reactions must be 
distributed to the individual landing gear units in a rational or 
conservative manner.
    (e) In addition to the requirements of Sec. 25.493(d), ``Braked 
roll conditions,'' the sudden application of maximum braking effort 
must be defined taking into account the behavior of the braking system. 
Failure conditions of the braking system not shown to be extremely 
improbable must be analyzed in accordance with the following criteria:
    (1) At the time of occurrence. A realistic scenario, including 
pilot corrective actions, must be established to determine the loads 
occurring at the time of failure and immediately after failure.
    (i) For static strength substantiation, these loads multiplied by 
an appropriate factor of safety that is related to the probability of 
occurrence of the failure are ultimate loads to be considered for 
design. The factor of safety (F.S.) is defined in Figure 2.
[GRAPHIC] [TIFF OMITTED] TP20MR02.006

    (ii) For residual strength substantiation, the airplane must be 
able to withstand two thirds of the ultimate loads defined in paragraph 
(e)(1)(i).
    (iii) Failures of the system that result in forced structural 
vibrations (oscillatory failures) must not produce loads that could 
result in detrimental deformation of primary structure.
    (2) Consideration of certain failure conditions may be required by 
other sections of part 25, regardless of calculated system reliability. 
Where analysis shows the probability of these failure conditions to be 
less than 10-9, criteria other than those specified in this 
paragraph may be used for structural substantiation to show continued 
safe flight and landing.
    (3) Warning considerations. For system failure detection and 
warning, the system must be checked for failure conditions, not 
extremely improbable, that degrade the structural capability below the 
level required by part 25 or significantly reduce the reliability of 
the remaining system. The flightcrew must be made aware of these 
failures before flight. Certain elements of the control system, such as 
mechanical and hydraulic components, may use special periodic 
inspections, and electronic components may use daily checks, in lieu of 
warning systems to achieve the objective of this requirement. These 
certification maintenance requirements must be limited to components 
that are not readily detectable by normal warning systems and where 
service history shows that inspections will provide an adequate level 
of safety.
    (4) Dispatch with known failure conditions. If the airplane is to 
be dispatched in a known system failure condition that affects 
structural

[[Page 12907]]

performance, or affects the reliability of the remaining system to 
maintain structural performance, then the provisions of these special 
conditions must be met for the dispatched condition and for subsequent 
failures. Flight limitations and expected operational limitations may 
be taken into account in establishing Qj as the combined probability of 
being in the dispatched failure condition and the subsequent failure 
condition for the safety margins in Figure 3. These limitations must be 
such that the probability of being in this combined failure state and 
then subsequently encountering limit load conditions is extremely 
improbable. No reduction in these safety margins is allowed if the 
subsequent system failure rate is greater than 10-3 per 
hour.''
[GRAPHIC] [TIFF OMITTED] TP20MR02.007

Qj = (Tj)(Pj) where:
Tj = Average time spent in failure condition j (in hours).
Pj = Probability of occurrence of failure mode j (per hour).

    (f) In lieu of the requirements of Sec. 25.495, ``Turning,'' the 
following apply:
    (1) The airplane is assumed to execute a steady turn by nose gear 
steering, or by application of sufficient differential power, so that 
the limit load factors applied at the center of gravity are 1.0 
vertically and 0.5 laterally.
    (2) The airplane must be designed for the condition prescribed in 
paragraph (f)(1), taking into account:
    (i) The effects of tire characteristics on the sharing of lateral 
loads on each tire of the landing gear system, and
    (ii) The effect of airframe and landing gear flexibility on the 
sharing of loads on the different legs of the landing gear system.
    (g) In lieu of the requirements of Sec. 25.503, ``Pivoting,'' the 
following apply:
    (1) The main and center gear units and supporting structure must be 
designed for the scrubbing or torsion loads, or both, induced by 
pivoting during ground maneuvers produced by:
    (i) Towing at the nose gear, no brakes applied, and
    (ii) Application of symmetrical or unsymmetrical forward thrust to 
aid pivoting and with or without braking by pilot action on the pedals.
    (2) The airplane is assumed to be in static equilibrium, with the 
loads being applied at the ground contact points.
    (3) The limit vertical load factor must be 1.0, and:
    (i) For wheels with locked brakes applied by pilot action on the 
pedals, the coefficient of friction must be 0.8.
    (ii) For wheels with brakes not applied, the ground tire reactions 
must be based on reliable tire data.
    (4) The failure conditions must be analyzed in accordance with 
paragraph (e) of these Special Conditions.
    (h) In lieu of paragraph (b) of Sec. 25.723 ``Shock absorption 
tests,'' the center landing gear should not fail in a test 
demonstrating its reserve energy absorption capacity at design landing 
weight, assuming airplane lift no greater than the airplane weight 
acting during a 12-feet-per-second airplane landing impact, taking into 
account both main and center gear acting during the impact. Landing 
should be considered on a level runway or a runway having a convex 
upward shape that may be approximated by a slope of 1.5 percent with 
the horizontal at main landing gear stations, whichever is the most 
critical.

    Issued in Renton, Washington, on February 28, 2002.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 02-5876 Filed 3-19-02; 8:45 am]
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