[Federal Register Volume 67, Number 98 (Tuesday, May 21, 2002)]
[Rules and Regulations]
[Pages 35715-35722]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-12608]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM211; Special Conditions No. 25-200-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: Final special conditions.

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SUMMARY: These special conditions are issued for the 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.

EFFECTIVE DATE: May 10, 2002.

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:

Background

    On November 14, 1996, Airbus Industrie applied for an amendment to

[[Page 35716]]

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 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,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., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Airbus Industrie Model 
A340-500 and -600 airplanes 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 
airplanes 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  11.38 and become part of the type 
certification basis in accordance with 14 CFR 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 14 CFR 21.101(a)(1).

Novel or Unusual Design Features

    The Airbus Model A340-500 and -600 airplanes 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 were 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 Model A340-500 and -600 airplanes 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.

Discussion of Comments

    Notice of proposed special conditions No. 
25-02-03-SC for the Airbus Industrie Model 
A340-500 and -600 airplanes was published in the Federal 
Register on March 20, 2002 (67 FR 12903). No comments were received, 
and the special conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Airbus Model A340-500 and -600 airplanes. 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  21.101(a)(1).
    Under standard practice, the effective date of final special 
conditions would be 30 days after the date of publication in the 
Federal Register; however, as the certification date for the Airbus 
Model A340-500 and A340-600 airplanes is imminent, the FAA 
finds that good cause exists to make these special conditions effective 
upon issuance.

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 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 A340-500 and 
A340-600 airplanes.
    The following special conditions are issued 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 
 25.477, the requirements of  25.473

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and  25.479 through 25.485 apply, except as noted:
    (a) In addition to the requirements of  25.473, 
"Landing load conditions and assumptions," and 
 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  25.483, 
"One gear landing conditions," the condition represented by 
Figure 1 also applies:

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[GRAPHIC] [TIFF OMITTED] TR21MY02.000

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    (c) In lieu of the requirements of  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  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  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 as follows:
[GRAPHIC] [TIFF OMITTED] TR21MY02.001

    (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

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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 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. Figure 3 follows:

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[GRAPHIC] [TIFF OMITTED] TR21MY02.002

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    (f) In lieu of the requirements of  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  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  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 May 10, 2002.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 02-12608 Filed 5-20-02; 8:45 am]
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