AGARD R-800 - FTP Directory Listing - Nato

1-6
Many nonstructural components may be designed to be
interchangeable from carrier based to land based
designs. By using equal piston diameters, common
components such as separator pistons, gland nuts, and
strut bearings may be incorporated. Also, system type
components such as steering valves may be completely
com mon .
To benefit from design commonality, both carrier based
landing gear requirements and the maximum
operational runway/taxiway roughness should be
considered at the beginning of the design process.
History has shown that landing gears initially designed
for land base use are impractical for carrier operations
and entirely new designs are required. If carrier
requirements are considered initially, the landing gear
may be more easily adapted to multi role uses in the
future and at the same time much higher roughness
tolerance potential can be achieved.
9. CONCLUSIONS
Specifications for landing gear design ground loads are
not always explicit in describing operational
requirements on rough runways. The lack of clarity of
operational requirements with respect to braking levels
while on rough surfaces can lead to designs with
reduced operational capability, i. e. limited to unbraked
taxi or free rollout where the possibility of roughness
resonance exists.
Navy carrier based aircraft specifications (MIL-A-
8863) require landinghakeoff operations from lower
amplitude rough surfaces than the corresponding MIL-
A-8862 surfaces; however, additional capability is
inherent over corresponding Air Force gears from other
requirements associated with Navy shipboard
operations. When severe roughness combined with
other load sources is considered, weight differences in
Navy and Air Force landing gears may diminish.
Airfield roughness capability of two landing gears with
different stroke lengths using MIL-A-8862 roughness
specifications have been compared for a hypothetical
aircraft. The landing gears were sized by Air Force
and Navy Landing Impact Criteria. The landing gear
weight penalty to provide operational capability with
braking to Air Force gears has been estimated from
this comparison at approximately 0.9 percent of aircraft
weight.
10. Recommendations
Landing gear design and user technical personnel need
to improve, clarify, and develop realistic ground
roughness performance requirements definitions to
avoid potential problems in landing gear/vehicle
integration. Wheel well sizing should be based on the
maximum stroke lengths and tire sizes that could be
anticipated for future, perhaps multi service usage of
the airframes.
Future studies should focus on the inherent capabilities
of gears designed for shipboard operations to establish
benefits for use on rough runways.
Additional work is needed to rapidly quantify landing
gear weight as a function of required capability through
improvements in automated loads and stress analysis.
Modeling tools of this type must be available and
utilized from the earliest design stages.
It is recommended that cost reduction methods,
including simplified gear retraction geometry, be given
high priority in the initial gear design. Sizeable cat
savings might be realized, both in development and
manufacturing with more progress toward standardized
gear arrangements, and by reduced gear complexity
which enable the use of common parts and forgings.
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REFERENCES
Currie, Norman S., "Aircraft Landing Gear
Design: Principles and Practices," AIAA
Education Series, American Institute of
Aeronautics and Astronautics, Inc. ,
Washington, D. C., 1988, p.35.
Williams, W. W., Williams, G. K., and
Garrard, W. C. J., "Soft and Rough Field
Landing Gears," SAE Paper 650844, October, - -
1965.
Airplane Strength and Rigidity, Landplane
Landing and Ground Handling Loads, MIL-A-
8862A, MarchJ971.
Airplane Strength and Rigidity, Ground Loads
for Navy Acquired Airplanes, MIL-A-
8863B(AS), 6 May 1987.
Aircraft Structures, General Specification For,
MIL-A-87221, 28 February, 1985.
Conway, H. G., "Landing Gear Design,"
Chapman and Hall Ltd., London, 1958. , p.
184
Anon, "Aircraft Operation on Repaired
Runways," Report of Working Group 22 of
the Structures and Materials Panel,
NATO/AGARD, Paris France, AGARD-R-
731, August, 1990.