Aeronautics and astronautics – Landing gear – Retractable
Reexamination Certificate
2002-10-22
2004-01-20
Barefoot, Galen L (Department: 3644)
Aeronautics and astronautics
Landing gear
Retractable
Reexamination Certificate
active
06679452
ABSTRACT:
TECHNICAL FIELD
The following disclosure relates generally to aircraft landing gears and, more particularly, to aircraft landing gear support assemblies for use with aircraft wings.
BACKGROUND
Many aircraft have retractable landing gears attached to their wings. These landing gears are generally movable between a static deployed position for supporting the aircraft on the ground and a static retracted position for reducing aerodynamic drag during flight. Because of high landing loads, these landing gears are typically attached to the wings with a very strong support assembly. In addition to being very strong, this support assembly must also accommodate movement of the landing gear between the static deployed and static retracted positions.
FIG. 1
is a partial cutaway top view of an aircraft
100
having a retractable landing gear
112
attached to a wing
108
in accordance with the prior art. The landing gear
112
, which is depicted in
FIG. 1
in a static retracted position for flight, can pivot downwardly and outwardly about an axis
114
to position a wheel truck
113
for landing. The landing gear
112
is attached to the wing
108
with a landing gear support assembly
110
that includes a forward trunnion support
121
and an aft trunnion support
119
. The forward trunnion support
121
is attached to a rear wing spar
106
, and the aft trunnion support
119
is attached to a beam
102
extending between the rear wing spar
106
and a fuselage
104
. Accordingly, landing loads from the landing gear
112
are transferred to the rear wing spar
106
via the forward trunnion support
121
, and to the rear wing spar
106
and the fuselage
104
via the aft trunnion support
119
and the beam
102
.
One downside associated with the landing gear support assembly
110
is that the beam
102
must be relatively large, and hence relatively heavy, to transfer the high landing loads from the aft trunnion support
119
to the rear wing spar
106
and the fuselage
104
. This additional weight can adversely affect aircraft performance.
FIG. 2
is a top isometric view of another landing gear support assembly
210
configured in accordance with the prior art.
FIG. 2
is taken from a perspective looking outboard and slightly forward relative to a rear wing spar
206
. The landing gear support assembly
210
includes a forward trunnion support
221
attached to the rear wing spar
206
, and a landing gear aft trunnion support beam
215
attached to the rear wing spar
206
outboard of the forward trunnion support
221
. The forward trunnion support
221
includes a spherical bearing
222
configured to receive a pin
213
to pivotally support a forward pivot portion
218
of a landing gear main strut
212
. The landing gear aft trunnion support beam
215
is at least partially cantilevered from the rear wing spar
206
, and includes an aft trunnion support
219
. The aft trunnion support
219
is laterally offset from a longitudinal axis
250
of the aft trunnion support beam
215
, and is configured to receive a fuse pin
217
to pivotally support an aft pivot portion
216
of the landing gear main strut
212
. The term “fuse pin” is used herein to denote a cylindrical pin that has been designed to fail under a preselected force.
As best understood by the applicants, the lateral offset between the aft trunnion support
219
and the longitudinal axis
250
, in combination with the fuse pin
217
and the spherical bearing
222
, enables the landing gear main strut
212
to break free of the aft trunnion support beam
215
and the rear wing spar
206
in the event of an overload condition. As used herein, an “overload” or “overload condition” is defined as a design load condition at which a landing gear support is designed to fail. Breaking free of the aft trunnion support beam
215
and the rear wing spar
206
in this manner apparently prevents the landing gear main strut
212
from causing damage to the rear wing spar
206
. This failure mode is desirable because many aircraft carry fuel in their wings directly forward of the rear wing spar and adjacent to the landing gear. Thus, rupturing the rear wing spar in such aircraft could potentially cause a substantial fuel leak.
One shortcoming associated with the landing gear support assembly
210
is that the lateral offset between the aft trunnion support
219
and the longitudinal axis
250
causes the landing gear main strut
212
to put a significant torsional load into the aft trunnion support beam
215
about the longitudinal axis
250
when vertically loaded. As a result, the aft trunnion support beam
215
must be relatively large, and hence relatively heavy, to carry this torsional load without failure. As mentioned above with reference to
FIG. 1
, this additional weight can adversely affect aircraft performance.
SUMMARY
Aspects of the invention are directed to landing gear support assemblies for attaching landing gears to aircraft wings. In one aspect, an aft trunnion support beam for use with an aircraft landing gear support assembly includes a base portion and an aft trunnion support spaced apart from the base portion. The base portion can be configured to be attached at least proximate to a rear wing spar. The aft trunnion support can be configured to pivotally support at least a portion of a landing gear main strut. The aft trunnion support beam can further include a shear center axis extending from the base portion toward the aft trunnion support. The shear center axis can be at least approximately vertically aligned with the aft trunnion support.
In another aspect of the invention, the base portion of the aft trunnion support beam can be attached to the rear wing spar with at least a first breakable element, such as a fuse pin. The first breakable element can be configured to break and release the aft trunnion support beam from the wing spar when the landing gear main strut exerts a preselected force against the aft trunnion support.
In a further aspect of the invention, a method for mounting a landing gear to an aircraft wing includes attaching a forward trunnion support at least proximate to a rear wing spar, and attaching a base portion of an aft trunnion support beam at least proximate to the rear wing spar. The aft trunnion support beam can further include an aft trunnion support spaced apart from the base portion and a shear center axis extending from the base portion toward the aft trunnion support. The shear center axis can be at least approximately vertically aligned with the aft trunnion support. The method can further include pivotally connecting a forward pivot portion of the landing gear main strut to the forward trunnion support and pivotally connecting an aft pivot portion of the landing gear main strut to the aft trunnion support.
REFERENCES:
patent: 2750134 (1956-06-01), Hawkins, Jr. et al.
patent: 4087062 (1978-05-01), Masclet
patent: 4155522 (1979-05-01), Sealy
patent: 4345727 (1982-08-01), Brown et al.
patent: 4392622 (1983-07-01), McClaflin
patent: 4392623 (1983-07-01), Munsen et al.
patent: 6318669 (2001-11-01), Dazet et al.
Composite Wing Box—Testing, Testing of a McDonnell Douglas Composite Wing Box Landing Gear Attachment, ©2000 (3 pages) http://www.structures.ucsd.edu/casl/projects/wing_box/testing.htm [Accessed Jul. 24, 2002].
A340 Wing, Main Landing Gear Pick Up Structure, Feb. 1990.
Cottet Justin D.
Meneghetti Michael J.
Whitmer Brett D.
Barefoot Galen L
Perkins Coie LLP
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