Adjustable two-stage aircraft landing gear system

• US 4,869,444 A
• Filed: 06/17/1988
• Issued: 09/26/1989
• Est. Priority Date: 09/30/1986
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Ralph, Harry C.
• Primary Examiner(s): Barefoot, Galen L.
• Application Number:
  US07/208,364
• Time in Patent Office: 466 Days
• Field of Search: 244/100 R, 244/102 R, 244/104 R, 244/104 FP, 280/707
• US Class Current: 244/104.0FP
• CPC Class Codes: B64C 25/60 Oleo legs

Abstract

A two-stage aircraft gear. The landing gear includes a cantilever landing gear whose lower end is attached to a trailing arm (or articulated) landing gear. The cantilever gear is a collapsible piston-cylinder assembly, and the trailing arm gear also has a shock absorber connected between a fixed portion of the trailing arm gear and the movable wheel support arm. When landing, the load imposed is first absorbed by the trailing arm landing gear. After the trailing arm gear has been fully compressed, the cantilever gear begins to compress. The cantilever and trailing arm landing gear can be combined to provide the desired performance. The landing gear static position can be designed to be in the static load curve of the first component, allowing the aircraft to be stably supported and yet difficult to overturn. Adjustable orifice plates contained within one or both of the cantilever and articulated stages can be controlled as a function of the vertical descent velocity and/or distance. If desired, differential pressure measurements within the two stages can be used to give the landing gear any desired damping and/or landing gear extension characteristic.

Claims

1. An adjustable landing gear for use with an aircraft, comprising, in combination:

means for measuring a vertical descent velocity of said aircraft and producing a velocity signal in response thereto;

a first strut having first and second ends defining a first axis, said first and second ends being separated by a variable first distance, said first strut including means for receiving said velocity signal and controlling the rate at which said first distance varies as a first function of a first compressive force applied to said first strut along said first axis, said first strut being attachable to said aircraft at said first end;

a trailing arm having an upper first end pivotally secured to said second end of said first strut;

a wheel attached to a lower end of said trailing arm, said wheel being rotatable about a horizontal axis; and

a second strut pivotally connected to said trailing arm and being pivotally supported through said second end of said first strut, said second end of said first strut and said connection of said second strut to said trailing arm defining a second axis and being separated by a variable second distance, said second strut being subjected to a second compressive force along said second axis, said second strut including means for receiving said velocity signal and controlling the rate at which said second distance varies as a second function of said second compressive force.

2. The adjustable landing gear of claim 1 wherein said first strut comprises a fluid container enclosing a first fluid and including variable orifice means adapted to receive said velocity signal, said first fluid being caused to act upon said variable orifice means in response to said first compressive force and being urged to pass through said variable orifice means as said first compressive force varies.

3. The adjustable landing gear of claim 2 wherein said variable orifice means comprises first and second mating orifice plates, said plates being continuously adjustable with respect to each other between a minimum flow position and a maximum flow position, said first and second plates each including a plurality of orifices therethrough, the plurality of orifices through said first plate being alignable with the plurality of orifices through said second plate, the total area of the aligned portions of said plurality of said orifices being continuously variable from a predetermined minimum when said plates are adjusted to said minimum flow position to a predetermined maximum when said plates are adjusted to said maximum flow position.

4. The adjustable landing gear of claim 3, further comprising means for adjusting said plates with respect to each other in response to said velocity signal.

5. An adjustable landing gear for use with an aircraft, comprising, in combination:

means for measuring a vertical descent velocity of said aircraft and producing a velocity signal in response thereto;

a first strut having first and second ends defining a first axis, said first and second ends being separated by a variable first distance, said first strut including a fluid container enclosing a first fluid and first variable orifice means including adjustable first orifices through which said first fluid can pass, said first variable orifice means being adapted to receive said velocity signal, to produce a first desired rate signal indicative of a desired rate of change of the said variable first distance, and to adjust said first orifices in response to said first desired rate signal, said first fluid being caused to act upon said first variable orifice means in response to said first compressive force and being urged to pass through said first variable orifice means as said first compressive force varies, said first strut being attachable to said aircraft at said first end;

a trailing arm having an upper first end pivotally secured to said second end of said first strut;

a wheel attached to a lower end of said trailing arm, said wheel being rotatable about a horizontal axis; and

a second strut pivotally connected to said trailing arm and being pivotally supported through said second end of said first strut, said second end of said first strut and said connection of said second strut to said trailing arm defining a second axis and being separated by a variable second distance, said second strut being subjected to a second compressive force along said second axis, said second strut including a fluid container enclosing a second fluid and second variable orifice means including adjustable second orifices through which said second fluid can pass, said second variable orifice means being adapted to receive said velocity signal, to produce a second desired rate signal indicative of a desired rate of change of the said variable second distance, and to adjust said second orifices through which said second fluid can pass in response to said second desired rate signal, said second fluid being caused to act upon said second variable orifice means in response to said second compressive force and being urged to pass through said second variable orifice means as said second compressive force varies, said first and second struts being independently compressible.

6. The adjustable landing gear of claim 5 wherein said first and second struts further respectively include means for producing actual first and second rate signals in response to the actual rates of change of said first and second distances, means for respectively producing first and second rate error signals in response to the differences between said respective first and second desired and actual rate signals, and means for respectively adjusting said respective first and second variable orifice means in response to said respective rate error signals.

7. The adjustable landing gear of claim 6 wherein said first and second variable orifice means each comprise a pair of mating orifice plates, each said pair of plates being continuously adjustable with respect to one another between a minimum flow position and a maximum flow position, each plate in each said pair of plates including a plurality of orifices therethrough, the plurality of orifices through one of each said pair of plates being alignable with the plurality of orifices through the other of each said pair of plates, the total aligned area of the plurality of said orifices in each of said pairs of plates being continuously variable from a predetermined minimum when each said pair of plates is adjusted to said minimum flow position to a predetermined maximum when each said pair of plates is adjusted to said maximum flow position.