Short take off jump mode for airplane landing gear struts

• US 4,524,929 A
• Filed: 09/30/1982
• Issued: 06/25/1985
• Est. Priority Date: 09/30/1982
• Status: Expired due to Term

• Current Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Original Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Inventors: Gebhard, David F.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/430,657
• Time in Patent Office: 999 Days
• Field of Search: 244/63, 244/100 R, 244/102 SS, 244/102 SL, 244/104 FP, 244/104 CS, 188/300, 188/322.21, 267/64.12, 60/636, 92/15, 91/41, 91/44
• US Class Current: 244/63
• CPC Class Codes: B64C 2025/008 Comprising means for modifying their length, e.g. for kneeling, for jumping, or for leveling the aircraft
• CPC Class Codes: B64C 25/001 Devices not provided for in the groups B64C25/02 - B64C25/68
• CPC Class Codes: B64C 25/60 Oleo legs

Abstract

A telescoping energy-dissipating oleo landing gear shock strut set which can provide both the main landing gear and forward landing gear function, and which is affixed to an airplane, is restrained in an unenergized, shortened condition. A high pressure gas charge is then provided between the extendible element of the strut and the element affixed to the airplane. Early in the takeoff run, the charge gas in the forward strut is released so as to jump the nose and rotate the airplane to a high angle of attack appropriate for takeoff. Subsequent to this rotation, but before the conventional takeoff speed is reached, the charge gas in each of the main struts is released to impart a vertical velocity to the entire airplane, thus jumping it into the air. Both the forward strut and main struts incorporate a hydraulic flow bypass function, so that the landing shock dissipation function does not compromise the aforesaid energy release. The struts also incorporate valves to discharge enough residual gas immediately at the end of the jump stroke so that the landing energy dissipation mode is not compromised.

Claims

1. A method of facilitating early takeoff of an airplane or, alternatively, increasing the payload of the airplane without increasing takeoff ground roll, said airplane having a telescoping, energy-dissipating oleo shock strut affixed to an extendible from the nose of said airplane, said method comprising the steps of

restraining said shock strut in unenergized shortened condition;

energizing said strut;

accelerating said airplane from standstill;

releasing said strut during the takeoff run acceleration of said airplane, whereby the energy of said strut extends said strut from said airplane and is dissipated thereby increasing the angle of attack of said airplane, causing an upward increase in lift which decreases gravity effect during acceleration of said airplane and shortens its takeoff roll; and

immediately restoring the landing shock energy dissipation condition of said strut thereby immediately reinstituting the normal landing function of said strut.

2. A method of facilitating early takeoff of an airplane or, alternatively, increasing the payload of the airplane without increasing takeoff ground roll, said airplane having a telescoping, energy-dissipating oleo nose shock strut affixed to and extendible from the nose of said airplane and telescoping, energy-dissipating oleo main shock struts affixed to and extendible from said airplane, said method comprising the steps of

latching said shock struts in their shortened condition;

pressurizing the interiors of said shock struts while they are latched;

accelerating said airplane from standstill to a predetermined velocity;

unlatching said nose shock strut during takeoff run acceleration of said airplane, whereby the internal pressure of said nose strut extends said nose strut from said airplane and is dissipated, thereby increasing the angle of attack of said airplane, causing an upward increase in lift which decreases gravity effect during acceleration of said airplane and shortens its takeoff roll;

immediately restoring the landing shock energy dissipation condition of said nose strut thereby immediately reinstituting the normal landing function of said nose strut;

unlatching said main shock struts after rotation of said airplane whereby the energy of said main struts extends said main struts from said airplane and is dissipated thereby pushing said airplane upward, causing a trajectory which decreases gravity effect during acceleration of said airplane and further shortens its takeoff roll; and

immediately restoring the landing shock energy dissipation condition of said main struts after lift-off of said airplane thereby immediately reinstituting the normal landing function of said main struts.

3. A method of facilitating a short takeoff roll for an airplane or, alternatively, increasing the payload of the airplane without increasing takeoff ground roll, said airplane having a telescoping, energy-dissipating oleo nose shock strut affixed thereto and extendible from the nose of said airplane and telescoping, energy-dissipating oleo main shock struts affixed to and extendible from said airplane, said struts having compressed gas therein and landing wheels mounted on the free ends thereof, said method comprising the steps of

bleeding gas from said shock struts to collapse them;

latching said shock struts in their shortened attitude;

supplying compressed fluid to said shock struts;

accelerating said airplane to begin its takeoff run;

releasing the latching of said nose shock strut thereby providing a maximum extension of said nose strut and dissipating the pressure, thereby increasing the angle of attack of said airplane to effect a rotation of the wind velocity vector to permit an upward increase in lift and decreased gravity effect with sufficient balance to shorten the takeoff roll of said airplane;

immediately restoring the landing shock energy dissipation condition of said nose strut thereby immediately reinstituting the normal landing function of said nose strut;

sensing the reaching of a predetermined angle of attack by said airplane;

releasing the latching of said main shock struts upon the sensing of said predetermined angle of attack whereby the energy of said main struts extends said main struts from said airplane and is dissipated thereby pushing said airplane upward, causing a trajectory which decreases gravity effect during acceleration of said airplane and further shortens its takeoff roll; and

immediately restoring the landing shock energy dissipation condition of said main struts after lift-off of said airplane thereby immediately reinstituting the normal landing function of said main struts.

4. A method of rotating an airplane early in the takoff ground run to a high angle of attack which provides lift for early takeoff or, alternatively, increasing the payload of the airplane without increasing takeoff ground roll, said airplane having a telescoping, energy-dissipating oleo shock strut affixed to and extendible from said airplane at a forward position of said airplane, said method comprising the steps of

bleeding gas from said strut to collapse it;

restraining said strut in an unenergized shortened condition;

energizing said strut with compressed gas;

releasing said strut during the takoff ground run whereby the energy of said strut extends said strut from said airplane and is dissipated thereby jumping the nose of said airplane upward, increasing the angle of attack at a point in the takeoff ground run where there is insufficient speed to achieve rotation by conventional pitch control means; and

immediately restoring the landing shock energy dissipation condition of said strut thereby immediately reinstituting the normal landing function of said strut.

5. A method of providing a shortened takeoff ground run or a payload increase without an increase in takeoff ground run of an airplane, said airplane having a propulsion system, a telescoping, energy-dissipating oleo forward shock strut affixed to and extendible from said airplane at a forward portion of said airplane and telescoping, energy-dissipating oleo center shock struts affixed to and extendible from said airplane near the center of gravity of said airplane, said method comprising the steps of

bleeding gas from said shock struts to collapse them;

restraining said shock struts in an unenergized shortened condition;

energizing said struts with compressed gas;

releasing said forward strut during the takeoff ground run whereby the energy of said forward strut extends said forward strut from said airplane and is dissipated thereby jumping the nose of the airplane upward and increasing the angle of attack of said airplane to cause an increase in lift and counteracting gravity effect;

immediately restoring the landing shock energy dissipation condition of said forward strut thereby immediately reinstituting the normal landing function of said forward strut;

sensing the reaching of a predetermined angle of attack by the airplane;

subsequently releasing said center struts upon the sensing of said predetermined angle of attack after the nose-up rotation of said airplane whereby subsequently the energy of said center struts extends said center struts from said airplane and is dissipated thereby pushing said airplane upward, resulting in an initially upward, downwardly curved, trajectory which produces a generally upward centrifugal force, said trajectory being defined by a continuously diminishing gravity effect due to the sum of any thrust lift, the increasing wind lift and the substantial horizontal acceleration provided by the propulsion system of said airplane, so that said airplane does not return to earth and there is a substantial reduction in the takeoff ground run; and

immediately restoring the landing shock energy dissipation condition of said center struts after lift-off of said airplane thereby immediately reinstituting the normal landing function of said struts.

6. A method as claimed in claim 5, wherein energy is dissipated from said forward and center struts by venting off residual pressurizing gas as necessary after jumping of said struts to provide the proper gas charge for the landing shock absorption function.

7. A jump strut device for facilitating early takeoff of an airplane or, alternatively, increasing the payload of the airplane without increasing takeoff ground roll, said airplane having a telescoping, energy-dissipating oleo shock strut affixed to and extendible from the nose area of said airplane, said device comprising

latching means for latching said shock strut in its shortened condition;

pressure means for pressurizing the interior of said shock strut while it is latched;

release means for unlatching said latching means during takeoff run acceleration of said airplane, whereby the internal pressure of said strut extends said strut from said airplane and is dissipated, thereby pushing said airplane upward and increasing the angle of attack of said airplane, causing an increase in lift and a decrease in gravity effect during acceleration of said airplane and shortening its takeoff roll; and

restoring means for immediately restoring the landing shock energy dissipation condition of said strut thereby immediately reinstituting the normal landing function of said strut.

8. A jump strut device as claimed in claim 7, wherein said shock strut includes an upper cylinder affixed to said airplane and an extendible piston cylinder coaxially slidably mounted in said upper cylinder for movement in axial directions, said piston cylinder having a free end farthest from said airplane and mounting a landing wheel of said airplane in a manner whereby said wheel is at a first predetermined distance from said airplane when said shock stut is in shortened condition and is at a second predetermined maximum distance from said airplane when said shock strut is in extended condition.

9. A jump strut device as claimed in claim 8, wherein said pressure means comprises a source of compressed fluid and valve means for selectively controlling the flow of said fluid to said upper cylinder thereby controlling the axial position of said piston cylinder and,, accordingly, the distance between said landing wheel and said airplane.

10. A jump strut device as in claim 8, wherein said fluid includes hydraulic fluid and gas under pressure.

11. A jump strut device as claimed in claim 8, wherein said strut further includes an orifice, an orifice support tube coaxially positioned in said piston cylinder and a metering pin in said piston cylinder coaxially slidably mounted in said orifice support tube and said orifice, and said pressure means comprises a source of compressed fluid and a check valve which permits fluid to bypass said orifice when said piston cylinder is moving away from said airplane but limits fluid to flow through said orifice when said piston cylinder is moving toward said airplane.

12. A jump strut device as claimed in claim 8, wherein said shock strut further includes an orifice, an orifice support tube coaxially positioned in said piston cylinder and a metering pin in said piston cylinder coaxially slidably mounted in said orifice support tube and said orifice, and said release means comprises a load release sleeve coaxially positioned with and abutting part of said latching means when said latching means is locked, said load release sleeve maintaining said metering pin in locked position in said orifice support tube and, when moved, permitting said part of said latching means to expand, thereby permitting another part of said latching means to collapse and releasing said metering pin to release said latching means from its locked position.

13. A jump strut device as claimed in claim 12, wherein said latching means comprises a lock ring, intermediate latch parts, a load release sleeve coaxially positioned with said intermediate latch parts so that said lock ring is maintained in a radially expanded condition which locks said metering pin and said piston cylinder to said orifice support tube and said upper cylinder, axial movement of said load release sleeve permitting said intermediate latch parts to move so that said lock ring contracts radially, releasing said metering pin and said piston cylinder from said orifice support tube and said upper cylinder.

14. A jump strut device as claimed in claim 13, wherein said strut further includes a valve for bleeding off residual gas after the jumping of said airplane and a valve for supplying high pressure gas to said strut.

18. A jump strut device as claimed in claim 12, wherein said pressure means comprises a source of compressed fluid and valve means for selectively controlling the flow of said fluid to said upper cylinder thereby controlling the axial position of said piston cylinder and, accordingly, the distance between said landing wheel and said airplane.

19. A jump strut device as claimed in claim 18 wherein said fluid includes hydraulic fluid and gas under pressure.

15. A jump strut device for facilitating early takeoff of an airplane or, alternatively increasing the payload of the airplane without increasing takeoff ground roll, said device comprising

a telescoping, energy-dissipating oleo shock landing gear strut having an upper cylinder for hydraulic fluid affixed to and extendible from the area of the nose of said airplane and a piston cylinder coaxially mounted in said upper cylinder for movement in axial directions and mounting a wheel of said airplane thereon;

latching means for locking said piston cylinder at a first predetermined position in said upper cylinder to maintain said wheel and said airplane at a first predetermined distance from each other for normal takeoff and landing operation; and

control means including pressure means for controlling the flow and pressure of fluid in said upper cylinder thereby to control the axial position of said piston cylinder in said upper cylinder and the distance between said wheel and said airplane, for releasing said piston cylinder thereby permitting the pressure of fluid in said upper cylinder to move said piston cylinder and said wheel to second predetermined positions at which they and said airplane are farther away from each other and then to dissipate whereby the angle of attack of said airplane is increased to effect an increase of lift and a lessening of gravity effect while the velocity of said airplane is increasing to effect takeoff after a shortened roll distance without settling of said airplane toward the ground, and for immediately restoring the landing shock energy dissipation condition of said strut thereby immediately reinstituting the normal landing function of said strut.

16. A jump strut device for facilitating early takeoff of an airplane or, alternatively, increasing the payload of the airplane without increasing takeoff ground roll, said airplane having a telescoping, energy-dissipating oleo nose shock strut affixed to and extendible from the nose of said airplane and telescoping, energy-dissipating oleo main shock struts affixed to and extendible from said airplane, said device comprising

latching means for latching said shock struts in their shortened condition;

pressure means for pressurrizing the interior of said shock struts while they are latched;

release means for unlatching said latching means during takeoff run acceleration of said airplane, whereby the internal pressure of said nose strut extends said nose strut from said airplane and is dissipated thereby increasing the angle of attack of said airplane, causing an upward increase in lift and a decrease in gravity effect during acceleration of said airplane and shortening its takeoff roll;

restoring means for immediately restoring the landing shock energy dissipation condition of said nose strut thereby immediately reinstituting the normal landing function of said nose strut;

sensing means at the tail of said airplane for sensing the reaching of a predetermined angle of attack by said airplane;

release means for unlatching said main shock struts upon the sensing of said predetermined angle of attack, whereby the internal pressure of said main struts extends said main struts from said airplane and is dissipated thereby pushing said airplane upward, causing a trajectory which decreases gravity effect during acceleration of said airplane and further shortens its takeoff roll; and

restoring means for immediately restoring the landing shock energy dissipation condition of said main struts after lift-off of said airplane thereby immediately reinstituting the normal landing function of said main struts.

17. A jump strut device as claimed in claim 16, wherein each of said shock struts includes an upper cylinder affixed to said airplane and an extendible piston cylinder coaxially slidably mounted in said upper cylinder for movement in axial directions, said piston cylinder having a free end farthest from said airplane and mounting a landing wheel of said airplane in a manner whereby said wheel is at a first predetermined distance from said airplane when said shock strut is in shortened condition and is at a second predetermined maximum distance from said airplane when said shock strut is in extended condition.

20. A jump strut device as claimed in claim 17, wherein each of said shock struts further includes an orifice support tube coaxially positioned in said piston cylinder and a metering pin in said piston cylinder coaxially slidably mounted in said orifice support tube, and said release means comprises a load release sleeve coaxially positioned with and abutting part of said latching means when said latching means is locked, said load release sleeve maintaining said metering pin in locked position in said orifice support tube and, when moved, permitting said part of said latching means to expand, thereby permitting another part of said latching means to collapse and releasing said metering pin to release said latching means from its locked position.

21. A jump strut device as claimed in claim 17, wherein each of said struts further includes an orifice support tube coaxially positioned in said piston cylinder and a metering pin in said piston cylinder coaxially slidably mounted in said orifice support tube and said pressure means comprises a source of compressed fluid and a check valve which permits fluid to bypass said orifice when said piston cylinder is moving away from said airplane but limits fluid to flow through said orifice when said piston cylinder is moving toward said airplane.