LANDING GEAR

• US 20090050736A1
• Filed: 08/04/2006
• Published: 02/26/2009
• Est. Priority Date: 08/04/2005
• Status: Active Grant

• Current Assignee: Messier-Dowty Limited (Safran SA)
• Original Assignee: Messier-Dowty Limited (Safran SA)
• Inventors: Bennett, Ian, Lang, Richard C., Menezes, Robert A.
• Granted Patent: US 8,104,711 B2
• Time in Patent Office: Days
• US Class Current: 244/102.R
• CPC Class Codes: B64C 25/22 fluid
• CPC Class Codes: B64C 25/34 wheeled type, e.g. multi-wheeled bogies
• CPC Class Codes: B64C 25/58 Arrangements or adaptations of shock-absorbers or springs shimmy-dampers B64C25/50
• CPC Class Codes: B64C 25/60 Oleo legs

Abstract

A semi-levered landing gear for an aircraft comprises a main shock absorber strut (1) connected to the airframe; a bogie beam (4) extending fore and aft of the airframe with forward and aft wheels (J, T) and a main pivot connection (5) to the strut (1) between the forward and aft wheels (7, T) and an auxiliary actuator (49) connected between the strut (1) and the front of the bogie beam (4) at an auxiliary pivot (14). The auxiliary actuator (49) comprises a two stage telescopic hydraulic unit comprising a first stage piston and cylinder actuator (59, 63) and a second stage piston and cylinder actuator (56, 50) operating coaxially within an outer casing (50). A respective piston rod (65, 60) each extends from each end of the casing (50) and is connected to a respective one of said (strut 1) and bogie beam (4). The first stage actuator (59, 63) is operable to an extended position, and the second stage actuator (56, 60) is operable between a retracted position (FIG. 11) and an extended position (FIG. 12) defined by respective end stops (75, 77) within the outer casing (50) and serves to control the tilt position of the bogie beam (4) relative to the strut (1). The second stage actuator (56, 60), when in the retracted position with the first stage actuator (59, 63) in the extended position, limits the length of the auxiliary actuator (9) between its connections (62, 67) to the strut (1) and bogie beam (4), so as to assume a predetermined intermediate length in which the bogie beam (4) is restrained to tilt about the auxiliary pivot (14) and thereby lengthens the landing gear during take-off. The second stage actuator (56, 60), when in the extended position with the first stage actuator (59, 63) in the extended position, allows the length of the auxiliary actuator (49) to assume a predetermined maximum length in which the bogie beam (4) is tilted about the main pivot (5) to a stowing position for stowing the landing gear in the aircraft.

Claims

1. :

A semi-levered landing gear for an aircraft comprising;

a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe;

a bogie beam to extend fore and aft of the airframe with at least one forward axle and one aft axle for respective forward and aft wheels and a main pivot between the forward and aft axle pivotally connected to the lower portion of the main shock absorber strut;

and an auxiliary actuator having an upper connector pivotally connected to the upper portion of the main shock absorber strut and a lower connector pivotally connected to the bogie beam at an auxiliary pivot, the auxiliary actuator comprising a two stage telescopic hydraulic unit comprising an outer casing with a first stage piston and cylinder actuator and a second stage piston and cylinder actuator operating coaxially within the outer casing, each of the first and second stage actuators incorporating a piston rod which extends from a respective end of the casing and is connected to a respective one of said upper and lower connectors, wherein the first stage actuator provides damping of pivoting movements of the bogie beam about the main pivot and is operable to an extended position and the second stage actuator is operable between a retracted position and an extended position defined by respective end stops within the outer casing and serves to control the tilt position of the bogie beam relative to the main shock absorber strut, the second stage actuator, when in the retracted position with the first stage actuator in the extended position, limiting the length of the auxiliary actuator between the upper and lower connectors so as to assume a predetermined intermediate length in which the bogie beam is restrained to tilt about the auxiliary pivot and the landing gear is lengthened during take-off of the aircraft, and the second stage actuator, when in the extended position with the first stage actuator in the extended position, allowing the length of the auxiliary actuator between the upper and lower connectors to assume a predetermined maximum length in which the bogie beam is tilted about the main pivot to a stowing position for stowing the landing gear in the aircraft.

2. :

A landing gear as claimed in claim 1 in which the first stage actuator comprises a first cylinder on which said second piston rod slides and seals coaxially, and a first piston head slidable in the first cylinder with a first piston rod that extends from the first piston head through a gland in said respective end of the outer casing and carries one of said upper and lower connectors at its outer end.

3. :

A landing gear as claimed in claim 2 in which the first piston incorporates a restricted hydraulic aperture connecting both sides of the piston within the first piston rod for a damping action.

4. :

A landing gear as claimed in claim 3 in which the bore of the first cylinder is connected to the bore of the outer casing on the piston rod side of the second piston via an aperture in the rod of the second piston.

5. :

A landing gear as claimed in claim 3 in which a hydraulic connection is made to the bore of the first cylinder via the bore of the first piston rod.

6. :

A landing gear as claimed in claim 2 including a hydraulic control valve connectable to hydraulic pressure and return sources and operable to switch hydraulic pressure and return between an output connection to the second piston.

7. :

A landing gear as claimed in claim 6 in which the output connection to the second piston is connected to one side of the second piston, and the other side of the second piston is permanently connected to one of pressure or return sources.

8. :

A landing gear as claimed in claim 6 in which the hydraulic control valve is operable to connect the bore on the head side of the second piston to pressure to extend the second stage actuator, and to return to retract the second stage actuator.

9. :

A landing gear as claimed in claim 8 in which the bore on the piston rod side of the second piston is permanently connected to the pressure source in operation.

10. :

A landing gear as claimed in claim 9 in which a non-return valve is incorporated in said permanent connection to the pressure source to allow fluid flow into the said bore.

11. :

A landing gear as claimed in claim 10 including a pressure relief valve connected between the bore on the piston rod side of the second piston and return so as to allow fluid flow out of the bore when a set pressure is exceeded.

12. :

A landing gear as claimed in claim 6 in which the hydraulic control valve is operable to stop the second piston at an intermediate point in its travel so as to define a second predetermined intermediate length of auxiliary actuator different to said first predetermined intermediate length.

13. :

A landing gear as claimed in claim 6 in which the hydraulic control valve has a first position in which pressure and return sources are connected to opposite sides of the second piston, a second position in which pressure and return sources are connected to said opposite sides of the second piston in the opposite sense to the first position, and a third position in which the connections to opposite sides of the second piston are closed to lock pressure on opposite sides of the second piston.

14. :

A landing gear as claimed in claim 13 in which the hydraulic control valve forms part of a servo-control system which determines an intermediate position in which the second piston can be stopped between fully retracted and fully extended positions.

15. :

A landing gear as claimed in claim 14 in which a mechanical lock is provided on the casing which locks the second piston in the retracted position when activated, the mechanical lock being hydraulically activated by differential pressure in the system corresponding to retraction of the second piston.

16. :

A landing gear as claimed in claim 6 in which the hydraulic control valve remains in the same state for landing, taxiing and take-off.

17. :

A semi-levered landing gear for an aircraft comprising;

a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe;

a bogie beam to extend fore and aft of the aircraft fuselage with at least one forward axle and one aft axle for respective forward and aft wheels and a main pivot between the forward and aft axles pivotally connected to the lower portion of the main shock absorber strut;

and an auxiliary actuator having an upper connector pivotally connected to the upper portion of the main shock absorber strut and a lower connector pivotally connected to the bogie beam at an auxiliary pivot, the auxiliary actuator comprising a two stage telescopic hydraulic unit comprising an outer casing with a first stage piston and cylinder actuator and a second stage piston and cylinder actuator operating coaxially within the outer casing, each of the first and second stage actuators being connected to a respective one of said upper and lower connectors, wherein the first stage actuator is operable by spring means to an extended position defined by axial engagement of an end stop between the piston and cylinder of the first stage actuator and provides spring resistance to retraction of the first stage actuator, and the second stage actuator is operable between a retracted position and an extended position defined by respective end stops within the outer casing and serves to control the tilt position of the bogie beam relative to the main shock absorber strut, the second stage actuator, when in the retracted position with the first stage actuator in the extended position, limiting the length of the auxiliary actuator between the upper and lower connectors so as to assume a predetermined intermediate length in which the bogie beam is restrained to tilt about the auxiliary pivot and the landing gear is thereby lengthened during take-off of the aircraft, and the second stage actuator, when in the extended position with the first stage actuator in the extended position, allowing the length of the auxiliary actuator between the upper and lower connectors to assume a predetermined maximum length in which the bogie beam is tilted about the main pivot to a stowing position for stowing the landing gear in the aircraft.

18. :

A landing gear as claimed in claim 17 in which the first stage actuator also acts as a damping unit to damp pivoting movements of the bogie beam about the main pivot.

19. :

A landing gear as claimed in claim 18 in which the first stage actuator comprises a hydraulic unit.

20. :

A landing gear as claimed in claim 17 in which one of the components of the first stage actuator is shared in common with one of the components of the second stage actuator so that the two actuators nest together when the auxiliary actuator is in a fully retracted state.

21. :

A landing gear as claimed in claim 20 in which the end stop of the first stage actuator is mounted on said common component.

22. :

A landing gear as claimed in claim 21 in which the second stage actuator, when in the extended position, moves the end stop of the first stage axially so as to allow the first stage actuator to extend further in it'"'"'s extended position so that the auxiliary actuator assumes said predetermined maximum length.

23. :

A landing gear as claimed in claim 22 in which the second stage actuator comprises a second piston slidable within a bore of the outer casing to engage a stop at a closed end of the outer casing to define the retracted position, the closed end of the outer casing being connected to one of the upper or lower connectors.

24. :

A landing gear as claimed in claim 23 in which the second piston is connected to a second piston rod which is tubular and extends from the second piston through a gland in the end of the outer casing opposite said closed end of the outer casing.

25. :

A landing gear as claimed in claim 24 in which the first stage actuator comprises a first piston slidable within a bore of the second piston rod, and a first piston rod which extends through a gland in the end of the second tubular piston rod remote from said second piston, and carries the other of said upper and lower connectors at its outer end.

26. :

A landing gear as claimed in claim 25 in which the first piston incorporates a restricted hydraulic aperture connecting both sides of the piston within the second piston rod for a damping action.

27. :

A landing gear as claimed in claim 26 in which a hydraulic aperture connects the bore of the second piston rod with the bore of the outer casing on the piston rod side of the second piston.

28. :

A landing gear as claimed in claim 26 in which a hydraulic connection is made to the bore of the second piston via the bore of the first piston rod.

29. :

A landing gear as claimed in claim 23 including a hydraulic control valve connectable to hydraulic pressure and return sources and operable to switch hydraulic pressure and return between an output connection to the second piston.

30. :

A landing gear as claimed in claim 29 in which the output connection to the second piston is connected to one side of the second piston, and the other side of the second piston is permanently connected to one of pressure or return sources.

31. :

A landing gear as claimed in claim 30 in which the hydraulic control valve is operable to connect the bore on the head side of the second piston to pressure to extend the second stage actuator, and to return to retract the second stage actuator.

32. :

A landing gear as claimed in claim 31 in which the bore on the piston rod side of the second piston is permanently connected to the pressure source in operation.

33. :

A landing gear as claimed in claim 32 in which a non-return valve is incorporated in said permanent connection to the pressure source to allow fluid flow into the bore.

34. :

A landing gear as claimed in claim 33 including a pressure relief valve connected between the bore on the piston rod side of the second piston and return so as to allow fluid flow out of the bore when a set pressure is exceeded.

35. :

A landing gear as claimed in claim 29 in which the hydraulic control valve is operable to stop the second piston at an intermediate point in its travel so as to define a second predetermined intermediate length of auxiliary actuator different to said first predetermined intermediate length.

36. :

A landing gear as claimed in claim 27 in which the hydraulic control valve has a first position in which pressure and return sources are connected to opposite sides of the second piston, a second position in which pressure and return sources are connected to said opposite sides of the second piston in the opposite sense to the first position, and a third position in which the connections to opposite sides of the second piston are closed to lock pressure on opposite sides of the second piston.

37. :

A landing gear as claimed in claim 36 in which the hydraulic control valve forms part of a servo-control system which determines an intermediate position in which the second piston can be stopped between fully retracted and fully extended positions.

38. :

A landing gear as claimed in claim 30 in which a mechanical lock is provided on the casing which locks the second piston in the retracted position and is hydraulically operated by differential pressure in the system corresponding to retraction of the second piston.

39. :

A landing gear as claimed in claim 29 in which the hydraulic control valve remains in the same state for landing, taxiing and take-off.

40. :

A landing gear as claimed in claim 23 in which the second piston has a second piston rod which is tubular and extends towards the closed end of the outer casing.

41. :

A landing gear as claimed in claim 24 in which the first stage actuator comprises a first piston slidable within a bore of the second piston rod, and a first piston rod which extends from the first piston through a sealed aperture in the second piston and a gland closing an end of the outer casing opposite the closed end of the outer casing.

42. :

A semi-levered landing gear for an aircraft comprising;

a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe;

a bogie beam to extend fore and aft of the aircraft fuselage with at least one forward axle and one aft axle for respective forward and aft wheels and a main pivot between the forward and aft axle pivotally connected to the lower portion of the main shock absorber strut;

and an auxiliary mechanism comprising a lever unit, a spring unit and a positioning unit, with a first one of said units pivotally connected to the upper portion of the main shock absorber strut so as to pivot between a predetermined lower position for take-off and landing and an upper position, a second one of said units pivotally connected at an upper end to the upper portion of the main shock absorber strut and pivotally connected at a lower end to the first one of said units, and a third one of said units pivotally connected at a lower end to the bogie beam at an auxiliary pivot and connected at an upper end to the lever, the positioning unit assuming one of a contracted state or extended state for taxiing, take-off and landing, and the other of the contracted or extended state for stowing the landing gear after take-off, and the spring unit providing spring resistance to pivotal movements of the bogie beam about the main pivot during taxiing.

46. :

A semi-levered landing gear as claimed in claim 42 in which the positioning unit is a hydraulic unit.

47. :

A semi-levered landing gear as claimed in claim 42 in which the spring unit is a hydraulic unit.

48. :

A semi-levered landing gear as claimed in claim 47 in which the spring unit is connected to a hydraulic pressure supply and derives its resilience from flow of hydraulic fluid.

43. :

A semi-levered landing gear for an aircraft comprising;

a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe;

a bogie beam to extend fore and aft of the aircraft fuselage with at least one forward axle and one aft axle for respective forward and aft wheels and a main pivot between the forward and aft axle pivotally connected to the lower portion of the main shock absorber strut;

and an auxiliary actuator mechanism comprising a lever pivotally connected to the upper portion of the main shock absorber strut so as to pivot between a predetermined lower position for take-off and landing and an upper position, a spring unit pivotally connected at an upper end to the upper portion of the main shock absorber strut and pivotally connected at a lower end to the lever, and a positioning unit pivotally connected at a lower end to the bogie beam at an auxiliary pivot and connected at an upper end to the lever, the positioning unit assuming a contracted state for taxiing, take-off and landing, and an extended state for stowing the landing gear after take-off, the positioning unit transferring to the lever and to the spring unit, pivotal movements of the bogie beam about the main pivot during taxiing, and the positioning unit and lever restraining the bogie beam to tilt about the auxiliary pivot and to lengthen the landing gear during take-off.

44. :

A semi-levered landing gear as claimed in claim 43 in which the lever has an abutment portion which abuts the upper portion of the main shock absorber strut to define said predetermined lower position of the lever.

45. :

A semi-levered landing gear as claimed in claim 43 in which the lever has a second abutment portion which abuts the positioning unit to define a maximum raised position of the positioning unit.

49. :

A landing gear as claimed in claim 43 in which the spring unit is also a damping unit.

50. :

A semi-levered landing gear for an aircraft comprising;

a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe;

a bogie beam to extend fore and aft of the aircraft fuselage with at least one forward axle and one aft axle for respective forward and aft wheels and a main pivot between the forward and aft axle pivotally connected to the lower portion of the main shock absorber strut;

and an auxiliary actuator mechanism comprising a lever pivotally connected to the upper portion of the main shock absorber strut so as to pivot between a predetermined upper position for take-off, and a lower position, a spring unit pivotally connected at an upper end to the lever and at a lower end to the bogie at an auxiliary pivot forward of the main pivot, and a control linkage connected between the lever and the upper portion of the main shock absorber strut to define said upper predetermined position of the lever, the control linkage being connectable to an anchor point that moves relative to the upper portion of the main shock absorber strut during stowing, whereby the control linkage is operated by initial stowing movement of the stowing mechanism to lower the lever from said upper position to a stowing position.

51. :

A semi-levered landing gear as claimed in claim 50 in which the control linkage comprises a folding link connected between the lever and the upper portion of the main shock absorber strut so as to straighten and hold the lever in said predetermined upper position and a control link connected at one end to part of the folding link and connectable at the other end to said anchor point so that the folding mechanism causes the folding link to fold and lower the lever to the stowing position.

52. :

A semi-levered landing gear as claimed in claim 51 in which the folding link comprises a pair of links pivotally connected at their centre and incorporating stops to define a straightened position, the control link being connected to one of said pair of links.

53. :

A semi-levered landing gear as claimed in claim 50 in which the spring unit comprises a hydraulic unit.

54. :

A landing gear as claimed in claim 50 in which the spring unit is also a damping unit.

55. :

An auxiliary actuator for semi-levered landing gear of an aircraft having a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe, and a bogie beam extending fore and aft of the aircraft fuselage with at least one forward axle and wheels and one aft axle and wheels, and a main pivot between the forward and aft axles pivotally connected to the lower portion of the main shock absorber strut, the auxiliary actuator comprising a two stage telescopic hydraulic unit comprising an outer casing with a first stage piston and cylinder actuator and a second stage piston and cylinder actuator operating coaxially within the outer casing, one of the first and second stage actuators being pivotally connectable via an upper connector to the upper portion of the main shock absorber strut, and the other being pivotally connectable via a lower connector to the bogie beam at an auxiliary pivot, wherein the first stage actuator is operable by spring means to an extended position defined by axial engagement of an end stop between the piston and cylinder of the first stage actuator and provides spring resistance to retraction of the first stage actuator, and the second stage actuator is operable between a retracted position and an extended position defined by respective end stops within the outer casing and serves to control the tilt position of the bogie beam relative to the main shock absorber strut, the second stage actuator, when in the retracted position with the first stage actuator in the extended position, limiting the length of the auxiliary actuator between the upper and lower connectors so as to assume a predetermined intermediate length in which the bogie beam is restrained to tilt about the auxiliary pivot and the landing gear is thereby lengthened during take-off of the aircraft, and the second stage actuator, when in the extended position with the first stage actuator in the extended position, allowing the length of the auxiliary actuator between the upper and lower connectors to assume a predetermined maximum length in which the bogie beam is tilted about the main pivot to a stowing position for stowing the landing gear in the aircraft.

56. :

An auxiliary actuator mechanism for semi-levered landing gear of an aircraft having a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe, and a bogie beam extending fore and aft of the aircraft fuselage with at least one forward axle and wheel and one aft axle and wheel, and a main pivot between the forward and aft axle pivotally connected to the lower portion of the main shock absorber strut, the auxiliary actuator comprising a two stage telescopic hydraulic unit comprising an outer casing with a first stage piston and cylinder actuator and a second stage piston and cylinder actuator operating coaxially within the outer casing, one of the first and second stage actuators being pivotally connectable via an upper connector to the upper portion of the main shock absorber strut, and the other being pivotally connectable via a lower connector to the bogie beam at an auxiliary pivot;

wherein the first stage actuator provides damping of pivoting movements of the bogie beam about the main pivot and is operable to an extended position and the second stage actuator is operable between a retracted position and an extended position defined by respective end stops within the outer casing and serves to control the tilt position of the bogie beam relative to the main shock absorber strut, the second stage actuator, when in the retracted position with the first stage actuator in the extended position, limiting the length of the auxiliary actuator between the upper and lower connectors so as to assume a predetermined intermediate length in which the bogie beam is restrained to tilt about the auxiliary pivot and the landing gear is lengthened during take-off of the aircraft, and the second stage actuator, when in the extended position with the first stage actuator in the extended position, allowing the length of the auxiliary actuator between the upper and lower connectors to assume a predetermined maximum length in which the bogie beam is tilted about the main pivot to a stowing position for stowing the landing gear in the aircraft.

57. :

An auxiliary actuator mechanism for semi-levered landing gear of an aircraft having a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe, and a bogie beam extending fore and aft of the aircraft fuselage with at least one forward axle and wheel and one aft axle and wheel, and a main pivot between the forward and aft axle pivotally connected to the lower portion of the main shock absorber strut, the auxiliary actuator mechanism comprising a lever pivotally connectable to the upper portion of the main shock absorber strut so as to pivot between a predetermined lower position for take-off and landing and an upper position, a damping unit pivotally connectable at an upper end to the upper portion of the main shock absorber strut and pivotally connected at a lower end to the lever, and a positioning unit pivotally connectable at a lower end to the bogie beam at an auxiliary pivot and connected at an upper end to the lever, the positioning unit assuming a contracted state for taxiing, take-off and landing, and an extended state for stowing the landing gear after take-off, the positioning unit transferring to the lever and to the damping unit, pivotal movements of the bogie beam about the main pivot during taxiing, and the positioning unit and lever restraining the bogie beam to tilt about the auxiliary pivot and to lengthen the landing gear during take-off.

58. :

An auxiliary actuator mechanism for semi-levered landing gear of an aircraft having a main shock absorber strut with upper and lower telescoping portions, with the upper portion connectable to the airframe, and a bogie beam extending fore and aft of the aircraft fuselage with at least one forward axle with wheel and one aft axle with wheel, and a main pivot between the forward and aft axle pivotally connectable to the lower portion of the main shock absorber strut, the auxiliary actuator comprising a lever pivotally connectable to the upper portion of the main shock absorber strut so as to pivot between a predetermined upper position for take-off, and a lower position, a spring unit pivotally connected at an upper end to the lever and connectable at a lower end to the bogie at an auxiliary pivot forward of the main pivot responding to pivoted movements of the bogie beam about the main pivot during taxiing, and a control linkage connected at one end to the lever and connectable at the other end to the upper portion of the main shock absorber strut to define said upper predetermined position of the lever, the control linkage being connectable to an anchor point that moves relative to the upper portion of the main shock absorber strut during stowing, whereby the control linkage is operated by initial stowing movement of the stowing mechanism to lower the lever from said upper position to a stowing position.

59. :

A semi-levered landing gear for an aircraft comprising;

a main shock absorber strut with upper and lower telescoping portions, with the upper portion pivotally connectable to the airframe;

a bogie beam to extend fore and aft of the airframe with at least one forward axle and one aft axle for respective forward and aft wheels and a main pivot between the forward and aft axle pivotally connected to the lower portion of the main shock absorber strut;

and an auxiliary actuator mechanism comprising a spring unit pivotally connected at a lower end to an auxiliary pivot on the bogie forward of the main pivot, and at an upper end to an anchor point offset from the pivot connection of the upper portion to the aircraft fuselage so that during stowing both the strut and spring unit pivot together about different pivot points, which causes a relative longitudinal movement between the main pivot and auxiliary pivot that further tilts the bogie beam to a stowing position.