GB1464413A - Aircraft undercarriages - Google Patents

Abstract

1464413 Aircraft undercarriages AUTOMOTIVE PRODUCTS Ltd 30 May. 1975 [6 June 1974 9 Sept 1974] 25248/74 and 39322/74 Heading B7G An aircraft undercarriage is provided with a ride control valve which in flight is inoperative but is activated automatically upon landing to control vertical movements of the aircraft during theground running period. A telescopic strut 12 is pivoted at 13 to an airframe for retraction and extension by an actuator strut (41, not shown), the telescoping cylinder 17 of strut 12 carrying a pivotally mounted wheel-carrying arm 33. The cylinder 17 is hollow and carries a floating piston 24 which forms two chambers, one 26 filled with nitrogen gas and the other 25 filled with hydraulic fluid which connects with a chamber 29 in outer cylinder 16 through a metering orifice 20 and a one way valve orifice 30 formed in the top wall of cylinder 17. The chamber 29 communicates through a duct 47 with a ride control valve 44 which has a port 45 connected to the aircraft main hydraulic pressure supply and a drain port 46 connected to the hydraulic return line, the chamber 29 being connectible to ports 45 or 46 through a ride control valve 48 actuated through a link 68 and a bellcrank which has a weight 64 on the extremity of an arm which is supported by a dashpot 75, in turn balanced on a pivoted arm 69 connected to the lower end of cylinder 17 by a springbox link.72, whereby vertical movement of cylinder 17 during ground running operates valve 48 to apply compensating pressure variations within chamber. 29. Shut-off valves 56, 57 under the control of the pilot through a console 109, 110 are provided whereby the ride control mechanism can be rendered inoperative after the aircraft has taken off. Prior to landing the pilot moves lever 109 to operate the undercarriage lowering strut and upon landing a switch 117 is operated by a cam 118 to open shut-off valves 56 and 57 to bring the ride control mechanism into operation. A further embodiment is described using an electro-hydraulic link in place of the springbox link 72.