Patent GB-809260-A (GB)
Title: Improvements in or relating to undercarriages for aircraft
Inventor: ORLOFF GEORGE
IPC: B64C25/08
Filed: 1956-04-30
Abstract: 809,260. Aircraft undercarriages. BRITISH MESSIER Ltd. April 30, 1957 [April 30, 1956], No. 13260/56. Class 4. [Also in Group XXXIV] An aircraft undercarriage comprises a landing skid mounted on a shock-absorbing leg 11 and comprising a first part 15 pivoted to the leg and a second part 37 hinged to the first, the pivot and hinge axes being transverse to the skid and spaced along it, and means for turning the first part about the pivot and hinge to jack up the leg onto the second part for attachment of a wheel unit for take-off. In Fig. 1, the leg is pivoted to the aircraft by an oblique bearing 12 to retract rearwardly and outwardly. A hollow pivot pin 18 passes through the lower forked end 13 of the leg, a boss 14 on the first skid part 15, and a crank arm 17, being secured to the latter. Second and third skid parts 37, 36 are pivoted to the first part at 39 and 38, and for landing are urged downwardly by hydraulically contractable and extensible as springs 48, 42, being prevented from passing the position of alignment with the first part by abutments 52, 51. A rod 62 extends between an arm 63 on skid part 37 and the crank arm 17, and the pivot pin 18 has a fixed liner 19, Fig. 4, the outer faces (one shown) of which have cam surfaces 20 comprising recesses and ridges 21. The wheel unit comprises a U-shaped axle 22 having spindles 24 each supporting a wheel 30 and containing a sleeve 26 in a bore 25. Each sleeve has an inner cam face complementary to the cam 20 and is urged inwardly by a spring 27. A hand wheel 34 can be rotated to withdraw sleeve 26, compressing the spring. In operation, the aircraft takes off on the wheel unit. The springs 42 and 48 are then contracted, folding the skid to facilitate stowage, and rotating the pivot pin 18 through arm 63, rod 62 and crank 17. Each sleeve 26 is thus urged outwardly by the cam faces 20, and the wheel unit is jettisoned, descending by pilot and main parachutes in housings 60, 61. An over-centre device may be provided so that the sleeves spring outwardly when moved by the cam faces beyond a certain point. The rod 62 may be hydraulically contractable or contain a lockable lost motion device so that the wheel unit may optionally be retained and retracted. For landing, the leg and skid are as shown in Fig. 1. To replace the wheel unit, spring 42 is contracted and spring 48 extended, jacking the leg up onto the skid part 37. The sleeves 26 are retracted by handwheels 34, and extended again when the sleeves are aligned with the pivot pin 18. For jacking up on soft ground, an earth plate normally attached to the wheel unit and comprising a bridge portion and two ground contacting portions, may be placed to straddle the skid part 37 and engage under transverse extensions of the pivot pin 58 of the airspring 48, relieving the skid of ground pressure. A brake member 65 working in a slot in the skid section 15 may be urged into contact with the ground by a hydraulic jack, or when the wheel unit is in place, may contact a second similar brake member mounted on the wheel unit axle and thereby urge it into contact with the ground. Cooperating abutments on the axle and the leg take up torque due to braking.