Patent GB-552673-A (GB)
Title: Improvements in the steering of aircraft
IPC: B64C25/50
Filed: 1941-09-10
Abstract: 552,673. Aircraft landing-gear. GENERAL AIRCRAFT, Ltd., and WILLIAMS, D. L. H. Sept. 10, 1941, No. 11627. [Class 4] A landing element movable for steering an aircraft during taxiing by a control member which also actuates a rudder or other control surface, is provided with damping means to resist oscillatory movements, which means are only effective upon the control member when the aircraft is supported upon its undercarriage in order that there may be no restriction upon the movements of the control surface during flight. In one form, the oleo leg 9, Fig. 1, of a steerable wheel has a plug 10 formed with a tubular extension 13 in which slides a piston 12 having a flange 14 supporting a friction disc 15. A passage 11 in the plug. admits 10 fluid from the oleo leg when the latter shortens under load to raise the piston 12 and bring the disc 15 into contact with a fixed disc 17. A pin 19 engaging a groove in the piston 12 prevents relative rotation of the piston and the tubular extension 13. When the undercarriage is not under load the piston is lowered by a spring 16 so as to separate the friction discs. The leg is rotated for steering by an arm 22 coupled to the control member. The passage 11 may be restricted to prevent separation of the friction discs during momentary relief of load on the undercarriage. Fig. 2 shows a modification in which the leg is only coupled to the steering arm 24 and the damping device when the undercarriage is under load for which purpose a piston 32 is raised by pressure in the leg to project a member 36 into engagement with a squared hole in a member 25 on which the arm 24 is mounted. The member 36 also engages a squared stem 27 on a disc 28 carrying a friction disc 29 and forces the disc 29 against a fixed disc 31. In two other forms, movement of a piston corresponding to the piston 32 raises one half of a dog clutch into engagement with the other half which is connected to the steering arm in one case and to a permanently acting friction device in the other case. In the first of these forms a pair of friction discs, one mounted on the leg, are permanently in contact, and in the second of these forms the steering arm is mounted on the leg. In another modification the damping is effected hydraulically, a lever on the leg displacing a piston in a cylinder to force fluid through.a closed circuit provided with a valve operable by a diaphragm or piston movable by the pressure fluid in the leg. When the leg is unloaded the fluid displaced by oscillations of the leg can circulate freely but when the leg is loaded the valve closes the free passage and'the fluid can only circulate through a restricted passage which can be adjusted by a needle valve. Fig. 8 shows another form in which a steering arm 95 is coupled to the leg by a plunger 96 which enters a hole 97 in the arm when the leg is under load. The plunger 96 is connected to the wheel support 98 by a spring telescopic member to allow for the case where the aircraft alights when the hole 97 is not in register with the plunger. The leg 84 slides in a normally fixed tube 83 which can pivot about trunnions 101 for retracting the leg. The upper end of the leg 84 carries a cam 87 co-operating with a cam 88 fixed on the tube 83 to centre the wheel when the latter is unloaded. The tube 84 also carries a friction disc 86 which contacts with a resiliently mounted disc 90 when the aircraft is on the ground. A pivoted link 102 in the plunger 96 accommodates the retraction movement of the leg.