GB734315A - Improvements in or relating to controls for helicopter multiple speed transmissions - Google Patents

Abstract

734,315. Helicopters. EASTERN ROTORCRAFT CORPORATION. March 27, 1953 [April 14, 1952], No. 8518/53. Class 4. A helicopter rotor drive system comprises an engine, a multiple ratio transmission connected to said engine and the rotor, shift mechanism connected to said transmission having a piston and cylinder unit incorporated therein, a control system including an hydraulically operated valve with an hydraulic connection to said cylinder, and a pilot actuated control means for operating said valve. The rotor blades 7 are controlled for cyclic pitch adjustment by a pilot actuated member 20 and for collective pitch adjustment by a lever 23 which operates a linkage 24, 26, 25 and 27, the rotor being driven by an engine 16 through a centrifugally operated clutch 19, an overrunning clutch (not shown), a shaft 15, tail rotor take-off gear 13, a two-speed ratio change unit 12 and a main reduction gear unit 11. The engine 16 is enclosed by a cowling 17 which, at its upper end, surrounds a cooling fan 18. The lever 30 for changing the gear ratio is controlled by a double acting jack 31 to which pressure liquid is selectively admitted through conduits 35 or 36 by a solenoid controlled piston-type valve 34, having a stem biassed to either operative position by a spring-loaded toggle 48. The hydraulic circuit is completed by reservoir 38, engine driven pump 37, by-pass valve 41, check valve 42 and conduits 39, 40 and 46. The lever 23 carries a conventional engine throttle control member 28 and a push-button switch 52 and it operates a quadrant 55 adapted to close one or the other of a pair of switches 53, 61 which energize respectively valve solenoids 50, 51. By this means when the collective pitch lever is moved to the coarse pitch setting, with the switch 52 closed, the low speed gear is selected automatically, and when moved to fine pitch it selects the high speed gear. With the switch 52 open, collective pitch change may be made with the transmission in either gear. U.S.A. Specification 2,648,386 is referred to.