GB657345A - Improvements in or relating to helicopter control apparatus - Google Patents

Abstract

657,345. Helicopters. SPERRY CORPORATION. Dec. 23, 1948, No. 33153. Convention date, Dec. 31, 1947. [Class 4] An apparatus for controlling the collective pitch and the cyclical pitch of the rotor blades of a helicopter is provided with means for producing automatically in response to an operation for changing the cyclical pitch, a co-related change of the collective pitch in order to prevent the retreating rotor blade from stalling by limiting its maximum angle of attack. Each blade 11 is connected by a pitch control arm 13 and a link 15 to the rotary part 17 of a swash-plate 19 arranged to be inclined in any azimuth about a pillar 18 coaxial with the rotor drive shaft 20. The pillar 18 is provided with a rack 22 engaged by a pinion 23 rotated through a differential gear 25 by a lever 24 to effect collective pitch variation. A plurality of arms 27 are secured to the pillar 18 above the rack 22 and each arm supports a pivotally mounted lever 29 connected by a link 32 to the fixed part of the swash plate 19 and rotated by bevel gears 35, 37 and one of a pair of shafts 39 positioned on the longitudinal axis of the aircraft. Each shaft 39 is coupled to a pilot's control member 58 by gears 42, 44, a cranked arm 46, a lever 51, a rod 53 and a lever 57 attached to the transverse torque tube 55 on which the member 58 is mounted. Transversely located shafts (not shown), similar to the shafts 39 are coupled to a control circuit 40 so that inclination of the member 58 in any azimuth will produce a corresponding cyclical pitch change of the rotor blades. The member 58 is provided with a depending portion surrounded by arcuate fingers 62, pivoted to the aircraft at 66 and interconnected by links 72. The whole system of fingers are urged into contact with the member 58 by a spring 74 and one finger carries an arm 84 fast therewith and positioned between a pair of contacts 85 formed on the periphery of a commutator switch 81 connected by gearing 83, 82, a flexible drive shaft 95 and further gearing 94 to the differential gear 25. Movement of the member 58 in any direction to effect cyclical pitch control will displace the fingers 62 and move the arm 84 into engagement with the appropriate contact 85 to energize an electric motor 91 connected by a gear train 93 and the gears 94 to the differential gear 25. Thus, the pinion 23 will be rotated to effect the appropriate degree of collective pitch change. After a given movement the commutator switch 81 will be rotated by " feed back " through the drive 95 to restore the contacts 85 and the arm 84 to their original relative positions to de-energize the motor 91. Specification 628,214 is referred to.