GB910678A - Improvements in or relating to flying control systems of rotary wing aircraft with coaxial contrarotative rotors - Google Patents

Abstract

910,678. Rotary wing aircraft. SHAPIRO, J. S., MEADS, B. A. G., and PRESTON, R. L. Oct. 22, 1959 [July 25, 1958], No. 23934/58. Class 4. In a rotary wing aircraft having two coaxial contra-rotating lifting rotors, collective and cyclic pitch control is obtained by two independent swash plate assemblies, that for the lower rotor being connected thereto by conventional linkages, and that for the upper rotor being below that for the lower rotor, and being connected to its rotor through coaxially nested push-pull tubes slidable within the hollow contra-rotative shafts of the rotors. In the Figure, contrarotating drive shafts 2, 4 support upper and lower hubs 6, 8, on which blades 10, 12, 14, and 16 are mounted by pitch change bearings, the blades having pitch control arms 18, 20, 22, 24. The arms 22, 24 of the lower rotor are connected by links 26, 28 to the inner rotary race 30 of an upper swash plate, the outer non- rotary race 32 being supported by a gimbal ring 70 on the ends of screw jacks 74, 80. The arms 18, 20 of the upper rotor are connected by links 34, 36, to levers 38, 40, respectively pivoted on coaxial shafts 42, 44 nested within shaft 2, the levers also being connected by links 46, 48, to a bracket 50 secured to shaft 2. The lower ends of shafts 42, 44, pivotally support levers 60, 62, each connected at one end by a link 56, 58 to a bracket 54 on shaft 2, and at the other end by a link 64, 66, to the inner race 52 of a lower swash plate, the outer race being supported by a gimbal ring 72 on the ends of screw jacks 76, 82, Inclination of the swash plate effects cyclic push-pull movements of the shafts 42, 44, and corresponding cyclic pitch alterations of blades 10 and 12. Tilting of swash plate 30, 32, conventionally effects cylic pitch changes of blades 14 and 16, and vertical movement of either swash plate effects collective pitch control of the corresponding blades. The screw jacks 74, 76 are engaged by oppositely handed threads on a common member 78 rotatable by a pinion engaging a rack 90 controlled by a cable 144, and screw jacks 80, 82 are similarly controlled by a cable 146. The two sets of screw jacks are mounted in stirrups 98 (one shown) in a frame 100 pivoted to the aircraft at 102 and having a handle 124, being the pilots collective pitch control. Raising or lowering of the handle raises or lowers the screw jacks bodily, raising or lowering the gimbal rings 70, 72, and both swash plates, to impose collective pitch changes on both rotors in the same sense, though not necessarily of the same magnitude, to increase or decrease the lift generated. Cables 144, 146, are operated in opposite senses by racks 140, 142 respectively, engaging a pinion 138 rotatable by pedals 126, 128 operable by the pilot. Such operation rotates both sets of screw jacks, to vary the distance between the gimbal rings 70, 72, and the swash plates. This imposes collective pitch changes on the rotors in opposite senses, though not necessarily of equal magnitude, to control the aircraft in yaw by setting up differential rotor torques. For (simultaneous) cyclic pitch control of the rotors, a tube 108 is suspended by three arms 110 from three rods 112 depending from race 32 of the upper swash plate. Slidable within the tube is a rod 106 connected by three arms 104 to the race 52 of the lower swash plate. A rod 116 slidable and rotatable in a fixed bearing 118 has one arm 120 ball jointed at 122 to a member slidable in tube 108, and has another arm ending in a pilot's cyclic pitch control 114. The control 114 may be rotated to left or right, and moved bodily fore and aft, and effects corresponding inclination of tube 108 to the vertical, the arms 104, and rods 112 and arms 110, effecting corresponding tilting of both swash plates. The cyclic pitch changes imposed on both rotors have the same azimuth datum line, but need not be of equal magnitudes. As an alternative to the levers 38, 40, 60, 62, and the associated links, the arms 18, 20 and the swash plate race 52 may be pivoted to arms rigid with shafts 42, 44, though this imposes bending loads on the shafts. The Provisional Specification discloses an alternative to the screw jacks 74, 76, 80, 82, in which the frame 100 is in two parallel parts, the upper supporting gimbal ring 70, and the lower, gimbal ring 72. The two parts are movable together by handle 124 to displace the gimbal rings in the same sense, and are movable closer or farther apart by turnbuckles operable by pedals 126, 128, to displace the gimbal rings in opposite senses. This embodiment also discloses a remote cable connection between the engine throttle, frame 100, and a lever on handle 124, affording automatic throttle adjustment with collective pitch change on both rotors in the same sense, and an independent pilot's throttle control.