GB617290A - Improvements in and relating to helicopters - Google Patents

Abstract

617,290. Helicopters. CIERVA AUTOGIRO CO., Ltd., PULLIN, C. G., and SHAPIRO, J. S. Sept. 23, 1946, No. 28458. [Class 4] In a helicopter having two or more rotor assemblies with horizontally spaced centres, each assembly comprising a pair of closely associated rotors driven in opposite directions, control in yaw is obtained by unbalancing the reaction torques of the rotor assemblies, by differential variation of the collective pitches of the individual rotors of each assembly, and control in pitch or/and roll is obtained by differential variation of the lifts of the rotor assemblies by variation of the collective pitches of the individual rotors in the same sense. The invention is shown applied to a helicopter with three assemblies of coaxial, contra-rotating rotors 3a, 3b, 3c, of which the rotor 3a is placed forwardly of the centre of gravity and on the longitudinal axis, and the rotors 3b, 3c are disposed side by side to the rear of the centre of gravity. The rotors are driven by two engines 5a, 5b through junction and distribution gear-boxes 6, 7 and transmission shafts 8a, 8b, 8c. Each rotor assembly, Fig. 4, comprises non-articulated blades 25, 26 mounted on coaxial sleeves 19, 20 rigid with bevel wheels 17, 18 meshing with a pinion 16 at the end of the associated transmission shaft. Pitch control arms 30 of the upper blades are actuated hy a yoke 37 carried by a central shaft 38 connected to a lever 65 and the control arms 31 of the lower blades are operated by a second yoke 36 mounted on a control ring 39 actuated by a lever 47 and link 51. The members 51, 65 are connected to the floating lever 53 of a differential linkage operated by push-pull rods 11, 12. Movement of the rod 11 results in bodily vertical movement of the lever 53, thereby applying equal pitch changes of the same sign to both rotors, while movement of the rod 12 causes tilting of the lever 53 about the point 54 to apply equal pitch changes of opposite sign to the rotors. The rudder bar or pedals are arranged to operate the three rods 12 equally in the same sense to create equal unbalanced reaction torques in the three rotor assemblies, fore-and-aft movement of the control column displaces the rods 11 to increase the lift of the forward rotor assembly and decrease that of the rear rotors, or conversely, while lateral movement of the control column displaces the rods 11 of the rear rotors to cause differential variations of their respective lifts. An additional control lever is provided for effecting simultaneous collective pitch control to all six individual rotors. Specification 616,227 is referred to.