Patent GB-616227-A (GB)
Title: Improvements in aircraft with sustaining rotors disposed forward and aft of the centre of gravity
IPC: B64C27/54
Filed: 1946-08-30
Abstract: 616,227. Rotary wing aircraft. CIERVA AUTOGIRO CO., Ltd., PULLIN, C. G., WATSON, K., and SHAPIRO, J. S. Aug. 30, 1946, No. 26169. [Class 4] In an aircraft having sustaining rotors with upright axes and flapping blades, some of the rotors being in front of and some behind the centre of gravity of the aircraft, a single control member simultaneously causes changes of mean pitch of the rotors whose algebraic sum is zero and which are symmetrical about the pitching axis, and to a proportional extent causes equal cyclical pitch changes in all the rotors, the azimuth of zero pitch change lying fore-and-aft, and the sense of the pitch changes being such that a decrease in the mean pitch of the front rotors is accompanied by a forward inclination of the lift vectors of all the rotors. As shown for an aircraft with three rotors, the arms 16, 27, 28 of a spider 18 are disposed in plan relatively to the universal mounting 19 of the spider in a manner corresponding to the lines joining the rotors to the centre of gravity of the aircraft, and are each connected by a link 31, 29, 30 to means controlling the mean pitch of the corresponding rotor which means may be as described in Specification 591,982. The arms 41, 39, 40 of a similar spider 37 control the amplitudes of cyclical pitch change in each rotor, the azimuth of zero pitch change lying fore-and-aft. Each spider may be tilted about its transverse and longitudinal axis and may be raised or lowered bodily. Forward movement of the control column 1 about a pivot 2 is transmitted through a rod 5 to a bell crank lever 6 pivoted on a bracket 12 fixed to the pillar 13 supporting the spider 18, and thus, through link 14 tilts the spider 18 about a transverse axis to cause differential changes in the mean pitch of the rotors tending to pitch the aircraft forwardly. Simultaneously a bell crank 32 is operated through a rod 32 to raise the pillar 35 on which the spider 37 is mounted and to cause like cyclical changes of pitch of the rotors inclining the lift vectors forwardly, while a further bell crank 46, connected through a link 47 to the arm 41 of the spider 37 tilts this spider to apply a differential cyclical control altering the dihedral angle. Transverse movement of the control column 1 rotates a shaft 3 and thus, through crank 7, link 8, bell crank 9, link 10, bell crank 11 mounted on the bracket 12, and link 15, moves an arm 17 on the spider 18 to tilt the spider about a longitudinal axis. This applies a differential mean pitch control tending to bank the aircraft. The rudder bar 56 is connected by a linkage 51, 54, 53, to a bell crank 50 connected by a link 51 to an arm 52 to tilt the spider 37 transversely, thus applying differential changes of cyclical pitch amplitude inclining the lift vectors of the rotors on one side of the aircraft forwardly and those of the rotors on the other side rearwardly, to steer the aircraft. A pitch change lever 20 is connected to raise and lower the spider 18 bodily to alter the mean pitch of all the rotors in the same sense.