Patent GB-634865-A (GB)
Title: Improvements in rotative-winged aircraft
IPC: B64C27/04
Filed: 1947-07-29
Abstract: 634,865. Helicopters. AUTOGIRO CO. OF AMERICA. July 29, 1947, No. 20389. Convention date, July 30, 1946. [Class 4] - A helicopter comprises a sustaining rotor mounted well forward of the centre of gravity of the aircraft and a second rotor mounted well to the rear of the centre of gravity of the aircraft at an elevation above the first rotor and so disposed that in plan view the two rotor discs overlap, the lift vectors of the forward and rear rotors being independently inclinable in the rolling plane of the aircraft. The helicopter body 5 is supported on wheels 8, 9, the wheel 9 being retracted about a pivot 9c by a shock absorbing retracting element 9d housed in the upswept tail portion 5a. Forward and rear rotors 10 and 11 of equal diameter are supported on the body 5 and rotate in opposite directions so that their torques are balanced. The rotors are interconnected by the shafts 41, 42 and 45 and a gearbox 40 driven by an engine 7 through a clutch mechanism 39, preferably containing both manually controllable and over-running clutches. The blades of each rotor are subject to a cyclic pitch variation to produce lateral inclination only of the rotor lift lines and are also subject to collective pitch variation. Collective pitch increase of the blades of the rear rotor will produce a nose down attitude of the aircraft causing the lift line of each rotor to provide a forward thrust component to effect forward translational flight. Fig. 3 illustrates the aircraft control system. Pitching control is obtained by fore-and-aft movement of a control column 20 which operates a cable circuit 23 and a jack 16a to vary the collective pitch of the rear rotor. Rolling control is obtained by lateral movement of the column 20 to actuate a cable circuit 34 and a jack 17 to cyclically vary the pitch of the forward rotor blades. Simultaneous collective pitch adjustment of the blades of both rotors to effect vertical ascent and descent is obtained by fore-and-aft movement of a further control member 26 which actuates a cable circuit 28 and a jack 16 to effect collective pitch control of the blades of the forward rotor and simultaneously actuates a cable circuit 27 and a sliding bar 25 provided with pulleys 24 to lengthen or shorten the cables 23 to effect collective pitch adjustment of the blades of the rear rotor. Fore-and-aft trim is obtained by interposing in the circuit 28 a manually operable screw jack 32 and pivoted double bell-crank 30 so that the collective blade pitch of the forward rotor may be adjusted relatively to that of the rear rotor. Yawing control is obtained by movement of the pedals 36 which actuate a cable circuit 35 and a jack 17a to cyclically vary the pitch of the rear rotor blades to effect a lateral inclination of the rotor lift line. In an alternative control arrangement (Fig. 4, not shown) the pedals 36 are associated with a further cable circuit which actuates a double bell-crank provided with pulleys interposed in the cable circuit 34. Movement of the pedals 36 to effect lateral tilting of the rear rotor lift line simultaneously adjusts the cable 34 and the cyclic pitch control jack 17 to laterally tilt the lift line of the forward rotor in an opposite sense to the tilt applied to the rear rotor. Specifications 393,976 and 612,703 are referred to.