GB627117A - Improvements in or relating to jet-propelled rotary wing aircraft - Google Patents

Abstract

627,117. Helicopters. FORSYTH, A. G. (Doblhoff, F. L.). April 22, 1947, No. 10730. [Class 41 [Also in Group XXVI] A helicopter of the type in which the rotor is driven by reaction jets at the blade tips is provided with a gas turbine and compressor, the delivery from the latter being divided into two portions, one passing to the turbine and the other to the reaction jets. In the arrangement shown in Fig. 1, air from the compressor 1 passes through a heat exchanger 2, formed with tubes through which pass the exhaust gases from the turbine 3, and then passes into ducts 4, 9, the former leading to the blades 7 and jet outlets 8, and the latter to the combustion chamber of the turbine. The turbine blades are cooled by air drawn by a fan 11 from the atmosphere through a pipe 12. The air delivered to the jets 8 may be further heated by auxiliary burners. In the embodiment shown in Fig. 4, the rotor is mounted on a universal joint 5a, and the turbine exhaust is directed downwardly through a vertical duct 108. Control in yaw is effected by brakes 27, 28 adjacent the rotor hub and turbine respectively. The gyroscopic effect of the compressor and turbine serve to stabilize the aircraft. As shown in Fig. 2, the outlet area of the jets 8 may be varied in accordance with rotational speed by a centrifugal mass 20, connected by links 17 and a bell-crank lever 18 to flaps 14 controlling the jet outlet. Alternatively, the bell-crank may be connected to a piston working in a cylinder to which a pitot head is connected, Fig. 3 (not shown). Fig. 5 shows an arrangement for yaw control, in which the exhaust gases from the turbine are discharged through an outlet 35 at the tail of the aircraft and pass over a rudder 36. In the further embodiment shown in Fig. 12, air from the compressor operates a spring-loaded piston 141 in a cylinder 140 in the rotor hub to control the pitch setting arms 138 of the rotor blades. A choke 147 may be provided to damp out rapid pressure fluctuations and prevent blade flutter. A bottle 149 of compressed gas may be used to augment the air from the compressor as shown in Fig. 14, a flap valve 148 being mounted in parallel with the choke 147 and arranged to open automatically when the pressure in the pipe 144 rises so that the blade pitch may be rapidly increased, while the pitch is gradually reduced by the action of the choke if the pressure in the main conduit 130 falls.