Patent GB-1057818-A (GB)
Title: Apparatus for controlling the propulsion unit of jet propelled helicopters
IPC: B64C27/18
Filed: 1963-10-25
Abstract: 1,057,818. Centrifugal compressors. M.A.N. TURBO. Oct. 25, 1963 [Oct. 27, 1962], No.42188/63. Heading F1C. Propulsion nozzles on the rotor blade tips of a jet-propelled helicopter are supplied with air by a centrifugal compressor 7, Fig. 2, driven by an internal combustion engine such as a gas turbine engine 4. A speed governor 16 and other auxiliaries, such as a starter and fuel and lubricant pumps are connected to the gas turbine through a gear box 15. After the engine 4 has been brought from its idling speed to its operating speed by means of a manual lever 19 which controls the setting of the speed governor 16, the inlet guide blades 9 of the compressor 7 are moved from the closed position by means of a manual lever 12' to obtain the desired compressor output. A control device responsive to the exhaust gas temperature of the engine 4 may be interposed in the linkage 12 so that for a given portion of the lever 12', the opening of the inlet guide blades decreases as the exhaust gas temperature increases. The levers 12', 19 may be replaced by a single lever connected to the speed governor 16 through a spring and to the guide blades 9 through a lost-motion linkage. Initial movement of the lever adjusts the speed governor 16 only. After the operating speed setting of the governor 16 has been reached, the spring, yields and, the lost motion having now been taken up, further movement of the lever opens the guide blades 9 instead. In a further single-lever arrangement, the lever is connected to the speed governor 16 and the guide blades 9 through cams, the arrangement being such that after the idling speed has been reached, further increase of speed is accompanied by an opening of the guide blades, which become approximately half-open just before the operating speed is reached. Further movement of the lever brings the guide blades to the fully open position and increases the speed to the full operating value. Fig. 7 shows an arrangement in which the manual lever 312' acts on the guide blades 309 through a pneumatic servomotor comprising a piston valve 300 connected to the lever through a toothed sector 303 and a rack 302'. Over the portion b of the travel of the lever 312', valve ports 304, 305 overlap to admit combustion air from the gas turbine engine to the space 300'. When the pressure of the combustion air reaches a value corresponding to the operating speed of the engine, a servo piston 308 is moved against the action of a return spring 311, with the assistance of a spring 310, to open the guide blades 309. If the engine exhaust gas temperature becomes excessive, the vapour pressure in a mercury vapour thermometer 319 rises to a value at which it expands a bellows 318 against the action of a spring 316 to open a vent valve 315. This reduces the pressure applied to the servo piston 308, thereby reducing the opening of the guide blades 309. This pressure may also be controllable in accordance with atmospheric pressure. The pistons may be replaced by diaphragms. A servomotor having a follow-up piston may be used.