GB738624A - Improvements in or relating to propeller control systems - Google Patents

Abstract

738,624. Variable pitch propellers. UNITED AIRCRAFT CORPORATION. Sept. 22, 1953 [Oct. 14, 1952], No. 26095/53. Class 114. A control for a propeller having adjustable pitch blades 12 and means for moving the blades to increase and decrease their pitch comprises a rheostat 56 connected with the blades for producing a signal proportional to the pitch, a rheostat 50 connected to a control mechanism 48 for producing a signal proportional to the position of the control mechanism, signal comparing means 54 connected to both rheostats 50, 56 for providing a resultant signal dependent on the preponderence of one signal over the other which is used to cause increase or decrease of the pitch. The resultant signal is used to operate a switch 80 which either connects a battery 64 to line 82 and to a switch 60 which is closed by the mechanism 48 when set to a pitch angle below 7 degrees. whereby current is supplied to a pitch decreasing valve 28, or to line 94 whereby current is supplied to a pitch increasing valve 38, the valves 28, 38 disabling the governor 16. The switch 80 is connected to the battery either through a switch 84 actuated by the propeller in accordance with its pitch and a switch 86 closed by contact of the aircraft with land or water/or through a switch 96 closed by a "start-run" lever 118. A feather control button 106 is pushed to energize a hold and timer device 108, 110, to close switch 114 which starts the feathering pump 44 and to supply current to the pitch increase valve 38. Pulling button 106 supplies current to operate the feathering pump 44 and to the pitch decrease valve 28, through a switch 116 controlled by the "startrun" lever 118. The mechanism 48 is also connected to and controls the engine throttle control 102 which during movement of the mechanism 48 in one direction closes the throttle then opens it again as the blades are reversed. In order to prevent stalling of a turbine when the blades are moved to reverse pitch the circuit may be modified by applying to the rheostat circuit 50 of the means 54 a reference voltage which is modified by the turbine speed and which feeds a signal to the means 54 when the signal voltage from the rheostat 50 is less to decrease the reverse pitch. Specifications 636,402 and 683,906 are referred to.