GB1244160A - Engine, propeller and rotor installations - Google Patents

Abstract

1,244,160. Rotary wing aircraft; controlling aircraft. DOWTY ROTOL Ltd. 1 Nov., 1968 [17 Nov., 1967], No. 52496/67. Headings B7G and B7W. In an engine, propeller and rotor installation including an engine-driven variable-pitch propeller and at least one rotor which is drivable with the propeller, the blade pitch of the propeller is adjustable by a pitch control system in response to input or datum signals and in response to signals themselves dependent upon the torque output of the engine or engines, said torque-responsive signals being applied to the system in such manner, that whilst the rotor and propeller are being driven together when said torque-responsive signals exceed a predetermined magnitude, change in the propeller blade pitch is in consequence effected by said system as, without substantially reducing the power transmitted to the rotor, will reduce power absorption by the propeller by an amount necessary for the engine or engines to avoid reaching a stalled condition. In operation at a position of vertical lift (or descent) or at hover a main rotor and tail rotor (not shown) are driven through shafts 11, 20. Suitable gearing 12-19 also drives a fluid coupling 35 connected in parallel across a synchronizing coupling 26. These are uncoupled and a propeller 70 is stationary. Pumps 36-39 are being operated, 36, 37 for lubrication and 38, 39 connected to drain. A desired datum is set by a lever 97 settling a valve 88 which is operative on a pitch-control valve 55. A start switch 156 is closed which causes solenoids 132, 133 of solenoid valves 48, 54 to be energized. The spool of solenoid valve 48 is moved to the left in the drawing which diverts the fluid from pump 37 to the fluid coupling 35. This drives the output side 27 of coupling 26 and the propeller 70 bringing them up to the speed of the input shaft 25. The propeller, which is in a fine pitch condition now absorbs increasingly the engine power for forward flight. Simultaneously the solenoid valve 54 directs fluid to the right hand side of a piston 82 in pitch control valve 55, the piston and thus a spool 59 move to the left under the action of a plunger 99 from a bellows 100 connected to an engine torque-response means. Movement of spool 59 allows fluid to pass into fine pitch chamber 75a of the propeller hub 71 moving the propeller to its maximum fine pitch setting. Also simultaneously fluid from solenoid valve 54 flows through pipe 109 to, and through, a solenoid valve 110, via a pipe 111 to the righthand side of a piston 113 of a coupling actuator 114. The piston 113 moves to the left, the energy of which movement is stored by a spring box 126. When the coupling 26 is synchronized and operative the energy of spring box 126 moves a lever 122 clockwise to lock the coupling 26. During this movement a switch 129 is closed and at the lock position a plunger 120 engages a notch in a cam face of a lever 122. Movement of plunger 120 also causes movement of a projecting portion 131 which opens a switch 130, causing solenoids 132, 133 to deenergize. The fluid to actuator 114 is then cut off, lever 122 remaining in the locked position, and the fluid coupling 35 is connected to drain. Also the fluid flow from solenoid valve 54 to pitch-control valve 55 is redirected from the right hand to the left-hand side of piston 82. The piston moves to the right moving the spool 59 against the bellows plunger 99 to connect the coarse pitch chamber 75b to valve 55. When operating conditions have been reached as dictated by the datum setting of valve 88 spool 59 of the valve 55 assumes a neutral position, cutting off both pitch chambers 75a, 75b of the propeller. The propeller now absorbs all power and main rotor autorotates driving auxiliary rotor. If there is any torque change this is shown by movement of bellows 100 which automatically allows coarse, or fine pitch movement of the propeller until the datum conditions are restored. The datum can be changed in flight. To change from forward to hover or vertical lift and thus stop propeller 70, switch 153 is opened which energizes solenoids 132, 133, 134. The propeller is tuned to fine pitch as the rotor begins to absorb power. Solenoid 134 of solenoid valve 110 moves spool 137 to the right, causing the piston of actuator 114 to contract against the efforts of the spring box 126. When the pitch and torque are balanced plunger 120 is depressed allowing the stored energy of spring box 126 to rotate lever 122 anti-clockwise and disengage coupling 26. Fluid coupling 35 has meantime been brought into operation. Movement of lever 122 opens switch 129 which deenergizes a relay 162 and thus solenoids 132, 133, 134. Coupling 35 exhausts and propeller runs down. The pitch-control valve 55 is biased to maximum fine pitch condition of the propeller in overriding conditions. In an alternative embodiment pitch change is effected by a manual-initiated follow-up servo system. Clockwise movement of a lever displaces a valve member causing fluid to flow into the coarse pitch chamber of the propeller pitch motor. When the blade pitch has coarsened it shuts off its fluid supply. If movement of the lever demands a total torque greater than the engines are rated for (i.e. for both rotor and propeller), a torque signal applied internally to a bellows will displace a spool valve to move an actuator of the lever assembly against a spring box. This causes said valve member to move towards a fine pitch condition. If engine output is below maximum and an over-excessive torque is applied a further valve element is openable by an engine-speed sensitive governor when a predetermined reduction in engine speed is reached, this causing the spool valve to move to actuate said valve member to a fine-pitch condition.