Patent GB-648679-A (GB)
Title: Aviation trainer
IPC: G09B9/16
Filed: 1947-05-28
Abstract: 648,679. Ground trainers for pilots. LINK AVIATION, Inc. May 28, 1947, No. 14180. Convention date, May 28, 1946. [Class 4] A ground trainer for pilots comprises a dummy throttle lever and dummy altimeter, the latter being operated through a mechanism including a transmission device of the friction disc and roller type, the driving member of which is rotated at constant speed and the transmission ratio of which is varied in accordance with changes in the throttle lever setting. General arrangement.-The invention is shown applied to a trainer of the type described in Specifications 370,128 and 481,375, in which the attitude of the fuselage is controlled by pneumaticallyoperated bellows and its rotation is effected by a motor controlled by dummy rudder pedals. A dummy manifold pressure gauge 138e is controlled by a manifold pressure unit 118, while a dummy air speed indicator 312 is operated by an air speed unit 306, 308. In addition an altitude unit is provided, embodying a dummy vertical speed indicator 474 and dummy altimeter 540. Manifold pressure unit.-The operation of this unit is controlled by a link 114 connected to the dummy throttle lever 100, and by a bellows 222 connected by a pipe 214 to the altitude valve 184, so as to be responsive both to the throttle setting and assumed altitude. Air speed unit.-The bellows 300 of the dummy air speed indicator 312 is connected to a suction source 302 through a bellows 292 and control valve 252, the latter being connected by a link 248 to the differential lever 242 of a pitch action linkage. One end of the lever 242 is connected to a link 240 which is moved in response to variations of engine power output consequent upon movement of the throttle lever 100, and it is also connected to a lever 246 which is rotated by a sector 278 operated by pitching movements of the fuselage. The reading of the indicator 312 is thus dependent upon the engine power output and the pitching attitude of the fuselage. Vertical speed indicator.-The vertical speed indicator 474 is operated by links 358, 382, 406, the former being connected to a lever 354, the position of which is dependent upon the fuselage attitude and assumed air speed. When the fuselage tilts, the lower end of the lever 354 moves as the result of rotation of the arm 246, to which it is connected by studs 362, 364. The Selsyn transmitter 306 of the air speed indicator operates a receiver 316, which also operates the link 358 through a pinion 339, lever 350 and link 352. Movement of the link 406 is transmitted to a reciprocating block 438 through a linkage 418, 436, Fig. 10, the block carrying a rack 446 which operates a shaft 452 connected to a Selsyn transmitter 464 controlling the indicator 474. The link 406 is provided with a spring compensating assembly 410, 412 so that there is a lag between changes in the reading of the indicator 474 and changes in fuselage attitude and operation of the air speed unit. Operation of altimeter.-Assumed altitude is produced by integrating the assumed vertical speed with time, by a mechanism comprising a friction disc 490 driven by a constant speed electric motor 480, the disc being engaged by a roller 510 carried by the block so that its distance from the centre of the disc 490 is dependent upon the assumed vertical speed. The roller 510 is carried by a splined shaft 508 connected to the input sun wheel 520 of a differential gear 516, the output wheel 522 of which is connected to a Selsyn transmitter 530 controlling the dummy altimeter 540. A second constant speed motor 562 drives a secondary input wheel 526 of the differential 516, the apparatus being so adjusted that when the assumed vertical speed is zero the wheel 510 is driven at the speed necessary to nullify the input to the differential due to rotation of the wheel 526. The shaft of the rotor 530 is also connected to the altitude valve 184 through a link 560, shaft 556 and spur-andbevel gearing 554. The motors 480, 562 are controlled by micro-switches 582, 584 respectively, and the arrangement is such that when the altimeter reading corresponds with the assumed ceiling of the aircraft, the switch 584 is opened to stop the motor 562. Also, when the altimeter reading approaches zero the switch 582 is opened and stops the motor 480, by which it is impossible for the reading of the instrument to fall below zero. Rough air effects.-These are simulated by a unit 625, Fig. 13, comprising a number of cams 632, 634, ... 650, whose edges are provided with irregular depressions which may be brought into contact with spring-loaded arms 850, 852, ... 866 by rotation of a control wheel 900. The arms are connected to valves 730, 732,...748 in the various pneumatic lines controlling the banking and pitching bellows, air speed indicator, vertical speed indicator, and altimeter, rotation of the cams causing irregular movements of the valves to cause fluctuations in the pressures in the pipe lines with consequent variations in the attitude of the trainer and in the readings of the instruments. In order to ensure that the rough air cycle is repeated at very long time intervals, the cams 648,650 are rotated at a slightly different speed from the remaining control cams.