Patent GB-766184-A (GB)
Title: Improvements in or relating to aircraft training apparatus
IPC: G09B9/18
Filed: 1953-08-11
Abstract: 766,184. Flight training apparatus. CURTISS-WRIGHT CORPORATION. Aug. 11, 1953 [Aug. 22, 1952], No. 22119/53. Class 4. A simulating apparatus representing the operation of a variable pitch airplane propeller in association with engine responsive propeller pitch controls, for aircrew training, comprises an electrical system adjustable to represent blade angle, a selector means for controlling the system selectively according to simulated " automatic " or " manual " propeller pitch control operation, a summation computer responsive to simulating means representing functions of airspeed, propeller blade angle, engine brake horsepower, and engine R.P.M. for producing a potential representing the called-for blade angle change for controlling the blade angle system in simulation of automatic pitch control operation. and a plurality of propeller condition establishing control means representing distinct conditions of manual pitch control operation, which are respectively operable in response to calls for changes in blade angle variable in sense and degree to introduce potentials of corresponding senses to the servosystem ; the automatic operation of which is a simulation of the changes in blade angle in response to engine control operation. Simulation of engine operation. In Figs. 1, 2 an airspeed (V<SP>T</SP>) simulating servosystem comprises servo amplifier 1 energized by plural voltages representing thrust, drag, and gravity in a four engined aircraft energizes a biphase motor 2 also energized by a quadrature reference voltage e 1  to drive a biphase generator 3 energized by a quadrature reference voltage e 2  to produce in winding 9 a rate voltage Efb representing aircraft acceleration dv/dt which is fed back to the amplifier input. The motorgenerator shaft is geared to drive a simulated airspeed indicator (not shown) and the slider of a linear potentiometer 15 energized by antiphased alternating reference voltages to develop a voltage representing a function -f(V<SP>T</SP>) of simulated airspeed, which energizes through a phase reversing amplifier 17 and transformer 18 a divided potentiometer driven through gearing from the propeller blade angle (#p) simulating servosystem 20 (Fig. 3 seq.) to develop a voltage representing the function +f (V<SP>T</SP>) Ï (#p) of airspeed and blade angle for positive blade angles, or C4Ï (#p) for negative blade angles, which energizes, together with a voltage E 2  representing a constant C 2 , the propeller load (PL) summation amplifier 23 whose output transformer 24 develops two voltages PL in phase opposition, simulating propeller loading, of which the one voltage energizes over line 26 a linear potentiometer driven by the blade angle (#p) servosystem to develop at slider 28 a voltage representing the function f (PL) f (#p) while the other 180 degrees phase shifted PL voltage energizes a linear potentiometer driven by the air density (p) servosystem to develop at its slider 32 a voltage representing the function f(PL) f(p) which in turn energizes a potentiometer driven by the engine brake horsepower (BHP) servosystem to develop at its slider 34 a voltage representing the function f(PL) f(BHP) f(p). The automatically self-balancing air density (p) simulating servosystem comprises an A.C. motor energized by the output of a summation amplifier 40 wherein are combined a degenerative signal representing (p) from the slider of a follow up potentiometer 41 energized by a constant alternating voltage E and driven by the motor, a voltage representing datum air density #p derived from a centretapped constant A.C. energized potentiometer 44 operated by the instructor, and an alternating voltage representing a function f(H) of altitude derived from an A.C. energized potentiometer 37 driven by the altitude (h) simulating servosystem 36. Slider 32 is thus positioned according to the simulated air density prevailing at the simulated altitude and datum air density. The simulated throttle control 45 operates the slider 47 of an A.C. energized potentiometer 48, to derive a voltage representing a function of simulated engine manifold pressure f (MAP) which energizes a potentiometer 49 driven by the R.P.M. (M) simulating servosystem 50 to develop a slider voltage representing f (MAP) f (RPM) to energize the amplifier 52 of the engine horsepower (BHP) simulating servosystem, together with a follow up signal from A.C. energized potentiometer 53 driven by the system, and a degenerative rate signal Efb from the servosystem tachometer generator, so that the slider of potentiometer 34 is positioned according to the simulated engine power to develop a corresponding voltage on terminal 35. The master RPM control 55 operates the slider 57 of A.C. energized potentiometer 58 to develop a voltage representing the ruling speed (RPMm) of the master engine, which over amplifier 60 and transformer 61 energizes addition amplifier 64 together with voltages representing functions f(PL) f(#p) from slider 28, fŒ(PL) f(BHP) f(p) from slider 34, and a fixed alternating voltage representing a constant c ; and the output of the amplifier 64 over transformer 66 is shown to represent at terminal 65, ##p the required blade angle variation for the given conditions of engine and propeller operation. This voltage is supplied through normally closed contact 69 of relay 74 to the input of RPM simulating servosystem 50 together with the (RPMm) voltage through normally closed contact 72, a balance voltage from potentiometer 84 driven by the servomotor, a voltage representing the product of true airspeed and a constant when blade angle is negative, or zero voltage when it is positive, derived from a divided potentiometer 7a, b, c driven by the blade angle (#p) simulating servosystem, of which the upper portion 7b is earthed and the lower portion 7c is energized by a voltage representing the true simulated airspeed V T , derived through amplifier 77 and transformer 78 from the slider of A.C. energized potentiometer 76 driven by the true airspeed (V T ) simulating servosystem. The RPM (M) simulating servosystem operates to reduce the sum of the input voltages to zero by adjustment of A.C. energized potentiometer 84 supplying a follow up voltage to the servosystem input; and it is shown that the servosystem displacement represents the simulated engine R.P.M. for both positive and neagtive simulated blade angles and drives an A.C. energized potentiometer 85 to derive a proportionate voltage which operates a voltmeter 86 simulating the engine tachometer. The remaining engines of the aircraft are simulated by identical combinations of servosystems representing blade angle (#p) blade angle variation (##p) engine power (BHP) propeller loading (PL) and engine speed (RPM) each system being provided with relay 74 and associated contacts, and all being responsive to the master (RPMm) signal derived from amplifier 60 and transformer 61 over conductor 63 as described. Simulation of automatic airscrew operation. Selector switch arm 142 is placed on contact 143 to apply a direct voltage EDC over operated contacts 149 of relay 150 normally energized over instructor's main switch 151, normal contact 168 of instructor's malfunction switch 153, normal closed circuit breaker contacts 155, and terminal 156 to energize relay 90, Fig. 3, over normally closed contact 209 of relay 211. Relays 102, 94, 107, 112 are at the same time deenergized, Figs. 3, 4, 5, and the voltage simulating ##p from amplifier 64 and transformer 66 is supplied over normal contacts 95 of relay 94 and operated contacts 93 of relay 90 to the input of the blade angle (#p) simulating servosystem 20, together with a retroactive voltage Efb from the servosystem biphase tachometer generator while the remaining input for simulated manual control signals is grounded over normal contact 101 of relay 102, normal contact 96 of relay 94, the operated contact 92 of relay 90 and the upper or positive portion 10c of a divided potentiometer lOb, c, d driven by the servosystem (which is similar to the airspeed (VT) simulating servosystem shown in Fig. 1) and which runs until the resultant input is zero, at which it is shown that the simulated blade angle #p is such that the individual engine RPM simulating servosystem takes up a position corresponding to the R.P.M. demanded by the master control 55. Simulation of manual control of engine R.P.M. The selector arm 142 is moved to engage either " increase " contact 144 or " decrease " contact 145 against spring detent 146. For simulated speed increase, relay 107 is energized over slider 15a and the earthed upper conductive part 15c of potentiometer 15b, 15c driven by the blade angle (#p) simulating servosystem when the simulated blade angle exceeds +15 degrees ; the relay circuit being interrupted for low and reverse values of simulated blade angle by the lower insulating part of the potentiometer. Relay 107 is also energized by placing malfunction switch 153 on contact 159 to simulate propeller overspeed. Contacts 108, 109 are operated to apply a fixed alternating voltage, Fig. 5, over a speed limit voltage divider 118, 119 to the input of the blade angle (#p) simulating servosystem over normal contact 111 of relay 112, normal contact 92 of relay 90, the upper conductive portion 10c of potentiometer 10, b, c, d, driven by the servosystem, slider 10a, normal contact 96 of relay 94 and normal contact 101 of relay 102 in such phase that the servosystem is driven to a position representing a lower simulated airscrew pitch angle until the selector lever is restored to contact 143 to de-energize relay 107. Simulation of speed increase. Relay 112 is energized over contact 145 and normal contact 163 of relay 94 to operate contacts 111, 113 whereby a fixed alternating voltage from slider 13a of potentiometer 13b, 13c driven by the blade angle (#p) simulating servosystem is applied through a speed limit voltage divider 116, 1