Patent GB-884859-A (GB)
Title: Simulated aircraft nose-wheel steering system
Inventor: COHEN CHARLES L
IPC: G09B9/20
Filed: 1959-04-16
Abstract: 884,859. Flight training apparatus. ACF INDUSTRIES Inc. April 16, 1959, No. 12934/59. Class 4. An aircraft flight trainer comprises nose-wheel steering wheel means, nose-wheel position-means, and means responsive to the mechanical position difference between the abovementioned means for affecting the nose-wheel position means to tend to eliminate the difference between the nose-wheel steering wheel means and the nosewheel position means. An electro-mechanical nose-wheel position system comprises a demodulator 11, a magnetic clutch 12 tachometer generator 13 and nose-wheel position shaft 3 having potentiometers 30, 31 and 32 connected thereto. Conductors 15, 19 and 21 feed voltage proportional to the angular position of the position shaft 3 of the nose-wheel (not shown) back to the input 9 of demodulator 11 when a relay 18 (which indicates if the nose-wheel is on the ground) is de-energised. A simulated steering wheel 2 connects through a mechanical shaft 8 to a mechanical differential 5 to which the other input is the nose-wheel position shaft 3. The difference between the inputs is translated to an output shaft 4 which is urged into a neutral position by centring springs 6 and operates cam switches 73, 74 of relays 71, 72 and the wiper of a potentiometer 35, to be described. Two pairs of brake pedals 36-39 operate through diode magnitude selectors 47, 49 the wipers of potentiometers 41-44 pick off voltages fed to magnitude selectors 47 and 49 whose outputs are then fed through input impedances 61-64 to a summing amplifier 110 which sums all of the force voltage analogous of the nose-wheel on the ground. Voltage analogous to turning movement of the aircraft is fed through impedance 65 and a castoring restoring force connected through conductor 50 and impedance 66. The relay 71 has a connection 78 to amplifier 110 through a " hydraulic pressure " potentiometer 33, " landing gear down " contacts 79 and impedance 67. The output of the amplifier is connected to the extremities and the centre of the potentiometer 35 the wiper arm of which provides one of two inputs to a phase selector 48, which is provided to baulk any input through potentiometer 33, so that whenever there is sufficient deflection of wheel 2 to close either relay 71 or 72, selector 48 is put into operation. Diodes 46 are provided to balance the effects of the plus or minus voltage from selector 48. When the simulated nose-wheel lifts off the ground the castoring restoring force analogue voltage is removed from the input and a centering cam restoring force voltage analogue 19 is applied to input 9 of demodulator 11 from a source 31 when relay 18 becomes energised. Other inputs to demodulator 11 are derived at a potentiometer 30 and supplied over connector 15 and impedance 16 for the purpose of representing limitation of movement of shaft 3, normally provided by mechanical stops ; and velocity feedback from generator 13 over connector 14. A voltage proportional to nosewheel position is derived at potentiometer 32 and, when relay 18 is energised is fed over connectors 20, 22 to provide one term for calculating turning rate Wz used in other flight computation forming no part of the invention, and also to a potentiometer 34 where it is multiplied by a function of Mach number to provide the input 66 to amplifier 110.