Patent GB-754354-A (GB)
Title: Improved control loading simulating apparatus for flight trainers
IPC: G09B9/28
Filed: 1954-05-19
Abstract: 754,354. Training apparatus for aircraft pilots. DEHMEL, R. C. May 19, 1954, No. 14758/54. Class 4. [Also in Group XXXVI] Apparatus for loading a simulated aircraft altitude control of a grounded flight training apparatus having flight computing means for producing control quantities responsive to the operation of altitude and velocity cortrols, are of said control quantities representing a function of airspeed; comprising means jointly responsive to the displacement of a respective control and the airspeed function quantity for producing a resultant control quantity representing the resultant of the aerodynamic reaction forces on such control, and a torque motor energized in response to the resultant control quantity which is connected to resist displacement of such control from its neutral position in simulation of the reaction due to the equivalent control setting under flight conditions. Fig. 2 shows a system for applying a simulated flight .reaction to the elevator control stick 10 of a grounded aircraft trainer wherein a reaction force computer 80 comprises amplifier 55 additively combining over series resistors at inputs 56, 57, the alternating voltage analogues of simulated angle of attack, (airspeed)<SP>2</SP>, Mach number, pitch velocity, and further aerodynamical parameters depending on the response accuracy required, which are derived from a known simulated flight computer of the electronic type comprising plural interrelated and interconnected servo-systems operating according to known aerodynamical laws in response to student-operated flight controls. The amplifier also receives over series resistors at inputs 58, 59 the analogue voltages representing the settings of the simulated studentoperated elevator and elevator trim controls 10, 31 as functions of (airspeed)<SP>2</SP>, which are derived from potentiometers 21c, 35 linked to the appropriate controls which are centretapped to earth and energized by antiphased alternating voltage analogues of (airspeed)2 derived from the flight computer. The amplifier inputs 60, 61 also receive over series resistors retroactive velocity and acceleration damping voltages derived as set forth below. The output of amplifier 55 defining the flight control reaction force energizes one winding of a biphase torque motor 63 also energized from a reference A.C. source to drive over shaft 23 a biphase generator 65 whose field is energized from the reference source to develop a degenerative velocity feed-back voltage E# applied to the amplifier through input 60, together with a D.C. generator 68 developing a unidirectional damping velocity voltage which after amplification is differentiated by capacitor 69 and resistor 70, and chopped by vibrator 72 operated by the reference A.C. source to an alternating inertial acceleration voltage Eα which is transformer coupled over a series resistor to amplifier input 61 in appropriate phase and amplitude to simulate the control system inertia. Shaft 23 imposes a control reaction torque on elevator control stick 10 over gear-box 21A which is linearly related to the combined amplifier input voltage and correctly reproduces the inertia of the control system of the aircraft; such torque being zero for control neutral under correct trim conditions and progressively increasing with control deviation according to known aerodynamical laws. A similar system is applied to the rudder and aileron controls of the trainer in response primarily to rudder or aileron deflection and trim, and to the appropriate aerodynamical parameters derived from the flight computer. A non-linear torque servo-system may be employed, together with a torque measuring device developing a control feedback voltage to the amplifier input which produces a linear system response to the combined input control voltage.