Patent GB-771636-A (GB)
Title: Improvements in or relating to grounded aircraft trainers
IPC: G09B9/28
Filed: 1955-06-03
Abstract: 771,636. Aircraft ground trainers. CURTISS-WRIGHT CORPORATION. June 3, 1955 [June 14, 1954], No. 16055/55. Class 4. An aircraft trainer comprises a dummy control stick movement of which is opposed by forces derived from quantities representing the aerodynamic force acting on the simulated elevator computed as a function of the lift, and the force acting on a bob weight attached to the simulated control stick. The Fig. shows the relevant parts of an analogue computer controlling a motor 87 which applies forces to a dummy control stick 18. The aerodynamic force on the elevator is computed as Fa=9A Che (Sfw, TSfw, Se, x, Ste)+9A Che, (Wy) where 9=¢ Sv<SP>2</SP>, S being the air density, and v the true air speed, A is a constant for a particular aircraft, and Che is the elevator hinge moment coefficient, being the sum of components due to Sfw, the wing flaps angle, T and S[w, the effect of thrust and wing flap angle, Se, the elevator angle, a, the angle of attack, and Ste, the elevator tab angle, and of a component Che(Wy), due to the rate of pitch Wy. Accordingly, a summing amplifier 6 is fed with five inputs. One comes from the pick-off 3 of a potentiometer 2, adjusted by the pilot's wing flap dial 1, and represents Che (Sfw). A further potentiometer 8, the slider of 7 which is actuated by dial 1, is fed from a transformer 11 providing a voltage representing the thrust coefficient T, thus the amplifier 6 receives an input representing Che (TSfw). The control stick 18 positions the slider 17 of a potentiometer 16. deriving a signal fed to amplifier 6, representing Che (Se). An angle of attack servo 21 forming part of the complete computer, positions a slider 31 of potentiometer 25 to feed a signal Che(α) to amplifier 6. The pilot can also adjust an elevator tab dial 34, which positions the slider 36 of a potentiometer 37, to feed a signal Che(Ste) to amplifier 6. The resultant output from amplifier 6 is fed to a transformer, and applied across a potentiometer 43, the slider 45 of which is positioned by an indicated airspeed servo 42, computing Vi<SP>2</SP> = sv<SP>2</SP>/so So being a standard density and V i  the indicated air speed. The signal from slider 45 is thus proportioned to 9 Che (Sfw, TSfw, Se, α, Ste), and this is fed to a summing amplifier 47. The term 9AChe(Wy) is computed as Ap(W-L/m), where W is the aircraft weight, L the lift, and in the mass. Means for computing this term include an amplifier 48, the ouput W-L/m of which is fed to a transformer, 50 connected by a line 52 to a potentiometer 53 in the air density servo system 54. This includes an altitude servo system 98 positioning a slider 63 feeding the air density summing amplifier 65, which positions slides 83 and 55, the former providing an " answer signal " modified by the outside air temperature servo system 59. Slider 55 thus derives a signal S W-L/m fed to amplifier 47 through a relay contact 57. The signal Fb representing the effect of the bob weight, is computed as K (W-L/m) where K is a constant. This signal is taken from the secondary of transformer 50 over line 85 to summing amplifier 47 through a relay contact 86. The relay 58 is energized when the simulated aircraft is on the ground. Amplifier 47 sums the feel force control quantities and energizes a motor 87 to apply these forces to the control stick 18.