Patent GB-1101317-A (GB)
Title: Airplane instrument for furnishing a bias signal to offset the effects of forward components of gusts during landing approach
IPC: G05D1/06
Filed: 1966-02-28
Abstract: 1,101,317. Measuring electrically. L. M. GREENE. Feb. 28 1966 [March 4, 1965] No. 8689/66. Heading G1N. The system disclosed in Specification 927, 276 for indicating total available lift of an aircraft (or for automatically controlling the aircraft throttle to obtain the maximum safe angle of climb or descent) is modified so that when making a landing approach it will command increases in throttle opening and so compensate for temporary reductions in air-speed due to gusts of tail-wind. The additional signal to effect this command is derived from the rate of reduction of air-speed and the change of lift above or below a predetermined value. In one embodiment, a bellows 22 responsive to air-speed adjusts a potentiometer 42 to provide a D. C. air-speed signal which is differentiated by capacitor 54. The deceleration component of the signal is amplified by a re-setting magnetic amplifier 10 and charges a capacitor 102. The voltage across this capacitor is added to the output of the measuring system disclosed in Specification 927, 276 and represented at 114 by means of a second re-setting magnetic amplifier 120 in such sense as to cause the meter 116 (provided in the prior system) to indicate that an increase in air-speed is required. The time constant of capacitor 102 and resistor 104 is about one minute so that the indicated requirement for increased air-speed is maintained after the gust has died away. The change in lift due to the increased air-speed is measured by the rearward movement of a spring-centred, pivoted vane 28 located at the nose of the aircraft so as to be subjected to variation in pressure caused by shifting of the stagnation point over the nose of the wing. The angular position is a measure of prevailing lift and a D. C. signal proportional to lift is derived from a bridge comprising the two parts of a potentiometer 74 adjusted by the vane 28 and the two parts of a potentiometer 68 adjusted manually to provide the predetermined datum value. The signal due to increased lift is applied to a second control winding on the magnetic amplifier 10 so as to oppose the deceleration signal and so prevent the charge on capacitor 102 from being increased. An integrating network R84, C82, with a 5 second time constant delays the build-up of the lift signal. In a modification, Fig. 2 (not shown) deceleration is again measured by differentiating the air-speed signal, but the lift is considered to be proportional to air-speed which is measured by a second potentiometer and fed to the amplifier 10. In another modification, Fig. 3 (not shown) the lift signal is obtained from a pivoted vane that measures the angle of attack of the aircraft. In another modification, Fig. 4 (not shown) the lift signal may be obtained either as in Fig. 1 or as in Fig. 3 but the deceleration signal is computed from the rate of change of vertical acceleration (measured by a spring-supported mass adjusting a potentiometer, the output voltage from which is differentiated) and the rate of change of lift.