GB1477656A - Aircraft flight path guidance - Google Patents

Abstract

1477656 Automatic control of aircraft BODENSEEWERK GERATETECHNIK GmbH 19 Sept 1974 [27 Sept 1973] 40902/74 Headings G3N and G3R In a system in which an aircraft is controlled by a first closed loop in which at least an elevator is adjusted in response to an altitude error signal and a second closed loop in which at least engine thrust is adjusted in response to an error in aerodynamic condition of flow, e.g. angle of attack or lift coefficent, the engine thrust is controlled in addition by an open loop signal derived from a vertical flight path generator which also provides the desired value for the altitude loop. The flight path generator 10, also Fig. 4 (not shown) produces a desired height signal h soil and, preferably, a glide angle signal γ soil as a function of range from a landing point measured by a glide path radio receiver. It is shown mathematically that the engine thrust S should be adjusted proportionally to the glide path angle so signal γ soll is combined with the closed loop signals for the engine at 72. Alternatively, the open loop thrust signal may be made proportional to aircraft weight times the quotient of the commanded rate of descent and the commanded or actual air speed, or the air speed may be assumed to be constant and represented in the signal generator by a fixed resistor. The figure shows how the elevator 68 and engine 70 are controlled by a combination of signals; in the figure the following are measuring devices:- angle of attack 32, rate gyro 42, longitudinal and vertical accelerometer 44, barometric altimeter 16, glide path receiver 18, radio altimeter 20. An OR logic 14 selects the appropriate one of the latter three devices for the actual value of height for comparison at 12 with the desired value from 10 to form altitude error #h. A second function generator 30 produces either the desired angle of attack α soll or lift coefficient as a function of range, or alternatively it produces two different but fixed signal levels selected at prescribed heights; in all cases this generator produces the desired "aerodynamic condition of flow" signal from which the error in this quantity is produced at comparator 34. The devices 36, 46, 54, 56 and 22 process the measured values by differentiation and integration to produce the following outputs:- proportional and integral 38, 40 of the "aerodynamic condition" error, angular acceleration in pitch 48, pitch rate 50, pitch angle 52, a signal corresponding to the rate of elevator movement, by double differentiation, 53, longitudinal speed 58 and acceleration 60, vertical speed from 56 and from 22 at 24, and proportional and integral values 26, 28 of the altitude error. These outputs are combined in a matrix unit 66 as shown to control the elevators and engine.