Patent GB-757891-A (GB)
Title: Improvements in or relating to control device for airplane
Inventor: ATWOOD JOHN L
IPC: G05D1/06
Filed: 1952-10-24
Abstract: 757,891. Automatic steering control systems. NORTH AMERICAN AVIATION, Inc. Oct. 24, 1952, No. 26727/52. Class 38 (4). [Also in Group XXIX] In an aircraft control system vertical gusts produce an electrical signal which is utilized to change wing lift to counter the gust, the electrical signal being modified by a further electrical signal dependent on the position of the wing lift changing means. Several forms of detector producing an electric signal dependent in sense and magnitude on the sense and magnitude of gust perpendicular to the path of travel are described. In one form, Fig. 8, a casing 1b, carried by a boom B projecting forwardly of the aircraft wing, contains upper and lower openings 32, 33 leading to pipes 31, 34 associated with a bellows 25 so that difference of pressure due to a vertical component of airflow operates the rotor of a variable inductive device 30 to produce the gust signal. To neutralize the effect of changes of attitude due to persistent effects such as prevailing winds or change of airspeed, casing 1b carries a vane 2b and is pivoted to boom B by means associated with damping dashpots (not shown) so that the casing ultimately sets itself in a neutral position. In a modified form upper and lower openings are associated with each side of a flexible diaphragm 64, Fig. 2, which forms with fixed plates 62, 63 a differential condenser producing the gust signal by unbalance of a bridge circuit. In another form a horizontal vane is mounted on booms projecting forwardly of the wing and strain gauges associated with upper and lower surfaces of each boom are connected to form a bridge circuit unbalance of which produces a gust signal. In yet another form temperaturevariable resistance wires carrying current and mounted on upper and lower surfaces of the wing are connected in a bridge circuit unbalance of which, due to unequal cooling on a gust, produces a gust signal. A gust signal produced by the first form of detector described above is amplified and controls one or other of two electromagnetically operated brakes so that a continuously running electric motor associated with planetary gearing and a flywheel adjusts a wing flap in the appropriate direction to counter a gust. Follow-up is provided by feedback to the amplifier from a variable inductive device operated by the flap. An electromagnetically controlled hydraulic servomotor may alternatively control the flap. Fig. 2 shows the differential condenser type of gust detector associated with resistors 69, 70 to form a bridge circuit any gust signal from which is amplified at 71, 73 and 78 to energize the appropriate field winding 80, 81 of an amplidyne generator 82 so that motors 83, 84 adjust a trimming tab 79 and hence a wing flap 74 in the appropriate direction to counter the gust. Follow-up is provided by feedback to amplifier 71 from a potentiometer 75 operated by flap 74. Differential components of the gust signal and the positional error signal are derived at 87 and 93 respectively and injected into amplifier 78. In this arrangement the effect of change of attitude due to change of airspeed is compensated by an airspeed responsive bellows 128 adjusting a reactance 129. Gusts may be countered by adjustment of wing lift by spoilers or by boundary layer control involving control of an air supply to a wing slot. The Specification refers to a plurality of gust detectors each controlling a plurality of units, which may be of different types, adjusting wing lift. Adjustment of tail plane lift may be effected in addition.