Patent GB-491920-A (GB)
Title: Automatic stabilizing device for aircraft
IPC: G05D1/08
Filed: 1937-03-09
Abstract: 491,920. Fluid-pressure servomotors. ALKAN, R. March 9, 1937, No. 6873. Convention date, Sept. 4, 1936. [Class 135] A device for automatically stabilizing aircraft in response to amplitude, speed and acceleration of deviation about each of the three axes of stabilization, comprises a director element controlled by means defining the axis of reference and adapted to be displaced according to amplitude of deviation, follow-up means for said director element operated by compressedair and connected with a speed-multiplying gear which causes the movement of the followup means to be retarded proportionally to the speed and the acceleration of deviation, and totalizing means for actuating a servomotor in accordance with amplitude, speed and acceleration of deviation, the servomotor causing the deflection of a control surface. For controlling movements in azimuth, the apparatus comprises a disc 3, the director element, freely rotatable about an axis 4 and having a part cut away to form diametral edges. Such a director element is provided for each of the three control surfaces, but it is under a different kind of control in each case. The disc 3 is so disposed as to oscillate in front of, and close more or less, orifices 5, 6 formed in extensions of pistons 7, 8 working in cylinders 9, 10 which contain also secondary pistons 11, 12. The pistons 7, 8 are connected to a lever 13, and the pistons 11, 12 to a lever 14. Compressedair is supplied at 15 equally to the two cylinders. The lever 13 is connected, through a speedmultiplying train 18, 19 with a flywheel disc 20 the movement of which is braked by Foucault currents generated by an electromagnet 21. The lever 14 moves under the control of a spring blade 22 restrained at 23 to exert a centralizing action. The two levers 13, 14 are connected by links 24, 25 to a lever 26 the pivot 27 of which is connected to a floating lever 34 which itself is connected to a slide valve 33 of a servomotor 29, 30 and to a lever 36 connected to the pistons 31, 32 of the motor. The lever 36 is connected to the control surface 37. Normally the orifices 5, 6 are uncovered to the same extent and the pressures in the cylinders 9, 10 are equal. Upon deviation from the set course, the orifices 5, 6 become uncovered unequally with the result that the pressures in the cylinders 9, 10 are unequal and movement of the pistons occurs. If no resistance were offered to the movement of the pistons they would move rapidly to follow up the disc so as again to give equal openings to the orifices, but this rapid movement of the control surface would produce such a rapid return of the aircraft that it would overshoot the set course and oscillation would occur before the set course was reached. To prevent this, the movement of the lever 13 is braked, by the inertia of the flywheel disc in proportion to speed and by the Foucault currents in proportion to acceleration of deviation. The lever 26 serves as a totalizing device for movements proportional to amplitude, speed and acceleration of deviation and its movement actuates the servomotor through the follow-up device 33 .. 35. For control of the ailerons, the disc 3 of Fig. 1, controlled by a gyroscope, is replaced by a loaded disc serving as a pendulum and moving between the poles of a magnet which serves as a damping device. For control of an elevator, the disc 3, shown in Fig. 1, is replaced by a disc 3<11>, Fig. 4, actuated by a differential manometer consisting of capsules 40, 41 connected by tubes to an air-speed sensitive device 42. The capsules are connected to a lever 43 loaded by a spring and connected to the disc 3<11>. If the aircraft pitches, the pressure in capsule 40 is decreased whilst that in the capsule 41 remains substantially constant due to the lateral apertures around the tube to capsule 40. The disc 311 is thereupon tilted and the action is the same as that described with reference to Fig. 1. The pistons and cylinders of Fig. 1 may be replaced by bellows. The Specification as open to inspection under. Sect. 91 describes modifications in which the flywheel disc 20 of Fig. 1 may be replaced by (1) a clockwork escapement, (2) a fan, or (3) a frictional centrifugal regulator. This subject-matter does not appear in the Specification as accepted.