Patent GB-732183-A (GB)
Title: An improved safety device for aircraft
IPC: G01S1/02
Filed: 1953-05-12
Abstract: 732,183. Automatic control systems. SPERRY CORPORATION. May 12, 1953 [May 14, 1952], No. 13298/53. Class 38 (4). [Also in Group XL (c)]. A safety device for aircraft produces an emergency control signal whenever an error signal produced by navigation equipment in the aircraft in dependence on departure of the craft from a radio defined approach path exceeds a predetermined limit, General description.-An automatic pilot comprises the usual compass 1, Fig. 1, controlling the rudder 6, and a pitch-and-roll gyroscope 2 controlling the ailerons 7 and the elevators 13. By moving switch 23, the rudder 6 may also be controlled by signals received at 14 from an omnidirectional radio-transmitter so as to bring the aircraft near the landing area. By further moving switch 23, the control from the omnidirectional transmitter is replaced by control from transmitters directional in bearing and elevation whose signals are received at 14, 19 respectively, so that the aircraft follows the landing path defined by the directional beams. If now, the aircraft deviates from the defined path either in bearing or elevation by more than a prescribed amount, the elevators are automatically operated to lift the aircraft out of the path to a safe level, and re-set the automatic pilot to be under the control of the usual compass and gyroscope alone. A switch button 36 allows the automatic pilot to be reset for control by the directional radio-beams again. Normal operation of automatic pilot.-With switch 23 actuated so that switch arms 24, 25, 26, 27, Fig. 2, are in their lowest positions, the rudder 6, Fig. 1, is controlled by signals from the compass 1 over amplifier 4 and servomotor 5; the ailerons 7 and elevators 13 are controlled by signals from the roll-and-pitch gyroscope 2 over amplifiers 9, 11 and servomotors 8, 12 respec. tively; the rudder signal from 3 is integrated at 10 and applied to amplifier 9 to correlate roll and turn signals for the rudder. Since switch arm 24, Fig. 2, is in its lowest position, the mixer 3, Fig. 1, receives a signal from A.C.-fed transformer 73, Fig. 2, over resistance 115; this signal is manually controlled by knob 48, Figs. 1 and 2, to allow manual control of bearing of the aircraft. Since switch 25, Fig. 2, is in its lowest position, relay 46 is energized to clutch in knob 47, Figs. 1, 2, and allow a manually controllable signal from transformer 72, Fig. 2, to be injected into the elevator amplifier 11, Fig. 1, and thus provide for manual control of the pitch of the aircraft. Control by omnidirectional radio - beam.- Switch 23 is moved to its central position, and radio-receiver 14 is tuned to the beam wavelength. The signal received at 14 is fed to mixer 15 together with its differential developed at 16, and applied over modulating amplifier 17 to circuit 18 over transformer 111, Fig. 2. Since switch 24, Fig. 2, is in its central position, the output of transformer 111 is applied over switch arm 33 to the mixer 3, and the manual control 48 is rendered ineffective. Switches 25, 26, 27 in their central positions leave the remainder of the control circuits unaffected, so that the pitch of the aircraft is still controlled by the gyroscope 2 and the manually operable knob 47. Normal control by directional bearing and elevation radio-beams.-Switch 23 is moved to its highest position, and receivers 14, 19 are moved to the wavelengths of the bearing and elevation radio-beams. Switch 24, Fig. 2, in its highest position leaves the rudder control as it was when the omnidirectional beam was operative. Switch 25 in its highest position de-energizes relay 46 to de-clutch knob 47 and thus render manual variation of elevation or pitch ineffective. Switch 27 in its highest position removes the short-circuit from leads 105, 106; as a result, the signal received at 19, Fig. 1, together with its differential developed at 21, passes through the modulating amplifier 22 to the transformer 102, Fig. 2, and thence to the elevator amplifier 11, Fig. 1, so that the aircraft follows the directional beams. Development of "fly-up" signa,l on deviation from directional beams.-The deviation of the aircraft from either of the directional beams can be detected by variation of the received signals or by variation of the roll or bank or rate of yaw signals fed to the amplifiers controlling the servomotors. In the first case, the received signal from the receiver 14 is fed over switch 53, Fig. 1, as shown, to an amplifier 54, the gain of which is varied by a bias developed by a distance measuring device 56 so that as the aircraft nears the ground, the deviations are increasingly amplified. The output of 54 is rectified at 67 and fed to a relay 34, Figs. 1, 2. If the deviation is such as to make the landing unsafe, relay 34, Fig. 2, is actuated and holds on over contact 34a and actuates relay 28 over contact 30. Relay 28 charges over contacts 29, 31, 32, 33. Changing contacts 29, 31 to the lower position energizes motor 39 which, through a slipping clutch 44, drives contact arm 42 clockwise to gradually reduce the signal from transformer 102 and to inject into leads 105 to the elevator amplifier 11 a "fly-up" signal from transformer 49, and simultaneously close contact 51 by cam 50. Change-over of contact 32 energizes relay 46 and renders manual control knob 47 operative, while change over of contact 33 cuts out the control of the rudder by the output of amplifier 17, leaving the rudder under the control of the compass 1, and manual control knob 48. The output of rectifier 67 may be coupled to the relay 34 over a variable time delay circuit, so that deviations of small duration do not produce "fly-up." The pilot may reset the circuit by actuating knob 23, which de-energizes relay 34 by opening contact 26 to de-energize relay 28, thus charging over contacts 29 ... 33. Change-over of contacts 29, 31 energizes motor 39 in the reverse direction so that contact 42 is traversed anti-clockwise until contacts 51 are opened to de-energize the motor 39. Similarly variations from the radio directional beam in elevation may be rectified at 55, Fig. 1, to actuate relay 35, Figs. 1 and 2, to produce the same result as actuation of relay 34. Instead of feeding rectifiers 67, 55 from the receivers 14, 19, they may be fed over switches 53, 71 from the gyroscope 2 respectively. Specification 691,017, [Group XL (c)], is referred to.