Patent GB-778162-A (GB)
Title: Automatic pilot system
IPC: G05D1/08
Filed: 1954-04-23
Abstract: 778,162. Automatic steering control systems. BENDIX AVIATION CORPORATION. April 23, 1954 [May 18, 1953], No. 11842/54. Class 38 (4). In an aircraft automatic pilot a signal dependent on altitude or heading is combined with a signal dependent on pitch or bank respectively, and the time integral of one of the signals is added to control a servomotor operating a control surface. Heading and bank control.-In an aircraft automatic pilot, Fig. 1, deviations, from a desired heading are detected by a gyro-stabilized earth inductor compass 155 applying signals to the stator of an inductive device 173. Signals from the rotor of inductive device 173 are amplified at 177 and cause a servomotor 183 to drive the rotor to a null position. When an electromagnetic clutch 193 is energized by manual operation of a switch 216 to engage the automatic pilot at the desired heading, servomotor 183 also adjusts an inductive device 115 to produce a heading error signal which controls, through a combined thermionic and magnetic amplifier, an A.C. electrical servo-system operating the ailerons to maintain correct heading. Also controlling the aileron servo-system is a signal derived from the bank pick-off 111 of a gyro-vertical 120 to maintain the aircraft level transversely. To avoid a condition of balance between these two signals with heading and bank errors which thus cancel out, the heading error signal from inductive device 115 is also applied to input terminals AB of an integrator 117 the output from terminals CD of which is also applied to the aileron servosystem so that correct heading is ultimately assured. This arrangement also assures that unbanked flight in the desired direction is also attained even if the automatic pilot is engaged with a wing low. The integrator is a motoroperated rate feedback device incorporating thermionic and magnetic amplification, Fig. 4 (not shown). Position and rate feedback is applied to the aileron servo-system through a potentiometer 5. The heading error signal from inductive device 115 is also applied through a transformer 432 to control a servo-system operating the rudder. An inductive pick-off 440 associated with a rate-of-turn gyro 430 introduces a rate signal into the rudder servo-system, position and rate feedback also being applied through a potentiometer 4. Changing heading.-When it is desired to change heading, operation of a manually controlled knob 150 first opens a switch 222 to deenergize clutch 193 thus rendering compass 155 ineffective while knob 150 is positioned to adjust inductive devices 148 and 434 to introduce signals into the aileron and rudder servosystems to produce a co-ordinated turn. Accurate co-ordination of rudder and ailerons is ensured by signals applied to the rudder servosystem from an inductive pick-off 461 associated with a pendulum 436 detecting side-slip. Altitude and pitch control.-Deviations from a desired altitude are detected by an aneroid 530 which, when a switch 520 is manually operated to energize a clutch 516 and thereby engage altitude control, operates an inductive device 536 signals from which control an A.C. electric servo-system adjusting the elevators to maintain correct altitude. Also controlling the elevator servo-system is a signal derived from the pitch pick-off 500 of gyro-vertical 120 to maintain the aircraft level longitudinally. To avoid a condition of balance with altitude and pitch errors which cancel out, the altitude error signal from inductive device 536 is also applied to input terminals AB of an integrator 504 the output from terminals CD of which is applied to the elevator servo-system so that correct altitude is ultimately assured. This arrangement also ensures that correct altitude is attained even if the altitude control is engaged when the aircraft is climbing or diving. Position and rate feedback is applied to the elevator servo-system through a potentiometer 6. Changing altitude.-When it is desired to change altitude manual operation of switch 520 de-energizes clutch 516 and renders aneroid 530 ineffective while a knob 512 is positioned to adjust an inductive device 501 to introduce a signal into the elevator servo-system to produce climb or dive. To change from one assigned altitude, to the next lower assigned altitude when aircraft are " stacked " prior to landing switch 520 is operated to disengage altitude control and a switch 600 is operated to connect the output of integrator 504 to its input so that the signal from the integrator dies away to cause a dive. Manual control.-When the automatic pilot is disengaged by the manual operation of switches 216 and 520 the craft may be steered by means of a manual control column 240 and rudder pedals 242. In this condition although the servomotors are de-clutched from the control surfaces they normally operate to maintain the amplifier inputs at zero in readiness for reengagement. Clutches 193 and 516 are deenergized and spring urged levers 202 and 532. return the inductive devices 115 and 536 to null positions. The integrators 117 and 504 are also rendered inoperative. If the automatic pilot is engaged with a wing low, the input to the aileron servo amplifier is reduced to zero by trimming the ailerons manually until an indicator (not shown) associated with the amplifier indicates zero. Energization of a solenoid 220 is maintained on operation of knob 150, to prevent levers 202 from causing a sudden signal change. H.T. failure in the servo-amplifiers causes operation of a relay to cut off the A.C. supply to the magnetic amplifier section and to give aural and visual warning. The amplifier A.C. supply is also cut off automatically if thermal fuses melt when predetermined transformer temperatures are exceeded. Specifications 662,853 and 778,163 are referred to.