Patent GB-559327-A (GB)
Abstract: 559,327. Electric control systems. BENDIX AVIATION CORPORATION. June 19, 1942, No. 8466. Convention date, June 21, 1941. [Class 40. (i)] In an apparatus for indicating the magnetic heading of a craft comprising a rate of turn gyroscope co-operating with a device (including a magnetic compass) responsive to the earth's magnetic field the direction indicating mechanism is operated an angular amount in accordance with the angle of turn of the craft, by integrating mechanism energized by the precession of the gyroscope and subject to corrective control by the device responsive to the earth's magnetic field. During substantially straight flight the magnetic compass exerts primary control of the indicator whilst during turns the integrator predominates. As shown, the precession axle 32 of a rate of turn gyroscope is connected to the rotor 34 of an Autosyn transmitter supplied with alternating current through a frequency doubler 42 and connected by leads 39 to the three phases of a receiver stator 21. When the craft turns, the gyroscope precesses and moves the rotor 34 through a corresponding angle thereby setting up a corresponding stator voltage which is passed by the leads 39 to the receiver windings 21. The resultant voltage in the receiver rotor 22 is transmitted bv conductors 44 to a power amplifier 45 and thence to one phase of a two-phase induction motor 10 the other phase of which is supplied with alternating current through leads 43. The motor thus energized rotates a drag-cup 14 carrying a permanent magnet 17. The permanent magnet, acting on a drag cup 26 turns the receiver rotor 22 against the opposition of a spring 27 until the receiver rotor is maintained in almost angular agreement with the rotor 34 when the voltage in the rotor coil is just sufficient after passing the power amplifier 45 to maintain the induction motor 10 at constant speed and proportional to the rate of turn of the craft, The induction motor, operating through reduction gearing 47, 50 rotates a shaft 52 an amount equal to the angle of craft turn and this new magnetic heading is indicated by a pointer 64b actuated through a transmitter 54 and a distant receiver stator 64 fed with alternating current. The pointer continues to indicate the new heading when the craft turn has terminated. During straight flight or minor deviations, the magnetic compass exerts primary control For this purpose, the magnetic compass 87 is situated adjacent a pick-up device, which may be of the type described in Specification 549,528 and is provided with three legs carrying coils 70, 71, 72 connected by leads 75 to the field windings 76, 77, 78 of a compass Autosyn. The junction of the three legs carries an energizing winding 73 supplied with alternating current through leads 74. When a minor angular displacement of the craft (and pick-up device) occurs the relative displacement between the compass magnets and the pick-up device varies the induced voltages in the leads 75 and windings 76, 77, 78. A voltage is induced in the rotor coil 80 and passed through a voltage amplifier 82 and thence through the power amplifier 45 and leads 46 to the second phase of the induction motor which now operates to drive the rotor coil 80 to a no-voltage position, thereby de-energizing the induction motor and at the same time adjusting the pointer 64b. When such an adjustment occurs, a small movement is imparted to the receiver rotor 22 which will consequently have a voltage induced therein and will oppose the action of the pick-up device, thus damping the movement of the pointer 64b. During a turn, the pick-up device 66 provides a small voltage which influences to a minor extent the voltage induced in the receiver rotor 22 thereby varying the speed of the inductor motor. The turn indicator device and the magnetic compass are thus mutually corrective. To overcome the lag between gyro precession and speeding up of the induction motor, the initial movement of the induction motor 10 may be arranged, by the employment of intermediate epicyclic gearing, to displace the receiver motor 22 sufficiently to maintain the speed of the induction motor proportional to the rate of turn of the craft.