Patent GB-801550-A (GB)
Abstract: 801,550. Controlling aircraft. SPERRY RAND CORPORATION. March 13, 1956 [March 21, 1955], No. 7819/56. Class 4. [Also in Group XXXVIII] A gyroscope vertical is controlled by a reference external to the aircraft for example a radial beam. The invention describes control of the gyro about its roll axis by the lateral acceleration of the aircraft and about its pitch axis by the vertical velocity. As shown, Fig. 3, a signal from a radio receiver 42 is a measure of the lateral distance y of the aircraft from the radial guidance beam and is fed through a reversing switch 43 to take account of aircraft direction, modulator 44, mixer 45, amplifier 47 and motor generator set 46, 48. The output of the generator is proportional to y and is fed back to mixer 45 and through demodulator 56 and differentiating circuits 53. This produces y which is fed to mixer 69 where it is compared with the output of the roll synchro 14 on the roll axis of the gyro and the difference signal is fed through amplifier 32 to control torque motor 27 on the pitch axis and thus control the roll attitude. A signal which is an integral of y is added in mixer 63 to eliminate static errors due to the earth rotation. This integral signal is derived from motor 60 which drives a feed-back generator 61 and, through reduction gearing GR, a generator 62 which provides the integral signal. The gyro vertical is erected in relation to its pitch axis by torque motor 28 on the roll axis. The angle of attack is sensed by a conventional vane-operated pick-off on the craft the output of this pick-off is modified at 121 in accordance with the flap adjustment by means of a pick-off 120 whose motor is connected to the flap surface. Output lead 122 carries a signal proportional to the angle of attack α. The flight path angle y is obtained by computing the ratio between the craft's vertical speed and forward speed. The vertical speed is determined by an aneroid bellows 123 which positions an element of pick-off 125. The output of this pick-off is amplified at 127 and used to drive a motor generator providing an output proportional to h (see Fig. 2), a feed-back signal being applied to mixer 126. The h signal is applied to a potentiometer 133 whose wiper is positioned in accordance with the reciprocal of true air speed derived from true air speed meter 135 and reciprocal computer 136. A cam 137 is positioned by a follow-up system comprising amplifier 138, motor 139, generator 140 providing a feed-back signal and reduction gearing GR. Cam follower 142 assumes an angular position the cosine of which is proportional to the position of cam 137. An electrical signal representing the angle y is derived from potentiometer 145 and combined in mixer 147 with the signal a to compute the pitch angle # of the aircraft. This angle # is fed to a burther mixer circuit 149 where it is compared with the output of the pitch synchro 18 and used to control motor 28 on the roll axis. As before the signal is combined with its integral to remove static errors. Fig. 4 shows an arrangement in which the gyro vertical is combined with an automatic pilot. When the bank command pick-off 74 is set manually its output is compared with that of roll synchro in a mixer 73 to control the aileron 72 through the aileron servo system. Manual setting of the bank command pick-off disables the output of the lateral radio receiver by operating switch 77. As the craft banks pickoff 14 provides an input to mixer 73 to oppose that on the command pick-off and the rolling ceases only when these signals are equal. The gyro vertical is also controlled in relation to its pitch axis by the output of vertical receiver 78 which is differentiated to give a signal representing vertical speed h, Fig. 2, by amplifier 81 and motor generator 82, 83 which also provides a feed-back voltage to mixer 80. A voltage h may also be derived from the aneroid arrangement described with reference to Fig. 3, the appropriate signal being selected by switch 99. The voltage h has an integral voltage derived in the manner already described added to it at 102 and controls motor 28 to position the gyro about its pitch axis. The output of pitch command pick-off 115 is compared with that of pitch synchro 18 in mixer 112 and controls elevator 113 until the signals are equal. During climb or dive the output of pitch command pick-off 155 and the differentiating arrangement should be the same so that it is unnecessary to disable the output h. When the output of the pitch command pick-off is zero the output h controls the motor 28 to maintain the pitch axis of the gyro correct. Switch 39 may be used to put the gyro vertical under control of level switches 20,.27 in known manner.