GB624844A - Improved apparatus for indicating the air speed and direction of aircraft - Google Patents

Abstract

624,844. Airspeed indicators. SPERRY GYROSCOPE CO., Inc. Aug. 11, 1944, No. 15359. Convention date, Aug. 13, 1943. [Class 69 (i)] [Also in Group XXXVIII] In a rotary-winged aircraft, means are provided for measuring the cyclical variation in the air-speed of a rotating wing. As shown, the dynamic and static orifices 37, 34, of a pitot tube 31, mounted on the end of a rotating wing 32, and which is directed into the wind by a vane 46 and a rotatable mounting 44, are connected to a bellows 49 and a static chamber 48 respectively. An electromagnet 52 is connected to the bellows 49, the other end of which electromagnet is slidable within a fixed coil 57 in which voltages are induced dependent on the amplitude of the variation in air-speed and which may be measured by an A.C. voltmeter graduated in miles per hour. Since the variations in air-speed during one revolution of the wing have a definite phase relation with the direction of motion of the aircraft through the air, a signal having a fixed phase relation to the rotating wing may be compared with the phase of the induced voltage and the direction of motion obtained. An alternating voltage generated by a generator 71, driven through gears 73 and 72 from the rotor shaft 33, is compared with the phase of the voltage obtained from the coil 57 by a phase-meter 77 and a pointer may be used to indicate the direction of motion. The pitot tube may be replaced by a rotatably-mounted vane or by a resistance operated by the angle of the wing relative to a plane perpendicular to the axis of rotation, Figs. 11 and 8 (not shown). The direction of motion and air-speed may be indicated on one instrument, Fig. 4, wherein the pitot tube is replaced by a hot-wire anemometer 81, the leads from which are connected through slip-rings 89 and 91 on the rotor 86 and brushes 92 to a series circuit comprising a battery 96 and the primary coil 98 of a transformer 101, the secondary winding 125 of which is connected by slip-rings to the coil of a rotatable electromagnet 114 driven through gearing 133 and 134 by the rotor 86. A universally mounted pointer 137, having a polarized armature 135 is moved radially an amount depending on the amplitude of the variation produced by the hot-wire 81, thus indicating the air-speed, and in a direction dependent on the phase difference between these signals and the signals produced by the rotating electromagnet, thus indicating the direction of motion.