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Method and apparatus for the determination of the air velocity, in particular for helicopter
Method and apparatus for the determination of the air velocity, in particular for helicopter
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机译：确定空气速度的方法和设备，特别是直升机
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摘要
839,405. Electrical measuring systems. SPERRY GYROSCOPE CO. Ltd. Oct. 10, 1958 [Oct. 23, 1957], No. 33127/57. Class 40 (1). Airspeed measuring apparatus comprises a pitot head mounted at a fixed radius from an axis to rotate continuously about the axis and means to determine the airspeed in a predetermined direction by determining the pitot pressure difference when the pitot head axis is in the two positions substantially parallel to the predetermined direction. Fig. 1 shows a pitot tube 1 connected to a sealed chamber 5 which is separated from a second sealed chamber 6 by a flexible diaphragm 7. The second chamber 6 is connected by a tube 4 to the static air pressure. The diaphragm 7 carries a ferromagnetic armature 9 positioned adjacent the pole pieces of the coils 8 so that when the coils 8 are connected in bridge circuit as in Fig. 3 and bed with 400 c/s. alternating voltage from source 11 any difference in pressure in chambers 5, 6 results in a displacement of the armature 9 and an unbalance of the bridge. The unbalance voltage is amplified by a transistor circuit 12 and rectified at 21. The rectified output is fed to the rotor of a distributing switch 24 synchronized with the rotor of the helicopter. The pitot head 1 is attached to one of the helicopter blades 2. When the blade is in positions 15, 17 capacitors 32 are respectively charged to a voltage dependent on the effective airspeed in these positions. The difference in these voltages is fed via resistor 33 to one coil 34 of a ratiometer 42 calibrated in forward airspeed. The voltages in positions 16, 18 are used to charge capacitor 38 so that a voltage dependent on the sum of the voltages in these positions is fed via resistor 39 to the other coil 41 of the ratiometer. It is shown that the quotient of these voltages is proportional to forward airspeed. The coils of a further ratiometer calibrated in sideways airspeed may be respectively fed with the sum and difference of the voltages dependent on the airspeed in positions 16, 18.
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