GB1100743A - Improvements in or relating to apparatus for sensing lift - Google Patents

Abstract

1,100,743. Aircraft instruments; hydrofoils. BOWLES ENGINEERING CORPORATION. 14 April, 1965 [14 April, 1964], No. 16047/65. Headings B7A and B7W. [Also in Division G3] A system for sensing lift forces acting on an aerofoil or a hydrofoil when in motion comprises a pressure-sensitive device within the foil and arranged to produce an output signal which is a function of the difference between the fluid pressures at two ports in the foil adjacent its leading edge, wherein said pressure sensitive device is a pure fluid amplifier having a power nozzle, at least two fluid-output passages for receiving fluid from said power nozzle, and a pair of control nozzles connected respectively to said two ports through separate passages. A foil 10a is formed with ports 12, 13 which connect through passages 22 and 23 provided respectively at their ends with flow restrictors 24, 27 and 26, 28 and intermediate their ends with metering or restricting orifices 19, 21 incorporated in a supply line 16, 17 from a source of pressure fluid 14. The restrictors in the passages 22 and 23 establish a minimum pressure in the passages which is changed by variation of flow over the ports 12, 13 as by variation in the angle of attack of the foil 10. Source 14 delivers pressure fluid to a nozzle 30 which directs it towards output passages 31, 32 and 33, passages 31 and 33 being connected to a lift indicator 35 or other utilization device. Passage 32 connects back to source 14 or spills overboard. Variation in pressure in passages 22 and 23 resulting from variation in angle of attack of the foil deflects the flow from nozzle 30 to influence or unbalance the pressures in passages 31, 33 to operate device 34. The ports 12 and 13 may be located at different distances from the leading edge and in a further embodiment flexible diaphragms are inserted across ports 12 and 13.