GB685292A - Apparatus for measuring the lift-coefficient of an aircraft - Google Patents

Abstract

685,292. Pressure gauges. BRAILSFORD, E. N. Dec. 5, 1949 [Dec. 11, 1948], No. 32099/48. Class 106. (ii). A lift - coefficient measuring apparatus for aircraft comprises a plurality of inlet port means adapted for parallel connection to an indicator operable in accordance with the air pressure at all the ports, the latter including a first port directed forwardly to receive total head air pressure, and at least two further ports located symmetrically on opposite sides of the longitudinal axis of the aircraft, and means for averaging the pressures at the further symmetrically located ports before passing to the indicator. Fig. 1 shows in an aircraft 1 inlet ports at 2, 3, 4 and 5, averaging manifolds at 6 and 6A, a mechanical indicator at 8, an electro-mechanical unit at 9 and various pipe connections 7, 10, 11, 12. The port means at 2 receives the total head (pitot) pressure, port 3 receives the ambient (static) pressure and ports 4, 5 the aerofoil static pressure. As shown in Fig. 5, the body of the indicator 8 contains two prime movers shown as bellows 20, 21. Bellows 20 is responsive to total-head pressure internally via pipe 10, bellows 21 is responsive to aerofoil static pressure internally supplied by pipe 12, and both bellows are responsive to ambient pressure externally, admitted to the body of the indicator by pipe 11. The indicator resolves the equation C LA =C 1 (H-S 0 /H 0 -S 0 )+C 2 or C LA =X[yC 1 (H-S 0 )/(H 0 -S 0 )+C 2 ] where C LA = Average lift coefficient for the aircraft. H = Aerofoil static pressure. H 0 = Total-head (pitot) pressure. S 0 = Ambient (static) pressure. CC 2 = Constants of the installation and apparatus. x, y = Functions of Mach number and other variables. The indicating mechanism is responsive to the linear movement of the output stage 22 and the movement of pointer 23 relative to the scale 24 is proportional to the lift coefficient C LA as defined by the above equation.