Flight measurements of the drag of a swept-wing aircraft (hunter Mk. 1) at mach numbers up to 1.2, together with some measurements of lift-curve slope

Abstract

Flight tests have been made to determine the drag of a Hawker Hunter F Mk. I aircraft. The results show that at low Mach number the drag coefficient at zero lift is 0.0125 and the effective induced-drag factor K is 1.09, both values being corrected to a constant Reynolds number of 34 x 10power6. Above a certain C L the drag due to lift increases rapidly, the C L at which this occurs falling from 0.76 at M = 0.3 to 0.41 at M = 0.7. Some approximate measurements of K made at supersonic speeds suggest that virtually all the leading-edge suction on the wing is lost beyond M = 1.0. At C L = 0.1, the compressibility drag rise commences soon after M = 0.8, the drag rising rapidly beyond M = 0.92 and attaining a peak C D of 0.0565 at M = 1.15. The compressibility drag rise obtained from high-speed wind-tunnel tests agrees well with that obtained in flight although this agreement may be largely fortuitous in view of the low tunnel Reynolds number. Measurements of incidence show that the lift-curve slope at M = 0.3 is 3.5 rising to 4.6 at M = 0.9. The zero-lift angle remains constant with Mach number at about 0.4°. Agreement with wind-tunnel tests is reasonably good when allowance is made for differences in geometry and in Reynolds number.