Flight tests at high mach number on E28/39 W4041 (single-engined jet-propelled aircraft)

Abstract

This report describes fright tests at Mach numbers up to 0.816 on the E 28/39 W4041, the first iet-propelled aircraft to be flown in this country. For these tests the aircraft was fitted with wings of "high-speed" section (EC 1240/0640). Alternative wings of conventional section (NACA 23012) were also available ; it was intended to repeat the tests with these wings, but before this could be done the aircraft was required for other purposes. Measurements of incidence, aileron and elevator angles, stick force and aircraft drag were made. In addition, measurements of pressure distribution were made at a section of the wing, and the profile drag of the same wing section was measured by the "pitot comb" method. The results showed that, as the Mach number increased above about 0.75, there was a large nosedown trim change and an increase of drag. For a given Mach number, both these effects were found to be more serious on this aircraft than on a Spitfire, suggesting that this "high-speed" type of section (EC 1240/0640) may be less suitable for flight at high Mach numbers than the conventional section (NACA 2212) of the Spitfire. A pronounced "hysteresis" effect was observed in the wing pressure distributions at high Mach numbers, leading to different results for increasing and decreasing Mach number, at the same Mach number and lift coefficient. This apparent "hysteresis" has not been explained and no corresponding effect was found in the profile drag measurements.