The External Drag of Fuselage Side Intakes: Rectangular Intakes with Compression Surfaces Vertical

SUMMARY An experiment designed to measure the external drag of fuselage side intakes is described. The scope of the experiment and the techniques employed are discussed and an assessment is made of the accuracy of results. Measurements of the external drag of rectangular intakes installed on the sides of a fuselage are presented. Results at subsonic speeds show that drag at full flow is independent of compressmn surface geometry, so that substantial flow spillage may be achieved for little drag penalty provided that the intake throat Mach number is kept high by elevation of the compression surface. For a given total turning of the flow by th2 compression surface, splllage drag is found to be uniquely related to the inlet mass flow ratio (as distinct from capture mass flow ratlo). Radius of the cowl lip 1s found to affect the drag of the intake at full flow but becomes less Important as flow is reduced. Drag at full flow for Intakes with swept end walls is lower than for a conflguration in which they are unswept but the spillage drag rise is greater. At supersonic speeds the variation in full flow drag with compression surface geometry may be predlcted from consideration of the changes in shock geometry but there is generally a small positive increment which is not accounted for in the calculation. Calculation methods based on theoretical shock geometry are found to over estimate spillage drag.