Transonic off-design drag and performance of three mixed-compression axisymmetric inlets

An experimental investigation was conducted to determine the off-design drag and pressure performance of three axisymmetric supersonic inlets in the transonic speed range. For typical engine airflows at Mach 0.8 the drag coefficient varied from 0.045 to 0.09; at Mach 1.2 the largest drag coefficient measured was 0.25. Below Mach 0.9 a lower drag resulted when all or at least part of the excess weight flow was spilled over the cowl rather than through the bypass doors; above Mach 1.1 the lowest drag was obtained by bypassing excess flow.