A normal-shock positioning control which utilized the bypass of a supersonic inlet to set the required air flow for a J34 turbojet engine was investigated to Mach number 2.0 in the Lewis 8- by 6-foot supersonic tunnel. A small static probe extending from the cowl was used to position the normal shock slightly ahead of the cowl lip and gave subcritical inlet operation. Continuous control was provided through a hydraulic servoactuator.

The effects of diffuser dynamics (for supercritical diffuser operation) and controlled engine dynamics on the diffuser control requirements of a supersonic turbojet engine were studied with the aid of an electronic analog. The investigation indicated that a pressure disturbance in the diffuser had only a small effect on engine speed, whereas a disturbance in engine speed had a large effect on diffuser pressure and could impose severe requirements on diffuser control response.