The servosystem design of a high-response airflow bypass valving system for supersonic mixed-compression inlets or other industrial or aerospace pneumatic systems is described. The valve utilizes a multislotted plate to achieve flow area change with minimum stroke and mass of moving parts. The servosystem utilizes a hydraulic piston-in-cylinder actuator close-coupled to a two-stage electrohydraulic servovalve. Using electronic compensation the small-amplitude response of the system, modulating 14 percent of its full flow area, is flat within 0 to -3 dB to 110 Hz. (161 cm [to the second power] ). A mathematical model of the system is presented and analytical responses are compared with experimental data.

February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index.

Two engine research experiments were recently completed in Moscow, Russia using an engine from the Tu-144 supersonic transport airplane. This was a joint project between the United States and Russia. Personnel from the NASA Lewis Research Center, General Electric Aircraft Engines, Pratt & Whitney, the Tupolev Design Bureau, and IBP Aircraft LTD worked together as a team to overcome the many technical and cultural challenges. The objective was to obtain large scale inlet data that could be used in the development of a supersonic inlet system for a future High Speed Civil Transport (HSCT). The first experiment studied the impact of typical inlet structures that have trailing edges in close proximity to the inlet/engine interface plane on the flow characteristics at that plane. The inlet structure simulated the subsonic diffuser of a supersonic inlet using a bifurcated splitter design. The centerbody maximum diameter was designed to permit choking and slightly supercritical operation. The second experiment measured the reflective characteristics of the engine face to incoming perturbations of pressure amplitude. The basic test rig from the first experiment was used with a longer spacer equipped with fast actuated doors. All the objectives set forth at the beginning of the project were met.