A Throat-Bypass Stability System Tested in a YF-12

Results of a wind-tunnel investigation are presented. The inlet was modified so that airflow can be removed through a porous cowl-bleed region in the vicinity of the throat. Bleed plenum exit flow area is controlled by relief-type mechanical valves. Unlike valves in previous systems, these are made for use in a high Mach f l ight environment and include refinements so that the system could be tested on a NASA YF-12 aircraft. The valves were designed to provide their own reference pressure and hence do not respond to slowly varying disturbances. However, the results show that the system can absorb internal-airflow transients that are too fast for a conventional bypass door control system and that the two systems complement each other quite well. Increased tolerance to angle-of-attack and Mach number changes is indicated. The valves should provide sufficient time for the inlet control system to make geometry changes required to keep the inlet started.