F/A-18 inlet/engine compatibility flight test results

Abstract

The U.S. Navy F/A-18A fighter aircraft inlet engine compatibility flight test results obtained during the fullscale development program are reviewed. All of the critical maneuvering conditions, both subsonic and supersonic, were flight tested with special emphasis on the aircraft prime combat maneuvering region. The instrumentation design and assessment approach used to successfully evaluate inlet/engine compatibility during the flight test program are also presented. The inlet rake, used to measure inlet distortion at the engine face, features 40 close-coupled lowand high-response probes, in an 8 leg, 5-ring configuration located 4 in. ahead of the engine nose dome. An analog distortion calculator is used to screen the large quantities of recorded highresponse distortion data for subsequent digitization in selected regions of peak distortion. Dynamic distortion data and patterns are included that show increase in inlet distortion with angle of attack and sideslip. Dynamic inlet distortion has been measured on the instrumented aircraft at extreme maneuvering conditions. The distortion points fall within the engine distortion experience boundary. No engine stalls occurred during either the fixedor variable-throttle compatibility testing for subsonic maneuvering excursions well beyond the design goal envelopes. Satisfactory engine operation has been demonstrated, and inlet distortion measured up to 65 deg angle of attack and 20 deg sideslip. Compatible subsonic maneuvering excursions well beyond the variablethrottle design goal envelopes are also demonstrated on the instrumented aircraft using the worst-case throttle transient (max-idle-max bodie). Inlet dynamic distortion levels during supersonic aircraft maneuvers are low and well within the engine distortion experience boundary.