Flight and Wind-Tunnel Test Results of a Mechanical Jet Noise Suppressor Nozzle

This paper presents, for the first time, comprehensive acoustics and propulsion data from tests of a mechanical jet noise suppressor designed to the requirements of a future supersonic transport. Details from static, wind tunnel, and flight tests (British Hawker Siddeley HS-125 aircraft) are presented illustrating forwardflight effects for correcting static acoustics and propulsion results. Flight test results are presented for a large scale mechanical suppressor/ejector model. The flight program was a joint effort by McDonnell Douglas, RollsRoyce, Ltd., and the British Aerospace Corporation. The test aircraft had an uprated Viper engine providing pressure ratios approaching advanced supersonic transport engine designs. The Royal Aircraft Establishment provided the airplane. Results show the suppressor/treated ejector configuration provides a potential noise reduction at large scale of 16 EPNdB from that of the conventional conical nozzle at the highest pressure ratio tested (approximately 2.5). The nacelle, engine, and nozzle configurations from the HS-125 were tested with NASA's cooperation in its Ames Research Center 40- by 80- Foot Wind Tunnel for propulsion performance. The nozzle efficiencies derived from preliminary wind-tunnel data are compared with previous data obtained in the McDonnell Douglas static test facility.