ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

1pPA5. USAF flight test investigation of focused sonic booms.

Micah Downing

USAF Armstrong Lab., 2610 Seventh St., Wright-Patterson AFB, OH 45433

Noel Zamot

USAF TPS, Edwards AFB, CA 93524

In April 1994, the USAF Armstrong Laboratory in cooperation with USAF Test Pilot School conducted a measurement study of controlled focus booms generated by supersonic maneuvers. The objective of this study was to collect focus and post-focus booms and to assess the ability of aircrews to control the placement of the focal region during basic maneuvers. Forty-nine flights were performed and included level linear acceleration, level turn, accelerating dives, and climbout/pushover maneuvers. Sonic booms were collected by up to 25 boom event analyzer recorders (BEARs) placed in a 13 000-ft linear array. The BEAR units were spaced 500 to 2000 ft apart with the denser spacing at the expected focal region. This spacing was chosen to evaluate the thickness of both the focal and post-focal regions. Of the 49 flights, a focus boom was successfully placed within the array 35 times which demonstrated the ability to place controlled focus booms. This ability of the aircrew can be employed to avoid collateral damage to noise sensitive receptors. Along with capturing focus U waves, complex N--U signatures were recorded at distances away from the foci. Turbulent conditions had a defocusing effect, resulting in smaller maximum overpressures.