Saberliner Flight Test And Results For Forward Looking Detection and Avoidance Of Airborne Windshear

Bruce D. Mathews

Abstract:	An important aspect in the design of a” airborne radar for low level windshear avoidance is the false alert rate. To be used and trusted by pilots, any enunciations and/or displays of false hazards must be infrequent. A ‘clean scope” design aima to preserve detection performance and eliminate dhtracting false alerts. For lookdown radar, urban discrete8 and ground moving vehicle traffic dominate the false alert design problem. Depending upon their relative locatioq, spatial extent, and relative amplitude, these returns will compete nlth microbunt win&hear obaervables and may furnish false alert candidates of significant area extent. Westinghouse conducted a flight test with its Sabreliner AN/APG-Ba instrumented radar to wea the urban diicrete/grou”d moving vehicle clutter environment. Glide&ape approaches were flown into Washington National, BWI, and Georgetown, Del. airports employing radar mode timing, waveform, and processing configuration plausible for microburst rindahear avoidance. The perceptiona, both general and specific, of the clutter environment furnish a” empirical foundation for beginning low false alert detection algorithm development. The salient concern upon entering the flight was the adequacy of the sidelobes to reject urban clutter. The radar operated with increasing depression angle on each of four successive elevation bars. Each complete sea” produced a history of returns and investigated the adequacy of the far-aidelobes, near sidelobea and main beam akirt. The steepest scan placed the mainbeam edge along the glideslope while the uppermost xan wan slightly up-look. FFT data H(LI collected below 2000 ft. altitude over Washington, D.C. with proximity of the Washington Monument in both mainbeam and sidelobe regions. Low altitude (between 728 and 298 ft.) data WM collected over Glen Burnie on approach to BWI. The observations and interpretation of these data indicate that the far sidelobes of ostensible SO in. diameter flat plate phased arraya are adequate. There were no indications of exceptional altitude protrusions. However, the antenna edge can only be pointed within about 1 degree of the glideslope. This emphasizes the importance of antenna tilt management.
Published in:	Proceedings of the 1991 National Technical Meeting of The Institute of Navigation January 22 - 24, 1991 Sheraton San Marcos Hotel Phoenix, AZ
Pages:	405 - 410
Cite this article:	Mathews, Bruce D., "Saberliner Flight Test And Results For Forward Looking Detection and Avoidance Of Airborne Windshear," Proceedings of the 1991 National Technical Meeting of The Institute of Navigation, Phoenix, AZ, January 1991, pp. 405-410.
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