Low altitude windshear phenomena has been causally linked to numerous civil transport aircraft incidents with fatalities and injuries exceeding 800, covering a period of more than 25 years. The recent crash of a USAir DC-9 at Charlotte, N.C. on July 2, 1994 has caused an increased focus on windshear and microburst activity. Three sensor systems were investigated; radar, laser radar (lidar), and infrared imaging, with the pulsed Doppler radar consistently detecting both wet and dry microbursts indicative of hazardous windshear conditions at longer ranges than the other two. Numerous documents were reviewed, including the NASA Airborne Doppler Radar together with meetings held with Allied Signal, Rockwell Collins and Westinghouse to verify radar parameters needed to analyze and present the tester concept described herein. The weather and windshear models defined use the identical criteria established for the Doppler radar in terms of F-factor. The basic concept of the tester is to transmit coherent simulated radar returns in response to the airborne radar's transmission while mounted on a tripod in the far field of the radar when parked on the ramp. The varying amplitude of the received radar pulses are analyzed and put into memory as the tester antenna is illuminated by the scanning main beam and side lobes of the radar's antenna patterns. The tester transmissions, incorporating microburst, storm and previously defined, can thereby test the aircraft radar system performance in various hazard environments. The tester is designed to; verify operational performance of the radar, demonstrate installed radar performance, verify crew reports and minimize radar or LRU's removal for maintenance, test before and after a repair and verify radome effects on radar performance.
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