The first EC-137 made its maiden flight on 9 February 1972, with the fly-off between the two radars taking place from March to July of that year.[1] Favorable test results led to the selection of Westinghouse's radar for the production aircraft.[9] Hughes' radar was initially thought to be a certain winner due to its related development of the APG-63 radar for the new F-15 Eagle. The Westinghouse radar used a pipelined fast Fourier transform (FFT) to digitally resolve 128 Doppler frequencies, while Hughes's radars used analog filters based on the design for the F-15. Westinghouse's engineering team won this competition by using a programmable 18-bit computer whose software could be modified before each mission.