the three completed prototypes, filper helicopter (n9712c), filper beta 200a (n5000f) and filper beta 400a (n5003f) began a testing regime at livermore municipal airport, livermore, california. all three helicopters crashed, with a fatal accident taking place on november 7, 1967 that occurred when a rotor failed during a high-speed test. the test pilot on loan from north american aviation died in the crash while another test pilot was injured in a second accident.