Abstract:When an aircraft encounters emergency during flight test, the emergency is usually treated by the test pilot and the flight commander with rich technology and experience. However, because the traditional disposal means are affected by the special environment and test pilots’ mood at the time, they are prone to the errors of judgment which can lead to major accidents. In the light of the characteristics of flying emergency and the application of expert system in fault diagnosis, on the basis of research on the fault tree diagnosis and reasoning machine technology, this paper establishes flight test emergency disposition system based on expert system technology is used to the solve. The application results show that the system is stable, the response speed is fast, and has a very good application value.