In 1985 the new Advanced Technology Testing Aircraft System ATTAS will be operable at the DFVLR in Braunschweig. Owing to the wide application spectrum of ATTAS and the varied range of users, a flight test instrumentation system having a very high degree of flexibility and testability was required. It was therefore decided that a versatile built-in test and calibration system called GIMICS should form an integral part of the ATTAS flight test instrumentation system. GIMICS is an intelligent, computer-controlled system having dedicated access to the ATTAS subsystems. The system architecture and application flexibility of GIMICS is presented.