An In Flight Investigation To Develop Control System Design Criteria For Fighter Airplanes PDF Download

The effects of control system dynamics on the longitudinal flying qualities of fighter airplanes were investigated in flight, using the USAF/CAL variable stability T-33 airplane. Two pilots evaluated a total of 57 different combinations of control system and short-period dynamics at two flight conditions, while performing tasks representative of the 'combat' phase of a fighter's mission. The pilot rating and comment data from this investigation indicate that the dynamic modes of the flight control system can cause serious flying qualities problems, even if the short-period mode is well behaved. The data do not correlate with the control system requirements of MIL-F-8785B. In addition, the data demonstrate that the C* criterion does not adequately account for the effects of control system dynamics. Pilot-in-the-loop analysis of the data is shown to describe effectively the pilot's difficulties in control of pitch attitude, providing insight into how the pilot flies the airplane. A design criterion, based on this analysis, is shown to be applicable to a wide range of short-period and control system dynamics. A simplified version is also presented to provide the designer with preliminary estimates of flying qualities.