Determination of the Pitch and Roll Gain Limits for the F-111C Automatic Flight Control System
AIRCRAFT RESEARCH AND DEVELOPMENT UNIT EDINBURGH (AUSTRALIA)
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A manual Automatic Flight Control System AFCS gains changer was designed into the flight-test F-111C, A8-132, for F-111C flight flutter trials. The system was designed to be adjusted in flight to enable a worst case aircraft flutter response to be evaluated during flutter testing. Technical Note Aero No 81 tasked Aircraft Research and Development Unit to conduct flight tests to determine the range of the self adaptive AFCS gains that occur normally within the F-111C flight envelope and to determine the highest gain values the could be set before the aircraft demonstrated dynamic instability. The flight-test results showed that the self-adaptive pitch and roll gain values were higher than indicated by General Dynamics. The results further showed that the aircraft response varied with feedback gain setting and that at air speed above 400 KCAS the gains could be set to values to induce neutral dynamic response in the test aircraft. A gains envelope was determined for F-111X flight flutter testing at a level 10 below the neutral stability setting. Keywords Australia Pitch gain Roll gain.
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