Active Control for Fin Buffet Alleviation

Abstract : Commencing June 1, 1992, and supported by USAF Flight Dynamics Directorate under Contract F33615-92-C-3605, RANN, INC., undertook a 1 year program of research with the following objective: for fighter aircraft with twin vertical stabilizers, which operate to high angle of attack alpha, to examine the possibility that active control can alleviate the response to buffeting and enhance fatigue life of the structure. Although there is no way that the phenomenon could have been anticipated during the initial phases of their design, 'fin buffeting' as a consequence of high-alpha maneuvers has been encountered on several military aircraft with such twin tails. Other affected fighters include F-14 and F/A-18. Future designs for which some level of buffeting is anticipated are F-22, with measurements on a wind-tunnel model already reported. Although they have single, center-line vertical stabilizers, similar phenomena have occurred at high alpha on X-29 and X-31; for measurements of associated vortex behavior on the latter research vehicle.

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