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Mallemort, France

Massett A.P.,U.S. Air force | Groult R.G.,Istres Flight Test Center | Ungerman R.T.,U.S. Air force | Honabarger J.B.,U.S. Air force | And 3 more authors.
42nd Annual International Symposium of the Society of Flight Test Engineers 2011, SFTE | Year: 2011

Limit Cycle Oscillation (LCO) is a self-sustained airframe structural response due to interaction between airframe aeroelastic properties and flight condition aerodynamic effects. F-16 LCO has typically resulted in lateral motions of the fuselage and crew that could have operational impacts on such things as pilot fatigue, weapons tracking or structural integrity. Historic flight test data could not isolate the effect that aerodynamic differences had on LCO over mass and inertia differences. This test observed and compared LCO characteristics (onset, frequency and amplitude) for an F 16D with common store loadouts, varying only AIM-9 aerodynamic properties while keeping mass and inertia properties fixed. The AIM-9 missiles used for testing were capable of having all control surfaces removed, and are denoted as "dummy AIM-9s". When control surfaces were removed, ballast was added to the dummy AIM-9 bodies to match the mass and inertia properties of the dummy AIM-9s with the control surfaces attached (referred to as "fins on"). The general objective was to observe and compare F-16 LCO characteristics between store loadouts with dummy AIM-9 fins on and fins off. Of interest were minimum Mach for LCO at lg, LCO wingtip acceleration amplitude and LCO frequency. A quantifiable difference in minimum LCO Mach number and LCO wingtip acceleration amplitude was found between fins on and fins off configurations. There was no consistent trend in minimum LCO onset between the two configurations. Fins configuration did not appear to have an effect on LCO frequency. From statistical analysis, the significant main factors affecting the LCO response were ambient static pressure, Mach, wing fuel, fins configuration and normal acceleration. The results from this testing will ultimately contribute to enhancing aircrew safety and mission effectiveness. Additionally, the data and statistical analysis will aid in updating current aerodynamic models in order to better understand, and more accurately predict, LCO. Source

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