A Comprehensive Rapid-Assessment-Of-Flutter/Ejection-Loads (RAFEL) Software System for Aircraft/Store Compatibility

Abstract : This report documents a design scheme for a rapid assessment of flutter and limit cycle oscillation of aircraft with multiple store configurations. Using the F-16A as a baseline aircraft, three different aeroelastic instability responses, including classical flutter, typical LCO, and non-typical LCO, have been successfully identified. These three distinct responses are representative of the broad spectrum of aeroelastic responses encountered by fighter aircraft with external stores. To rapidly compute the flutter prediction of the aircraft with multiple store configurations, a procedure is proposed to efficiently reuse the aerodynamic influence coefficient (AIC) matrices of aircraft with multiple stores. The procedure used the ZAERO code, that contains a unified aerodynamic module for all Mach numbers, as the basic software system. To discern the difference between the flutter and LCO responses, and to correlate the numerical predictions with the flight altitude, the matched point option of the g-method of ZAERO was used. The influence of the aerodynamic stores on the aeroelastic instability is investigated using a number of aerodynamic models, including the isolated wing-tip launcher model, and the whole aircraft with and without stores. Using a more refined aerodynamic model, the results show good agreement between the present numerical predictions and flight flutter test data, including the oscillation frequency and the onset speed of the three flutter and LCO cases.