Nonlinear Transonic Flutter Prediction for F-16 Stores Configuration Clearance

摘要

Limit cycle oscillation (LCO) has been an issue for the F-16 since its operational deployment. Configuration validation requires large investments in time and resources due to the very specific and stringent guidelines used during flight test to ensure the aircraft does not encounter classical flutter or excessive LCO. A new approach, incorporating inherent nonlinearities that drive LCO is investigated using the Transonic Equivalent Strip method to account for wing thickness effects and shock structure. The g-method flutter solution is used to include first-order aerodynamic damping effects. Two F-16 store configurations are examined to correlate predicted flutter onset speeds, frequencies, and character with those found in flight test, as well as the aerodynamic effect of modeling underwing stores on the flutter solution. Results show small changes in the tuning of the structural model resulted in large changes in the flutter boundary. The aerodynamic influence of underwing stores proved significant, particularly for the two most outboard wing stations. Most importantly, the character of the instability was predicted by the new method.