Evolution in Buffet Loads Determination for Tilt Rotor

This work presents the state-of-the-art of the validated buffet loads determination methodology developed by Leonardo Helicopters, with particular attention to the aerodynamic modelling and the related structural loads calculation. The modern CFD, validated by WT data, is the first major topic addressed in the paper: simulations are performed with ANSYS Fluent to characterize the oscillatory pressure distributions generated by the wing stall. The structural loads calculation is the next part of this process, with a focus on the interface with the aerodynamic input and on the necessary statistical analyses to predict safe loads. Buffet is considered a random phenomenon, which is robust and repeatable only in terms of statistic quantities, and, to estimate the maximum likely values, a probabilistic approach is used to calculate a reasonable safety factor. The last topic is the analysis of actual flight data in compatible high angle of attack conditions in order to substantiate both the load analysis deterministic results and the statistical approach to predict peak values for aircraft design.