ON SIMPLIFIED ANALYTICAL FLUTTER CLEARANCE PROCEDURES FOR LIGHT AIRCRAFT

Abstract

In the case of conventional gliders and light aircraft, flutter investigations can be simplified. From the results of a simplified ground vibration test, it can be determined whether an empirical estimation without flutter calculation is possible. In general, the measures to be taken according to this method consist of frequency shifting and mass balancing. The requirements are more severe than those obtained by flutter calculations. Therefore, it may be advantageous in certain cases to carry out an analytical investigation based on the test data. Nevertheless, if the conditions for the empirical approach are met, it can be considered an admissible procedure. It must be noted that even sophisticated flutter computations have their limitations of accuracy, for example due to the presence of
nonlinearities. The empirical estimation of flutter as well as design recommendations which emphasize aeroelastic effects, offer the designer markedly simple tools for flutter prevention. To broaden the scope of the empirical method, more flutter incidents and their remedies should be incorporated into the data collection. Corresponding flutter computations should be made to further check the validity of flutter investigation methods. Therefore manufacturers and pilots of small airplanes should be encouraged to contribute observations of aeroelastic vibrations. Through attempting to thoroughly explain these observations, accuracy of flutter prediction will improve in the future.