The Aeroservoelasticity Qualification Process in Alenia

Since the beginning of aviation history, flutter was recognized as a catastrophic event for an aircraft, consequence of a dynamic instability when speed is too high, due to the interaction between the aeroelastic forces acting on wing and tail and their dynamic characteristics. With the progress of aircraft design, aircraft speed increased and the consolidation of the monoplane configuration led to a lower torsional stiffness of wings than biplanes. The consequence was that flutter became a serious problem, as demonstrated by the series of accidents usually accompanied by the destruction of the machine. It was evident the necessity was to develop theories and methodologies able to predict the phenomenon and to validate the design for the maximum speed to be achieved. This development is still continuing and has provided the modern aeronautical engineer with very powerful tools but still not sufficient to exclude specific flight trials aimed to confirm the prediction of aircraft speed margins before flutter. This chapter has been intended to explain flutter to an audience with limited knowledge on aeronautics and to present the design and verification processes followed by engineers to produce aircraft that, accordingly to aeronautical regulations, are free from flutter within their flight envelope.