Analysis of flutter and flutter suppression via an energy method

The design of modern high-performance aircraft is toward increased aerodynamic efficiency, decreased structural weight, and higher flight speeds. Preliminary designs often exhibit a flutter instability within the desired operating envelope of the aircraft. Passive methods which have been used to solve the flutter problem include added structural stiffness, mass balancing, and speed restrictions. These methods may result in significant weight penalties. Studies by Boeing (ref. 1) show that weight penalties as high as 2 to 4% of the total structural weight may be required to solve the flutter problem passively by increasing the structural stiffness. Therefore, there is considerable interest in alternative methods of increasing the flutter speed beyond the original unaided value.