Flutter problems of high-speed aircraft

Abstract

The flutter problems of high-speed aircraft are considered generally and specific consideration is then given to the new problems introduced by the use of new wing plan forms. The theoretical and experimental results on the coupled ('classical') symmetrical flutter of swept (including 'barbed' and cranked forms) and delta wings is reviewed and presented to show the effect and importance of the body freedoms of the aircraft on the critical flutter speed and frequency. A criterion is proposed for deciding the 'dangerous type' of fundamental normal mode to be considered in flutter calculations. The danger here is that the fundamental normal mode can combine with the body freedoms and give rise to a form of flutter which is independent of the wing torsional stiffness. It is suggested that the deciding feature is the shape of the nodal line in the fundamental mode. If it is such as to indicate rotation of the fore-and-aft wing sections near the tip, then the mode is considered to be dangerous.