Incorrectness of the k Method for Flutter Calculations

Introduction It has been appreciated by aeroelasticians for many years that results from the V -g or k method of flutter analysis may be difficult to interpret or even misleading. 1–3 The purpose of the present Note is to consider this difficulty with the k method in an especially simple setting, i.e. with steady-flow aerodynamics. As Pines showed many years ago in a different context, the use of highly simplified aerodynamics can be especially illuminating. In the special case of steady-flow aerodynamics and zero structural damping, the principal result of the present Note shows one way that the V -g or k method may lead to difficulties. For this special case, a particularly clear understanding of the nature of these difficulties can be obtained. This note adds a modest but new and, the authors believe, helpful addition to the rich literature on this perplexing issue. It is well known that k and p methods of calculating flutter speeds are quite different. 5