Elevator flutter involving two tabs

Abstract

An account is given of a theoretical flutter investigation in connection with an accident to a Sea Venom aircraft. The investigation covers both symmetric and antisymmetric flutter of the tailplane-elevator-tab system. The main (symmetric) calculations include six degrees of freedom, comprising three structural modes and movements of elevator, spring-tab and trim-tab respectively. The parameters that are varied include elevator mass-balance, position and magnitude of mass-balance on each tab independently, structural damping and stiffness of the tab circuits, chord and mass of the trim-tab, and flexibility of the elevator mass-balance attachments. The investigation shows the symmetric flutter to be a probable cause of the accident and confirms the efficacy of the remedial measures adopted, which consisted of modifications to the tab mass-balances combined with a reduction in chord and inertia of the trim-tab. Several points of general interest are discussed.