Theoretical investigations of ternary lifting surface - control surface - trimming tab flutter and derivation of a flutter criterion

Abstract

Theoretical investigations have been made of the flutter of an idealised trimming tab system having three degrees of freedom - normal translation of the main lifting surface, rotation of the control surface and rotation of the tab. All the structural parameters of the system have been varied except the out-of-balance moment of the control surface. The cases in which the system is free from flutter have been particularly investigated. From these investigations criteria for the avoidance of flutter have been derived. If the structural parameters of the system satisfy these criteria, flutter of the system with these three degrees of freedom should be impossible. The resutts are applicable to trimming tabs, servo-tabs with zero follow-up ratio, and generally to all systems in which the tab can be regarded as connected elastically only to the control surface.