A Note on Flutter of Asymmetric Controls

This Paper attempts to give some guidance on the question, of how best to approximate to an aircraft with an asymmetric elevator control for the purpose of flutter calculations. Two examples of asymmetric controls that are.common in practice are (1) the design case of a partitioned elevator each part having its own separate power unit and with one such unit having failed, and (2) the asymmetric arrangement of tabs on the elevator. Several instances of flutter involving asymmetric tab arrangements are known to have occurred in practice, but for the purpose of the calculations reported in this Paper the elevator itself is made asymmetric; this was done to reduce the work to manageable proportions. It is concluded that the more stable side of the aircraft can be replaced by a mirror image of the less stable side without serious error, at least for calculations of the type described. This appears to give a rather better approximation than taking the asymmetric aircraft and constraining it to vibrate in either symmetric or antisymmetric modes.