Note on differential gearing as a means of aileron balance

Abstract

It has been suggested in some American investigations that differential gearing, combined with adjustment of the aileron floating angle by means of a tab, may be a powerful method of balancing ailerons. This report sets out the theory of this method of balance and analysesit in relation to the most pressing problem of aileron design, which is to obtain close balance at high speed without overbalance in any part of the range, or uncomfortable lightness at slow speed. It is shown that this result can be achieved more directly by differential balance than by any other method if the differential and the tab setting are nicely adjusted to the natural floating properties of the aileron. Thus if the aileron tends to float up as incidence increases, a differential giving more downward than upward movement must be used, and this must be combined with an upward-set tab ; while if the aileron tends to float down as the incidence increases, a differential giving more upward than downward movement must be used, combined with a downset tab. After examining the possible disadvantages of the downward differential, and the loads set up by the tab, it is concluded that there is a strong case for exploration in flight of differential gearing as a major means of aileron balance. Some notes on the geometry of differential gearing are given in an Appendix.