Proposal for an elevator maneuverability criterion

Abstract

The approximate theory of response to elevator developed by Bryant, Gandy and Gates yields a compact formula for a criterion of manmuvrability Q, the 'stick force per increment in g' ; there is an anMogous but less useful criterion 51 terms of stick travel. It is recommended that Q be adopted for designers' use, that its limits of validity be checked by careful tests on one aeroplane, and that more force measurements in pull out from dives be made on a number of aeroplanes in order that numerical standards may be attached to Q. Reference is made to American standards and to experimental work already done in this country. The rate of growth of acceleration, which is not represented in the criterion, is discussed and illustrated by a numerical example. From this it appears that within limits which probably apply to a pilot's normal control movements :-- (1) The rate of application of force affects the time to reach maximum acceleration but not the value reached. (2) The acceleration produced by a given stick force is independent of speed if the static margin is fixed, but the time to reach it is inversely proportional to the speed. (3) The acceleration produced by a given stick force increases with altitude ; this effect is the greater the less the static stability. The bearing of this on the difficult control of high altitude fighters near the ceiling is discussed. The close connection between the problems of maneuvrability and safety is noticed throughout. The inertia weight is not ideal as a deterrent to the production of high acceleration, and more promising variants of this device are referred to.