A Momentum Rule for Optimum Aircraft Performance in the V/STOL Transition Regime

摘要

By applying momentum theory to lifting wings and to propulsion systems with deflected thrust, it is shown that when these components are combined in a single lifting system, minimum ideal thrust or power is required in any flight condition when the momentum deflection angles of the wing wake and of the propulsive jet or slipstream are approximately equal. Those V/STOL aircraft systems having closely coupled or 'integrated' wing and propulsive flows may more or less automatically satisfy this general rule, and therefore might be expected to approach minimum ideal thrust or power requirements. Comparisons of the theory with available flight and wind tunnel performance measurements for a variety of V/STOL aircraft types seem to bear out this prediction even when the lift due to power does not extend across the whole wing span, provided only that wing stalling is prevented. (Author)