Thrust Efficiency of Powered Lift Systems

Two efficiencies have been introduced to facilitate the comparison of powered high lift systems for low approach speed and for acceleration after lift-off. The corresponding minimum thrust and total impulse required by an idealized unpowered wing are used as reference parameters. The efficiencies are shown as a function of installed thrust to weight ratio and minimum flight speed, non-dimensionalized by a reference velocity with dynamic pressure equal to the wing loading. Incorporated in the efficiencies are the effects of wing aerodynamics, engine thrust loss due to power extraction, duct loss and thrust recovery.