ESDU 82034 provides a simple method of predicting, at the project stage of the design of an aircraft, the lift, drag and pitching moment increments arising from a lift augmentation system in which the jet efflux of an underwing-mounted engine impinges on the wing and trailing-edge flaps. The method is semi-empirical in that theory, combined with the empirical correlation of a wide range of wind-tunnel test data, was used in its development. The method is applicable to turbo-jet or turbo-fan powered aircraft with underwing nacelles and is also applicable to all widely-used trailing-edge slotted-flap systems, whether single- or multi-element. The experimental data used in developing the method related largely to transport-type aircraft with aspect ratios varying from about 5 to 8 and quarter-chord sweeps varying from 0 to 28 degrees. Two comprehensive worked examples are included, dealing with typical twin-engine and four-engine transports.