IHS ESDU Energy method for analysis of measured airspeed change in landing airborne manoeuvre. 92020

ESDU 92020 gives a method that correlates measurements of airspeed changes in the airborne manoeuvre on the basis of energy considerations to yield changes in lift and in drag-minus-thrust between screen and touch-down. The method applies to fixed wing aircraft and can be applied to any set of flight test measurements although it is most effective when the landings have a common "style". Examples would be those flown for civil certification purposes, or those representative of operational practice. The use of the correlation to calculate touch-down speed from a knowledge of the airborne time and the screen speed is explained, and methods of calculating the airborne time are suggested. The prediction of the airborne distance from the speeds and airborne time is straightforward in still air, but the effect of a steady wind and a wind gradient, is considered. A worked example illustrates the use of the method, and the scatter on some points is investigated in relation to the "style". Examples of the application of the method to particular sets of test data are shown for jet-, fan- and propeller-driven civil and military aeroplanes and to an unpowered aircraft. They contain large ranges of approach angle, speed, power-cut height and landing "style".