ESDU 98017:2003

For aerofoils, the method of ESDU 98017 predicts the centre of lift position based on thin-aerofoil theory with empirical correction to obtain agreement with extensive experimental data. This is combined with the predicted increment in aerofoil lift coefficient from ESDU 94028 to estimate the pitching moment coefficient increment. For wings with full-span trailing-edge plain flaps, factors dependent on planform geometry are applied to the pitching moment coefficient increment on an aerofoil section that is representative of the wing in order to allow for three-dimensional effects, with ESDU 97011 used to calculate the section lift coefficient increment in order to reflect the observed difference between the efficiency of plain flaps on wings as opposed to aerofoils. For wings with part-span trailing edge flaps, additional factors are introduced that are dependent on the wing taper ratio, aspect ratio and sweep as well as on the spanwise extent of the flaps. The method applies in free air and at Mach numbers below 0.2.
Sketches illustrate the accuracy of prediction and Tables give the ranges of parameters covered in the construction of the Item. For aerofoils, 92% of the data for the position of the centre of the lift increment are predicted to within ± 0.02 of chord length and 95% of the data for the pitching moment coefficient increment are predicted to within ± 0.04. For wings, 93% of the data for the
pitching moment coefficient increment are predicted to within ± 0.02. A worked example illustrates the use of the method.