Aerofoil and wing pitching moment coefficient at zero angle of attack due to deployment of trailing-edge double-slotted and triple-slotted flaps at low speeds.
ESDU 99014 predicts for aerofoils the centre of lift position based on thin-aerofoil theory with empirical correction. This is combined with the predicted increment in aerofoil lift coefficient from ESDU 94031 to estimate the pitching moment coefficient increment. For wings with full-span trailing-edge double-slotted or triple-slotted 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. For wings with part-span trailing-edge flaps@ additional factors are introduced that are dependent on the wing taper ratio and on the spanwise extent to the flaps@ and the effect of wing aspect ratio and sweep is also accounted for in the procedure. 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 method. For aerofoils@ 90 per cent of the data for the position of the centre of the lift increment are predicted to within 0.02 of chord length and 90 per cent of the data for the pitching moment coefficient increment are predicted to within 0.04. For wings@ 86 per cent of the data for the pitching moment coefficient increment are predicted to within 0.04. Worked examples illustrate the use of the method.