Increments in aerofoil lift coefficient at zero angle of attack and in maximum lift coefficient due to deployment of a plain trailing-edge flap@ with or without a leading-edge high-lift device@ at low speeds.
ESDU 94028 presents an estimation method based on first approximations from the theory for a thin hinged plate modified using empirical correlation factors to account for the geometry of practical aerofoils and high-lift devices. To allow for the effects of chord extension@ the flap chord ratio and lift coefficients are based on an aerofoil extended chord. The data for aerofoils with trailing-edge flaps deployed from which the methods were developed were extracted from wind-tunnel tests reported in the literature covering a wide range of practical geometries. Fewer data were available for aerofoils with both leading- and trailing-edge devices deployed. The methods apply to Reynolds numbers greater than a million and freestream Mach numbers less than 0.2. The predicted and test data for the lift coefficient increments at zero angle of attack and at maximum lift are correlated to within 20 per cent. The use of the methods is illustrated by worked examples. To obtain results for an aerofoil with both leading-edge devices and plain flaps deployed@ ESDU 84026 is used in conjunction with this document and ESDU 94027.