Abstract:

ESDU 87024 gives a simple estimation method developed by correlating the available wind-tunnel data taken from the literature. The resulting correlation is presented in the form of a graph and an equation for the increment in terms of flap deflection, which may be up or down, and the ratio of flap-to-wing chord. A Fortran program of the method is also provided as ESDUpac A8724. Predictions are within 0.01 in the drag coefficient increment for the range of data studied which covered aerofoils and wings of aspect ratio up to 10 (rectangular or tapered), flap-to-wing-chord ratios up to 0.3 and flap deflections up to 30 degrees. This method for a full span flap on an isolated wing may be used for a practical configuration with ESDU 97003 to obtain the effect of body interference and ESDU Aero F.02.01.07 to convert data to a part-span case. The method applies when the flow upstream of the flap is fully-attached, and a prediction for the limiting angle of attack is suggested. A possible extension of the method to the case of a flap on a swept wing is also included.