ESDU Aero F.01.01.09 has been superseded by ESDU 95021 but is retained because other documents still current in the Series make reference to it. It is restricted to full-span flaps on an unswept wing but the factors in ESDU 74012 may be used to correct results obtained from it to apply to part-span flaps; it is also restricted to double-slotted flaps or to the case when the second element of the high-lift system is a split flap. The method of ESDU 95021 applies to flaps that may be part-span on a wing that may be swept and the flaps may be double- or triple-slotted. The correlation presented in ESDU 95021is based on that developed for the two-dimensional case in ESDU 94031; for the methods for both the wing and the aerofoil more recent data were available than could be used for that developed in ESDU Aero F.01.01.09. For those reasons ESDU 95021 should always be used to obtain the lift increment due to the deployment of double- or triple-slotted flaps. For single-slotted flaps ESDU 93019 should be consulted.