ESDU 72023 provides a means of estimating the changes in the lift-curve@ drag@ tailplane lift@ and downwash from the wing of an aircraft due to ground effect in incompressible flow@ typically for use in calculations of aircraft take-off and landing performance. It is assumed that the free-air conditions are known. The data are applicable to any aircraft except those with pointed slender wings@ which are considered in ESDU 71007. The equations and graphical data are generally applicable to aircraft with mechanical high-lift devices or having flaps with boundary layer control giving free air lift coefficients less than 4 for wings of quarter-chord sweepback less than 45 degrees and for height/chord ratios greater than 0.3. The methods are semi-empirical and in general consider the changes in free air conditions as the ground is approached at constant aircraft lift coefficient and hence changing incidence. In the consideration of lift@ however@ the changes due to ground effect on incidence at constant lift coefficient or in lift coefficient at constant incidence may be found. A computer program of the method is provided as ESDUpac A7223.