ESDU AERO A.08.01.05 gives a curve that allows the ratio of the chordwise position of the aerodynamic centre in incompressible flow (h0) to that in incompressible inviscid flow (h0T) to be obtained for known ratios of incompressible to incompressible inviscid lift curve slopes, which may be obtained from ESDU AERO W.01.01.05. An equation is given for h0T and another graph provides values for functions required to evaluate that. It is noted that ESDU 72024 provides a more accurate estimate of h0T but such values must not be used in the method of given here. The method is accurate to within 0.005 of aerofoil chord.