ESDU Aero W.S.02.04.13 gives curves of profile drag of biconvex aerofoils plotted against transition position as a fraction of chord for values of freestream Mach number of 1.5, 2.5 and 5, thickness chord ratios of 0.05 and 0.1 and three Reynolds numbers. It is recommended that the curves of ESDU Aero W.S.02.04.12, which apply for a thickness chord ratio of zero, be used to guide extrapolation to thickness chord ratios below 0.05 as shown in the worked example of the use of the curves. The wave drag coefficient to be added to the profile drag coefficient to give the total drag coefficient may be obtained from ESDU Aero W.S.00.03.04.