Effects of compressibility on maximum lift coefficients for six propeller airfoils

An extension of'previously reported data on the variation of maximum lift coefficient with Mach number, camber, and thickness ratio Is presented.The data were obtained from pressure-distribution tests In the Langley 8-foot high-speed tunnel of six propeller airfoils of l-foot chord.It was found that the maximum lift coefficients of all the airfoils were markedly affected by compressibility at Mach numbers as low as 0.2.At Mach numbers above the order of 0.45,1arge increases in maximum lift coefficient occurred.The combination of a thickness ratio of 0.15 and a design lift coefficient of 0.7 was found to be critical, with adverse effects on maximum lift coefficient occurring over most of the speed range investigated.