Effect of Mach and Reynolds Numbers on Maximum Lift Coefficient

A knowledge of the effects of Mach and Reynolds numbers on the maximum lift coefficient is becoming of greater importance as the speeds and altitudes attainable by modern airplanes continually increase. Since most maximum-lift tests conducted to date have been either at full-scale Reynolds numbers and low Mach numbers or at high Mach numbers and small Reynolds numbers, very little is known about the inter-related effects of these two parameters on the maximum lift coefficient. In order to obtain quantitative information on these effects, flight tests were conducted at Ames Aeronautical Laboratory on six airplanes, three having NACA conventional airfoil sections, two having NACA low-drag sections, and the sixth having a North American Aviation - NACA compromise low-drag section. The results of these tests which cover a range of Mach numbers from 0.15 to 0.72 and of Reynolds numbers from 4,400,000 to 19,500,000 are assembled, together with a considerable quantity of pertinent wind-tunnel data, and analyzed in the present report. From this analysis, general conclusions have been reached indicating the manner in which the maximum lift coefficient is influenced by variations of Mach and Reynolds numbers.