6)kAerodynamic Characteristics of Three Helicopter Rotor Airfoil Sections at Reynolds Numbers From Model Scale to Full Scale at Mach Numbers From /0.35 to 0.90.S LEf

SUMMARY An investigation has been conducted in the Langley 6- by 28-Inch Transonic Tunnel to determine the two-dimensional aerodynamic characteristics of three helicopter rotor airfoils at Reynolds numbers from typical model scale to full scale at Mach numbers from about 0.35 to 0.90. The model-scale Reynolds num-bers ranged from about 0.7 x 106 to 1.5 x 106 and the full-scale Reynolds num-bers ranged from about 3.0 x 106 to 6.6 x 106. The airfoils tested were the NACA 0012 (00 Tab), the SC 1095-R8, and the SC 1095. Both the SC 1095 and the SC 1095-R8 airfoils had trailing-edge tabs. The results of this investigation indicate that Reynolds number effects can be significant on the maximum normal-force coefficient and all drag-related parameters; namely, drag at zero normal force, maximum normal-force-drag ratio, and drag-divergence Mach number. In general, the increments in these parameters at a given Mach number owing to the model-scale to full-scale Reynolds number change are different for each of the airfoils