An Aerodynamic Comparison of Two Airfoils Based Upon Full Scale Rotor Whirl Tests

For the past several years considerable interest has been expressed in the possibility of employing airfoils other than the standard NACA 00 series for helicopter rotor blades. This is primarily because the stall characteristics and drag divergence properties of the 00 series airfoils are not conducive to high speed flight potential for pure helicopters. Because of this industry-wide desire to investigate the possible use of airfoils with better stall characteristics and reduced Mach number effects, a comparative aerodynamic performance study was undertaken by Propulsion Laboratory.