Hovering Performance of a Helicopter Rotor Using NACA 8-H-12 Airfoil Sections

A helicopter rotor employing an NACA 8-H-12 airfoil section has been tested on the Langley helicopter test tower. Two blade surface conditions were investigated, first with a filled blade which was within 0.002 inch of true airfoil shape obtained by use of plastic filler, and second with the filler removed resulting in a surface condition within 0.020 inch of true airfoil shape. Tests were conducted for the two sur-face conditions at a tip speed of 455 feet per second and over a tip-speed range from 455 to 650 feet per second for the blades with filler removed. The NACA 8-H-12 blades with the filled surface showed an aver-age reduction of 6 to 7 percent in total torque coefficients.