Louis S. Stivers, Fred J. Rice, Jr.
Four NACA airfoil sections, the NACA 7-H-12, 8-H-12, 9-H-12, and 10-H-12, suitable for use as rotor-blade sections for helicopters and other rotary-wing aircraft have been derived and tested. These airfoil sections have comparatively low drags in the range of low and moderate lifes and small pitching moments that are nearly constant up to maximum lift. The undesirable adverse changes in aerodynamic characteristics at higher lifts and the undue sensitivity to roughness, which were found for the airfoil sections report in NACA CB No. 3I13, are minimized for the airfoil presented. A comparison of calculated profile-drag losses for a rotor successively incorporating the NACA 3-H-13.5 (reported in NACA CB No. 3I13) and the 8-H-12 airfoil sections showed that the NACA 8-H-12 had smaller profile drag losses in nearly every operating condition presented. From aerodynamic considerations, the NACA 8-H-12 and 9-H-12 airfoil sections appeared more promising for use as rotor-blade sections than any other airfoils thus far tested at the NACA laboratories.
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