AN-EXPERIMENTAL INVESTIGATION OF THE EFFECT OF VARIOUS PARAMETERS INCLUDING TIP MACH NUMBER ON THE FLUTTER OF SOME MODEL HELICOPTER ROTOR BLADES

摘要

Experimental studies were made to evaluate some of the effects of -parameters such as Mach number, blade angle, and structural damping on the flutter of model helicopter rotor blades in the hovering condition. The model blades had NACA 23012 and 23018 airfoil sections and each was tested to chordwise center-of-gravity locations of approximately 27.5 and 37 percent chord. Data were obtained at test medium densities ranging from 0.0012 to 0.0030 slug per cubic foot and at various pitch angles up into the stall. Mixtures of air and Freon-12 were used for the test medium in order to extend the tip Mach number range of the tests to slightly above unity.