This Bell helicopter main rotor was submitted tor electric motor whirl testing in order to obtain readings of thrust, torque, vibratory stress and blade deflection and to determine the ultimate strength of the rotor blades under centrifugal loading.nThe blades of this helicopter main rotor were constructed with an impregnated plywood leading edge, solid white ping trailing section, and a 5/16 x 1-1/2 inch steel strip inserted in the canter of the aft edge of the plywood and (attending the full length of the blade. The blade structure was covered with aircraft fabric and doped.nThe rotor was calibrated for thrust, torque, and blade deflection, and measurements of vibratory stress were recorded for various values of r.p.m. and blade pitch angles. At the conclusion of these calibrations the rotor was whirled to destruction.
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