New composite main rotor blades for the Sikorsky S-61 have been designed, constructed and flight tested. Design criteria are described and the geometry of the new blade is shown. Results of an extensive flight test program conducted to obtain a Supplementary Type Certificate from the FAA for these blades are presented. The flight test program included an investigation of the performance and stability and control characteristics, and measurement of the structural loads. The flight test program was conducted with the aircraft as currently equipped with metal blades and the aircraft with new composite blades, so that direct load comparisons could be made. The flight test data show that the new blades provide a considerable increase in the hover lift capability and a significant improvement in level flight performance. Critical oscillatory control loads with the new blades are shown to have amplitudes lower than those of the aircraft with metal blades and the vibration characteristics of the aircraft are not appreciably changed by the new blades. Pilot comments indicate that the handling characteristics of the aircraft are improved with the new blades.

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