What was found
SUBMITTER STATED THIS MDR AFFECTS S-64E MODEL. ACFT WAS FLYING UNDER NORMAL CONDITIONS WHEN NR 1 AND NR 2 GEN WENT OFF-LINE AND INVERTER POWER WAS NEEDED FOR A/C TO RETURN TO LANDING. INITIAL INSP REVEALED ALL WIRES CONNECTED AND CB'S IN CORRECT POSITIONS. ALSO, NR 1 AND NR 2 GENERATOR SPLINED QUILL SHAFTS WERE SHEARED ALLOWING GEN DRIVE GEARS IN REAR ACCY COVER TO SPIN FREELY. NEW SPLINED QUILL SHAFTS INSTALLED IN GENERATORS AND A/C CONTINUED IN SERVICE. INVEST SHOWED EXCESS WEAR EXISITED RESULTING IN SLIPPAGE AND RE-ENGAGEMENT OF TTO FREE WHEEL UNIT. SPLINED QUILL SHAFTS IN NR 1 AND NR 2 GENERATORS WERE BROKEN BECAUSE OF POLAR INERTIA OF GEN ROTORS WHEN TTO FREE WHEEL UNIT SLIPPED AND RE-ENGAGED.