20001201023589A

(-23) On December 1, 2000, at 1625 CST, a Bell 206B helicopter, N222LN, was substantially damaged following a loss of engine power near Rockport, TX. The helicopter was owned and operated by American helicopters, inc. of galveston, TX. The commercial pilot, sole occupant, was not injured. Visual meteorological conditions prevailed and a company VFR flight plan was filed for the 14 CFR part 91 positioning flight. The flight originated from the matagorda 603 offshore platform located in the gulf of Mexico, and was destined for the aransas county airport, Rockport, TX. The pilot reported that when the helicopter was about 4.5 miles from its intended destination, the engine lost power. The pilot initiated an autorotation to the water and deployed the floats. The helicopter landed on the water and remained upright and afloat. After the main blades stopped turning, the pilot exited the helicopter, then the waves overturned the helicopter. An examination of the helicopter by the FAA inspector revealed that the tail rotor drive shaft was severed. The allison 250-C20 turbine engine N1 gas producer would not turn. A detailed examination of the engine is pending. (.4) the helicopter was returning to shore from an oil platform. The pilot had just made a "5 mile advisory call" announcing his intention to land at his destination when the engine chip light illuminated; this was followed by an immediate loss of engine power. The pilot initiated an autorotation, inflated the floats and made a mayday call. During the descent, he "had full [aircraft] control to include tail rotor authority." During landing, the tail rotor blades entered the water resulting in sudden stoppage of the tail rotor, which twisted the tail rotor drive shaft apart. Following the landing, the helicopter remained upright, and the pilot exited the helicopter after the main rotor blades came to a stop due to the "waves and wind." After he moved away from the helicopter, it rolled over. The pilot reported that the wind was from 045 degrees at 15 knots gusting to 25 knots. An examination of the turbine engine revealed that the N1 gas producer would not turn. Disassembly of the engine revealed that the compressor coupling adapter was fractured. Metallurgical examination indicated that the compressor coupling adapter had failed due to fatigue initiating from fretting at the outer surface where it contacted the impeller. The source of the fretting could not be determined.