Pilot and Flight Details
A private helicopter pilot with 1,350 hours of experience verified that the helicopter's fuel tanks were full, free of contamination, and the engine oil level was "normal" prior to departure. The pilot and two passengers departed for a private residence located near a lake; no abnormalities were noted during departure or en route to the residence.
Engine Power Loss and Impact
The pilot reported that within a few miles of his destination, he reduced power to 21 inches and gradually descended to 900 feet mean sea level (msl). Without any indication of a problem, the engine lost power. The pilot lowered the collective just as the low-rotor warning light illuminated and horn sounded. The pilot flared about 50 feet above the water; however, the helicopter impacted the surface of the water with "significant force."
Post-Accident Examination
The helicopter was retrieved from the lake and a visual inspection of the engine failed to note any pre-impact abnormalities. An external power source was connected to the helicopter, and the "manual override" was used to disengage the engine and rotor/transmission. The engine was then turned by hand; thumb compression was obtained on all cylinders and engine continuity was established through the engine. Additionally, the carburetor heat control was found in the "automatic" position.
A review of the Carburetor Icing chart reveals that the temperature/dew point spread placed the flight in the "Serious icing - descent power" operating realm. A check of the Fixed Base Operator (FBO) fuel records revealed that on 27 May 2006, the helicopter was filled with 38.5 gallons of 100LL aviation fuel.
On 29 June 2006, under the supervision of an NTSB representative, an additional examination of the engine was conducted at the factory. Both the ignition and fuel systems were checked. The engine was removed from the airframe, placed in an engine test cell, and prepared for an engine run. The engine was run at various power settings for 20 minutes. A reason for the reported loss of engine power could not be determined.