NTSB Identification: CHI98LA190.
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Accident occurred Wednesday, June 03, 1998 in LEXINGTON, NE
Probable Cause Approval Date: 05/19/1999
Aircraft: Rotorway EXEC 90, registration: N132RS
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

According to the pilot/builder, the homebuilt helicopter was in cruise at 1000 feet agl when he initiated a 200-300 foot per minute descent. After approximately one minute, at an altitude of approximately 500-700 feet agl, the engine lost power. He executed an autorotation and forced landing into a corn field. The pilot stated that the helicopter had some forward velocity on landing, causing one of the skids to sink and get caught in the soft terrain. The helicopter subsequently nosed over and was substantially damaged. The temperature and dewpoint on the surface was reported to be 42 degrees F and 38 degrees F respectively. According to carburetor icing charts, the accident flight was operating in conditions favorable to carburetor icing. Post accident investigation revealed that the carburetor heat system was operating. The pilot stated that during the descent phase of flight, the engine temperatures were indicating in the low end of the green arc, but he did not notice the carburetor temperature gauge indication. The Vice President of RotorWay, International agreed to issue an Advisory Bulletin to all registered owners of RotorWay helicopters having the RI-162 engine, informing them of the background of this accident, as well as alternate way of carburetor icing prevention and avoidance.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

An improper autorotation by the pilot in command. Factors contributing to this accident were the accumulation of ice in the carburetor resulting in a total loss of engine power, and the soft terrain.

Full narrative available

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