NTSB Identification: CHI95FA242.
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Accident occurred Thursday, July 27, 1995 in OSHKOSH, WI
Probable Cause Approval Date: 04/18/1996
Aircraft: REVOLUTION HELICOPTER MINI-500, registration: N500ZZ
Injuries: 1 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The amateur-built helicopter was conducting a demonstration flight during the annual EAA convention. During the first flight after re-jetting of the carburetor, the helicopter experienced a total loss of engine power. During the autorotation into a crop field, the helicopter was substantially damaged when the skid shoes caught in the terrain, failing the left skid and fracturing the shoe on that skid. Subsequent examination of the engine revealed that the rear piston had seized in the cylinder. The owner of the company which produces the helicopter stated that the re-jetting of the carburetor was made in an attempt to achieve what were thought to be correct readings in main rotor RPM and EGT after replacement of both gauges. The company owner attributed the piston seizure to the re-jetting. The skid shoes were new and had been tested only on concrete. The owner said that the design contributed to the damage to the helicopter.

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

the inadequate design of the helicopter skid shoes. Factors related to the accident were: false indications of rotor rpm and EGT which led to seizure of the piston.

Full narrative available

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