NTSB Identification: LAX96LA210.
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Accident occurred Wednesday, May 22, 1996 in CHANDLER, AZ
Probable Cause Approval Date: 08/20/1996
Aircraft: Rotorway EXEC 9, registration: N89678
Injuries: 2 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.

The dual student began to apply power during a normal approach to landing when the main rotor rpm needle went into the yellow arc on the engine gauge. The CFI applied full power but the rpm continued into the lower portion of the arc. The helicopter made ground contact with low rotor rpm and the right skid collapsed. The helicopter bounced and rolled over. Examination of the engine revealed that a section of the piston from the dome to the first ring groove had broken away. The upper ring was broke and pieces were found in the combustion area. Normal carbon buildup was found on the cylinder sleeve above the top ring surface except in the area of the piston breakage, indicating that the engine had been operating for a period of time after the damage had taken place and before the accident.

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

a loss of engine power due to a failed piston and piston ring in a critical phase of flight.

Full narrative available

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