NTSB Identification: LAX00LA173.
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Accident occurred Thursday, April 06, 2000 in CHANDLER, AZ
Probable Cause Approval Date: 11/01/2001
Aircraft: Rotorway EXEC 162F, registration: N21901
Injuries: 2 Uninjured.

NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The helicopter landed hard collapsing the left skid and resulting in the main rotor blades striking the tail boom. While in the traffic pattern, during the downwind leg, the pilot heard a loud noise from the rear of the helicopter. He entered an autorotation and checked the cockpit instruments. Noting no anomalies, he rolled on the throttle and discovered that the engine speed would increase but the rotor speed would not. The pilot flared to avoid a fence then landed hard. Subsequent examination of the engine secondary shaft that transmits power to the main rotor through drive belts revealed that the shaft had failed in fatigue. There were numerous longitudinal and circumferential score marks on the secondary shaft indicating removal and reinstallation of the shaft many times. The fatigue fracture originated at one of the circumferential score marks and exhibited oxidation, indicating it had been fractured for some time.

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

The inadequate maintenance inspection of the secondary shaft which resulted in its fatigue failure that emanated from a corroded circumferential score mark. A factor was the fence that the pilot flared to avoid, resulting in a hard landing.

Full narrative available

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