NTSB Identification: SEA95LA051.
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Accident occurred Monday, February 13, 1995 in MARBLEMOUNT, WA
Probable Cause Approval Date: 07/24/1995
Aircraft: SIKORSKY S-58JT, registration: N1099T
Injuries: 1 Serious.

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 MAIN ROTOR DRIVESHAFT FAILED DUE TO FATIGUE FAILURE WHILE THE PILOT WAS CONDUCTING HELICOPTER LOGGING OPERATIONS. THE MAIN ROTOR DRIVESHAFT HAD 952 HOURS SINCE NEW, AND HAD BEEN INSTALLED NEW AT THE MOST RECENT GEARBOX OVERHAUL. OVERHAUL PERIOD AND MAIN ROTOR DRIVESHAFT RETIREMENT TIME ARE 2500 HOURS. THE PILOT WAS NOT AT AN ALTITUDE OR AIRSPEED WHERE A SUCCESSFUL AUTOROTATION COULD BE ACCOMPLISHED.

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

FATIGUE FAILURE OF THE MAIN ROTOR DRIVESHAFT.

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