NTSB Identification: SEA91LA077.
The docket is stored on NTSB microfiche number 43260.
Accident occurred Sunday, March 31, 1991 in WAITSBURG, WA
Probable Cause Approval Date: 05/05/1993
Aircraft: BELL BH-47G2A, registration: N38926
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.

WHILE THE PILOT WAS LOWERING THE COLLECTIVE PITCH AFTER LANDING TOUCHDOWN, THE MAIN ROTOR SEPARATED FROMT HE MAST. THE EXAMINATION REVEALED THE IMPROPER INSTALLATION OF THE MAST NUT AND LOCK WASHER WHEN THE MAIN ROTOR WAS INSTALLED.

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

THE IMPROPER INSTALLATION OF THE MAIN ROTOR MAST NUT AND LOCK WASHER BY MAINTENANCE PERSONNEL WHICH RESULTED IN THE SEPARATION OF THE MAIN ROTOR SYSTEM.

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