NTSB Identification: SEA87FA106.
The docket is stored on NTSB microfiche number 33709.
Accident occurred Thursday, May 28, 1987 in SHELTON, WA
Probable Cause Approval Date: 07/05/1988
Aircraft: HILLER UH-12E, registration: N28875
Injuries: 1 Fatal.

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 PILOT WAS PROPERLY CERTIFICATED FOR THE FLIGHT; HOWEVER, DUE TO OPERATOR INSURANCE RESTRICTIONS, ALL PRIOR COMMERCIAL FLIGHTS HAD REQUIRED THE OWNER/OPERATOR TO ACCOMPANY THIS PILOT, THEREFORE THIS WAS THE PILOT'S FIRST COMMERCIAL FLIGHT AS SOLE PILOT. RETURNING TO BASE AFTER A ROUND-TRIP PASSENGER FLIGHT, HAVING DISEMBARKED PASSENGERS, THE AIRCRAFT WAS OBSERVED PROCEEDING AT HIGH FORWARD SPEED IN STRONG BUT INTERMITTENT WIND CONDITIONS. ALSO, PASSENGERS REMARKED ABOUT TURBULENCE ALONG THIS SAME ROUTE OF FLIGHT EARLIER. INVESTIGATION REVEALED THE MAIN ROTOR SEPARATED IN FLIGHT DUE TO MAST BUMPING, A PHENOMENON ASSOCIATED WITH TEETERING ROTOR SYSTEMS, INDUCED BY EXCEEDING THE NORMAL FLIGHT ENVELOPE FOR THE AIRCRAFT.

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

ROTORCRAFT FLIGHT CONTROLS..EXCESSIVE..PILOT IN COMMAND

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

ROTOR DRIVE SYSTEM,MAIN ROTOR MAST(DRIVE SHAFT)..FAILURE,TOTAL

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

ROTOR SYSTEM..SEPARATION


Contributing Factors

WEATHER CONDITION..WINDSHEAR


Contributing Factors

LACK OF TOTAL EXPERIENCE IN TYPE OF AIRCRAFT..PILOT IN COMMAND


Contributing Factors

WEATHER CONDITION..TURBULENCE

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