NTSB Identification: SEA83FA135.
The docket is stored on NTSB microfiche number 21126.
Accident occurred Monday, June 27, 1983 in KENT, WA
Aircraft: ENSTROM 280C, registration: N652H
Injuries: 1 Minor,1 Uninjured.

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.

DURING A TRAFFIC REPORTING FLT FOR A RADIO STATION, THE PLT NOTED THE ONSET OF A SEVERE VIBRATION WHICH HE FELT THROUGH THE ANTITORQUE PEDALS. HE STATED THAT WITHIN SECONDS, THE HELICOPTER LOST DIRECTIONAL CONTROL & BEGAN A RAPID, UNCONTROLLED SPIN TO THE RIGHT. REPORTEDLY, THE HELICOPTER TUMBLED OUT OF CONTROL FOR A TIME. HOWEVER, THE PLT WAS ABLE TO REGAIN PARTIAL CONTROL AS IT ROLLED THRU A RELATIVELY UPRIGHT ATTITUDE. BEFORE CRASHING, THE RATE OF DESCENT WAS SLOWED WITH FULL COLLECTIVE & A ROTATING IMPACT OCCURRED IN A HORIZONTAL ATTITUDE. AN INVESTIGATION REVEALED THE TAIL ROTOR DRIVE SHAFT SPLINE COUPLING, PN 28-13609, HAD BECOME WORN. THE TEETH OF THE COUPLING WERE WORN AWAY & THERE WAS IRON OXIDE & CARBONIZED LUBRICANT WITHIN THE COUPLING. THE SPLINED MALE END OF THE COUPLING WOULD ROTATE WITHIN THE SPLINED FEMALE HOUSING. IT HAD ACCUMULATED 149.1 HRS SINCE LUBRICATED. THE LUBRICATION CHART & CHECK SHEET (PAGES MM-3-5 & MM-3-6 OF THE MAINTENANCE MANUAL) SHOW THAT THE COUPLING SHOULD BE LUBED AT 100 HR INTERVALS

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

ROTOR DRIVE SYSTEM,TAIL ROTOR GEARBOX(90 DEG)..WORN

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

MAINTENANCE,LUBRICATION..INADEQUATE..OTHER MAINTENANCE PERSONNEL

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

ROTOR DRIVE SYSTEM,TAIL ROTOR GEARBOX(90 DEG)..OTHER


Contributing Factors

DIRECTIONAL CONTROL..NOT POSSIBLE..PILOT IN COMMAND


Contributing Factors

AUTOROTATION..PERFORMED..PILOT IN COMMAND

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