NTSB Identification: MIA94LA176.
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Accident occurred Saturday, July 09, 1994 in SANFORD, FL
Probable Cause Approval Date: 11/18/1994
Aircraft: ROBINSON R-22, registration: N22431
Injuries: 2 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.

THE HELICOPTER WAS IN A 15 FOOT HOVER WHEN IT BEGAN TO SPIN TO THE RIGHT AND DESCEND. THE PILOT WAS UNABLE TO CONTROL THE HELICOPTER AND IT CRASHED INTO THE WATER. A WITNESS ON THE GROUND OBSERVED THE TAILROTOR SLOW DOWN JUST PRIOR TO THE HELICOPTER STARTING TO SPIN TO THE RIGHT. EXAMINATION OF THE HELICOPTER AFTER THE ACCIDENT INDICATED THE TAILROTOR DRIVESHAFT WAS SEPARATED AT THE LAST COUPLING PRIOR TO THE TAILROTOR GEARBOX. THE TAILROTOR GEARBOX WAS FREE TO TURN AND ONE TAILROTOR BLADE WAS BENT AT A 90 DEGREE ANGLE. THE OTHER TAILROTOR BLADE WAS NOT DAMAGED. METALLURGICAL EXAMINATION OF THE SEPARATED TAILROTOR DRIVESHAFT INDICATED IT SEPARATED DUE TO TORSIONAL OVERSTRESS IN THE NORMAL DIRECTION OF ROTATION. THE DRIVESHAFT HAD ACCUMULATED 887 TOTAL HOURS SINCE IT WAS INSTALLED NEW IN JUNE 1992. THE HELICOPTER HAD BEEN SUBJECTED TO AN OVERSPEED AND TWO GROUND DAMAGE OCCURRENCES TO THE TAIL STABILIZERS IN THE LAST 150 FLIGHT HOURS.

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

THE FAILURE OF THE TAILROTOR DRIVESHAFT FOR UNDETERMINED REASONS RESULTING IN LOSS OF TAILROTOR DRIVE. THIS RESULTED IN THE HELICOPTER SPINNING UNCONTROLLED AND DESCENDING FROM A HOVER UNTIL IT CRASHED IN THE WATER.

Full narrative available

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