NTSB Identification: MIA90LA134.
The docket is stored on NTSB microfiche number 41490.
Accident occurred Saturday, May 26, 1990 in VERO BEACH, FL
Probable Cause Approval Date: 02/12/1993
Aircraft: Ayres S2R-600, registration: N40145
Injuries: 1 Minor.

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 PLT STATED THAT WHILE MANEUVERING, HE FELT A SEVERE VIBRATION. HE DUMPED THE CHEMICAL & DURING THE FORCED LANDING, COLLIDED WITH TREES BEFORE COMING TO REST. EXAM OF THE ACFT REVEALED THAT THE NO. 2 PROP BLADE COUNTERWEIGHT BEARING SHAFT FAILED DUE TO FATIGUE. ACCORDING TO THE METALLURGIST, THE FATIGUE WAS DUE TO BENDING STRESS WHICH WAS CAUSED BY EXCESSIVE CLEARANCE BETWEEN THE SHAFT & THE BUSHED HOLE IT WAS POSITIONED IN. THIS ALLOWED CENTRIFUGAL FORCE TO POSITION THE BLADE TO HIGH PITCH, RESULTING IN UNEQUAL THRUST. THE PROP WAS OVERHAULED IN 1987 BUT THE TOTAL TIME SINCE THAT TIME COULD NOT BE DETERMINED. THE PROP WAS REPAIRED ABOUT 10 WEEKS PRIOR TO THE ACCIDENT BUT HAD ONLY ACCUMULATED 3.4 HRS SINCE THE REPAIR. ACCORDING TO THE PROP OVERHAUL FACILITY GENERAL MGR, THE PROP WAS RETURNED TO THE OPERATOR AFTER THE ACCIDENT BUT THE APPROVED FOR SERVICE LINE ON THE WORK ORDER WAS NOT SIGNED. ACCORDING TO THE CHIEF INSPECTOR OF THE REPAIR FACILITY, FURTHER INSP WAS NECESSARY TO DETERMINE IF THE PROP WAS AIRWORTHY.

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

THE OPERATION OF THE AIRPLANE WITH AN UNAIRWORTHY PROPELLER BY THE OPERATOR.

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