NTSB Identification: MIA97LA076.
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Nonscheduled 14 CFR
Accident occurred Monday, January 27, 1997 in TAMPA, FL
Probable Cause Approval Date: 02/02/1998
Aircraft: Cessna U206D, registration: N72074
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 pilot had flown the airplane once around the traffic pattern earlier in the morning with no discrepancies noted following removal and reinstallation of 4 of the 6 cylinders several days earlier. He then flew the airplane on a short positioning flight also with no discrepancies noted. The flight then departed on the chartered cargo flight and shortly after takeoff, the engine experienced a partial then complete loss of power. With unsuitable terrain ahead the pilot ditched the airplane. Following recovery of the airplane examination of the engine revealed the crankshaft was failed aft of the No. 2 main bearing due to fatigue then overload. Fretting was noted on both crankcase halves at the No. 2 main bearing saddle and the associated bearing was broken, extruded, and the bearing saddle was also extruded. Also, the No. 3 main bearing halves were found to be shifted. Review of the maintenance records revealed that overhauled cylinders were installed at all positions in August of 1996. The engine had been operated for 423 hours since at the time of the accident.

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

Inadequate torque of the cylinder base nuts and through bolt nuts by company maintenance personnel which allowed movement of the crankcase halves. As a result the No. 2 main bearing failed which allowed excessive movement of the crankshaft resulting in fatigue failure of the crankshaft. Contributing to the accident was unsuitable terrain encountered by the pilot during the forced landing.

Full narrative available

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