NTSB Identification: ATL97LA091.
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Accident occurred Saturday, June 28, 1997 in TULLAHOMA, TN
Probable Cause Approval Date: 04/24/1998
Aircraft: Beech E50, registration: N4265R
Injuries: 2 Serious,7 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 airplane was being used for sport parachute operations. During the initial climb after takeoff the right engine failed followed by the airplane's slow descending right turn into wooded terrain. The airplane crashed through trees and caught on fire. The fire was extinguished prior to the destruction of the airplane. Subsequent examination of the engine revealed that one crankshaft counterweight had broken its retaining lugs and was liberated inside the engine, resulting in sudden stoppage of the engine. The sudden stoppage prevented the pilot from feathering the propeller. Metallurgical examination of the crankshaft and counterweight revealed damage that was consistent with 'detuning' of the engine counterweights. Counterweight detuning results from excessively rapid throttle movements. Additionally, the engine log indicated that during an oil change 8 days before the accident, wear metal was found in the oil. The airplane continued to be flown with no further maintenance action taken.

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

improper operation of the engine that produced internal damage, and improper servicing of the airplane by the owner/pilot mechanic that resulted in the subsequent mechanical failure of the engine crankshaft counterweight. Contributing to the accident was the pilot's inability to feather the propeller.

Full narrative available

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