NTSB Identification: FTW97LA246.
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Accident occurred Wednesday, July 02, 1997 in KERRVILLE, TX
Probable Cause Approval Date: 01/07/1998
Aircraft: Cessna T210M, registration: N761FM
Injuries: 4 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 airplane was on its climb to cruise when the engine lost power. The pilot performed a forced landing short of the runway in rough and uneven terrain. An examination of the engine revealed that the #1 cylinder piston was seized in the cylinder, the piston rings were broken, the piston head was deteriorated around the edge down to the top compression ring with a portion of the ring missing, metal was deposited on the intake valve seat, and the intake valve was stuck in the open position. The #1 cylinder dome was damaged and scaring was noted on the cylinder walls. Aluminum particles were found in the #1 cylinder spark plugs and embedded in the #1 cylinder combustion chamber and internal components of the engine. According to the manufacturer, no discrepancies were found with the engine components that 'would have caused detonation/preignition to [the] number 1 cylinder.' The cylinder met the SAE chemistry requirements. The manufacturer's metallurgist stated that 'the burning of the piston crown most likely is the result of either detonation or pre-ignition.'

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

The disintegration of the #1 cylinder piston resulting from a detonation/pre-ignition condition due to an unknown reason. A factor was the lack of suitable terrain for the forced landing.

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