NTSB Identification: ATL94LA165.
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Accident occurred Friday, August 26, 1994 in SPRUCE PINE, NC
Probable Cause Approval Date: 04/27/1995
Aircraft: CESSNA 150J, registration: N50446
Injuries: 1 Minor,1 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.

DURING CRUISE FLIGHT OVER MOUNTAINOUS TREE COVERED TERRAIN, THE ENGINE LOST POWER. IT CONTINUED TO DECREASE TO IDLE AS THE PILOT GLIDED THE ACFT TO A SMALL CLEARING. THE AIRPLANE WAS LANDED UPSLOPE, ROLLED OVER A HILL, AND COULD NOT BE STOPPED BEFORE COLLIDING WITH TREES. THERE WAS NO BRAKING FRICTION BECAUSE OF WET GRASS. DURING A POST ACCIDENT INSPECTION, A STUCK EXHAUST VALVE WAS FOUND IN THE NUMBER 2 CYLINDER. THE HEAD OF THE VALVE STEM WAS DISCOLORED AND HAD THE APPEARANCE OF A VARNISH-LIKE COATING. MEASUREMENTS OF THE VALVE STEM AND GUIDE SHOWED THAT THE STEM WAS 0.0075 MICROMETERS LARGER THAN THE GUIDE. FOURTEEN MONTHS EARLIER A VALVE HAD STUCK IN THE NUMBER 4 CYLINDER. SINCE THE AVAILABILITY OF THE AUTO FUEL STC, THE ENGINE HAD BEEN OPERATED ABOUT 25%-50% OF ITS HOURS WITH AUTO FUEL. RECENT CYLINDER COMPRESSION CHECKS HAD BEEN WITHIN LIMITS.

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

A seized cylinder exhaust valve because of deposits on the valve and an oversized valve stem. The lack of suitable terrain for a forced landing was a factor.

Full narrative available

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