NTSB Identification: ATL06LA049.
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Accident occurred Tuesday, March 07, 2006 in Wetumpka, AL
Probable Cause Approval Date: 02/26/2007
Aircraft: Ercoupe (Eng & Research Corp.) E, registration: N94840
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 stated that while enroute to the Wetumpka Airport at 2,500 feet the engine began to vibrate and stopped. He contacted air traffic control personnel and declared an emergency. The pilot made an emergency landing in an open field where the airplane collided with a ditch on the landing rollout and nosed over inverted. Examination of the engine by an FAA inspector revealed that when the No. 2 upper spark plug was removed it had foreign object damage. A compression check was performed and the No. 2 cylinder had no compression. The crankshaft was rotated and gear and valve train continuity was established. The No. 2 cylinder was removed from the engine case and examination of the cylinder assembly revealed that the exhaust and intake valves were broken. A review of the engine logbook revealed that the new Superior cylinders were installed on December 12, 2000, and had a total operation time of 272 hours since the installation. The No. 2 cylinder, exhaust, intake valves, and piston were sent to the National Transportation Safety Board Material Laboratory for further examination. The valves from the No. 2 cylinder were disassembled and visually inspected. The exhaust fracture faces were so heavily damaged by post separation impacts that no original fracture features could be found. The fractures on the intake valve head were only slightly damaged with features consistent with overstress fracturing consistent with low temperature impact loading, secondary to the fracture of the exhaust valve.

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

The failure of the No. 2 exhaust, and intake valves for undetermined reasons, which resulted in a loss of engine power during cruise flight and damage to the airplane during the subsequent forced landing.

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