NTSB Identification: IAD01LA002.
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Accident occurred Wednesday, October 11, 2000 in PHILADELPHIA, PA
Probable Cause Approval Date: 08/26/2003
Aircraft: American Aviation Corp. (AAC) AA-1A, registration: N9394L
Injuries: 1 Minor.
NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The airplane was on a traffic observation flight when it experienced a total loss of engine power. The pilot performed a forced landing to a schoolyard and escaped uninjured. Initial examination revealed heat damage to the #4 cylinder and no oil in the engine. Removal of the #4 cylinder revealed a hole in the #4 piston at the 12 o'clock position beneath the piston ring lands. The hole carried through to the interior of the piston. Removal of the #2 cylinder revealed that the #1 connecting rod was separated from the crankshaft. In addition to the hole through the #4 piston, examination revealed a deep groove in the side of the piston in line with the forward piston pin plug. The plug was worn and heat damaged, with significant material loss. Material transfer in line with the piston plug was observed on the wall of the #4 cylinder. The oil-scraper piston rings on the #1 and #2 pistons were installed backwards. The #3 cylinder had 3 base nuts installed upside down. Examination of the #1 and #2 cylinder assemblies revealed they were Superior cylinders. The number #3 and #4 cylinder assemblies were reworked Lycoming cylinders. The individual piston part numbers could not be determined. Examination of the maintenance records revealed the owner/operator replaced the #3 and #4 cylinder assemblies 337 aircraft hours prior to the accident. The owner/operator serviced the engine with 80 weight oil, and returned the airplane to service. The #1 and #2 cylinder assemblies were replaced by a maintenance facility 235 aircraft hours prior to the accident, and the engine was serviced with mineral oil as recommended by the engine manufacturer.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A hole in the #4 piston for undetermined reasons which resulted in engine oil starvation and engine stoppage. Full narrative available
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