Aircraft: Piper Arrow. Injuries: 1 Serious. Location: Lock Haven, Pa. Aircraft damage: Substantial.
What reportedly happened: According to the pilot, when the airplane was in cruise flight at 7,500 feet, the engine began to “surge,” then stopped producing power. The pilot selected a forced landing area in a clearing, but the plane lacked enough altitude to make it to the field and it crashed in trees before reaching the clearing.
Examination of the engine at the scene revealed that it could not be rotated by hand, and metal particles were contained in the oil filter and the finger strainer.
Disassembly of the engine at the manufacturer’s facility revealed the oil sump contained debris associated with the No. 3 connecting rod, piston, and attachment hardware. The connecting rod had fractured at the crankshaft and punctured the crankcase, which resulted in oil starvation at the No. 3 connecting rod journals, which resulted in the rod’s separation from the crankshaft.
Metallurgical examination of No. 3 bearing fragments and intact bearings harvested from the engine revealed material and construction discrepancies between the aftermarket manufacturer’s parts drawings and the bearings themselves.
The connecting rods used in the accident engine were not approved for installation by the engine manufacturer, however, the bearings used with the connecting rods were properly matched to the rods installed. Because the connecting rods and, therefore, the connecting rod bearings, were not the correct parts for the engine, it is probable that the bearings failed from improper part selection and, therefore, possibly improper material selection.
Probable cause: The reinstallation of improper connecting rods at engine overhaul, which resulted in abnormal wear of the connecting rod bearings. While the bearings did not meet the manufacturer’s specifications, the use of the unapproved connecting rods more likely caused the bearing wear.
NTSB Identification: ERA13LA097
This December 2012 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.