What happened
A flight departed from Kissimme, Florida, while engaged in a forest fire spotting mission. During the flight, the engine began running roughly and subsequently lost power. The pilot performed an emergency landing in an orange grove, where the aircraft struck a tree.
The investigation
An examination of the engine revealed that improper connecting rod bolts had been utilized in the engine assembly. Specifically, the bolts in two connecting rods failed, which caused the overall failure of the engine.
Investigators determined that these bolts were manufactured during the 1980s and entered the U.S. market in February 1994. A repair station obtained the bolts in June 1994 and installed them into connecting rod assemblies that were already in storage. The work order for these stored assemblies was not updated to reflect the new components, so it continued to list an overhaul date of February 9, 1994. These assemblies were later installed in the engine during an overhaul performed in October 1994.
Findings
In March 1995, an Airworthiness Directive (AD) was issued requiring inspections for engines using connecting rod bolts installed on or after February 15, 1994. The engine involved in this accident did not receive the required inspection because the repair station had certified that the rod assemblies were overhauled on February 9, 1994, which predated the effective date of the AD.