Piper PA-28R-201 N62FC accident near Conway, South Carolina

Probable cause

The mechanic’s failure to install the required gasket on the vacuum pump drive pad in accordance with the maintenance manual, which resulted in oil exhaustion and the subsequent loss of engine power. Contributing to the accident was the Director of Maintenance’s failure to verify the installation of the vacuum pump gasket before returning the airplane to service.

NTSB analysis

Shortly after departure, on the first flight following maintenance, the pilot reported a loss of engine power. The pilot attempted a forced landing onto a gravel road, but the airplane impacted trees and powerlines on final approach. The airplane came to rest against a berm and a postcrash fire ensued.

A postaccident examination of the engine revealed that the Nos. 2, 3, and 4 connecting rods were separated from the crankshaft. The left side of the engine crankcase was fractured. The Nos. 3 and 4 connecting rods were separated from their respective crankshaft rod journals. During disassembly of the engine, a vacuum pump cover was removed from the vacuum pump drive pad and no gasket, or remnants of a gasket, were found. Other engine components were removed, and all had remnants of a gasket despite the thermal damage. When the crankshaft was removed, discoloration was present, consistent with exposure to high heat. It is therefore likely that the gasket had not been installed following the completion of maintenance work. Additionally, when the bottom of the empennage was examined, a sizeable quantity of oil was present near the tail tie down ring.

A review of the airplane maintenance records revealed that after a certificated airframe and powerplant mechanic had completed the work on the airplane, the Director of Maintenance, an airframe and powerplant mechanic with inspection authorization, signed off the paperwork to return the airplane back to service. The return to service entry stated that the vacuum pump had been removed but did not address the installation of the drive pad gasket or vacuum pump cover. In an interview, the mechanic who completed the removal of the vacuum pump and installation of the vacuum pump cover stated that that when he removed the vacuum pump, the gasket was still attached to it. He cleaned the mating surface of the cover and drive pad and then installed the cover. He stated that he thought he had replaced the gasket. A review of the work order showed that although the cover had been ordered, there was no record of a gasket being ordered.

It is likely that, following the removal of the vacuum pump and system, no gasket was installed between the vacuum pump drive cover and the engine accessory case. Additionally, the Director of Maintenance likely did not review the work in detail before signing for the airplane to return to service. As the oil temperature increased, the viscosity lowered, and the oil became thin and thus more easily able to escape from non-sealed areas.

Text from the NTSB. Open the NTSB docket for CEN22FA419 for the full record.