Piper PA32 N4079R accident near Eveleth, Minnesota

Probable cause

The seizure of the airplane’s engine-driven fuel pump due to internal contamination, which led to a total loss of engine power. The source of the contamination could not be determined based on available evidence.

NTSB analysis

The airplane’s engine lost power during cruise flight, and the pilot executed a forced landing to a wooded area. A postimpact fire ensued, and the airplane was destroyed.

Postaccident examination revealed that the engine-driven fuel pump drive shaft had fractured. No other anomalies were found. Further examination of the pump revealed internal corrosion and smeared material on the ends of the pump rotor vanes. The internal bypass spring was missing, but wear marks indicated that the spring had been in place sometime during the life of the pump. The investigation could not determine whether the spring had been removed or was destroyed and consumed internally. Heat discoloration observed on the rotor shaft was consistent with frictional heating of the shaft.

Disassembly of the engine-driven fuel pump revealed that the ends of the rotor vanes that interfaced with the pump sidewalls showed evidence of smeared material, transfer marks, and other oxidized particles, which were consistent with ferrous wear debris. Such contamination of the internal pump components likely resulted in increased friction, frictional heating, and the eventual seizure of the pump, which led to the total loss of engine power during the accident flight. The investigation was unable to determine the source of the contamination based on available evidence.

The engine driven fuel pump was subject to a Mandatory Service Bulletin. The service bulletin introduced pump design enhancements to improve relief valve housing sealing characteristics. These enhancements included actions to ensure that valve cover screws are tightened to correct torque values. The materials examination of the pump showed the gaskets were consistent with unmodified original components indicating the accident fuel pump had not been modified in accordance with the service bulletin. Had the service bulletin been complied with a visual inspection would have revealed gasket protrusion observed between the valve and the pump housing. This would have led to maintenance or replacement of the pump.

Maintenance records were destroyed in the airplane when the accident occurred and hence were not available to substantiate if the service bulletin had been complied with.

Text from the NTSB. Open the NTSB docket for CEN20LA263 for the full record.