What happened
During a cargo flight approaching runway 20 at Concord Regional Airport, North Carolina, the pilot reported that the engine began losing power while the aircraft was at approximately 2,000 feet and five miles from the runway. In an attempt to restore engine power, the pilot transitioned fuel selection from the left main tank to the right main tank. Although power was briefly regained, it subsequently decreased to 1,000 rpm. The pilot then switched from the right main tank to the auxiliary tip tanks, but no increase in engine power was observed.
The pilot notified the Concord Regional Airport tower that the aircraft was going down. The Cessna (type not specified in source) collided with a rock quarry located approximately one mile from the approach end of runway 20. There were no fatalities reported in the source text.
The investigation
Post-accident examination of the aircraft showed that the engine had been displaced aft. Investigators focused on a fuel pump, model RG17980D/M, serial number B-4766-3402. This unit had undergone a field repair during its service life and was originally shipped new prior to 1989. The investigation found no records of manufacturer overhauls, upgrades, or preventive maintenance for the unit.
Detailed examination of the fuel pump revealed severe wear at the rotor interface with the drive coupling, as well as worn rubber seal material on the rubber journal and severe wear to the rotor seal. The inside diameter of the rotor seal was found to be severely oversized, which compromised the sealing capability at the pumps drive end. Testing confirmed extensive leakage at this location.