On October 6, 2000, a Mooney M20K (registration N52202) operated by Marc W. Gordon was involved in an aviation accident near Monroe, WA. Investigators recorded the probable cause as: Oil Pump drive gear shaft separated in shear. A collision with a tree stump during the landing roll was a factor. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During cruise flight, a propeller overspeed prompted a diversion. On final approach, engine power was lost, resulting in a long landing, runway excursion into a swampy area, and collision with a tree stump. Investigation found the oil pump drive gear had separated from its drive shaft due to a shear separation from lateral force.
Event Summary
A pilot reported that while in cruise flight, the propeller experienced a sudden overspeed. The pilot reduced power and turned toward a nearby airport. While on final approach, the engine lost power. The aircraft landed long on the runway and ran off the end into a swampy area. During the landing roll, the aircraft collided with a tree stump.
Post-Accident Inspection
An inspection of the engine found that the oil pump drive gear had separated at its joint with the oil pump drive shaft.
Metallurgical Findings
A metallurgical examination determined that the shaft for the drive gear showed a shear separation as a result of something forced laterally with respect to its longitudinal axis.