MONROE, WA, USA
N52202
Mooney M20K
The pilot reported that while in cruise flight, the propeller experienced a sudden overspeed. Power was reduced and the pilot 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 and into a swampy area. During the landing roll, the aircraft collided with a tree stump. Inspection of the engine found that the oil pump drive gear separated at its joint with the oil pump drive shaft. 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.
HISTORY OF FLIGHT On October 5, 2000, about 1840 Pacific daylight time, a Mooney M20K, N52202, registered to Mooneagle Inc. and operated by the private pilot as a 14 CFR Part 91 personal flight, ran off the end of the runway at Monroe, Washington, following a loss of engine power. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft was substantially damaged and the pilot and his two passengers were not injured. The flight departed from Everett, Washington, about 15 minutes prior to the accident. In a written statement to the Monroe Police Department, and subsequent written statement on the NTSB Pilot/Operator Aircraft Accident Report, 6120.1/2, the pilot reported that while en route to Eastsound, Washington, the propeller experienced a sudden overspeed. The pilot reduced engine power, which reduced the propeller speed to the safe range. The pilot then turned toward the Monroe airport for landing. About two miles south of the airport, the engine lost power. The pilot stated that he extended full flaps, the landing gear was down and the speed brakes were out, however, he was unable to "hit target because of initial fear of giving up altitude too early and hitting fairgrounds." The aircraft landed long and overran the runway, coming to rest in a swampy area. During the landing roll, the left wing collided with a tree stump. AIRCRAFT INFORMATION The aircraft was recovered and the engine inspected. During the inspection, it was noted that the crankshaft would turn by hand, however, there was significant friction and "squeaking." The accessory section was opened and the oil pump drive gear was found loose in the bottom of the case. A significant rubbing mark in the case walls was noted. The oil pump drive gear separated at its joint with the oil pump drive shaft. The alternator was also inspected and the shaft was found bent. The alternator was assembled into the housing and it was noted that the rub marks in the case were also from the alternator drive gear due to the bent shaft. It appeared that the loose oil pump drive gear was free to move around which resulted in damage to the alternator drive gear. Due to the lack of oil pressure from the pump, the propeller governor lost oil pressure and the propeller went to full low pitch and the engine rpm increased. The lack of lubrication to the remainder of the engine resulted in internal friction and eventual stoppage. Maintenance records provided by the owner indicated that at the time of the accident the engine had accumulated a total time of approximately 1,563 hours and had never been overhauled. This was also the original oil pump on this engine that had been manufactured in 1988. A review of the records indicated that on June 2, 2000, approximately 105 hours prior to the accident, the engine experienced a loss of engine power. During the maintenance inspection, the alternator driveshaft had sheared, the vacuum pump drive shaft sheared, and the oil scavenge pump drive shaft sheared. (See attached maintenance records.) Personnel at the maintenance facility performing the repairs verified that they did not remove the accessory case, nor did they inspect the oil pump at this time. TESTS AND RESEARCH The accessory case cover, oil pump cover, two gears for the oil pump, and the fractured drive gear were sent to the National Transportation Safety Board Materials Laboratory Division for examination. The metallurgist reported that the shaft for the drive gear showed a shear separation. The metallurgist also reported that it appeared that something had caused the shaft for the gear to be separated (forced) laterally with respect to its longitudinal axis. ADDITIONAL DATA The airframe was released to the Treasurer of Mooneagle Inc. on October 27, 2000. The Accessory case and oil pump components were returned to Mooneagle Inc. by the NTSB Materials Laboratory Division in April 2001.
Oil Pump drive gear shaft separated in shear. A collision with a tree stump during the landing roll was a factor.
Source: NTSB Aviation Accident Database
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