On June 20, 1994, a Mooney M20J (registration N201NK) operated by Harry Kilpatrick was involved in an aviation accident near Big Bear, CA. Investigators recorded the probable cause as: A loose oil slinger ring in the magneto permitted crankcase oil to enter the electrical portion, causing spark plug misfire, a rich mixture, and smoke, which led to engine power loss. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 8 related events involving the same aircraft type or operator are linked below.
After takeoff, a pilot experienced a loss of engine power and ditched into a lake. Investigation revealed a loose oil slinger ring in the magneto allowed crankcase oil to enter the electrical portion, leading to spark plug misfire and smoke.
Accident Summary
Shortly after takeoff, the pilot experienced a loss of engine power and subsequently ditched the aircraft into a lake located off the departure end of the runway. Witnesses on the ground reported hearing the engine missing and observed smoke emanating from the cowling area.
Investigation Findings
A review of aircraft maintenance records showed that the magneto had been replaced with an overhauled unit approximately two months prior to the accident. Examination of the magneto revealed that the oil slinger ring was loose. This condition allowed lubricating oil from the crankcase to enter the electrical portion of the magneto. Consequently, the spark plugs failed to fire properly, resulting in a rich fuel-air mixture and the production of smoke. The loss of engine power necessitated the ditching.
Probable cause
A loose oil slinger ring in the magneto permitted crankcase oil to enter the electrical portion, causing spark plug misfire, a rich mixture, and smoke, which led to engine power loss.