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Aviation Accident

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NTSB Identification: CEN15LA279
14 CFR Part 91: General Aviation
Accident occurred Sunday, June 21, 2015 in Sheboygan, WI
Probable Cause Approval Date: 09/24/2015
Aircraft: MOONEY M20K, registration: N1168Z
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

Shortly after takeoff, the pilot advised air traffic control that he was returning to the airport due to low oil pressure. The engine subsequently lost power, and the pilot was forced to land in a wheat field 5 miles south of the airport. During on-site examination of the airplane, no oil was found in the crankcase, and subsequent examination of the engine and turbocharger revealed that the turbocharger was dry. Further examination of the engine revealed evidence of preignition in the No. 5 cylinder that appeared to have been caused by failed spark plugs. The top and sides of the piston head were eroded, which allowed the exhaust gases caused by the preignition to pressurize the crankcase and force engine oil out of the breather tube.


The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
  • Oil starvation due to preignition in the No. 5 cylinder as a result of failed spark plugs; the top and sides of the piston head were eroded, which allowed the exhaust gases caused by the preignition to pressurize the crankcase and force engine oil out of the breather tube.