Probable cause
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.
NTSB analysis
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.
Text from the NTSB. Open the NTSB docket for CEN15LA279 for the full record.
Event
- Date
- Jun 21, 2015
- Type
- Accident
- Place
- Sheboygan, Wisconsin
- Nearest airport
- Sheboygan County Mem (KSBM)
- Highest injury
- None
- Weather
- Instrument (IMC)
- Light
- Day
Mooney M20K
- N-number
- N1168Z
- Category
- Airplane
- Year built
- 1982
- Damage
- Substantial
- Operating rule
- Part 91 (general aviation)
- Purpose of flight
- Personal
From the NTSB aviation accident database: N-registered aircraft, events since 2008, data through Oct 28, 2026. The file is published monthly, so the latest weeks are incomplete and recent records can change. The official source is the NTSB aviation investigation search. CheckAero is independent and not affiliated with the NTSB.