Probable cause
The inadequate installation of the threaded insert in the No. 2 cylinder spark plug hole by maintenance personnel, which resulted in a loss of engine power during initial climb.
NTSB analysis
The student pilot conducted two takeoffs and landings without incident. During initial climb after the third takeoff, he heard a loud “pop,” and the airplane started to vibrate severely and lose engine power. He executed a forced landing to a nearby field. The airplane landed hard and nosed over during the landing roll. The examination of the airplane revealed that the lower spark plug from the No. 2 cylinder and its associated threaded insert were missing. The threads in the top portion of the spark plug hole were stripped, and only the bottom three threads remained. No other engine anomalies were observed. The engine maintenance logbook indicated that, 7 days prior to the accident, the Nos. 1 and 2 cylinders had new threaded inserts installed in the lower spark plug holes.
Text from the NTSB. Open the NTSB docket for CEN12LA077 for the full record.
Event
- Date
- Nov 22, 2011
- Type
- Accident
- Place
- Princeton, Minnesota
- Nearest airport
- Princeton Municipal Airport (PNM)
- Highest injury
- None
- Weather
- Visual (VMC)
- Light
- Day
Cessna 152
- N-number
- N6436P
- Category
- Airplane
- 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.