NTSB Identification: CEN12LA077
14 CFR Part 91: General Aviation
Accident occurred Tuesday, November 22, 2011 in Princeton, MN
Probable Cause Approval Date: 05/15/2012
Aircraft: CESSNA 152, registration: N6436P
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.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

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.

Full narrative available

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