NTSB Identification: ERA10LA187
14 CFR Part 91: General Aviation
Accident occurred Wednesday, March 24, 2010 in Moore, SC
Probable Cause Approval Date: 04/12/2011
Aircraft: CESSNA 152, registration: N93441
Injuries: 2 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 local instructional flight had departed from the airport about 30 minutes prior to the accident. After completing several aerial maneuvers, including slow flight and power-off stalls, the student pilot had begun a recovery from another power-off stall. When he applied throttle, the engine immediately began to run rough. The certificated flight instructor decided to perform a forced landing in a farm field. During the landing roll, the nosewheel came in contact with the soft soil and the airplane nosed over. A postaccident examination of the engine by a Federal Aviation Administration inspector revealed that the bottom sparkplug and associated helicoil on the No. 4 cylinder had separated from the cylinder. After new sparkplug and helicoil was installed in the engine, it ran normally.

The airplane's engine maintenance logbook showed that four days prior to the accident, the bottom sparkplug and helicoil had been replaced on the No. 4 cylinder due to a bad helicoil. The mechanic had installed a standard helicoil contrary to the engine manufacturer's recommendation to install oversize helicoil spark plug inserts.

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

The certificated mechanic's improper installation of a helicoil, which resulted in the separation of a sparkplug and the helicoil and led to a partial loss of engine power.

Full narrative available

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