History of Flight
On March 24, 2010, at about 1115 eastern daylight time, a Cessna 152, registration N93441, experienced a partial loss of engine power and subsequently made a forced landing in a field near Moore, South Carolina. The aircraft was substantially damaged during the landing roll when the nose wheel encountered soft soil, causing the airplane to nosed over and come to rest inverted. The certified flight instructor (CFI) and student pilot were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which had departed from Spartanburg Downtown Memorial Airport (SPA) at about 1045. The flight was conducted under 14 CFR Part 91.
The pilots had been performing maneuvers at 3,000 feet above mean sea level (msl) and began a descent to 2,500 feet msl using carburetor heat. According to the student pilot's written statement, after performing several maneuvers including slow flight and three approach-to-landing stalls, the engine made unusual noises and minor vibrations. The engine subsequently began running roughly, and the CFI decided to execute a forced landing in an open farm field. During the final approach, the CFI shut off the fuel valve but did not shut down the engine in case additional power was needed at touchdown.
Personnel Information
The CFI held a commercial pilot certificate with ratings for airplane single-engine land, multi-engine land, and instrument airplane, as well as a flight instructor certificate with ratings for single-engine and instrument airplane. Her most recent FAA second-class medical certificate was issued on April 1, 2008, at which time she reported 25,000 total hours of flight experience.
The student pilot held a third-class medical certificate issued on October 12, 2009, which also served as a student pilot certificate. She had accumulated 35 total hours of flight experience, all in the accident aircraft make and model.
Aircraft Information
The airplane was a 1982 Cessna 152, two-place, all-metal, high-wing, single-engine cantilever monoplane with fixed tricycle landing gear. It was powered by a Lycoming O-235-L2C engine. The most recent 100-hour inspection was completed on January 21, 2010, at which time the aircraft had 6,337.4 total hours time in service. A maintenance logbook entry dated March 20, 2010, indicated that a sparkplug in the No. 4 cylinder bottom position was fouled and the helicoil in the sparkplug hole was bad. The helicoil was replaced, a new sparkplug was installed and torqued, and the engine was run and flight tested, with the results reported as satisfactory.
Meteorological Information
The 1115 recorded weather observation at SPA, located approximately 5 miles northeast of the accident site, included wind from 030 degrees at 6 knots, clear skies, visibility 10 miles, temperature 18°C, dew point 11°C, and an altimeter setting of 30.10 inches of mercury.
Wreckage and Impact Information
The airplane came to rest inverted in an open plowed field approximately 5 miles from the intended destination airport. The wings, fuselage, and tail section sustained impact damage. According to the FAA investigator who arrived on scene, the airplane was righted, and a considerable amount of fuel was drained from the wing tanks; no contaminants were found. The engine cowling was removed, revealing that the No. 4 cylinder bottom sparkplug and helicoil had become unthreaded from the cylinder and were found hanging next to the engine, suspended from the sparkplug wire.
On March 25, 2010, the FAA inspector reported that a new sparkplug was inserted into the cylinder and the engine started and ran normally.
Additional Information
In a written statement, the mechanic who performed the earlier maintenance reported that he had replaced the helicoil on the No. 4 cylinder because it had come out with the plug. He stated that the helicoil had been cross-threaded and the plug was completely fouled. He also noted that the CFI had reported that the engine began to run rough after the student pilot applied full throttle abruptly. During a telephone interview, the mechanic stated that a standard-size helicoil was used.
In a follow-up interview with the CFI, it was confirmed that the student pilot had been instructed to apply power slowly on several occasions. However, after practicing power-off stalls, the student pilot became nervous and applied power very quickly. Immediately after that, the engine began to run roughly.
Textron-Lycoming Service Instruction 1043A, dated September 19, 1969, titled "Spark Plug Heli-Coil Insert Replacement," states in part that standard-size inserts have been found in holes with badly damaged threads that had not been repaired by retapping. The instruction does not recommend standard-size Heli-Coil inserts for replacement in spark plug holes and urges repair facilities to stock only 0.010-inch oversize Heli-Coil spark plug inserts.