Cessna 172N Emergency Landing at Posadas, Córdoba (EC-EJG)

Incident Overview and Flight Details On Tuesday, October 16, 2001, at approximately 11:30, a Cessna 172N with registration EC-EJG experienced a loss of engine power while operating as a general aviation dual instruction flight. The aircraft had departed from Córdoba Airport with Sevilla Airport as its destination. At the time of the power loss, the aircraft was near the locality of Posadas, Córdoba, at an altitude of about 2,000 feet. The pilot in command, a 40-year-old commercial pilot with 550 total flight hours and 350 hours on type, decided to return to Córdoba Airport and notified the Sevilla Control Center. As the aircraft gradually lost altitude, the pilot assessed that reaching Córdoba Airport was not feasible and initiated an emergency landing. The pilot identified a field free of vegetation, cables, and obstacles and landed there. ## Accident Sequence and Damage During the landing roll, the nose gear struck an irrigation pipe running perpendicular to the direction of landing. This impact caused the nose gear to fold backward, leading to the aircraft overturning. The aircraft came to rest inverted a few meters beyond the point of impact. Both occupants were uninjured. The aircraft sustained significant damage, including a broken nose gear and substantial damage to both wings, the propeller, the vertical stabilizer, and the rudder. ## Investigation Findings An inspection of the engine at the emergency landing site revealed that a spark plug from cylinder number 3 had dislodged from its housing because the helicoil installed in the spark plug housing had detached. The spark plug housing had previously been repaired by inserting a helicoil. During a subsequent routine 50-hour engine inspection, when the spark plug was unscrewed, the helicoil came out with it, indicating a poor fit between the helicoil and the cylinder head. Following the instructions in the Lycoming Overhaul Manual, a new helicoil with a diameter 0.010 inches larger was installed. At the time of this repair, the aircraft had a total of 5,535:35 hours, and at the time of the accident, it had 5,701:50 hours, meaning it had flown 166:15 hours since the second helicoil was installed. ## Probable Cause The repairs to the spark plug housing that detached were performed in accordance with the manufacturer's Overhaul Manual instructions. However, the insertion of the helicoil is a delicate operation that, if performed incorrectly, can damage the cylinder head threads. This condition is sometimes not obvious, making the helicoil appear properly installed when it is not. The detachment of the helicoil and spark plug from cylinder number 3 caused the engine to operate on three cylinders, resulting in a significant loss of power. The detachment of the helicoil was probably caused by its incorrect insertion.