What happened
On February 7, 2010, a Fournier RF-4D motor glider, registration I-BPLG, was conducting a VFR flight departing from Massa Cinquale airport. While flying along the coastline at approximately 700 feet, the pilot reduced engine power and began retracting the landing gear. During this maneuver, an abnormal metallic noise was heard, followed by a total engine failure.
After declaring an emergency via radio, the pilot evaluated landing options. To avoid obstacles and protect people on the nearby beach, the pilot opted for a forced landing on the sea. The aircraft successfully performed a water landing in the sea near Poveromo. Due to the shallow depth of the water, the pilot was able to exit the aircraft and reach the shore without injury.
The investigation
The ANSV examined the wreckage and the engine components to determine the sequence of mechanical failures. The investigation focused on the Rectimo 4 AR 1200 engine, which is a modified Volkswagen automotive engine.
Physical examination of the engine revealed significant internal damage. Specifically, in cylinder number 2, the exhaust valve was found to be separated from the head, and the exhaust valve stem had fractured. This failure caused the valve head to move freely within the combustion chamber, obstructing the piston's path. This obstruction led to a bent intake valve stem, a destroyed piston, and a bent connecting rod. The resulting debris entered the area of the camshaft, causing it to fracture in three places and ultimately resulting in the total seizure of the engine.
Findings
- The primary cause of the accident was the fatigue failure of the exhaust valve stem in cylinder number 2.
- The fatigue failure of the valve stem led to the valve head becoming loose, which caused catastrophic internal engine damage and subsequent engine seizure.
- The pilot's decision-making during the emergency was effective, as the choice of landing site prevented injury to bystanders on the beach.
- The engine lacks a specific Illustrated Parts Catalogue (IPC), and maintenance practices rely on generic automotive manuals, which complicates the identification of specific part numbers for components like the damaged valve.