What happened
On January 27, 2003, a Mooney M20-J, registration EC-EXK, was conducting a dual-instruction flight departing from Sabadell Airport. Approximately ten minutes into the flight, while climbing from 5,500 to 6,000 feet at 2,600 rpm, the crew experienced an engine malfunction. The pilot noted an unusual noise and observed engine revolutions exceeding 3,000 rpm, suggesting a propeller overspeed condition. Although the crew attempted to manage the power and propeller pitch, the engine continued to operate erratically for approximately three minutes before smoke emerged from the cowling and the engine failed completely.
The instructor performed an emergency landing in the municipality of Mollet del Vallés. Both occupants, the instructor and the student, were uninjured and were able to evacuate the aircraft on their own.
The investigation
The investigation focused on the mechanical failure of the Lycoming IO-360-A3B6D engine. Post-incident inspection revealed that the engine had seized and exhibited cracks in both upper halves of the crankcase. Significant internal damage was found, including numerous metal fragments from broken internal components.
Investigators examined the oil levels and found only about half a liter of oil remaining, a substantial drop from the standard 6-liter capacity. Analysis of the connecting rod-to-crankshaft contact surfaces for cylinders 3 and 4 showed evidence of dry friction at extremely high temperatures. While the oil pump appeared functional and the oil filter, drain plugs, and radiator components were in good condition, the investigation could not definitively pinpoint the exact origin of the oil loss or the initial component failure.
Findings
- The engine suffered a catastrophic failure characterized by internal component breakage and subsequent seizure.
- Evidence of high-temperature dry friction was present on the bearing surfaces of the third and fourth cylinders.
- The engine experienced a significant loss of oil during the flight, though the specific source of the leak (such as a failure in the oil filter area) could not be confirmed as all external components appeared intact.
- The aircraft's airworthiness certificate was valid at the time of the occurrence.