What happened
On 13 January 2008, a CESSNA TU2 .206G aircraft, registration G-BYIC, was performing its second scheduled parachute jump flight of the day, departing from the Santa Cilia aerodrome. Approximately 12 minutes into the flight, while cruising at 2,500 ft, the pilot and passengers heard a loud noise and observed the windshield becoming obscured by oil. The engine power dropped immediately before the engine ceased functioning.
Recognizing the imminent engine failure and the inability to return to the airport, the pilot notified the aerodrome and instructed the parachutists to bail out. Following the jump, the pilot attempted an emergency landing in a muddy area west of Abay, near Jaca. During the landing, the nose gear detached, causing the aircraft to rest on its propeller blades and engine cowl. While the pilot and three passengers escaped without injury, two passengers who landed in rough, rocky terrain sustained serious injuries.
The investigation
The investigation focused on the mechanical failure of the TELEDYNE Continental Motors TSIO 520M7 engine. Investigators examined the wreckage, including a broken connecting rod and pin from the no. 4 cylinder, which had been ejected through a hole in the crankcase.
Technical analysis of the engine components revealed that the crankshaft main bearings and connecting rod bearings showed signs of warping and material loss, consistent with extreme temperatures and a lack of lubrication. The investigation also examined the engine's maintenance history and the configuration of the engine baffles. It was noted that the left-side engine baffles were improperly adjusted, leading to air leaks and insufficient cooling on the left side of the engine.
Findings
- The engine failure was caused by the fracture of the no. 4 connecting rod.
- The fracture resulted from inadequate lubrication of the connecting rod bearings, which led to overheating.
- The lack of lubrication was likely caused by the oil flowing through the system at temperatures exceeding normal operating limits.
- Improperly adjusted engine baffles on the left side of the engine prevented effective cooling of the cylinders.
- The engine's lubrication system was functional enough to reach the rocker arms, suggesting the issue was related to oil temperature rather than a total loss of oil pressure.