What happened
On August 30, 2014, a Robin DR40MAN-120, registration F-BUPO, departed from Poitiers aerodrome for a local flight as part of an aerial rally. The aircraft was occupied by a pilot and a passenger. During the climb, the engine began to lose power. While the pilot maintained maximum power, the aircraft failed to maintain altitude at approximately 1,300 to 1,500 feet. The pilot attempted a turn, but the engine ceased to deliver power entirely.
Due to the pilot's limited flight experience, the more experienced passenger took control of the aircraft to perform an emergency landing in a field. During the landing roll, the aircraft struck a ditch and encountered heavy vegetation, resulting in heavy damage to the airframe. There were no fatalities or injuries.
The investigation
The investigation focused on the Lycoming O-235-K2B engine to determine the cause of the power loss. Investigators discovered a solidified deposit throughout the entire engine lubrication system. This deposit had clogged the oil suction strainer and caused significant friction, making the movement of internal engine components difficult or even impossible. Some moving parts were so heavily coated that they could not be disassembled.
Chemical analysis of the deposit revealed the presence of isocyanates, compounds commonly found in polyurethanes, adhesives, and certain paints, but not in standard lubricating oils. While the maintenance workshop used products containing isocyanates (such as polyurethane paint hardeners), the workshop manager stated that oil is stored separately from painting supplies. The investigation also considered the possibility of external interference, but the aero club president noted no history of malicious acts against the club.