What happened
On April 18, 2014, a Halley Kft. Apollo Fox 912 was climbing through approximately 2,000 feet AGL near St. Hubert, Belgium, when the pilot noticed a sudden drop in engine oil pressure to zero. Shortly after this drop, the engine ceased operation. The pilot attempted to deploy the aircraft's emergency parachute system, but the mechanism failed to activate after two attempts.
With the engine inoperative and the parachute unavailable, the pilot was forced to perform an emergency landing on extremely uneven terrain. During the impact, the nose landing gear collapsed, causing the aircraft to flip over. While the airframe sustained significant damage, the pilot, who was alone on board, exited the aircraft without any injuries.
The investigation
The AAIU(Be) investigation focused on the engine's lubrication system and the recent modifications made to the aircraft. The investigators established that the aircraft had undergone recent unauthorized modifications to its oil and water temperature regulation systems, which were performed by the owners using information found online.
Technical analysis revealed that the modification changed the nature of the oil flow within the system. Previously, the oil cooler hoses operated under suction; however, the new configuration subjected these same hoses to engine oil pressure. The investigation examined the physical state of the connectors and found that the existing design of the oil cooler hose connections was insufficient to withstand this increased pressure. Furthermore, the investigators examined the placement of the emergency parachute handle and found it was positioned behind a structural tube, making it difficult to operate in an emergency.
Findings
- The primary cause of the engine failure was a complete loss of oil pressure caused by a flexible hose disconnecting from an oil cooler connector.
- The modification to the lubrication system inadvertently transitioned the oil cooler lines from a suction-based system to a pressurized system, which the original hardware could not support.
- The emergency parachute system failed to deploy because the activation handle was located in an inadequate and uncomfortable position behind a structural component.
- The aircraft had several modifications that had not been submitted to or reviewed by the Belgian Civil Aviation Authority (BCAA).
- The pilot's experience as a glider pilot likely aided in the successful execution of the forced landing despite the multiple system failures.