What happened
On 4 January 2018, an amateur-built NG4 UL SPEEDY, registration EC-XGM, was performing a local VFR flight from the La Axarquía aerodrome in Málaga. Approximately five minutes after takeoff, while climbing through 6,500 ft, the pilot noticed a sudden drop in oil pressure. After leveling off at 3,500 ft, the pilot declared an emergency and attempted to return to the airfield via runway 30.
As the aircraft crossed a nearby highway at approximately 1,000 ft, the engine stopped completely. Due to the low altitude, the pilot executed an emergency landing in an avocado plantation near the runway threshold. During the landing, the left wing struck a tree, causing the aircraft to ground-loop and sustain significant damage. The pilot, who was also the aircraft's builder and owner, exited the aircraft uninjured.
The investigation
The investigation focused on the engine's failure and the subsequent loss of power. Examination of the wreckage revealed that the engine had suffered irreversible damage, including a fracture in the cylinder block. The oil tank was found to be empty, and the oil filter contained metallic particles, indicating severe internal friction.
Investigators analyzed the engine installation and found that the oil return line was connected to a position that resulted in a suboptimal layout. A spacer intended to keep the oil line away from the exhaust manifold had failed due to thermal stress. This allowed the oil line to come into direct contact with the hot exhaust duct, causing the synthetic rubber line to melt and develop a longitudinal crack. This rupture led to a rapid loss of all engine lubrication, causing the engine to seize.
Findings
- The engine stopped because the lack of lubrication caused a connecting rod to break, leading to a total engine seizure.
- The lack of lubrication was caused by a rupture in the oil return line.
- The rupture resulted from the oil line making contact with the exhaust manifold after a spacer failed due to high temperatures.
- The engine installation was improperly designed, as the installer chose a configuration that placed the oil line in close proximity to a heat source without adequate thermal protection.
- The airworthiness certification process failed to identify the risks associated with this specific engine and exhaust layout.