What happened
On 1 June 2025, a pilot operating a Micro Wings Cubby, registration ZU-DMU, departed Leppan Airfield in the Western Cape for a flight to Knysna Highway Airfield. The flight was being conducted under visual meteorological conditions as a private operation. Approximately 15 minutes after takeoff, while cruising at 1,500 feet, the pilot experienced engine spluttering. Despite attempts to troubleshoot by increasing power and activating the secondary electric fuel pump, the engine ceased functioning.
Seeking an emergency landing site, the pilot identified a cultivated field near Karatara. As the aircraft approached the site, the pilot encountered furrows in the field running perpendicular to the landing direction. During the touchdown, the main landing gear collapsed, causing the aircraft to nose over and come to rest in an inverted position. The aircraft sustained substantial damage to its wings, propeller, empennage, and landing gear, though the pilot escaped without injury.
The investigation
SACAA AIID investigators examined the aircraft's fuel system and engine configuration. The Micro Wings Cubby is equipped with two wing tanks that feed a triangular header tank via gravity. The engine, a Rotax 912 UL, had been modified with an aftermarket turbocharger. Post-accident inspections of the engine were successful, with a ground run demonstrating that the engine met all normal operating parameters.
Investigators were unable to determine the exact amount of fuel remaining at the time of the accident because the fuel had leaked from the tanks while the aircraft was inverted. However, based on the pilot's initial fuel endurance of 90 minutes, it was estimated that between 30 and 40 liters of fuel were on board at the time of the engine failure.
Findings
- The engine stoppage was likely caused by a disruption in the fuel supply to the engine.
- A potential contributing factor was the formation of a fuel vapor lock within the lines connecting the main tanks to the header tank.
- The investigation noted that the pilot's manual prohibits excessive maneuvers when fuel levels are below 30 liters; such maneuvers may have caused inconsistent fuel flow from the main tanks to the header tank, which was already at a low level.
- Environmental factors, specifically a relative humidity of 65%, were noted during the occurrence.