What happened
On the morning of 22 July 2022, a pilot operating a Sling 2 aircraft, registration ZU-FCT, departed from Brits Aerodrome (FABS) for a private flight. The intended route was to return to Wonderboom Aerodrome (FAWB) via Klipvoor Dam. After performing several touch-and-go landings at FABS, the pilot prepared for the return leg.
During the climb, the aircraft reached 1,500 feet before leveling off at a cruising speed of 90 knots. While flying over Klipvoor Dam, the engine suddenly lost power. Despite the pilot following emergency procedures and switching fuel tanks, the engine could not be restarted. The pilot declared a Mayday and performed an emergency landing in an open field in the Pretoria General Flying area. During the impact, the main landing gear separated from the aircraft and the nose gear strut broke. The aircraft sustained substantial damage, but the pilot escaped without injury.
The investigation
SACAA AIID investigators examined the wreckage and the engine components. While the airframe appeared structurally sound, the propeller showed a broken blade near the root, which was consistent with an engine operating at very low power during the landing.
Data downloaded from the Engine Control Unit (ECU) revealed a drop in exhaust gas temperatures for cylinders 1 and 3. Subsequent testing of the fuel injectors by a specialized agent confirmed that the nozzles for these cylinders exhibited an irregular spray pattern due to dirt build-up. Further inspection of the fuel system revealed that the left-wing fuel tank's coarse filter contained metal particles and fragments of aerospace sealant. These contaminants were also found in the fine fuel filter and the fuel pressure regulator housing, where they had obstructed the fuel flow to the injectors.