What happened
On 11 September 2022, a Stampe SV-4C aircraft, registration ZU-SVF, was performing circuit exercises at Krugersdorp Aerodrome in Gauteng under visual meteorological conditions. The flight, operated under Part 94 regulations, carried a pilot and one passenger. After taking off from Runway 26 and climbing to 6,300 feet, the engine ceased operation while the aircraft was executing a turn onto the right base leg.
Following the engine failure, the pilot attempted several restarts but was unable to restore power. This necessitated an emergency forced landing on the side of a mountain, approximately 1.36 kilometres north of the Krugersdorp Runway 26 threshold. Although the aircraft sustained substantial damage, there were 0 fatalities and no injuries to the occupants.
The investigation
SACAA AIID investigators examined the wreckage and the engine components. While the engine itself remained intact and attached to its cradle, examination of the wooden propeller indicated that no power was being delivered at the time of impact. Mechanical inspections confirmed that the magnetos, ignition harnesses, spark plugs, and fuel pumps were all in good working order, and fuel was present in the lines.
However, investigators identified a failure in the Ellison throttle body system. A Tygon plastic air hose, which is responsible for supplying pressurized air to move the diaphragm and regulate fuel metering, was found to be damaged. This damage interrupted the fuel supply to the carburettor, leading to the engine stoppage.