What happened
On the morning of 4 September 2021, a Bantam B22J aircraft, registration ZU-DVG, departed from Numbi Airstrip near Hazyview, Mpumalanga, bound for Da Gama airstrip near White River. The flight was being conducted under visual flight rules for private purposes. While cruising at approximately 800 feet above ground level, roughly 5 nautical miles south of the departure point, the engine began to sputter and eventually ceased operation.
The pilot attempted to locate a suitable site for an emergency landing and identified a ploughed field situated between banana plantations. However, the aircraft lost altitude too rapidly to reach the intended target. During the descent, the aircraft struck several banana trees before coming to a stop. While the passenger escaped without injury, the pilot sustained minor injuries to his back. The aircraft sustained substantial damage during the impact.
The investigation
SACAA AIID examined the engine and fuel systems following the accident. The investigation confirmed that the aircraft was airworthy and had undergone an annual inspection shortly before the flight. Records showed the aircraft had been refueled with 25 litres of Unleaded Octane 95 prior to the flight, with 35 litres remaining at the time of the accident.
Technical analysis of the engine revealed that the electric fuel pump was in good working order. However, the investigation focused on the primary mechanical fuel pump, which the engine relies upon when the electric pump is deactivated. Upon inspection of the engine components, investigators discovered the presence of sludge within the mechanical fuel pump.
Findings
- The engine failure was caused by fuel starvation.
- The primary cause of the fuel starvation was the presence of sludge inside the mechanical fuel pump, which restricted the flow of fuel to the engine.
- While the electric fuel pump was functional, the engine's reliance on the mechanical pump during the flight left it vulnerable to the blockage caused by the sludge.
- The source of the sludge within the mechanical fuel pump could not be determined.