What happened
On 28 August 2010, a private flight departed from Mossel Bay aerodrome (FAMO) in the Western Cape. Shortly after takeoff, while the aircraft was at approximately 1200ft AGL, the engine began losing power. The pilot attempted to restore engine performance by manipulating the fuel pump and valves, but these efforts were unsuccessful.
Seeking a safe place to land, the pilot identified a patch of burnt-out ground on a nearby farm, roughly 3NM east of the aerodrome. To avoid high-tension power lines crossing the field, the pilot attempted to fly underneath the wires. However, due to the upward slope of the terrain, the Cubby impacted the ground and was destroyed. Both the pilot and the passenger sustained serious injuries, though the impact was considered survivable as the cabin remained relatively intact and both occupants were properly restrained.
The investigation
SACAA AIID investigators examined the wreckage of ZU-FAV and reviewed the aircraft's maintenance and construction history. The investigation revealed that the aircraft was a newly built machine, constructed by its owner.
Technical inspections of the fuel system identified a significant deviation from the standard design. Unlike a standard Cubby, which utilizes a forward-facing vent tube to pressurize the tanks and ensure a consistent fuel feed, this aircraft featured a small 2mm vent hole located on the fuel caps. Furthermore, the investigation found no records of fuel flow tests conducted in a flight configuration, nor any verification of the engine's maximum fuel demand prior to the flight.
Findings
- The engine power loss was caused by fuel starvation.
- The non-standard fuel venting system failed to properly pressurize the tanks, leading to a reduced fuel supply to the engine.
- The pilot was experienced and flying with a valid license.
- The aircraft was within its weight limitations at the time of departure.
- The forced landing was unsuccessful due to the upward slope of the landing site.