What happened
On 26 June 2008, a pilot operating an Extra Flugzeugbau 300, registration ZU-EXT, was performing aerobatic training maneuvers within the Syferfontein Aerobatic Area. During the maneuvers, the pilot experienced a sudden loss of authority in the right rudder pedal, leading to the suspicion that the rudder cable had failed.
To ensure safety, the pilot elected to return to Rand Aerodrome, a licensed facility with available emergency services. After communicating the mechanical issue to Air Traffic Control, the pilot joined the circuit for Runway 1lar. While the pilot initially managed to maintain the runway heading using the left rudder and braking, the aircraft suddenly yawed left at approximately 40 knots. This caused the aircraft to veer off the runway and undergo a ground loop. The impact resulted in the right main landing gear strut severing from the fuselage, causing the right wing and two propeller blades to strike the ground. There were no injuries to the pilot.
The investigation
SACAA AIID investigators examined the wreckage and the aircraft's maintenance history. The investigation focused on the mechanical failure of the rudder control system. A Scanning Electron Microscope (SEM) examination of the failed cable revealed that the strands had undergone extensive scuffing in the area of the fairlead, where the cable passes through the fuselage. This scuffing had weakened the cable strands until they could no longer withstand operational forces.
Records showed the aircraft had recently been transported to Dubai for an aerobatic championship and reassembled in South Africa. While the aircraft's maintenance was within the required intervals—with the last annual inspection occurring roughly 28 hours prior to the accident—investigators noted that the cable was visible during both pre-flight and maintenance inspections. The investigation highlighted that the wear was not detected prior to the failure.
Findings
- The primary cause of the loss of directional control was the failure of the right rudder cable.
- The failure was driven by progressive scuffing of the cable strands at the fairlead area.
- The investigation concluded that the failure could likely have been prevented through more diligent visual inspections during pre-flight or maintenance checks.
- The pilot was fully qualified and the aircraft was being maintained according to the approved schedule.