What happened
On 24 October 2013, a Yakovlev YAK-18T, registration ZU-FLE, crashed on Ingiwi Farm, approximately 100 meters from the boundary of Stellenbosch Aerodrome. The aircraft, operated by a private owner, was performing a flight test following unscheduled maintenance.
Witnesses at the scene described a harrowing sequence of events. One observer noted that the engine sounded unusually loud and rough during the initial take-off roll. Shortly after becoming airborne, the engine was heard stuttering and cutting out repeatedly. The aircraft entered a steep, high-angle right turn at a very low altitude, with the wings nearly vertical. During this maneuver, the aircraft' and nose pointed toward the ground before impacting a strawberry farm. The impact triggered a fire that trapped the pilot, resulting in one fatality.
The investigation
SACAA AIID investigators examined the maintenance history and the technical state of the aircraft prior to the accident. The investigation established that the aircraft had been brought to a maintenance organization, Stellair CC, specifically to address an engine overheating issue. This overheating had reportedly begun after the pilot attempted to refit a loose magneto himself.
Technical inspections revealed that the maintenance performed to rectify the overheating involved adjustments to the magnetos, engine timing, and carburetor fuel metering settings. While a ground run test had been conducted to verify performance, the investigation focused on the quality of these recent adjustments.
Findings
- The primary cause of the engine failure was improper maintenance practices regarding the installation and adjustment of the magnetos, engine timing, and carburetor fuel metering settings.
- The engine experienced significant performance degradation due to the incorrect combination of these technical settings.
- The engine failure occurred during the critical take-off phase, leaving the pilot with insufficient altitude or airspeed to recover the aircraft.