What happened
On 16 February 2014, an Oliver TF-51, registration ZU-NCB, was conducting a scheduled test flight from Wonderboom Aerodrome (FAWB). The flight was intended to be a short circuit, departing from and returning to the same airfield. During the takeoff roll, just after the aircraft rotated, the pilot observed a high oil temperature warning on the electronic flight instrument system (EFIS).
As the pilot attempted to redirect the aircraft to Runway 24 because the remaining runway on Runway 11 was insufficient for a landing, the engine began emitting black smoke from the left exhaust stack. This was immediately followed by a total loss of engine power. Given the low altitude, the pilot executed a forced landing on the grass area to the left of Runway 11. The aircraft struck the ground with a high sink rate, causing the main landing gear to collapse and the propeller to sustain damage. The pilot escaped the incident without injury.
The investigation
SACAA AIID investigators examined the aircraft's engine and electronic control units (ECU) following the accident. The aircraft was powered by a recently installed General Motors LS 376 engine utilizing a dual Dicktator ECU system for redundancy. Previous ground testing had shown the engine performing well, though a secondary ECU had previously required replacement due to an over-voltage protection fault.
Post-accident inspections of the engine and both ECU units revealed no detectable malfunctions, and subsequent ground runs were completed without issue. Investigators also considered the possibility of fuel gasculation, but ruled this out based on the aircraft's successful flight history with a similar fuel configuration. A potential theory explored was the loss of a timing signal from the crank angle sensor due to engine vibration, which could have triggered a transient shutdown of the ECU.
Findings
- The pilot was properly licensed and medically fit for the flight.
- The aircraft was operating under a valid Authority to Fly and was considered airworthy.
- The primary cause of the accident was an undetermined engine failure.
- The high sink rate during the forced landing contributed to the landing gear collapse and subsequent damage to the fuselage and propeller.