What happened
On the morning of 12 August 2014, a Sling 2 aircraft, registration ZU-FVW, was conducting a private flight from Port Elizabeth International Aerodrome to Tedderfield. The flight, intended for pilot hour building, proceeded normally until approximately 95 minutes into the journey. While cruising at 950 feet, smoke began emanating from the cockpit instrument panel, accompanied by a burning electrical odor.
As the smoke intensified, the cockpit visibility degraded significantly, and the aircraft's electrical systems—including the transponder and electronic flight instrument system (EFIS)—became inoperative. The pilot attempted to restart the engine after the engine stopped, but was unsuccessful. Seeking a safe area, the pilot executed a forced landing on a private farm in the Cacadu district. During the touchdown, the nose gear collapsed and the propeller struck the ground, resulting in substantial damage to the aircraft's wings, landing gear, and cowling. No injuries were sustained by the pilot or the passenger.
The investigation
SACAA AIID investigators examined the aircraft's Engine Control Unit (ECU) logs, which revealed a series of critical voltage drops immediately preceding the accident. The data showed that the engine sensors failed to default values following three consecutive instances where the electrical voltage dropped below the required 10-volt threshold.
Technical inspection of the charging system identified that a voltage regulator on the fuse box had completely melted. Further examination of the engine's ignition housing revealed that the stator coils had sustained damage from overheating. This heat was traced back to the stator pickups rubbing against the flywheel housing.
Findings
- The primary cause of the engine shutdown was a loss of voltage to the ECU.
- An overvoltage condition occurred due to the melting of insulation on the stator coils.
- The overheating and subsequent electrical failure originated from the stator pickups making physical contact with the flywheel housing.
- The forced landing was unsuccessful in preventing structural damage to the aircraft's nose gear and propeller.