Incident Overview
On Monday, 5 July 2021, a pilot and a passenger aboard a Sling 2 aircraft, registration ZU-WCG, departed on a private flight from Mossel Bay Airport (FAMO) in the Western Cape province, with Port Elizabeth Airport (FAPE) in the Eastern Cape province as the intended destination. While flying at 1500 feet over the Tsitsikamma area, the engine began to run roughly. The pilot climbed to 3000 feet and reduced engine power, deciding to continue the flight.
Approximately 60 nautical miles from FAPE, both occupants detected a burning smell, which they suspected originated from the electrical wiring. Shortly thereafter, both alternator warning lights (lane “A” and “B”) illuminated on the instrument panel. After assessing the terrain and available landing options, the pilot shut down the engine and glided the aircraft to Seaview Airfield (FAEW), which was within gliding range. An uneventful landing was performed, and the aircraft sustained no damage. Both occupants were uninjured.
Findings
Following the incident, an aircraft maintenance engineer inspected the aircraft and determined that the “A” lane regulator had failed. This failure led to a secondary fault in the engine control unit, which subsequently damaged the “B” lane engine control unit.
After replacing the “A” and “B” lane regulators and the fuse box, a ground run of the engine was conducted. The engine met all required parameters for normal performance. The aircraft was then flown back to FAPE without further incident.
Probable Cause
The rough-running engine was caused by the “A” lane regulator that had failed, which led to a secondary fault in the engine control unit, resulting in the damage of the “B” lane engine control unit.