What happened
On 16 June 2006, a Dragonfly MK3, registration ZU-DYF, was conducting a ferry flight from Virginia Aerodrome to East London. The pilot, flying solo, had departed with the intention of avoiding the Durban Terminal Control Area by routing towards Cato Ridge. While climbing to 550 and 500ft AMSL at an indicated airspeed of 145kt, the aircraft's engine suffered a sudden failure.
As the engine failed, oil and cooling fluid began leaking from the engine onto the cockpit windshield, significantly obscuring the pilot's view. The pilot declared a mayday, which was heard by a nearby South African Airways crew. Attempting an emergency landing in a harvested sugar cane field in the Sawoti area, the aircraft struck a hill with the right-hand main landing gear and wingtip. The momentum carried the aircraft into a second hill, resulting in the total destruction of the aircraft. The pilot sustained serious injuries and was airlifted to a hospital in Durban.
The investigation
SACAA AIID investigators examined the wreckage and the engine, a Subaru EA82. The investigation focused on the mechanical cause of the engine failure and the circumstances of the landing. Metallurgical analysis was performed on the engine components to determine why the failure occurred. The investigation also looked into the pilot's authorization to operate this specific aircraft type and the maintenance history of the engine.
Findings
- The primary cause of the engine failure was a con-rod failure resulting from the incorrect fitment of a shim at the big-end bearing.
- The failure of this shim led to excessive wear and eventual seizure of the assembly, which caused the connecting rod to fracture and penetrate the engine crankcase.
- The leakage of oil and coolant onto the windshield acted as a contributing factor by impairing the pilot's vision, which led to a high approach speed during the forced landing.
- The pilot was a highly experienced professional but was not specifically type-rated for this non-type-certificated aircraft at the time of the accident.
- No flight plan had been submitted for the flight, and there was no documented evidence in the SACAA files confirming the pilot had received specific authorization to fly this type, despite verbal claims of a letter from the authority.