What happened
On 27 July 2009, a Micro Wings Tri Cubby, registration ZU-ENF, was conducting a private flight under visual flight rules from Kitty Hawk Aerodrome toward Bapsfontein Aerodrome. While approximately 3 nautical miles outbound from Kitty Hawk, the aircraft experienced a sudden loss of engine power, accompanied by engine surges and smoke emanating from the engine compartment.
The pilot initiated a forced landing in an open field on Ngweni Farm at Tierpoort. During the touchdown, the aircraft encountered uneven terrain featuring rocks and ant hills, which caused the landing gear to collapse. The aircraft skidded approximately 20 meters, resulting in substantial structural damage to the airframe. Both the pilot and the passenger survived the impact with no injuries.
The investigation
An investigation by the SACAA AIID established that the engine failure was triggered by the failure of the propeller reduction drive belt. As the belt failed, it ruptured the flexible pipe for the oil pressure gauge, leading to significant engine oil leakage. The observed smoke was caused by the friction generated between the slipping belt and the pulleys in the presence of leaking oil.
Investigators found that the belt installed on the aircraft was not a manufacturer-supplied part, but rather a third-party component. Furthermore, the investigation revealed that the previous owner, who was not an authorized person to perform such maintenance, had replaced the belt. There was no evidence that the belt had undergone the necessary tension or load testing required by the manufacturer.
Findings
- The primary cause of the loss of power was the failure of the propeller reduction drive belt.
- The belt failure was likely due to incorrect belt tensioning and the use of an incorrect, non-manufacturer-specified belt.
- The rupture of the oil pressure gauge pipe was a direct result of the belt failure.
- The landing gear collapse was caused by the rough, uneven surface of the landing site.
- Maintenance on critical engine components had been performed by an unauthorized individual.
- There was a lack of detailed maintenance procedures available to owners regarding the specific tensioning requirements for this belt type.