What happened
On June 19, 2012, a Beechcraft C9/90A, registration PT-WAH, departed from São Paulo (SBMT) en route to Lavras (SSOL) carrying a crew of two and two passengers. While cruising at FL135, approximately 22 minutes from the destination, the pilot detected unusual noises coming from the left engine accompanied by fluctuating engine parameters on the instrument panel.
In response to the anomaly, the commander executed the procedure to shut down the left engine. The crew then diverted to the nearest suitable airfield, Varginha (SBVG), for a precautionary landing. The aircraft landed safely as a single-engine aircraft, and all four occupants remained uninjured. The aircraft sustained superficial damage limited to the engine.
The investigation
The investigation focused on the mechanical failure of the left engine. Technical examinations were conducted by the Department of Aerospace Science and Technology (DCTA). The analysis revealed that the engine had suffered from a lack of lubrication, which led to overheating in the first-stage gears. This overheating caused the power turbine rotor to dislodge, resulting in blade failure due to overload.
Findings
- The engine failure was caused by a loss of lubricating oil, which escaped into the atmosphere through the oil inlet connection of the radiator.
- Upon inspection of the radiator service door after landing, the connection was found to be loose.
- The lack of lubrication resulted in overheating of the first-stage gears and subsequent blade failure (uncontained engine failure) in the left engine.