What happened
On September 22, 2020, a private Cessna 208B, registration HK4669G, departed from Guaymaral Airport (SKGY) in Bogotá, Colombia, bound for Flandes, Tolima. The flight was a general aviation operation intended to transport four passengers for personal business.
Shortly after takeoff, while the aircraft was performing a right turn at approximately 200 feet, an explosion occurred in the engine, followed by a significant loss of power. The pilot immediately identified the power loss through engine instruments and initiated emergency procedures. To avoid more serious consequences, the pilot selected an appropriate field for an emergency landing.
During the approach to the landing site, the aircraft's landing gear struck the structure of a house, causing the plane to lose speed. The pilot then performed a controlled landing on the ground, where the aircraft experienced a second impact. This second contact caused the landing gear to detach and the cargo pod to be destroyed as the aircraft slid along the terrain near a residential road. The accident resulted in three minor injuries among the occupants, while two passengers remained uninjured. The aircraft sustained substantial damage.
The investigation
The GRIAA investigation focused on the mechanical failure of the engine, the pilot's emergency response, and maintenance oversight. Investigators examined the Pratt & Whitney PT6A-114A engine and found that the failure was caused by the fracture of three blades on the high-pressure compressor rotor disk (CT compressor). This fracture caused severe downstream damage to the hot section, power section, and exhaust section, as well as damage to the fuel pump and fuel control unit.
Findings
- The primary cause of the accident was an emergency landing on unprepared terrain necessitated by a sudden loss of engine power.
- The engine failure was triggered by the fracture of three high-pressure compressor rotor disk blades.
- The operator had failed to comply with Airworthiness Directive (AD) No. 2014-17-08R1 FAA, which mandated the replacement of these specific compressor blades to prevent material fatigue failures.
- Maintenance processes were deficient, as routine borescope inspections performed by the contracted maintenance provider failed to detect the deteriorating state of the blades, a condition that was not detectable via borescope due to the underlying chemical composition errors in the manufacturing process.
- The operator failed to adequately verify the quality and compliance of the maintenance services provided by the third-party workshop.