What happened
During a takeoff for a mission involving a retardant drop, the aircraft experienced a significant event immediately after the landing gear was retracted. An explosion was observed originating from the left engine, which was followed by a steep left roll and a descent into the ground. Before the flight, the captain had provided a takeoff briefing and initially intended to operate the aircraft, though he later instructed the co-pilot to take command of the takeoff. The co-pilot did not perform a separate briefing.
As the aircraft began its initial climb, the captain reported a fire on the left side of the aircraft. The co-pilot noted that he was applying full right aileron to compensate. During the emergency, the crew did not follow company standard operating procedures regarding the jettisoning of the retardant load, nor did they verbally perform the engine fire emergency checklist. As the flight progressed, the airspeed dropped below the minimum speed required for effective control, leading to an increased roll rate and the eventual impact with the terrain.
Findings
Investigation into the engine failure revealed that the 11th stage compressor disc in the left engine failed due to fatigue. This failure caused a catastrophic breakdown of the compressor section and triggered the engine fire. Metallurgical analysis of the fracture showed multiple origin points located at small scratches on the disk's surface finish. These scratches were too minute to be detected using the company's approved inspection methods. While the inspection program itself was found to be compliant with FAA standards, the failure of the component led to the loss of the aircraft. There were no issues found with the remaining engines or the airframe that would have prevented normal flight.