What happened
On August 29, 2001, a CASA CN-235, registration EC-FBC, was performing a flight in the vicinity of Málaga Airport when an emergency sequence led to a loss of control. During the approach, the crew received a fire warning for the left engine. In accordance with the operator's emergency procedures, the crew executed actions to isolate the engine, which included cutting the fuel supply and activating the fire extinguisher discharge.
However, these actions resulted in the unintended shutdown of the engine. The sudden loss of power and the subsequent aerodynamic changes during the critical phase of flight caused the aircraft to deviate from its intended path. The aircraft ultimately impacted the ground near the airport, resulting in the destruction of the airframe.
The investigation
The CIAIAC investigation focused on the sequence of events in the cockpit and the technical integrity of the engine fire detection system. Investigators examined the flight data recorder (DFDR) and cockpit voice recorder (CVR) to reconstruct the crew's actions and the aircraft's performance. The investigation included a detailed disassembly and inspection of the engines, propellers, and the fuel control units (HMU).
Technical analysis also involved evaluating the ergonomics of the cockpit warnings and the effectiveness of the emergency procedures outlined in the operator's Manual of Flight Operations. The investigators specifically looked into the origin of the fire warning and the physical forces experienced by the aircraft during the impact.
Findings
- The primary cause of the accident was the execution of emergency procedures in response to a false engine fire warning, which led to the unintended shutdown of the left engine.
- The fire warning was triggered by a false indication, likely caused by moisture in the fire detection circuit connectors.
- The maintenance instructions for the fire detection system did not include specific actions to prevent moisture accumulation, despite manufacturer recommendations.
- The crew's decision-making was influenced by a lack of Crew Resource Management (CRM) training, which affected task distribution and cross-checking during the emergency.
- The emergency procedures allowed for significant, drastic actions—such as cutting fuel and discharging extinguishers—to be performed without verbal announcement or confirmation from the other pilot.