What happened
On May 28, 2012, a Saab 2000, registration YR-SBJ, operated by SC Carpatair SA, was taxiing toward runway 23 at Florence Peretola Airport for a scheduled flight to Timisoara. During the taxi on the Mike taxiway, the flight crew received a left engine fire warning, accompanied by a Master Warning and an EICAS alert.
The commander immediately halted the taxiing and applied the parking brake, following standard operating procedures. After performing the required memory items and emergency checklists, the crew discharged the first fire extinguisher bottle. Although the pilot observed no visible fire or smoke from the cockpit, a radio communication from another aircraft at the airport suggested smoke was present near the left engine.
Following the procedure, the commander decided to evacuate the 45 passengers and 4 crew members. Because the aircraft is not equipped with emergency slides, passengers had to jump from exits at a height of approximately 1.70 meters. While the evacuation was completed in about 40 seconds, the descent caused several injuries, including one passenger who suffered a multi-fragmentary fracture of the lower limb and required hospitalization.
The investigation
The ANSV investigation focused on determining the cause of the fire warning and the subsequent evacuation. Technical inspections of the left engine by the operator's certified technicians found no evidence of fire, overheating, carbon deposits, or burns. The fire detection system, including the sensor wire, was found to be fully functional.
Investigators examined the Maintenance Diagnostic Computer (MDC), which confirmed the fire warning message. While testing the engine fire detection system, technicians identified values outside of tolerance levels. The investigation determined that moisture in the sensor wire connectors was likely responsible for the false activation. Additionally, during the removal of the left engine exhaust nozzle diffuser, technicians discovered a broken weld on a V-band clamp. This defect could have allowed extremely hot air to reach the sensor wire, potentially triggering the warning.
Findings
- The activation of the left engine fire warning was a false alarm; no actual fire or overheating occurred.
- Moisture in the engine fire detection system connectors was a primary factor in the erroneous warning.
- A broken weld on the exhaust nozzle V-band clamp was identified as a potential secondary cause for heat reaching the sensor wire.
- The decision to evacuate was influenced by a radio report from another aircraft regarding smoke, which was likely actually the visible discharge of the fire extinguisher agent.
- The lack of emergency slides on the Saab 2000 necessitated jumping from a significant height, directly leading to passenger injuries.