What happened
During the engine start sequence of a Saab 340, a ground crew member disconnected the ground power unit (GPU) before receiving the required signal from the flight crew. This premature disconnection caused the left engine to lose power to the starter and begin decelerating while fuel was still being supplied. The resulting accumulation of fuel in the combustion chamber led to a tailpipe fire, characterized by visible flames and smoke.
In an attempt to manage the interrupted start, the captain initiated a motoring procedure to purge the engine. However, the marshaller, observing the flames and smoke, misinterpreted the situation and used non-standard hand signals to alert the crew. These signals caused the captain to cease the motoring process, which prevented the fire from being extinguished. As interstage turbine temperatures continued to rise and ground crew signals persisted, the captain eventually ordered an emergency evacuation. During the egress, two passengers sustained minor injuries.
The investigation
The investigation examined the sequence of events leading to the fire and the effectiveness of the emergency response. It was found that the ground crew member disconnected the GPU because they were preoccupied with preparing another aircraft for departure.
Investigators also looked into the communication between the flight deck and ground staff. Because direct radio communication was unavailable at the location, the crew relied on hand signals. The marshaller used a 'cut-throat' gesture and mouthed words rather than the standardized fire signal. Furthermore, the investigation reviewed the crew's decision-making, noting that the captain did not coordinate the response with the first officer and did not initially use the public address system to command the evacuation.
Findings
- A ground crew member disconnected the GPU without authorization, causing an interrupted engine start and the subsequent tailpipe fire.
- The use of non-standard hand signals by the marshaller increased the risk of miscommunication.
- The captain's decision to stop motoring the engine in response to the signals prevented the fire from being extinguished.
- The captain did not communicate the intent to evacuate to the first officer, which limited the crew's ability to manage the situation collectively.
- The evacuation was delayed because the flight attendant did not immediately recognize the chime signal, and passengers in the emergency exit row did not utilize all available exits.
- The delay in notifying air traffic control resulted in a two-minute delay in the arrival of emergency services.