What happened
While preparing an aircraft for flight, a flight attendant was ejected from the service door onto the tarmac, resulting in serious injuries. At the time of the event, the aircraft was being cooled by an external diesel-powered air conditioning cart. This specific equipment pressurizes the cabin whenever the aircraft doors are closed. Because the auxiliary power unit was inoperative, the use of this external cart was necessary.
The captain had briefed the flight attendant both before boarding and again within the cockpit to ensure one door remained open. However, the captain did not explain that the air conditioning cart would cause the cabin to pressurize if all doors were closed. After passenger boarding was finished, the flight attendant approached the cockpit, where the captain instructed her to close both the main cabin door and the service door.
The flight attendant closed the service door and then moved across the galley to close the main cabin door. Immediately following this, the captain experienced a rise in ear pressure and shouted for the door to be opened. As the flight attendant attempted to open the service door using the assist handle, the door unlatched and opened with significant force, ejecting her onto the ground.
Findings
Investigation of the ground operations revealed that while flight crewmembers and ramp operators are trained regarding the risks of cabin pressurization when an air conditioning cart is connected, flight attendants do not receive specific training regarding the operation or warnings associated with the external air conditioning cart.
The aircraft was equipped with two warning placards intended to instruct personnel to keep a door open while the air conditioning cart is in use: one located on the overhead console in the cockpit and another positioned on the fuselage skin directly above the external air conditioning cart connection point.