What happened
During a power-back maneuver from a terminal gate, ground personnel were utilized in accordance with standard procedures. A ground signal person and two wing walkers assisted the operation. After reverse thrust was applied and the aircraft began rolling backward, the signal person observed crossing ground traffic, specifically another aircraft.
Upon seeing the potential conflict, the signal person communicated an emergency stop signal to the pilot. When the captain acknowledged the signal, he immediately transitioned to using the brakes. This sudden deceleration caused a flight attendant to be thrown against the corner of a cart located in the galley, resulting in injury.
The investigation
The investigation focused on the adherence to power-back procedures and the mechanics of the emergency stop. Standard protocol dictates that the aircraft should be stopped during both normal and emergency situations by a signal for straight-ahead movement. Under these procedures, the captain is required to stop the plane by quietly disengaging reverse thrust and applying forward thrust.
Crucially, the use of brakes is prohibited while the aircraft is moving backward. The investigation revealed that the signal person had initially used the forward signal but then crossed his wands for a normal braking stop during the emergency stop sequence.
Findings
The primary finding relates to the deviation from standard operating procedures regarding the method of stopping the aircraft. The flight attendant sustained injuries due to the abrupt application of brakes during backward motion. The procedure explicitly forbids brake usage while the aircraft is rolling in reverse, requiring instead a transition to forward thrust for stopping.
The signal person's actions involved crossing wands for a normal stop after initially signaling for straight-ahead movement, which contributed to the confusion and the subsequent braking action that violated the no-brake rule during backward movement.