What is the first step to ensure the aircraft is immobilized on the ramp?

The first step to ensure an aircraft is immobilized on the ramp involves installing chocks. Chocks are devices placed against the wheels of the aircraft to prevent it from rolling or moving unintentionally. This is a critical safety measure, as it secures the aircraft in position, especially when it is parked and not actively in use. By placing chocks, ground personnel effectively minimize the risk of accidents or unforeseen movement, providing a stable environment for operations such as passenger boarding, fueling, and maintenance.

In contrast, connecting external power, starting engines, or removing safety barriers are actions that pertain to different operational phases and do not address the immediate need for securing the aircraft. Connecting external power comes into play after the aircraft is stabilized. Starting engines is performed when the aircraft is ready for departure, and removing safety barriers is typically conducted just before the aircraft begins to move or when guided by ground control instructions. Hence, installing chocks is the essential initial action to ensure safe and effective ramp operations.