Final answer:
The antiskid system becomes operational when the aircraft's wheels have spun up to a certain speed after landing, indicating that the plane is on the ground and moving, if the system is armed.
Step-by-step explanation:
The antiskid system becomes operational when the aircraft's wheels have spun up to a certain speed after touchdown, which indicates that the plane is on the ground and moving. This speed threshold is usually set by the system's design, based on factors like the type of aircraft and expected landing speeds. Once the wheels spin up and exceed this speed, the antiskid system, if armed, will actively modulate the brake pressure to prevent the wheels from locking up during braking, which could lead to a skid. This system is critical for maintaining directional control and stopping performance, especially under wet or icy runway conditions.