What is a condition for the system to switch pressure controllers?

The condition for the system to switch pressure controllers is that it occurs 3 minutes after landing. This time frame is critical because, upon landing, the aircraft needs to stabilize its systems and return to a normal operating environment. The switch in pressure controllers ensures that the aircraft transitions from flight operations to ground operations safely and efficiently.

The timing allows for proper stabilization of the aircraft's systems, enabling crew and equipment to manage cabin pressure and ensure passenger comfort without the complications that may arise immediately after landing. This transition is essential as ground pressure management may differ significantly from that in flight due to changes in altitude and environmental pressures.

Other scenarios listed, such as after takeoff, during fuel transfer, or when the APU door is closed, do not provide the necessary conditions for switching pressure controllers, as they either relate to different operational phases or involve equipment states that do not align with the requirements for a safe and effective transition.