What happens if the cockpit differential pressure exceeds 4.0 psi?

If the cockpit differential pressure exceeds 4.0 psi, a warning is triggered. This warning serves as a critical alert to the pilot, indicating that the cabin pressure has reached a threshold that could compromise safety and comfort, potentially leading to physiological effects or risks of structural integrity within the cockpit.

The design of the aircraft's pressurization system incorporates safety features to monitor the pressure levels consistently. When the pressure exceeds this limit, it indicates an abnormal condition that requires immediate attention.

The other choices do not reflect the specific designed response of the T-6B systems. While the system may engage various safety measures in response to pressure issues, the distinct action that takes place at the 4.0 psi threshold is the activation of a warning system to alert the crew of the concern. Hence, the emphasis is on providing prompt notification to manage the situation effectively before any further action becomes necessary.