What must be the status of powered cross-flow and gravity cross-flow systems for takeoff?

For takeoff in the CRJ 900, the powered cross-flow and gravity cross-flow systems must be in the OFF position. This is a critical safety precaution designed to ensure that fuel is managed correctly and to prevent fuel from transferring in a way that could adversely affect the aircraft's balance and performance during critical phases of flight, such as takeoff.

When these systems are OFF, it ensures that fuel is not unintentionally moved between tanks, which could lead to a shift in the aircraft's center of gravity. Maintaining a stable center of gravity is essential for safe takeoff and handling characteristics during flight. Keeping the systems off aligns with standard operational protocols to promote the aircraft's safety and stability.

In contrast, the other statuses (ON, AUTO, and MANUAL) could imply an operation that would allow for unintended fuel movement or management during a pivotal moment of the flight, which is why they are not suitable for use during takeoff. Understanding the appropriate configurations for the aircraft systems is crucial for all pilots to ensure compliance with operational standards and safety protocols.