In flight, with fuel MODE SEL in AUTO, what condition must occur for the center tank pumps to run?

The center tank pumps on the A320 are designed to operate under specific conditions to maintain fuel efficiency and safety. When the fuel MODE SEL is set to AUTO, the center tank pumps will run only if the slats are retracted. This condition is mandated to ensure that the fuel is properly balanced and to prevent the potential for fuel starvation or imbalance that could occur when slats are deployed.

When the slats are extended, the aircraft is typically in a configuration that requires more aerodynamic lift at lower speeds, such as during approach or landing phases. In this scenario, the risk of imbalance increases if the center tank were to feed fuel, as fuel transfer could change the aircraft's center of gravity and impact handling characteristics.

Therefore, for the center tank pumps to operate while in AUTO mode, the aircraft's flight condition must be such that slats remain retracted, allowing for stable fuel management while optimizing performance and safety during flight. This ensures the aircraft remains within operational limits during various phases of flight.