When a fuel imbalance occurs, which valve closes the motive flow line?

In the context of the T-6B aircraft, when a fuel imbalance occurs, the closing of the motive flow line is managed by the light tank valve. This mechanism is designed to enhance safety and operational efficiency during flight. The light tank, which holds fuel that is critical for maintaining balance during the aircraft's operation, will close to prevent further fuel from being drawn from it when an imbalance is detected.

By shutting off the motive flow from the light tank, the system prevents exacerbating the imbalance and allows for a more stable flight posture. This action ensures that the fuel distribution remains controlled, reducing the risk of fuel starvation or excess load on one wing, which could potentially lead to handling issues or require corrective actions by the pilot.

The importance of this system cannot be overstated, as fuel management is vital for safe flight operations, particularly during maneuvers that may involve varying loads and performance demands.