When does the fuel auto balance system start closing motive flow from the light tank?

The fuel auto balance system in the T-6A is designed to maintain an even distribution of fuel between the left and right fuel tanks. This system is crucial for ensuring optimal aircraft performance and stability.

The system will initiate the closing of the motive flow from the light tank when there is a fuel imbalance of 20 pounds or more for more than 30 seconds. This threshold is significant because a greater imbalance can affect aircraft handling and performance, especially during critical phases of flight. By waiting for a sustained imbalance of this magnitude, the system ensures that it does not react to minor fluctuations that might arise from routine fuel usage or temporary operational conditions.

In contrast, a smaller imbalance, such as one of 10 pounds or even an imbalance when the tanks are full, would not trigger the system to close motive flow, as these situations typically do not pose a risk to the aircraft's stability or require correction. The auto balance system is designed to operate efficiently, only engaging under circumstances where it is necessary to prevent performance degradation due to excessive fuel imbalance.