What is the condition under which fuel transfer is not allowed?

Fuel transfer is not allowed during takeoff due to safety considerations that prioritize aircraft stability and performance. During takeoff, the aircraft is at a critical phase where optimal thrust and balance are essential for a successful lift-off. Any alteration in the fuel distribution within the wings, which occurs during fuel transfer, can affect the aircraft's weight and center of gravity.

It’s important to maintain a consistent fuel load to ensure that the aircraft performs as expected. Additionally, transferring fuel while the aircraft is accelerating can introduce risks such as fuel system malfunctions or disruptions that could impede engine performance. Therefore, to mitigate these risks and ensure the safety of the flight, fuel transfer operations are strictly prohibited during takeoff.