When should the main fuel tanks be used for takeoff and landings?

The main fuel tanks should be used for takeoff and landings at all times regardless of fuel level primarily due to safety and operational considerations. Main fuel tanks are specifically designed to provide optimal fuel flow and distribution, especially during critical phases of flight like takeoff and landing.

Using the main fuel tanks ensures that fuel is maintained in a position that helps prevent fuel starvation to the engines, which is vital for maintaining engine performance and reducing the risk of engine failure. Additionally, main tanks typically incorporate better design features for fuel management that can cope with changes in aircraft attitude and maneuvers encountered during takeoff and landing.

While auxiliary tanks can be beneficial for extended range or increased fuel capacity, they should not be relied upon during critical phases when consistent fuel supply is paramount. This practice aligns with standard operating procedures which prioritize safety and reliability in flight operations.