Are airliners being refuelled only from one side of the aircraft, namely the right wing? If so, do pilots transfer fuel from one tank to another on the ground as part of their pre-flight preparation?
Is it true that a heavy aircraft, fully loaded with cargo, passengers, baggage; centre tank full with fuel but empty wing tanks, could snap its wings upon take off?
A plane can be refuelled on either the left or right tank. Again, it depends on the type of plane – some can be refuelled on the right side only. Even if both sides of the plane can uplift fuel, the right side is preferred as the fuel truck would not interfere with the boarding or disembarkation of passengers that is usually from the left side.
Fuel transfer from the right to the left tank is done automatically by the refueller, not the pilot.
In flight, any fuel in the centre tank must be used first and this is followed by the wing tanks. Additionally, there are limitations to be followed to prevent fuel imbalance as it may cause some control problems if one wing is heavier than the other.
Based on your scenario – a plane with full load with centre tank also full and wings tanks empty - would the wings snap upon take off?
I believe such a case would not arise as most planes are designed to have the wing tanks supplying the engines during the take-off and not from the centre tank. As such, the wing tanks are never empty.
For instance, a typical commercial plane with centre tank would manage its fuel consumption is this manner. The centre tank initially feed the engines, a short while later (about 3 minutes after engine start) the centre tank fuel pumps stop and the left and right fuel pumps of the wing tanks will turn on, feeding the number 1 and 2 engines. After take-off with the slat or flaps retracting, the centre tank will again feed the engines until the tanks run dry; then the left and right pumps of the wing tanks wll again turn on and feed their respective engines.
The wing of a plane is incredibly strong – see video below – and nobody has ever tried taking off with empty wing tanks to prove your point.
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