Why do airplanes store fuel in their wings, Why not in the fuselage?
Or is it to take advantage of the extra space of the wings?
All airplanes in service, can store fuel in the belly of the aircraft, in the wings, in the rear tail-plane and/or in the cargo sections (for extending the range).
Now, out of all the fuel storages available, airplanes carry around 70-80% of the fuel on board in its two wings.
While refuelling, the fuel is first filled in the wings and, if required at last, then only the centre tank is filled up.
But what is the main reason behind such fuel arrangement in most airplanes?
The Main and the only reason behind it is providing Wing Bending Relief.
In order to understand it, we must know what happens when the wing generates lift. When the wings are producing lift, the immense force under the wings causes them to bend upwards, specially towards the tips of the wings.
That doesn't mean that the wings will break up in flight. The wings are actually designed to be flexible enough to bear the structural loads in flight (especially G-forces due to gusts, turbulence, and turns), without breaking or discomforting the passengers inside. This is known as Wing Flex.
But as always, there are limits to such flexes. They also put stress on the wing roots while they bear those g-forces.
That is why, fuel is stored in the wings. When the wings are laden with tons of loads of fuel, it provides some sort of relief to the wings, when it comes to wing bending moments.
And the reason for not filling so much of fuel in the body tanks is keeping the fuselage of the airplane as light as possible.
Since the wings are now heavier, and the fuselage is lighter, it will reduce the stress on the wing roots.
And as stated in the question, it also utilizes the extra space in the wings, which would otherwise have gone wasted if not done so. But that's the secondary reason.
Credit: SHRIHARI MANGE
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