Aviation fuel is an important aspect, as it accounts to the aircraft’s performance during lift or take-off and also contributes to the additional weight of the aircraft that changes throughout the flight course of an aircraft. For these reasons, it is essential to pay attention to the storage of the fuel in the aircraft. Since history, fuels tanks have been installed in various regions of the aircraft body to attain maximum efficiency; Nose, Main body, Wings etc.

Fuel is stored in 3 tanks, however, contrary to popular belief, the 737–800 has 5 tanks. They are:

Fuel is stored in the wings of aircraft for primarily 3 reasons

1. Fuel acts as a counter stress for the wings shortly after takeoff when the great stress of the aircraft’s mass acts on them. This prevents a large change in the wingdihedral angle. This effect is so great on the Boeing 747, that if only the centre tank was filled (leaving the wing tanks empty) and the plane would take off, the wings would simply snap. Due to this reason, fuel is first consumed from the center tank and then the wing tanks. Conversely, during refueling, the wing tanks are filled initially and then the centre tanks.

2. Keeps the centre of gravity more or less in the desired position. If the tanks are at the nose or tail of the aircraft, there will be a large change of momentum as fuel is filled or consumed. Longitudinal center of gravity is vital for an aircraft’s stability, and any large change in its position is not conducive for flying.

3. The weight of the fuel provides rigidity to the wing, thereby reducing wing flutter. Flutter is the vibration of the wings due to the airflow. Large flutter is so hazardous that it can even result in total collapse of the wings. The following video explains how flutter acts on aircraft and other structures.

Quoted