Before an aircraft takes off, it is necessary to ensure that the various weights on board are well distributed. This is called the aircraft balance. It is a dedicated department within the airlines that is in charge of the calculations. It prepares a document called “weight and balance estimate” for each flight. It is up to the captain to validate it. This distribution has consequences on the behavior of the aircraft and therefore on the safety of the flight. This is the reason why cabin crew cannot always accede to your request if you wish to change seats in an aircraft that is not full. They will tell you that “the centering is done”. By complying, you are contributing to the safety of the flight.
The principle of centering is simple. If you take a pen and balance it on one finger of your hand, you have determined the pen’s center of gravity. “For an airplane it’s the same thing,” explains this captain. There is a center of gravity on which the forces are applied. This center of gravity depends on the distribution of the loads”. The center of gravity of an aircraft can be, depending on the case, a little more forward or a little more backward while remaining within the limits set by the manufacturer.
In the case of a forward C of G, the aircraft will be extremely stable but not very maneuverable. In the opposite case, the aircraft will be more maneuverable but also more unstable, all things considered. The aft C of G is preferred because it consumes less fuel.