How a multicopter moves
This is truly where a multicopter shines. A traditional helicopter is not symmetrical from every angle; therefore, as it flies sideways, the tail wants to swing to the rear and the nose points in the direction of the flight. The wind pushes the tail just like a weather vane. The pilot must counter this by yawing in the same direction of flight, or stability can become an issue. Multicopters are symmetrical from every direction. Therefore, moving sideways has the same feel as forward flight to the pilot.
Just like a traditional helicopter, a multicopter moves forward/backward and from side to side by tilting. Tilting the multicopter changes the direction of the thrust provided by the rotors. For example, by dipping the nose and raising the tail, the direction in which the air flow is pushed is not only down, but also to the rear of the multicopter. If every action has an equal and opposite reaction, pushing air to the rear of the multicopter pushes the multicopter forward. To make one side dip, the speed of the propellers is reduced, and to raise another side, the speed of the motors on that side is increased. The following diagram shows how directional flight is achieved:
It all seems rather simple, right? Increasing and decreasing the speed of each motor provides movement in any direction. The direction is only dependent on the combination of motors that are increased or decreased. There are less moving parts in a multicopter than in a traditional helicopter. The movement in one direction has the same feel as in any direction because the aerodynamics are symmetrical.
So, why do traditional helicopters exist at all? The reason is that the electronics and components of a multicopter have only recently (after the year 2000) begun to be practical and small enough to really make them work. Imagine controlling the speed of each motor independently to control your multicopter by feel. It would be impossible without the help of some very sophisticated electronics. This brings us to the next section.
