Four numbers

Four motor speeds

Now the drone climbs, flies forward, slides sideways and turns, one after another. Watch the panel at the top right. Only the four motor numbers change. All four harder: up. Front and back different: forward. Left and right different: sideways. Opposite corners different: turn.

Why?A helicopter needs a complicated machine that changes the tilt of its blades as they spin. A drone’s blades are fixed, and only the motor speeds change. With so few moving parts, drones can be small and cheap.

Go furtherThe catch is that all four speeds have to be set exactly right, all the time. No person could do that by hand. The last chapter shows who does it.