Opposite corners, opposite ways

Corners spin in opposite directions

So real drones spin the two propellers on opposite corners clockwise and the other two counterclockwise. But if you simply spin a propeller backward, it pushes air up instead. That is why counterclockwise propellers have blades tilted the other way, like a mirror image. All four still push air down.

Why?Run a fan backward and the wind blows out the back. The way a blade is tilted and the way it spins have to match for air to go down. So drone propellers come in clockwise and counterclockwise versions. Put them on the wrong motors and the drone will not lift off.

Go furtherPropellers are often marked with their direction. Clockwise is written CW, and counterclockwise is CCW.