How do the bullets not hit the propeller?

They developed a synchronization gear, or a gun synchronizer, sometimes rather less accurately referred to as an interrupter, is attached to the armament of a single-engined tractor -type aircraft so it can fire through the arc of its spinning propeller without bullets striking the blades.

Who invented the interrupter gear?

Raymond Saulnier
development of fighter aircraft …in the form of an interrupter gear, or gun-synchronizing device, designed by the French engineer Raymond Saulnier. This regulated a machine gun’s fire so as to enable the bullets to pass between the blades of the spinning propeller.

When was the interrupter gear invented?

1915
Then in 1915, a Dutch engineer named Anthony Fokker changed the world with his revolutionary “Interrupter Gear.” Read on to learn more about this deadly invention: Theo Mayer: An arms race in the sky was inevitable as each side tried to improve the capability, reliability, and the lethality of planes.

How do propellers work?

The propeller works by displacing the air pulling it behind itself (the action), this movement of air then results in the aircraft being pushed forward from the resulting pressure difference (the opposite reaction). The more air that is pulled behind the propeller the more thrust or forward propulsion is generated.

How did they fire machine guns through propellers?

Machine guns were mounted on the top of the fuselage, directly in front of the pilot, but that position placed the gun directly behind the propeller. The gun had to be designed to fire through the propeller without hitting it, which was not an easy task.

How do guns behind propellers work?

There are many different types of synchronization gear, but the simplest involves an irregular-shaped disk that triggers the gun to fire once per revolution, at a specific point. This produces a high rate of fire without the risk of hitting the propeller.