When fighter planes were first developed the pilots flew around the skies at about 100kmph and attempted to fire hand pistols at each other and even tried dangling grappling hooks from their planes like weird aerial fisherman (circa 1914). It was pretty clear that in order to fight effectively in the air they needed mounted machine guns.
They tried a couple of options, one was having a guy in the back with a swivel gun (Millennium Falcon style) and the other was wing mounted guns. The former option was ineffective because of the difficulty coordinating the shooting and the flying, the latter was a problem because it was hard to aim and if the guns jammed (which they often did) the pilot couldn’t climb out onto the wing and fix it. What they needed was a central forward facing machine gun, but there was a problem – that is where the propeller is.
The Allieds were the first to place a machine gun right in the middle of the plane aimed directly at their own propeller. However, using a cunning engineering trick they turned the rotational motion of the engine into the lateral motion of pulling the gun’s trigger (fig1), this meant they could synchronize the gun fire perfectly so each bullet would fly between the propeller blades. Yes you heard me correctly, the bullets would be timed exactly to fly between the propeller blades that are going so fast the human eye cannot distinguish the blades and just sees a fuzzy circle. Unfortunately, the Allied’s first used a gun that would often hangfire (delays between the pulling of the trigger and the firing of the bullet). This meant that often the bullets would hit the spinning propeller, but don’t worry the Allies were an industrious bunch and just attached shielding to the blades (this happened so often that it is said that the designers relied more on probability than engineering to ensure that most of the bullets missed the propellers). So yes, the pilots who are sitting 3 feet from the propeller are firing bullets straight at the only thing keeping them from crashing into the ground and bullets are hitting the propellers and ricocheting off if all sorts of random directions.
The first plane of this kind ever in combat shot down two (maybe 3) of the central powers’ planes and then the strain of the propellers and crankshaft (caused by the pilot shooting his own propellers) caused the plane to fail and crash land in Germany. Here the design was copied and perfected (although the Germans were already trying to design their own). The Germans then designed the plane the Fokker! The Fokker used a more reliable gun and so the bullets were always timed perfectly to fly between the blades, this led the Germans to have air supremacy for 6 months in what was called the Fokker Scourge of 1915 (those damn Fokkers!). The Allieds came back with their own perfectly timed plane which used more reliable hydraulics and the rest, as they say, is history.
Tristan Wadsworth