The previous lesson provided an overview of the developments in aviation during World War I, mentioning briefly the role played by the Fokker interrupter gear in the growth of aerial combat. This lesson will examine that technology in more detail.
After reviewing this module, you will be able to:
analyze the problems faced by pilots trying to use weapons and machines guns on propeller-driven aircraft;
describe how the interrupter gear works;
explain the significance of the Fokker Interrupter Gear to the growth of aerial combat.
In one of the videos in our lesson on World War I, you observed that initially pilots tried to use pistols, rifles, and even mounted machines guns to attack enemy planes and balloons. Both the pistol and rifle could be fired from the pilot's seat while flying, but often required flying close to, or even parallel with, the enemy to attempt to get an accurate shot on the opposing pilot or his aircraft. It was also difficult to get an accurate shot while flying the aircraft.
Machine guns mounted to the fuselage of the aircraft were more accurate, because the pilot could fly straight at the enemy and fire head-on. However, bullets fired using this method damaged the propeller or could even be redirected back at the pilot by the propeller. Machine guns mounted on the upper wing of the biplanes and triplanes in use at the time seemingly solved the issue of hitting one's own propeller, but they also required the pilot to stand up awkwardly in the cockpit to clear a jammed gun or to reload the machine gun. This meant the pilot had to stop flying the aircraft temporarily to deal with the weapon.
Given the growing uses for airplanes during war--from observation to bombing--it became increasingly important to have the ability to attack and shoot down enemy aircraft.
Roland Garros was a French reconnaissance pilot who developed one solution to the problem in April 1915. He put metal plates on his propellor to shield the prop from the bullets of his machine gun. He successfully shot down three German aircraft using this method in the span of two weeks before being forced to land his damaged plane behind enemy lines during a mission on April 18, 1915. German engineers, including Anton Fokker, studied his design once the plane was captured.
Fokker had been working on an interrupter gear for six months prior to the capture of Garros's plane, and ultimately Fokker's solution was to develop a synchronization gear, also called an interrupter gear.
Anton Fokker first became interested in flight when he observed the Wright brothers' demonstration flights in Europe during 1908. By 1911 he had built his own aircraft and was an accomplished pilot known for flying above his local town of Haarlem, Netherlands. In 1912 he moved to Germany and established his own aircraft company. When World War I broke out, the German government took control of his factory. He designed numerous aircraft for the Imperial German Air Service, including the Fokker Eindecker and the Fokker Dr.1 triplane (that was flown by German ace Manfred von Richthofen, better known as the Red Baron).
Ultimately Fokker's factory produced almost 700 aircraft for Germany during World War I, although with the rapid pace of development during the war of new aircraft, no one side or one aircraft design was able to dominate the air for long. Thus one of his most important and long-lasting contributions to aircraft design ended up being the interrupter gear.
In essence, the interrupter gear developed by Fokker prevents the machine gun from firing when the propeller is directly in front of the weapon. The cam wheel is attached directly to the engine and is also connected to the machine gun through a series of rods, as demonstrated in the video below. The "bump" on the otherwise smooth cam wheel activates the process to fire the weapon so that the bullet is fired only when the propeller is clear of the muzzle of the machine gun.
Fokker's design solved many of the issues noted above, as pilots could simply fly directly at the enemy (making it easier to aim and fire while piloting the aircraft). They were also able to fire the weapon without damaging their own plane using this mechanism. Reloading the gun and clearing a jammed bullet was simplified too since the weapon could be placed right in front of the pilot.
The combination of the interrupter gear technology with the superior design of the Fokker Eindecker aircraft allowed the Imperial German Air Service to gain superiority over British and French aircraft from August 1915 through the spring of 1916. This period was referred to as the 'Fokker Scourge' in the British press and it severely limited both French and British ground and aerial operations on the Western Front at the time.
German pilots Max Immelmann and Oswald Boelcke flew the Eindecker to devastating advantage over French reconnaissance aircraft and their fighter escorts, so much so that Sir Hugh Trenchard in charge of the Royal Flying Corps (British) ordered at least three fighters to escort every reconnaissance aircraft during missions over Germany. Although Immelmann and Boelcke developed the beginnings of aerial combat tactics with the technological advantages they had during this time (this is discussed more in the next lesson on Manfred von Richthofen), they still focused mainly on defending German territory. As a result, no Eindeckers with the interrupter gear were captured for the Allies to learn how Fokker accomplished this feat. Eventually the French Nieuport aircraft helped shift the advantage back to the Allies in the air--although it did not have an interrupter gear, the plane was more maneuverable than the Eindecker.
Anton Fokker's design for an interrupter gear allowed German aircraft to obtain air superiority over the Western Front during the fall of 1915 and into the spring of 1916. The gear enabled pilots to attack other aircraft by safely firing through their own propellers, a design for machines guns that would be used by aircraft designers up through World War II (when they begin to design jet aircraft, negating the need for a propeller).
You may want to check out a video on World War I machines guns produced by the BBC. This can help you picture what was involved to operate a machine gun, and how that would be complicated by the fact pilots were trying to do all of that while also flying the plane.