Anthony Fokker - The Interrupter Gear

The Interrupter Gear

Fokker is often credited with having invented the synchronisation device which enabled World War I aircraft to fire through the spinning propeller. His role was certainly significant but there were a number of prior developments before the result was achieved for which Fokker is commonly credited.

The famous French pilot, Roland Garros, was shot down on 18 April 1915. His aircraft had been fitted with a deflector device, whereby metal deflector wedges were fitted to the airscrew. Garros was able to set fire to the airframe before being taken prisoner but the aircraft's gun and the armoured propeller remained intact and came into German hands.

This initiated a phase of consideration of the interrupter gear concept in the Imperial German Army Air Service (Luftstreitkräfte). Fokker was heavily involved in this process but the story of his conception, development and installation of a synchronisation device in a period of 48 hours (first found in an authorised biography of Fokker written in 1929) has been shown to be not factual. The available evidence points to a synchronisation device having been in development with Fokker's company for perhaps six months prior to the capture of Garros' machine.

However the final result of the development was Fokker's pushrod control mechanism, Gestängesteuerung, which allowed the aircraft's forward-firing machine gun to fire only when the propeller was out of the line of fire. As incorporated into the famous Fokker Eindecker, its use directly led to a phase of German air superiority known as the Fokker Scourge.