Interrupter gear

The interrupter gear was a triggering device attached to a machine gun so that it would fire only at certain times. This allowed machine guns to be mounted directly infront of the pilot of a fighter aircraft , firing through the propeller . The interrupter guaranteed that the gun would only fire when thepropeller was not in the way.

The French pilot RolandGarros had fitted nose mounted guns to his planes in 1915 , simply by placing a metalwedge on the propeller to deflect the bullets. After a particularly bad month in which German aircraft were being shot down withincreasing numbers, his plane was forced down in German territory in April 1915 and the mystery was revealed.

Heinrich Lübbe , anengineer working for Anthony Fokker , felt Garros' solution wasparticularly poor, and set about inventing a better one. His solution was a cam attached tothe propeller shaft that pressed on a long rod running to the trigger of the guns. The cam was set such that the propeller washorizontal when it pushed on the rod, and the rod in turn pressed the trigger to fire a bullet. The trigger the pilot operatedpulled the rod into position over the cam.

The system was immediately fitted to the Fokker E.I design, first flying in July and leadingto the Fokker Scourge . The system was soon copied by all airforces.