Encyclopedia - Interrupter Gear

Photograph of Anton Fokker Improving upon the French invention of the so-called 'deflector gear', which enabled fighter pilots to use machine guns to fire through aircraft propeller blades, Anton Fokker devised the much-improved interrupter gear in 1915.

The key drawback to the French device - championed by French air ace Roland Garros - was that the machine gun would often fire bullets into the aircraft's propeller blades rather than always through them.  Thus the heart of the French device saw the attachment of steel blades to each of the propellers, a mechanism designed merely to avoid the loss of blades during action.

Following the capture of Garros - and, more importantly, his aircraft - behind German lines in April 1915, Fokker set to work upon producing an improved mechanism.  He devised the 'interrupter gear', a timing mechanism whereby the machine gun would only fire through the aircraft propellers, i.e. would cease firing whenever the propeller passed directly in front of the machine gun.  This removed the need for Garros' protective steel plates and proved much safer in practice.  Fokker's new device was unveiled on 1 July 1915 on the EI Eindecker.

Fokker's theories - which had in fact been pre-dated by early French research (among others) in 1914 - were subsequently implemented by each of the warring powers once its efficacy became apparent and such devices (in various modified forms) became standard within each air service.

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A 'Base Rat' was a soldier perpetually at the base, typically in conditions of comfort and safety.

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