Tractor Configuration - World War I Military Aviation

World War I Military Aviation

From a military perspective, the problem with single-engine tractor aircraft was that it was not possible to fire a gun through the propeller arc without striking the propeller blades with bullets. Early solutions included mounting guns (rifles or machine guns) to fire around the propeller arc, either at an angle to the side — which made aiming difficult — or on the top wing of a biplane so that the bullets passed over the top of the propeller.

The first system to fire through the propeller was developed by French engineer Eugene Gilbert for Morane-Saulnier and involved fitting metal "deflector wedges" to the propeller blades of a Morane-Saulnier L monoplane. It was employed with immediate success by French aviator Roland Garros and was also used on at least one Sopwith Tabloid of the Royal Naval Air Service.

The final solution was the interrupter gear, more properly known as a gun synchronizer, developed by Fokker and fitted to the Fokker E.I monoplane in 1915. The first British "tractor" to be specifically design to be fitted with synchronization gear was the Sopwith 1½ Strutter which did not enter service until early 1916.

Other solutions to avoiding the propeller arc include passing the gun's barrel through the propeller's spinner (the nose of the aircraft) or mounting guns in the wings. The latter solution was generally used from the early 1930s until the beginning of the jet age.