Tractor configuration

An aircraft constructed with a tractor configuration has the engine mounted with the airscrew in front of it so that the aircraft is "pulled" through the air, as opposed to the pusher configuration, in which the airscrew is behind and propels the aircraft forward. Through common usage, the word "propeller" has come to mean any airscrew, whether it actually propels or pulls the plane.

In the early years of powered aviation both tractor and pusher designs were common. However, by the midpoint of the First World War, interest in pushers declined and the tractor configuration dominated. Today, propeller-driven aircraft are assumed to be tractors unless it is stated otherwise.

As early as 1910, in the early years of flying, a distinction was made between a propeller ("pushes the machine", akin to a ship's propeller) and a tractor-[air]screw ("pulls the machine through the air"). The Royal Flying Corps called the tractors "Bleriot type" after Louis Bleriot to distinguish them from pushers, or "Farman type".

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.

...
Wikipedia