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Inaviation, atractor configuration is a propeller-driven fixed-wingaircraft with itsengine mounted with thepropeller in front, so that the aircraft is "pulled" through the air. This is the usual configuration; thepusher configuration places the airscrew behind, and "pushes" the aircraft forward. Through common usage, the word "propeller" has come to mean any airscrew, whether it pulls or pushes the aircraft.
In theearly years of powered aviation both tractor and pusher designs were common.[citation needed] However, by the midpoint of theFirst World War, interest in pushers declined and the tractor configuration dominated. Today, propeller-driven aircraft are assumed to be tractors unless stated otherwise.
The first successful airplanes to have a "tractor" configuration were the 1907Santos-Dumont Demoiselle andBlériot VII.
The first biplane airplane to have a "tractor" configuration was theGoupy No.2 (first flight on 11 March 1909) designed byMario Calderara and financed byAmbroise Goupy at the French firmBlériot Aéronautique.[1] It was the fastest airplane when it was made.[2] At that time 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").[3] TheRoyal Flying Corps called the tractors "Bleriot type" afterLouis Bleriot, and pushers "Farman type".
A disadvantage of a single-engine tractor military aircraft was that it was initially impossible to fire a gun through the propeller arc without striking the blades. Early solutions included mounting guns (rifles ormachine guns) to fire around the propeller arc, either at an angle to the side – which made aiming difficult – or on the top wing of abiplane so that the bullets passed over the propeller arc.[citation needed]
The first system to fire through the propeller was developed by French engineerEugene Gilbert forMorane-Saulnier, and involved fitting strong metal "deflector wedges" to the propeller blades of aMorane-Saulnier Lmonoplane, so that bullets fired when a propeller blade obstructed the line of fire were deflected rather than damaging the propeller. It was employed with immediate success by FrenchaviatorRoland Garros and was also used on at least oneSopwith Tabloid of theRoyal Naval Air Service.[citation needed]
A better solution was agun synchronizer, which utilized asynchronization gear to shoot only at instants when the line of fire was unobstructed, developed by aircraft pioneerAnthony Fokker and fitted to theFokker E.I monoplanein 1915. The first British "tractor" designed to be fitted with synchronization gear was theSopwith 1½ Strutter. which entered service in early 1916.[citation needed]
The problem of firing through the propeller's arc was avoided by passing the gun barrel through the propeller's hub or spinner – first used in production military aircraft with the 1917 FrenchSPAD S.XII [citation needed]– or mounting guns in the wings, as was used from the early 1930s until propeller engines were superseded in thejet age.