aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' include fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air aircraft such as h ...

, a tractor configuration is a propeller-driven fixed-wing

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

with its

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ge ...

mounted with the

propeller A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working flu ...

in front, so that the aircraft is "pulled" through the air. This is the usual configuration; the pusher 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 the early years of powered aviation both tractor and pusher designs were common. However, by the midpoint of the

First World War World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

, interest in pushers declined and the tractor configuration dominated. Today, propeller-driven aircraft are assumed to be tractors unless stated otherwise.

Origins

The first successful airplanes to have a "tractor" configuration were the 1907 Santos-Dumont Demoiselle and Blériot VII. The first biplane airplane to have a "tractor" configuration was the Goupy No.2 (first flight on 11 March 1909) designed by Mario Calderara and financed by Ambroise Goupy at the French firm Blériot Aéronautique. It was the fastest airplane when it was made. At that time a distinction was made between a propeller ("pushes the machine", akin to a ship's propeller) and a tractor- ircrew ("pulls the machine through the air"). The

Royal Flying Corps The Royal Flying Corps (RFC) was the air arm of the British Army before and during the First World War until it merged with the Royal Naval Air Service on 1 April 1918 to form the Royal Air Force. During the early part of the war, the RFC sup ...

called the tractors "Bleriot type" after Louis Bleriot, and pushers " Farman type".

Firing guns through the propeller

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 (

rifle A rifle is a long gun, long-barreled firearm designed for accurate shooting and higher stopping power, with a gun barrel, barrel that has a helical or spiralling pattern of grooves (rifling) cut into the bore wall. In keeping with their focus o ...

s 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 A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While ...

so that the bullets passed over the propeller arc. The first system to fire through the propeller was developed by French engineer Eugene Gilbert for Morane-Saulnier, and involved fitting strong metal "deflector wedges" to the propeller blades of a Morane-Saulnier L

monoplane A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple wings. A monoplane has inherently the highest efficiency and lowest drag of any wing con ...

, 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 French

aviator An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are also considered aviators because they a ...

Roland Garros and was also used on at least one Sopwith Tabloid of the

Royal Naval Air Service The Royal Naval Air Service (RNAS) was the air arm of the Royal Navy, under the direction of the Admiralty (United Kingdom), Admiralty's Air Department, and existed formally from 1 July 1914 to 1 April 1918, when it was merged with the British ...

. A better solution was a ''gun synchronizer'', which utilized a

synchronization gear A synchronization gear (also known as a gun synchronizer or interrupter gear) was a device enabling a single-engine tractor configuration aircraft to fire its forward-firing armament through the arc of its spinning Propeller (aeronautics), propel ...

to shoot only at instants when the line of fire was unobstructed, developed by aircraft pioneer

Anthony Fokker Anton Herman Gerard "Anthony" Fokker (6 April 1890 – 23 December 1939) was a Dutch aviation pioneer, aviation entrepreneur, aircraft designer, and aircraft manufacturer. He produced fighter aircraft in Germany during the First World War such ...

and fitted to the Fokker E.I monoplane in 1915. The first British "tractor" designed to be fitted with synchronization gear was the

Sopwith 1½ Strutter The Sopwith Strutter is a British single- or two-seat Multirole combat aircraft, multi-role biplane aircraft of the First World War.Lake 2002, p. 40. It was the first British two-seat tractor configuration, tractor fighter and the first Briti ...

. which entered service in early 1916. 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 French

SPAD S.XII The SPAD S.XII or SPAD 12 was a French single-seat biplane fighter aircraft of the First World War developed from the successful SPAD VII by Louis Béchereau, chief designer of the Société Pour L'Aviation et ses Dérivés (SPAD). Development ...

– or mounting guns in the wings, as was used from the early 1930s until propeller engines were superseded in the jet age.

References

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Origins

Firing guns through the propeller

References

See also