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FIG. 7. Early Wright Aeroplane. (Propeller Biplane.) (Elevators in Front ; Rudder in Rear.)

discussion, and on an aeroplane of this type Bleriot crossed the Channel in July igog. It was more cleanly designed than the biplane of that date and was regarded as the faster type. It was largely used for trick flying, and figured ever more widely in aeronautical exhibitions. At the outset of the war it had still a reputation for speed, but had found a rival in the better de-

FlG. 73. Early Farman Aeroplane. (Propeller Biplane.) (Elevator in Front; Rudder in Rear.)

FIG. 7b. Early B16riot Aeroplane. (Tractor Monoplane.) (Eleva- tors and Rudder in Rear.)

signed " tractor " biplanes. During the war the monoplane was more largely used by the French and the Germans than by the British. The names most associated with the monoplane are French: Bleriot, Morane, Nieuport. The " Fokker " mono- planes used by the Germans take their name from a Dutch designer probably inspired by the French designs. During the years 1914-8, the biplane was in the ascendant, but the mono- plane was afterwards revived in the form of the aeroplane with thick " cantilever " wings without external bracing. The monoplane appears to be a type convenient in small sizes, but unsuited for the larger aeroplanes.

FIG. 8. Modern Tractor Biplane.

Position of the Airscrew. Airscrews have been described as " tractor " or. " propeller " according as the airscrew shaft is placed in tension or in compression by the thrust, and cor- responding aeroplanes are usually called by the same names. The first biplanes, those of the Wrights and the Farmans, were of the "propeller" type, colloquially "pushers"; almost all monoplanes were " tractors."

In the tractor, monoplane or biplane, the order of disposition of the component parts is generally from front to rear: air- screw, engine, crew; and the body is prolonged to carry stabiliz- ing and controlling surfaces at the rear. In the pusher the order is reversed and the controlling surfaces are carried on an open frame (" outriggers ") in front, at the rear, or in both positions.

On a " pusher " the field of view forward is superior, and great stress was laid upon this by the British War Office after the military trials in 1912. The necessity of aerial fighting was proved in 1914, and the tractor was found unsuitable owing to the obstruction in the most effective direction for firing. Pushers were therefore ordered for fighting, at first carrying pilot and gunner, and later carrying only one man with a machine-gun fixed in the aeroplane. The situation was completely altered by the device of firing through the airscrew- disc. The blades were at first protected by deflector plates, but shortly after mechanism was used to time the fire between them, the inven- tion of Constantinescu, a Rumanian. The aeroplane was directed bodily at the target. The " tractor " then replaced the " pusher " fighting aeroplane; but " propeller " airscrews continued to be used on seaplanes, on aeroplanes for night duty against Zeppelins, and on large twin-engine aeroplanes.