At the start of the war, aircraft were used solely for observation. Over time though each side’s aeroplanes began to shoot at each other, trying to prevent aerial observation of their ground forces. On the Western Front the Germans gained an early advantage when they deployed the Fokker Eindecker. This monoplane had a machine-gun synchronised with the engine, meaning that it could fire directly forward through the propeller blades. This gave the Fokker a considerable advantage over British and French aircraft.
But now the Fokker’s dominance is coming to an end. The Allies have better aeroplanes deployed, ones that can successfully challenge the Eindecker. One is the British F.E. 2 is a “pusher”, with the engine at the rear. This allows a gunner to fire forward without having to worry about shooting off his own propeller blades. Pushers have limited performance compared to aeroplanes with propellers at the front, but the F.E. 2 is still able to give the Eindecker a run for its money. What really cooks the Fokker’s goose however is the French Nieuport 11. This has the engine at the front and gets around the propeller problem by having the gun mounted to fire over the blades. In speed and manoeuvrability it outclasses the Fokker Eindecker in all respects. The Nieuport is deployed in increasing numbers by both French and British air forces.
And now a new British aeroplane arrives on the Western Front, the Sopwith 1 1/2 Strutter. Like the Eindecker, this aeroplane has a forward firing gun synchronised with the engine to avoid shooting the propeller blades. This two-seater has a second gun firing from the rear cockpit.
The Eindecker’s ace card was its forward firing gun. Now that Allied planes have similar capabilities its limitations are revealed. Control of the skies begins to revert to the British and French.
Fokker Eindecker (Wikipedia)
Repica Nieuport 11 (Old Rhinebeck Aerodrome)
Replica Sopwith 1 1/2 Strutter (Wikipedia)
See also airwar19141918, a live blog of the British war in the air.