The Sopwith triplane is a British fighter aircraft from the First World War. The first N 500 prototype of this triplane first flew on 28th May 1916. (It is the plane for this cardboard model.) The machine first had 110 hp and later 130 hp and proved to be agile and efficient. (Top speed 187 km/h with 130 hp engine.) For example, it could fly a threefold looping only three minutes after take-off. The lightweight plane (only 500 kg when empty) was so successful and outstanding in action, that as a consequence, the German triplane Fokker DR I was developed as its counterpart. Fokker managed to get hold of a crashed Sopwith and could therefore analyse its construction and imitate it. (See Schreiber Sheet No. 666 of the Fokker DR I.) In spite of the successes, the Sopwith triplane was only in action for a short time. One of the reasons was that the machine was very difficult to repair and the construction was soon considered to be unstable, because the wing construction could collapse under great stress because the bracing wires were too weak.
Two original machines still exist in the Royal Air Force Museum in London and in a Russian museum. In addition, there are numerous reproductions.
One more comment regarding the engine: The Sopwith triplane had a rotary radial engine; that is, the crank shaft was attached to the plane and the whole engine rotated. Why was this strange construction used? Earlier engines struggled a lot with cooling problems. Pipes from the water coolers could become loose or burst. The rotary engine, however, worked with air cooling, because cooling was ensured through the rotation of the engine, even when the engine was running while the plane was standing.