The Triplane Fighter Craze of 1917

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Design is often dominated by the whimsical dictates of fashion. Aircraft design is no less subject to that principle than are clothes, music, architecture or automobiles.

For the brief period of a year, roughly from mid-1917 to mid-1918, the triplane format suddenly came to dominate the world of fighter plane design, particularly in Germany. The triplane would have become a mere footnote in the history books were it not for the fact that one of them, the Fokker Dr.I, became one of the most famous airplanes of World War I.

It is a basic premise that an airplane with one wing is more aerodynamically efficient than an airplane with two. After all, who has ever seen a biplane bird? Nature, however, cannot always be translated into machinery in a straightforward manner. Although many of the earliest aircraft were monoplanes, they were found to possess some very dangerous characteristics. The problems were mainly structural rather than aerodynamic.

A series of fatal accidents involving wing failures in early monoplanes resulted in a ban on them by the British Royal Flying Corps (RFC) in the summer of 1912. One of the world’s first formal aviation-crash inquiries was convened in 1913 to investigate the accidents. Despite the fact that the ‘Monoplane Committee exonerated the configuration, a prejudice against monoplanes persisted for more than 20 years.

Another reason for the distrust of monoplanes as fighters in World War I had to do with pilot visibility from the cockpit. In combat, the fighter pilot who saw his adversary first was usually the victor. Before the advent of radio, pilots needed a clear view of their flight commanders, who communicated with each other visually by means of hand signals and wing-waggling. They also had to be able to see their squadron mates to avoid accidental midair collisions.

The earliest successful fighter planes, the French Morane-Saulnier N and the German Fokker E.I, were monoplanes configured with the cockpit directly over the wing. From that position, the pilot enjoyed unlimited visibility to every quarter except downward, in which direction he could see nothing at all.

In many biplanes the pilot sat with one wing directly below him and another directly overhead, impairing his vision in both directions. A typical example was the British Sopwith Pup. Produced in 1916, the Pup was a beautifully proportioned little biplane that flew as great as it looked. British pilots, however, were less than satisfied with the visibility from its cockpit. Many photographs of Pups show portions of fabric cut away from the upper wing’s center section in an effort to improve the pilot’s view.

In retrospect, it may be said that the Sopwith Pup set a style that persisted for more than 20 years-that of the single-seat tractor biplane with synchronized machine guns firing through the propeller. At the time the Pup first appeared, however, the optimum configuration of a fighter was still in doubt. Today, the primary considerations for a fighter plane are speed, firepower and that newest of criteria, stealth. During World War 1, however, the emphasis was on rate of climb, maneuverability and pilot visibility.

In the spring of 1916, Herbert Smith, the chief designer at Sopwith, began work on a successor to the Pup. He set out to design a plane that could climb faster, fly higher, maneuver as well as if not better than its predecessor and, if possible, afford better visibility than the Pup. Surprisingly, the prototype that emerged from the Sopwith hangar on May 30, 1916, was not a biplane but a triplane.

The triplane configuration was not exactly a new concept that spring. Such pioneer aviators as Glenn Curtiss (founder of Curtiss Aircraft Co.) and AV Roe (founder of Avro, Ltd.) had already built successful triplanes in the United States and Britain, respectively. In Italy, Count Gianni Caproni di Taliedo, founder of Aeroplani Caproni, was producing a series of large, three-engine bombers, including several triplanes. In those earlier aircraft, however, the triplane format was simply a matter of expediency-an attempt to compensate for the low-powered engines of the period by building the greatest possible wing area, and consequently the maximum lift, into a reasonably compact airframe. Because speed was less of a consideration in bombers, the increased lift offered by the triplane format made sense. Herbert Smith, however, was adapting a refinement of the triplane concept to fighters. He sought to balance the advantages of extra lift and optimum maneuverability against the inherent disadvantage of increased drag.

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