An aircraft with three wings: this counts primary aerodynamic surfaces, but not the tail. Most aviation histories note the triplane as a footnote or a curiosity, due to its relatively short heyday around WWI. The idea for the triplane was born in the experimental department of the Sopwith during their search for a highly maneuverable fighter aircraft with a superior field of vision.
The original Sopwith triplane featured very short wings, with the middle (and longest) set flush with the top of the fuselage. The lower and upper sets were slightly shorter in span, and blocked as little of the pilot's view as possible. Because they had both small wingspan and short chord length, they gave the pilot a great vision advantage over biplanes, and the third wing surface made up for the small size of all of them, as compared to biplanes. The short chord meant that a small change of incidence resulted in a comparatively larger change in lift, which allowed a smaller fuselage; the short wingspan gave it relatively small drag during rolls.
The best measure of its success as an English warplane was in the sudden profusion of German and Austrian triplanes produced after its first appearance in combat. Innovative designers such as Fokker realized its brilliance right away, and WWI's skies were full of six-winged birds for the rest of the war. Progress, in its ineluctable way, caused an arms race of wings, and quadruplanes were born soon after, but with little marginal increase in performance. The redundancy of the extra wings was nice if you were damaged, but once engine technology advanced to the point where the cockpit needed to be closed, monoplanes came back into vogue for good.
Notable triplanes include:
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