In aviation, a multiplane is a fixed-wing aircraft-configuration featuring multiple wing planes. The wing planes may be stacked one above another, or one behind another, or both in combination. Types having a small number of planes have specific names and are not usually described as multiplanes:
While triplane, quadruplane and tandem designs are relatively uncommon, aircraft with more than four sets of wings rarely occur - none have proven successful.
The quadruplane configuration takes the triplane approach a step further, using efficient wings of high aspect ratio and stacking them to allow a compact and light weight design. During the pioneer years of aviation and World War I, a few designers sought these potential benefits for a variety of reasons, mostly with little success.
From ca. 1909 the American inventor Matthew Bacon Sellers II made a series of flights in the Sellers 1909 Quadruplane, progressively fitted with powerplants of decreasing power, in order to investigate low-powered flight. He eventually achieved flight on only 5 to 6 hp at a speed of 20 mph.
Pemberton-Billing Ltd. made two prototype Zeppelin killers, the Pemberton-Billing P.B.29E and Pemberton-Billing P.B.31E, respectively in 1915 and 1917. They were comparatively large, twin-engined fighters. After the company changed its name to Supermarine, the P.B.31E became known as the Supermarine Nighthawk.
Following test flights with the prototype Armstrong Whitworth F.K.9 in 1916, a small number of Armstrong Whitworth F.K.10 quadruplane reconnaissance fighters were produced, but none saw combat action.
The private-venture Wight Quadruplane scout fighter was flown in 1917.
The Euler Vierdecker of 1917 unusually featured a standard triplane arrangement of fixed wings with a fourth uppermost wing comprising left and right hand articulated surfaces which acted as full-span ailerons. Two examples were built, with different engines.