The gull wing, also known as Polish wing or Puławski wing, is an aircraft wing configuration with a prominent bend in the wing inner section towards the wing root. Its name is derived from the seabirds which it resembles and from the Polish aircraft designer Zygmunt Puławski who started using this design in his planes. Numerous aircraft have incorporated such wings for a diverse range of purposes. The gull wing was commonly used to improve visibility in a high wing arrangement, because such wing could be thinnest by the fuselage, and in theory should limit pilot's view no more than A-pillars of a windscreen in a car body. Gliders were the first aircraft to feature the gull wing, starting with the Weltensegler in 1921; it was not until the record-breaking Fafnir at the end of that decade did the configuration gain popularity. Beyond becoming popular for the next three decades amongst high-performance gliders, various ground-based aircraft and flying boats also adopted various forms of gull wings. It rose to particular prominence in Poland, where the Polish aviation designer Zygmunt Puławski developed a range of fighter aircraft during the late 1920s and early 1930s; in particular, the PZL P.11, which possessed various cutting-edge features for the era in addition to its high-mounted gull wing, has been described as being the most advanced fighter aircraft of its kind in the world upon its introduction. The PZL P.11 served as Poland's primary fighter aircraft during the mid to late 1930s, while its further development, the PZL P.24, served in the air forces of several countries and was a major success of the Polish aircraft industry. Various flying boats, such as the Short Knuckleduster, Dornier Do 26, and PBM Mariner, also adopted the gull wing configuration, primarily as it enabled the engines to be positioned higher above the water. A variant of the standard configuration, the inverted gull wing, has been used on numerous fighters to facilitate the use of shorter landing gear and to provide sufficient ground clearance for their propellers.
Sailplanes The gull wing was first implemented on a glider, specifically the Weltensegler, which performed its maiden flight in 1921. Its wings, which were externally braced, featured swept-back wingtips with negative incidence relative to the remainder of the main-plane. The Weltensegler also used a unique control system, consisting of a various pulleys and springs connected to a single control stick for the pilot, which warped the wing-tips as directed by the pilot. This unorthodox method relied upon the incidence changing with the increase and release of tension, and was also expected to confer increased stability in pitch and roll by automatic changes in wing-tip incidence; however, it gave no direct control over the wing-tips. The flying career of the Weltensegler was very brief, it being destroyed during the 1921 Rhön gliding competition after the wing failed during a sharp spiralling dive at excessive speed, resulting in the death of Willy Leusch, the Weltensegler's company test pilot. Following the Weltensegler's tragic loss, the gull wing was avoided by the majority of aircraft designers for almost a whole decade. During 1930, Alexander Lippisch's record-breaking Fafnir represented a high-profile comeback for the gull wing, which contributed to its resurgence shortly thereafter. Fafnir featured a laterally stabilising dihedral, an uncommon feature for gliders of the era, which spanned roughly 40 percent of the inner wing span. Lippisch had chosen to adopt this configuration for its increased wingtip clearance, as well as the ill-founded belief that it would improve its stability during turns; however, studies have shown that normal gull wing configurations result in significantly less severe and more easily recoverable stalls. Inverted gull wings exhibit the opposite stall behaviour, but both normal and inverted gull wings impede lift-to-drag ratio and climb performance. The performance demonstrated by Fafnir, such as a 220 km (140 mi) flight between the Wasserkuppe and Magdeburg in late August 1930 that established a new world record, quickly encouraged numerous aircraft designers to perform their own investigations into the gull wing. Accordingly, numerous other gliders, as well as other platforms, would soon feature broadly similar wing configurations as well. Having become a trend of the glider industry during the 1930s, the gull wing remained a staple feature amongst high-performance sailplanes through to the 1950s.
Notable gull wing sailplanes
Bowlus Senior Albatross DFS Habicht DFS Kranich DFS Reiher Göppingen Gö 3 Minimoa Lawrence Tech IV "Yankee Doodle" Lippisch Fafnir Ross RS-1 Zanonia Schweyer Rhönsperber Slingsby Kite Weltensegler Ikarus Košava
Seaplanes
The gull wing design found its way into seaplanes by the early 1930s. As engine power increased, so did the need for large propellers that could effectively convert power to thrust. The gull wing allowed designers to ensure adequate propeller tip clearance over the water by placing the engines on the highest point of the wing. The alternative was placing the engine on a pylon. The first flying boat to utilize the gull wing configuration may have been the Short Knuckleduster, which first flew in 1933. The Dornier Do 26, a high-speed airliner and transport platform, of which six aircraft were built, made its first flight during 1938. The configuration was also used on the US Navy's PBM Mariner and P5M Marlin maritime patrol aircraft. The emergence of long range, land-based jets in the 1950s and the subsequent demise of the seaplane prevented widespread use of the gull wing, although it was still used in some post-war designs, like Beriev Be-12 Chaika (the name means 'gull' in Russian). Examples:
Beriev Be-6 Dornier Do 26 Martin P5M Marlin Piaggio P.136 Short Knuckleduster
Landplanes
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