The company announced that the winglets fitted to a Gulfstream II reduced fuel consumption in the cruise phase by over 10%. The Spiroid winglet, a design currently under development by Aviation Partners, is a closed wing surface mounted at the end of a conventional wing. Julian Wolkovitch continued to develop the idea in the 1980s, claiming it was an efficient structural arrangement in which the horizontal tail provided structural support for the wing as well as acting as a stabilizing surface. Later proposals for closed-wing designs included the Convair Model 49 Advanced Aerial Fire Support System (AAFSS) and the 1980s Lockheed "Ring Wing" concept. ![]() The aircraft proved dangerously unstable despite the development and testing of several prototypes, and the design was abandoned. Postwar ĭuring the 1950s, the French company SNECMA developed the Coléoptère, a single-person VTOL annular wing aircraft. In 1944, the German designer Ernst Heinkel began working on an annular-wing VTOL multirole single-seater called the Lerche, but the project was soon abandoned. It was followed by a series of monoplanes, the last of the line remaining in use until 1914. Tilghman Richards built and flew several annular-wing aeroplanes in which the fore and aft segments were on the same level. It was able to leave the ground in small hops before being damaged beyond repair.īased on the work of G.J.A. The later Blériot IV replaced the forward annular wing with a biplane and added a canard foreplane to make it a three-surface aircraft. The lifting surfaces comprised two annular wings mounted in tandem. History Pioneer years The Blériot IV replaced the forward one of its predecessor's annular wings with a conventional biplane wingĪn early example of the closed wing was on the Blériot III aircraft, built in 1906 by Louis Blériot and Gabriel Voisin. Various types of closed wing have been described: ![]() The upshot is that although closed systems can produce large induced-drag reductions relative to a conventional planar wing, there is no significant aerodynamic advantage that uniquely accrues to their being closed rather than open. This is the key to explaining how the C-wing produces nearly the same induced-drag reduction as the corresponding fully closed system, as discussed below. This is because, regardless of what the circulation distribution is to start with, a constant circulation can be added to the closed-loop portion without changing the total lift of the system or the induced drag. For any lifting system (or portion of a lifting system) that forms a closed loop as viewed in the freestream flow direction, the optimum lift (or circulation) distribution that yields the minimum induced drag for a given total vertical lift is not unique, but is defined only to within a constant on the closed-loop portion.However, the induced-drag performance of the ideal closed box wing can be approached very closely by open configurations such as the C-wing discussed below. a rectangular box wing with lifting surfaces fully occupying all four boundaries of the allowed rectangular area. For a lifting system constrained to fit within a rectangular box of fixed horizontal (spanwise) and vertical dimensions as viewed in the freestream flow direction, the configuration that provides the absolute minimum induced drag for a given total vertical lift is a closed system, i.e.In addition to potential structural advantages over open cantilevered wings, closed wing surfaces have some unique aerodynamic properties: ![]() A closed wing avoids the need for wingtips and thus might be expected to reduce wingtip drag effects. Wingtip vortices form a major component of wake turbulence and are associated with induced drag, which is a significant contributor to total drag in most regimes. Although the closed wing has no unique claim on such benefits, many closed wing designs do offer structural advantages over a conventional cantilever monoplane.Ĭharacteristics The Spiroid winglet is a closed wing surface attached to the tip of a conventional wing. Like many wingtip devices, the closed wing aims to reduce the wasteful effects associated with wingtip vortices which occur at the tips of conventional wings. Closed wing designs include the annular wing (commonly known as the cylindrical or ring wing), the joined wing, the box wing, and spiroid tip devices. Aircraft wing configuration with a non-planar, continuous surface wingĪ closed wing is a wing that effectively has two main planes which merge at their ends so that there are no conventional wing tips.
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