Closed wing

With Boxwing (English: box or wing box -wing and wing joint ) a special arrangement for aircraft wings is called. By the use of two superimposed different wing shapes, which are connected together at the bearing ends, results in a very stable flight. In addition to the improved stability of the compact design is an additional argument for the use of the Boxwing - wings.

History

Early as 1906 Louis Blériot and Gabriel Voisin constructed with the Blériot III a biplane in a boxwing - like configuration. The first aerodynamic calculations to have been published in 1924 by Ludwig Prandtl. The first application of Boxwing concept in the form used today dates back to Alexander Lippisch, who designed the early 1930s a corresponding biplane, however, about the pilot phase is not it past. The upper wing was about unswept continuous while the lower was performed negatively swept. The vertical tail surfaces each set forth the connection between the wings. A strong resemblance to the Boxwing concept showed in 2001 a design by Luigi Colani, who designed a passenger plane with 80 m span.

Practical Application

In addition to the use in model aircraft wings this concept has also been implemented in some micro-light aircraft. These include the Ligeti Stratos, which flew for the first time in 1985, and the Sunny in 1989. The fixed-wing aircraft used complement each other. The upper surface has the layout of a swept delta wing. The surface rotates without control exposure to the wind. In gravity- controlled microlight airplanes of self-control behavior requires a constant counteraction of the pilot. In Boxwing aircraft this counter- force is canceled by the lower, straight wing. In practice, a pilot must not make balancing control interventions in crosswinds. The Sunny flying slightly sideways sliding without increased resistance, but without loss journey in the desired direction.

In addition, the Boxwing surface prevents stables of the aircraft. Since the upper surface produces 2/3 of the total buoyancy of the aircraft when driving loss simply takes the aircraft nose down and builds through the resulting higher speed again lift on. The lower surface always generates buoyancy and keeps the aircraft stably without generating a Abkippneigung.