Warsztaty Szybowcowe Wrona
The Warsztaty Szybowcowe Wrona (), or Kocjan Wrona after its designer, was the most numerous and widely used Polish pre-war primary glider. Design and development Designed by Antoni Kocjan, the Wrona was in competition with the Czerwiński and Jaworski CWJ flown in 1931. Both were simple, high-wing and open frame (flat, uncovered girder fuselage) gliders in the style of the earlier German Zögling. With LOPP funding five pre-production airframes were built by Warsztaty Szybowcowe, the first flying from Mokotów on 6 September 1932. Its two-part wing, mounted on top of the fuselage, was rectangular in plan and built around two spars. It was plywood-covered ahead of the forward spar, forming a torsion-resistant D-box, with the rest fabric-covered. On each side a pair of parallel struts braced the spars to the lower fuselage. Long, rectangular ailerons reached from strut to tip. The upper and lower longerons or chords of the open-frame fuselage were joined together with vertical and diagonal braces. The pilot sat, unprotected, under the wing leading edge on a seat on the forward vertical brace. Aft, the Wrona's triangular fin extended above and between the longerons and carried a tall, nearly rectangular rudder which reached down to the lower