After a series of numbered but unbuilt designs, Władyslaw Zalewski spent his spare time evolving the simplest and cheapest single seat aircraft on which to learn to fly. He concentrated on lightness and good handling rather than performance and, since he had no external funding, reused material from his first but uncompleted pre-
war W.Z.I
biplane. The W.Z.XI was the result. Part-time construction began slowly in 1926 in his workshop at
Milanówek, though in the following spring Zalewski made a determined attempt to have it ready for the First National Lightplane Contest, scheduled for that autumn. Despite his efforts the first flight, piloted by Zbigniew Babinski, took it to nearby
Warsaw only on the final day of the Contest. The
shoulder wings of the Kogutek were rectangular in plan, each built around two
spars and
fabric covered. They were mounted on the upper fuselage
longerons with some
dihedral. The W.Z.I legacy gave the wings a thin section, so they were wire braced, the upper wires attached above the fuselage to a pyramid of four
struts placed between the engine and
cockpit. The lower wires were fixed to the lower fuselage longerons. Both sets reached the outer parts of the wings via
kingposts attached to the forward spars which projected both above and below, an anachronistic feature by the later 1920s. Its
ailerons occupied most of the
trailing edges and increased in
chord outwards. The fuselage of the W.X.XI had a rectangular section structure defined by four longerons and was
plywood-covered. .The ply upper fuselage decking was rounded, interrupted by an open cockpit at mid-chord. Its engine was a Zalewski WZ.18 , five cylinder
radial engine designed and built in 1923, housed in a blunt, metal
cowling with its cylinders partly exposed for cooling. A hinged mounting allowed easy access for servicing. Fuel and oil tanks were behind the engine The
empennage of the W.Z.XI was conventional though large, with wooden structures and fabric covering. The horizontal tail was mounted at mid-fuselage and had an unusual plan which led to the "Cockerel" name: the wire-braced
tailplane's
leading edges tapered strongly from the root with concave curvature out to forward projecting spurs. It carried a single, semi-elliptical
elevator. Its
fin had a similar profile to the tailplane and mounted an
unbalanced, semi-circular rudder working above the elevator. The W.Z.XI's conventional, fixed
landing gear also followed earlier practice. The wheels, with rubber cord shock absorbers, were on a single axle attached to two skids mounted on the lower fuselage sides with a pair of cross-bracing struts between them. ==Operational history==