The ITS-IV was a high performance, two seat research
sailplane designed initially by Adam Nowotny to gather meteorological and airframe stress data. It was also intended to provide blind flying training. Franciszek Kotowski took over the design work after Nowotny's death in July 1934, producing the
ITS-IVB. It was an all-wood aircraft. The two part wing had a rectangular plan central section and gently tapering trapezoidal outer panels with blunted tips. Each part was built around a single
plywood D-box spar which formed the
leading edge. On each side an internal auxiliary drag strut ran diagonally from the spar at about mid-span to the rear of the
wing root and the whole area between spar and strut was ply-covered, forming another box. Elsewhere, the wings were
fabric-covered, as were the
differential ailerons which filled the
trailing edges of the outer panels. The wing bracing was unusual, with the normal rigid struts replaced by upper and lower steel ribbons on each side. Each upper ribbon ran from a central
cabane, formed from three steel tubes, to a reinforced region of the spar. The lower ribbons ran from the spars to the lower fuselage. They offered less air resistance and also provided a way to measure wing loads in flight. The fuselage was a ply-covered semi-
monocoque structure with an oval cross-section. It was unusually wide and deep in the central section, tapering away strongly aft of the wings. This variation allowed an uncramped, enclosed pilot's cockpit ahead of the wing and a very generous cabin for the observer, with
celluloid-paned underwing windows on each side and accessed via a port side door. The cabin also had a table which could be folded away to allow use of the dual flight controls under blind flying conditions. A sprung landing skid was mounted below. The
empennage was conventional, with a
cantilever, tapered
tailplane and
elevators mounted on top of the fuselage and a
fin carrying a full, rounded, deep,
rudder hinged behind the elevators. The fixed surfaces were ply-covered and the control surfaces fabric-covered. ==Operational history==