The DISCUS - designed to JAR 22, category "U" specifications - is successor to the STANDARD CIRRUS, of which more than 700 were built. As the winner of the World Chanpionships in 1985, 1987 and 1989 the DISCUS not only is the most successful Standard Class sailplane in recent years but has set new standards in this class in every respect.
While the fuselage of the DISCUS, except for some minor modifications, originates from the VENTUS, the wing is an entirely new design and easily recognized by its multi-stage swept-back leading edge.
This sweep-back - together with an optimum taper and chord of the outer wing region - contributes substantically to the prevention of drag effects caused by a lateral flow in the boundary layer along the tailing edge, ensuring the wing generates more lift at lower drag than conventional planforms.
The gain in performance, resulting from this concept, is real - not only in climb with high ballast loads but also in the glide at higher speeds - and is both admitted by competition pilots from all over the world and sufficiently proven by the countless successes of the DISCUS.
Neverless, this sailplane is by no means only suitable for the top pilots. Thanks to it's pleasant and docile flight handling characteristics, the DISCUS has long been a favorite with clubs too.
The two-piece wing has a tri-trapezoidal planform and a new laminar airfoil specifically developed for the DISCUS, with boundary layer control on the lower surface by means of turbulator strips.
The wing shells are constructed as a fiberglass/foam sandwich with spar flanges from carbon fiber rovings for strength and weight reasons. Inside the wing all actuating rods are sealed by bellows and a special tape covers the aileron gaps.
Double-panelled airbrakes (with spring cover strips) are on the upper wing surface and provide a very effective landing aid.
The wing assembly is straight-forward, with conventional tongue spar stubs, secured by a single main pin. Each wing panel weighs only about 61,5 kg (135 lb). Ailerons, airbrakes and water dump valves all automatically hook up when the DISCUS is rigged.
Water ballast is carried in an integral sealed compartment in each wing (capacity 2x84 liter/kg) and permits a maximum wing loading of about 10.24 lb/ft². The nose-heavy moment produced by high wing ballast loads my be compensated by an optional fin ballast tank.
The standard fuselage is very roomy and ideal for use in clubs. The smaller special fuselage, available on request, is only suitable for individuals up to 175 cm (5.7 ft) but produces slightly less drag.
Both versions are manufactured as pure glass or carbon/Kevlar fiber shells with an imbedded steel tube center frame and reinforced by foam/fiberglass webs in the rear portion and double skins in the cockpit area. Maintenance and, if needed, repairs are greatly simplified by this structure.
The retractable undercarriage is sprung and is housed in a selected box. The wheel brake is actuated by a stick-mounted lever. Instead of the standard rubber tail skid a pneumatic tail wheel (200x50) can be fitted on request.
A TOST c/g tow release mechanism is standard, an additional nose towing hook is available as an option, as is a "tilt-up" instrument panel.
The canopy - providing full vision for all flight phases - hinges sideways and is fitted with a reliable jettisoning mechanism. Ventilation air to the cockpit is supplied by an instake in the fuselage nose and is controlled by a knob on the instrument panel.
The pressure port for the pitot is in the nose intake. The static pressure ports are in the fuselage tail boom and below the spar recess. The fin accomodates the connection for a T.E. compensation probe, a blanked off line (for e.g. a Prandtl tube) and the VHF-antenna.
The elevator hooks up automatically when the tailplane is rigged. The stabilizer is a fiber-glass/foam sandwich constructen and the elevator halves are a pure fiberglass lay-up.
In addition to a battery mount at the base of the instrument console, further batteries may be fitted near the wheel box and in the fuselage nose, where there is also a mounting stud for trim ballast weights.
The standard equipment for the DISCUS also includes a spring type elevator trim, removable seat pan, seat cushion, side pockets, safety harness, adjustable (in flight) rudder pedals and a canopy dust cover. A seat back with integrated head rest, adjustable at its base on the ground and resettable in flight for an upright or reclining position, is an additional option.
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