In the quest to achieve both good soaring/slow speed and good cruising/high-speed characteristics many glider designers have studied variable geometry or polymorphic concepts. Unlike fast jet aircraft, variable wing sweep has very limited value for a slow flying glider, so glider designers favour concepts which involve changing the wing area rather than sweep angle. There are several methods of achieving variable area, including:- area increasing flaps extending from leading or trailing edges of the wing, telescopic variable span wings where an outer glove is extended or retracted over an inner section, and extending gloves which extend out from the fuselage over the existing wing. The FS-29 was designed and built to research the telescopic variable span wing. With the wing at full extension the FS-29 could thermal successfully in very weak conditions and land safely in small spaces, conversely with the wing fully retracted the FS-29 could cruise between lift at higher speeds, improving performance in distance/speed competitions, as well as perform aerobatics to higher load factors with faster control response.
Tail Unit: Glassfibre Re-inforced Epoxy + Foam Sandwich (derived from the tail of the Schempp-Hirth Nimbus-2).
Extension and retraction of the outer wings was made by a screw jacks and nuts operated by the pilot pumping a handle via two-way free-wheel mechanisms, toothed belts and torque shafts which pulled or pushed the outer wings over the inner wings as required. The gap between the inside of the outer wing and the skin of the inner wing could be as much as 3mm without causing excess drag or affecting the flying qualities. The FS-29 was demonstrated in flight at the 1996 ILA airshow at Berlin Tempelhof Airport, along with the Akaflieg braunschweig SB-10 and SB-13. The sole FS-29 was damaged in an accident during the summer of 1997, but is being re-built; meanwhile the FS-29 can be seen at the Deutsches Museum in Munich.