The Akaflieg Braunschweig or Akademische Fliegergruppe Braunschweig () is one of some fourteen German undergraduate student flying groups attached to and supported by their home Technical University. Several have designed and built aircraft, often technically advanced and leading the development of gliders in particular. In 1982 when the SB-13 design was first discussed no new
tailless glider had been built for thirty years, during which time
glass reinforced plastic materials had replaced wood in glider construction and much learned about
laminar flow wings; it was hoped that tailless designs would be lighter, simpler and cheaper. Work on the SB-13 Arcus, named after the
cloud formation, began in 1982. Because of the novelty of the layout, a one-third scale model of the early design was built and flown, revealing several serious problems. Strong
flutter was experienced even at modest speed, and the aircraft was susceptible to the
centre of gravity (c.g.) position. It
stalled readily when this was too far aft. Recovery from the
spin that followed was difficult. With the centre of gravity too far forward, a rapid longitudinal "pecking" oscillation set in, which was difficult to control due to its short duration. A major redesign involving extensive computer analysis led to a new wing with
carbon fibre stiffening on the main spar; in addition, both it and the wing plan were made curved. The new structure resisted flutter until was reached. The full-scale SB-13 finally flew in 1988. Its wing was straight-edged, with three slightly tapered sections of increasing sweep. The two inner panels occupied less than of the span, and the outer section
leading edge was swept at about 17°. All had a
dihedral of 4°. At its tips, where the
chord was , the wing turned upwards into tall, slightly swept
winglets, which carried
rudders.
Elevons occupied much of the outer panel
trailing edge and, further inboard, mid-chord mounted
airbrakes were fitted. The fuselage, onto which the wings were mounted between low and mid
position, was a short pod with its nose a little ahead of the centre section leading edge, extending aft about as far as the
trailing horizontal edge of the wing at its tip. The pilot reclined under a long, bulged, single piece
canopy, which was side-hinged to
starboard. The cockpit reached beyond the wing both forward and aft, with the main spar passing through it under the pilot's knees. Despite the modifications made to remove the handling problems predicted by the model, the full-scale SB-13 still "pecked" and spun readily; when the standard spin correction procedure was applied, a new spin started in the opposite direction. Over the next few years, several aerodynamic devices were tried, some of which at least improved the behaviour of the Arcus; one longer-lasting outcome from the project was the start of an investigation into whole aircraft rescue parachutes. The competition performance of the Arcus was on a par with that of the other 15 m gliders of the time, but it did not offer a significant improvement over them, which might have justified even more effort to improve the handling. ==Operational history==