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The Akaflieg Braunschweig SB-13 Arcus was an experimental tailless, single-seat, Standard Class glider designed and built in
Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
in the early 1990s. Though it performed as well as its conventional contemporaries, it did not offer sufficiently improved performance to compensate for its difficult handling characteristics.


Design and development

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 Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cl ...
materials had replaced wood in glider construction and much learned about
laminar flow Laminar flow () is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral m ...
wings; it was hoped that tailless designs would be lighter, simpler and cheaper. Work on the SB-13 Arcus, named after the
cloud formation In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may co ...
, 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 In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weighted relative position of the distributed mass sums to zero. For a ...
(c.g.) position. It stalled readily when this was too far aft. Recovery from the
spin Spin or spinning most often refers to: * Spin (physics) or particle spin, a fundamental property of elementary particles * Spin quantum number, a number which defines the value of a particle's spin * Spinning (textiles), the creation of yarn or thr ...
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 Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers ( Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon comp ...
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 The leading edge is the part of the wing that first contacts the air;Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, 1997. alternatively it is the foremost edge of an airfoil sectio ...
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 Wingtip devices are intended to improve the efficiency of fixed-wing aircraft by reducing drag. Although there are several types of wing tip devices which function in different manners, their intended effect is always to reduce an aircraft ...
, which carried
rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...
s.
Elevons Elevons or tailerons are aircraft control surfaces that combine the functions of the elevator (used for pitch control) and the aileron (used for roll control), hence the name. They are frequently used on tailless aircraft such as flying wings. ...
occupied much of the outer panel
trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 1997. ...
and, further inboard, mid-chord mounted airbrakes were fitted. The fuselage, onto which the wings were mounted between low and mid
position Position often refers to: * Position (geometry), the spatial location (rather than orientation) of an entity * Position, a job or occupation Position may also refer to: Games and recreation * Position (poker), location relative to the dealer * ...
, 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 Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an a ...
, which was side-hinged to
starboard Port and starboard are Glossary of nautical terms (M-Z), nautical terms for watercraft and spacecraft, referring respectively to the left and right sides of the vessel, when aboard and facing the Bow (watercraft), bow (front). Vessels with bil ...
. 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

The sole SB-13 was flown, modified and studied from 1988 to 2000 when it was damaged and set aside in favour of newer aircraft. In 2007 it went to the
Deutsches Museum The Deutsches Museum (''German Museum'', officially (English: ''German Museum of Masterpieces of Science and Technology'')) in Munich, Germany, is the world's largest museum of science museum, science and technology museum, technology, with a ...
,
Munich Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...
for exhibition.


Aircraft on display

* SB-13 ''D-1113'' is on display in the
Deutsches Museum Flugwerft Schleissheim Flugwerft Schleissheim is an aviation museum located in the German town of Oberschleißheim near Munich, it forms part of the Deutsches Museum collection and complements the aviation exhibits on display at the main site. The museum was opened on ...
.


Specifications


References


External links

* {{Akaflieg Braunschweig aircraft Tailless aircraft 1980s German sailplanes Akaflieg Braunschweig aircraft Aircraft first flown in 2000