The Akaflieg Stuttgart fs31 ''Ferdinand Porsche'' is a

tandem Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction. The original use of the term in English was in ''tandem harness'', which is used for two ...

seat, dual control

training Training is teaching, or developing in oneself or others, any skills and knowledge or Physical fitness, fitness that relate to specific practicality, useful Competence (human resources), competencies. Training has specific goals of improving on ...

glider Glider may refer to: Aircraft and transport Aircraft * Glider (aircraft), heavier-than-air aircraft primarily intended for unpowered flight ** Glider (sailplane), a rigid-winged glider aircraft with an undercarriage, used in the sport of glidin ...

designed and built in

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

between 1977 and 1981. The aircraft was intended to have high performance, yet to be robust enough for student use. It was not intended for production and remains in service with the Akaflieg after almost 40 years and 7,100 flying hours.

Design and development

The Akaflieg Stuttgart or Akademische Fliegergruppe Stuttgart ( en, The Stuttgart Academic Flying Group) is one of some fourteen German 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. The students of the Stuttgart Akaflieg designed the fs31 as a high performance, tandem seat training sailplane to replace their earlier aircraft, further inspired by the purchase of a set of wings from the

Grob G 103 Twin Astir The Grob G 103 Twin Astir is a glass-reinforced plastic two-seat sailplane that was developed in Germany in the 1970s by Grob Aircraft AG as a counterpart to the single-seat G 102 Astir then in production. Construction throughout is similar, ...

prototype in 1977. Furthermore, the then new

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

Kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...

hybrid material was to be used to reduce weight. Energy dissipation and a locally strong cockpit area were further design objectives. Benign stall characteristics and a strong, long-stroke,

monowheel A monowheel, or uniwheel, is a one-wheeled single-track vehicle similar to a unicycle. Hand-cranked and pedal-powered monowheels were patented and built in the late 19th century; most built in the 20th and 21st century have been motorized. ...

undercarriage Undercarriage is the part of a moving vehicle that is underneath the main body of the vehicle. The term originally applied to this part of a horse-drawn carriage, and usage has since broadened to include: *The landing gear of an aircraft. *The ch ...

also make it suitable for student pilots. The fs31 has mid-mounted, straight tapered wings with 4° of dihedral, taken from the Twin Astir prototype. Its

T-tail A T-tail is an empennage configuration in which the tailplane is mounted to the top of the fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs from the standard configuration in which the tailplane is ...

, from the

Glasflügel 604 The Glasflügel 604 is a high-wing, T-tailed, single seat, FAI Open Class glider that was designed and produced in West Germany by Glasflügel starting in 1970.Said, Bob: ''1983 Sailplane Directory, Soaring Magazine'', page 81, Soaring Society o ...

, has a narrow chord, weakly tapered

tailplane A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplane ...

. The aircraft's control surfaces are made from a Kevlar-sandwich. Instructor and pupil sit in tandem in a

cockpit A cockpit or flight deck is the area, usually near the front of an aircraft or spacecraft, from which a Pilot in command, pilot controls the aircraft. The cockpit of an aircraft contains flight instruments on an instrument panel, and the ...

placed forward of the wing, fitted with dual controls, under a long, 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 ...

. The

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...

, which narrows to a slender boom behind the wing

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. ...

, is similar to that of the Akaflieg Stuttgart fs29, though carbon/Kevlar replaces the earlier aircraft's GRP polymeric foam sandwich structure. Furthermore, the fuselage shells are split horizontally instead of vertically to improve pilot safety during a crash landing by eliminating a seam on the underside of the cockpit. The undercarriage is retractable and is also based on that of the fs29. The fs31 first flew on 30 December 1981. Some improvements were made to the

wing root The wing root is the part of the wing on a fixed-wing aircraft or winged-spaceship that is closest to the fuselage,Peppler, I.L.: ''From The Ground Up'', page 9. Aviation Publishers Co. Limited, Ottawa Ontario, Twenty Seventh Revised Edition, 1996 ...

-fuselage junction during flight testing in the summer of 1982. The aircraft's fuselage design served as the basis for the Schleicher AS 22-2, later developed into the ASH 25, the Akaflieg Stuttgart fs33, and the Akaflieg Braunschweig SB 15.

Operational history

The sole fs31 was still undergoing field trial when it won the Klippeneck gliding competition of July 1982. It entered service with the Akaflieg Stuttgart in April 1983 and since then it has served in its intended role of trainer for almost 40 years, logging over 7,100 flying hours and 23,000 takeoffs.

Specifications

References

External links

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Eppler E 603 airfoil
{{Akaflieg Stuttgart aircraft 1980s German sailplanes Glider aircraft T-tail aircraft Aircraft first flown in 1981 Akaflieg Stuttgart aircraft