Akaflieg Stuttgart fs31

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Akaflieg Stuttgart fs31

The fs31 is a single, unique German glider built by Akaflieg Stuttgart, a student flying group at Stuttgart University. It was designed and assembled between 1977 and 1981 to be a high‑performance two‑seat training sailplane that could withstand heavy student use. It was not meant to go into production, and it remained in service with Akaflieg Stuttgart for nearly 40 years, flying more than 7,100 hours.

Design and features
- Purpose: tandem two‑seat trainer with dual controls and a long, clear canopy.
- Wing and tail: mid‑mounted straight‑taper wings with 4° dihedral, using wings from the Grob G 103 Twin Astir prototype; a T‑tail with a narrow, weakly tapered tailplane inspired by the Glasflügel 604.
- Fuselage: made from carbon/Kevlar composites to save weight, with a slender rear boom. The fuselage shells are split horizontally (not vertically) to improve pilot safety in a crash, removing a bottom seam under the cockpit.
- Undercarriage: retractable main gear, based on the fs29 design.
- Cockpit and controls: kevlar‑sandwich control surfaces and a tandem cockpit located forward of the wing.

Development and impact
- The fs31 used wings tied to the Twin Astir project and its carbon/Kevlar construction aimed for energy dissipation and a robust cockpit area.
- Its fuselage design served as a basis for later gliders, including Schleicher AS 22‑2 (which evolved into the ASH 25) and influenced Akaflieg Stuttgart’s fs33 and Akaflieg Braunschweig’s SB 15.

Operational history
- First flight: 30 December 1981.
- In testing, improvements were made to the wing root–fuselage junction in 1982.
- The fs31 won the Klippeneck gliding competition in July 1982 while still in field trials.
- It entered service in April 1983 and has since been used as a trainer for almost four decades, with about 23,000 takeoffs and 7,100 flying hours.