fs28 – Avispa

Cooperation and Transfer of Know-How

The fs28 is an experimental aircraft created by a consortium of three groups, the Akaflieg Stuttgart, which served as the main design, development, and construction force behind the project, the Institute for Mechanics and Aircraft Construction of the University of Stuttgart, and the Wolf Hirth Aircraft Company from Nabern, a small town just outside of Stuttgart. The construction of this aircraft was made possible by the support of the Fraunhofer Society and the Ministry of Economics of Baden-Württemberg.

The goals of the project were:

  • use of the highly aerodynamic fuselage form of sailplanes in light motorized aircraft.
  • a study on the use of composite construction methods in light aircraft.

Said goals led to the following standpoints:

  • to create as little drag as possible, a pusher configuration was to be used. The pusher propeller was developed together with the company Hofmann
  • to reduce noise emissions, the exhaust would end at the upper part of the fuselage
  • the wings were to have a modern, self-designed profile: ET 530
  • the canopy was to be designed to allow for good visibility. This, coupled with the placement of the engine in the rear and the cockpit in front of the wing, gave pilots excellent all-round visibility.
  • aerodynamic requirements resulted in the incorporation of a retractable undercarriage and an inverted V-tail

New methods were tried out during construction:

  • the fuselage was made of a GRP-honeycomb sandwhich construction while the wings and tail had CONTICELL C-60 as a core material
  • the undercarriage strut was made of a multi-layer GRP laminate, which thanks to the form of the part provided good damping properties


Construction1969 – 1972
First flight20 December 1972
Method of constructionWings and tail: GRP-Foam sandwich
Fuselage: GRP-Honeycomb Sandwich
Tail spar: Alu
Wingspan9,4 m
Wing area12,7 m²
Aspect ratio7
ProfileEppler 530
Dihedral angle4,5°
Wing sweep6,75° (t/4)
Wing taper0,57
Aileron area0,4 m²
Length7,2 m
Height1,3 m
Empty weight688,8 kg
MTOW900 kg
Max. engine power122 kW at 2500 rpm
PowerplantLycoming IO-360 B1F
Max. cruise speed255 km/h
Economical cruise speed190 km/h – 200 km/h
Max. speed300 km/h
Range at MTOW800 km / 4h
3-side view