The Akaflieg Stuttgart fs28, nicknamed ''Avispa'' (Spanish:

Wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...

) is a single engine,

twin boom A twin-boom aircraft is characterised by two longitudinal booms (extended nacelle-like bodies). The booms may contain ancillary items such as fuel tanks and/or provide a supporting structure for other items. Typically, twin tailbooms support ...

pusher configuration light sports and utility aircraft designed at the University of Stuttgart in

West Germany West Germany is the colloquial term used to indicate the Federal Republic of Germany (FRG; german: Bundesrepublik Deutschland , BRD) between its formation on 23 May 1949 and the German reunification through the accession of East Germany on 3 O ...

in the 1970s. Unusually, it has an inverted

V-tail The V-tail or ''Vee-tail'' (sometimes called a butterfly tail or Rudlicki's V-tailGudmundsson S. (2013). "General Aviation Aircraft Design: Applied Methods and Procedures" (Reprint). Butterworth-Heinemann. p. 489. , 9780123973290) of an aircraft ...

. The sole example remained active as of 2010.

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 fs28 was their first powered aircraft. The project, supported by the

Fraunhofer Society The Fraunhofer Society (german: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., lit=Fraunhofer Society for the Advancement of Applied Research) is a German research organization with 76institutes spread throughout Germany ...

and the Ministry of Economics of Baden-Württemberg, was intended to transfer the knowledge about high performance aerodynamics and

composite materials A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...

gained from glider design to light powered aircraft. The fs28 is a twin-boom, pusher configuration low mid-wing monoplane. The wing has an Eppler profile, quite new in the 1970s, and is straight tapered with a swept

leading edge The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...

and unswept

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, 199 ...

, resulting in 6.75° sweep at quarter chord. It is constructed from a sandwich of glass fibre and rigid foam and has 4.5° of dihedral.

Fowler flap A flap is a high-lift device used to reduce the stalling speed of an aircraft wing at a given weight. Flaps are usually mounted on the wing trailing edges of a fixed-wing aircraft. Flaps are used to reduce the take-off distance and the landi ...

s, in two sections separated by the tail booms, fill the trailing edge out to the plain, untabbed

ailerons An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...

. Accommodation and engine are in a central

nacelle A nacelle ( ) is a "streamlined body, sized according to what it contains", such as an engine, fuel, or equipment on an aircraft. When attached by a pylon entirely outside the airframe, it is sometimes called a pod, in which case it is attached ...

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 clot ...

/honeycomb sandwich.

Side-by-side seating 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 ...

is enclosed under a generous, three section

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 ...

entered via upward, centreline hinged doors. A 115 hp (86 kW)

flat four A flat-four engine, also known as a horizontally opposed-four engine, is a four-cylinder piston engine with two banks of cylinders lying on opposite sides of a common crankshaft. The most common type of flat-four engine is the boxer-four engine, ...

Lycoming O-235 The Lycoming O-235 is a family of four-cylinder, air-cooled, horizontally opposed piston aircraft engines that produce , derived from the earlier O-233 engine.Textron Lycoming: ''Operator's Manual, Textron Lycoming Aircraft Engines, Series O-23 ...

piston engine, mounted in the rear of the nacelle with its output shaft well above the wing and booms and air-cooled via a semi-annular intake behind the cabin, drove a three-blade pusher propeller with a large

spinner Technology *Spinner (aeronautics), the aerodynamic cone at the hub of an aircraft propeller * Spinner (cell culture), laboratory equipment for cultivating plant or mammalian cells * Spinner (computing), a graphical widget in a GUI * Spinner (MIT Med ...

, designed to minimise noise. The three blade propeller was later replaced by a two-blade one. The tail booms are slender and linked at the rear by the unusual inverted Vee

empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third e ...

. The straight edged, fixed rear surfaces are constructed as the wing but the control surfaces are fabric covered, with spring tabs. The fs28 has a retractable

tricycle undercarriage Tricycle gear is a type of aircraft undercarriage, or ''landing gear'', arranged in a tricycle fashion. The tricycle arrangement has a single nose wheel in the front, and two or more main wheels slightly aft of the center of gravity. Tricycle g ...

with glass fibre shock absorbers, mainwheel

hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counte ...

brakes and a steerable nosewheel. The sole fs28, ''V-1, D-EAFS'', made its first flight on 20 December 1972.

Operational history

The fs28 was seriously damaged in an accident in May 1981 and its permit to fly (PTF) lapsed that November. With no rebuild under way, the registration ''D-EAFS'' was reallocated to another type in 1990. However, ''V-1'' was rebuilt, regaining its PTF in July 1997, when it was registered as ''D-EKFS''. It was on the German civil aircraft register in 2010, remaining active.

Design and development

Operational history

Specifications

References

Further reading