Alexander Schleicher ASK 21

Manufacture

ASK 21 is a two-seater Planeur out of composite materials with a wing in median position and an elevator in T. the ASK 21 was designed to make instruction but is also adapted for the flight in shift and the instruction with the stunt-flying.

History

The ASK 21 was conceived by Rudolf Kaiser like a modern counterpart of the ASK 13, to answer at the request of a modern two-seater for the training of the pilots. The ASK 21 is the true first two-seater sailplane built out of composite material by Alexander Schleicher GMBH & Co. The prototype accomplished its first flight in December 1978 and the production started in 1979. It currently remains in production, with 750 built specimens. In December 2004, Semi version ASK 21, on autonomous takeoff, carried out its first vol. Currently, the Semi ASK 21 has a development of the nose gear wheel director via the ordering of direction. It is engineer Michael Greiner who deals with this project.

Construction

This two-seater has a configuration out of tandem equipped in dual control, the pilots and the passenger can adjust the compensator, the ordering of direction and their seat.

The fuselage is composed of a tubular sandwich and thus offers passive safety with the minimum of weight. The wings are in two parts, in median position are assembled in Porte-à-faux and are locked by two axes. The wing is equipped with air-brake of the type Schempp-Hirth. The wing tips are curved downwards, which makes it possible to take off without the assistance of a person at the time of departure of rolling. The elevator is in form of T and the depth has a spring tab and its connection is automatic. The Gear landing consists of 2 or 3 fixed wheels. The principal wheel is behind the center of gravity and is slowed down by a hydraulic brake. The checking of the pressure of the tire is obstructed by the need to remove the fairing of wheel (that many clubs remove in a permanent way to facilitate regular maintenance and to reduce the risk of firing by the imprisoned grass which can return in contact with the brake.

Characteristic of Flight

The thick profile of wing gives to good characteristics at the fallback speeds (stalling speed roughly 65 km/h).

One can say that the characteristics of flight are extremely of good composition. It is difficult, however nonimpossible to enter in gimlet (all the plane will enter in gimlet). In flight as a single-seater, the ASK-21 rises in ascending currents as well as K8. Number of pilot pilots or pupils flew at least once on ASK 21.

Technical data

Sources

Alexander Schleicher GMBH & Co
Johnson R, has Flight Test Evaluation off the ASK 21, Soaring, July 1985
Thomas F, Fundamentals off Sailplane Design, College Park Press, 1999
Simons M, Segelflugzeuge 1965-2000, Eqip, 2004

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