| ASK 21 | |
|---|---|
 | |
| Schleicher ASK 21 | |
| Role | Two Seater-class or Club-class sailplane |
| National origin | Germany |
| Manufacturer | Alexander Schleicher GmbH & Co |
| Designer | Rudolf Kaiser |
| First flight | February 1979 |
| Introduction | 1979 |
| Number built | Over 1000 |
The ASK 21 is a glass-reinforced plastic (GRP) two-seat glider aircraft with a T-tail. The ASK 21 is designed primarily for beginner instruction, but is also suitable for cross-country flying and aerobatic instruction.
The ASK 21 was designed by Rudolf Kaiser to replace the popular ASK 13, providing a modern two-seat aircraft bridging the gap between initial training and single-seat performance flying. The ASK 21 is the first full-GRP two-seater produced by Schleicher, flying for the first time in February 1979 (6.2.1979). Production also began in 1979, remaining in production to this day (May 2018), over 900 units completed. In December 2004 the ASK 21 Mi, a self-launching version, made its first flight. In 2003 the operating time was extended to 18,000 hours [1] A revised and improved version, the ASK 21B was introduced in 2018. [2]
The two seats are in a tandem arrangement with dual controls, adjustable rudder pedals and seatbacks. The fuselage consists of a tubular sandwich and thus offers passive safety with low weight. The two-piece, mid-set, cantilever wing is a single-spar glass-fiber construction without flaps, but with upper side Schempp-Hirth-type air brakes. The wingtips curve downward, providing tip skids that allow take-offs without a wing helper (small wheel added with ASK-21 mi). The T-tail possesses a fixed horizontal stabilizer and an elevator with spring trim and automatic connections. The undercarriage consists of two or three fixed wheels. The main wheel lies behind the centre of gravity and has a hydraulically operated disc brake. Checking the tire pressure is hindered by the need for removing the wheel fairing. The tail unit has a rubber skid or a tailwheel.
The thick wing profile gives good low-speed characteristics (nominal stall speed approximately 65 km/h or 35 knots). The flight characteristics are docile; its stall is gentle, with ample vibration warning, and is easily recoverable. The nose does not noticeably drop, but the variometer indicates a high rate of descent and the vibration continues until back pressure is released and stall recovery is initiated.
The glider has little tendency to enter a spin. In order to make spinning possible for training purposes or demonstrations a spin kit is available from the manufacturer. It consists of ballast discs applied to the tail to change the center of gravity according to the weight of the crew. With this device the ASK 21 when slowed to stall speed with rudder input drops one wing and begins to rotate. Recovery is standard, utilizing neutralized ailerons, full opposite rudder until the rotation stops and then centralizing the rudder, relaxing back pressure to break the stall, and then easing the stick back to pull out of the dive.
When entering a side slip, which is not uncommon as an energy management technique, the rudder can aerodynamically over centre, requiring an input from the pilot for the rudder pedals to return to neutral.
Australia 
Portugal 
United Kingdom 
Canada United Kingdom 
United States 
Data fromJane's All the World's Aircraft 1988-89 [12]
General characteristics
Performance
The Schempp-Hirth Discus is a Standard Class glider designed by Schempp-Hirth. It was produced in Germany between 1984 and 1995 but has continued in production in the Czech Republic. It replaced the Standard Cirrus. It was designed by Klaus Holighaus.
The ASK 13 is a two-seater glider that was built by German sailplane manufacturer Alexander Schleicher Gmbh & Co. It was and still is widely used for basic training of glider pilots.
The Schempp-Hirth Mini Nimbus is a 15 Metre-class glider designed and built by Schempp-Hirth GmbH in the late 1970s.
The Schempp-Hirth Nimbus-2 is an Open Class glider built by Schempp-Hirth during the 1970s. The Nimbus-2 first flew in April 1971 and a total of over 240 examples of all subtypes have been built until the beginning of the 1980s. It replaced the Schempp-Hirth Cirrus.
The Schempp-Hirth Nimbus 3 is a glider built by Schempp-Hirth.
The PZL Bielsko SZD-50 Puchacz is a Polish two-place training and aerobatic sailplane.
The ASW 19 is a single-seat glider built by Alexander Schleicher GmbH & Co, first flying in 1975. It was originally designed as a Standard Class glider, but now mainly competes in the Club Class. The ASW 19 is known for its pleasant handling and some clubs use it as a training glider. It was succeeded by the all-new Schleicher ASW 24.
The G102 Astir is a single-seat glassfibre Club Class sailplane, designed by Burkhart Grob and built by Grob Aircraft. It was the first Grob-designed sailplane, with the first flight in December 1974. Grob had previously built the Schempp-Hirth Standard Cirrus under licence.
The Schleicher ASK 23 is a single-seat Club Class sailplane that was built by the German manufacturer Alexander Schleicher GmbH & Co.
The T.31 Tandem Tutor is a British military training glider, designed and built by Slingsby and used in large numbers by the Air Training Corps between 1951 and 1986.
The Slingsby T.21 is an open-cockpit, side-by-side two-seat glider, built by Slingsby Sailplanes Ltd and first flown in 1944. It was widely used by the Royal Air Force, Sri Lanka Air Force and by civilian gliding clubs.
The Standard Austria was a single-seat aerobatic glider that was originally designed and built in Austria from 1959 but production was moved in 1962 to Schempp-Hirth in Germany.
The Slingsby T.30 Prefect is a 1948 British modernisation of the 1932 single-seat Grunau Baby glider. About 53 were built for civil and military training purposes.
The Czerwiński Sparrow, sometimes known as the de Havilland Canada glider, was a single seat glider, designed and built by a group of de Haviiland engineers in Canada in 1942. It was intended to popularise gliding and be suitable for both basic training and thermal soaring.
The Schleicher Ka-4 Rhönlerche II, sometimes called the KA-4 or even K 4, is a West German high-wing, strut-braced, two-seat glider that was designed by Rudolf Kaiser and produced by Alexander Schleicher GmbH & Co.
The Schleicher K7 Rhönadler is a West German high-wing, two-seat, glider that was designed by Rudolf Kaiser and produced by Alexander Schleicher GmbH & Co.
The PZL Bielsko SZD-51 Junior is a Polish single-seat training and club sailplane.
The Scheibe Specht is a tandem seat training glider produced in Germany in the early 1950s. More than fifty were built.
The Schleicher Ka-2 Rhönschwalbe is a tandem two-seat training glider designed and built in Germany, in 1952.
The ASG 32 is a Two Seater Class glider manufactured by Alexander Schleicher. The prototype had its maiden flight in Poppenhausen on 31 May 2014. Deliveries began in 2015.
