M.Hardy. Gliders & Sailplanes of the world

Schleicher AS-K 21

  This tandem two-seater Open Class and training sailplane is the latest design of Rudolf Kaiser and is intended to succeed the well-known AS-K 13 as a trainer for the new high performance competition sailplanes. It is of ДальшеMore>>> the same basic layout, differing from the AS-K 13 in having a wing span increased to 17m (55ft 9 1/4 in), a T-tail, a more streamlined fuselage, and a non-retractable semi-recessed nose wheel, as well as a sprung fixed monowheel with drum brake and a steel-shod rubber tailskid. Originally an improved version of the AS-K 13 with glassfibre wings and T-tail was studied but the requirement for a new two-seater was met instead of the AS-K 21. Construction is mainly of glassfibre reinforced plastics/foam sandwich, instead of the AS-K 13's mainly wooden structure with welded steel tube fuselage. Production of the AS-K 21 began in 1979 and the prototype first flew in December 1978. The cantilever single-spar mid-set wings have Wortmann aerofoil sections and 4° dihedral, and there are Schempp-Hirth air brakes in the upper and lower surfaces. The wing tips are turned down to reduce tip stalling. The tailplane is fixed, with a separate elevator with spring trim. Unlike the ASK 13, there are two separate cockpit canopy sections, the front one opening forwards and the rear one rearwards, and the pilots sit in a semi-reclining position, with dual controls.


Span: 55 ft 9 1/4 in
Length: 28 ft 10 in
Height: 5 ft 3 in
Wing area: 193.2 sqft
Aspect ratio: 16.1
Empty weight: 772 lb
Max weight: 1,256 lb
Max speed: 136 mph
Max aero-tow speed: 96 mph
Min sinking speed: 2.13 ft/sec at 42 mph
Best glide ratio: 34:1 at 59 mph