Schleicher Ask 21

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The Schleicher ASK 21 is a two-seat glider that has become the world's most widely used sailplane for training and recreational soaring since its introduction in 1979. Built by Alexander Schleicher GmbH in Poppenhausen, Germany, the ASK 21 revolutionized glider instruction with its forgiving handling characteristics, side-by-side seating, and exceptional durability, qualities that made it the standard training platform for gliding clubs across Europe and beyond. The aircraft's all-fiberglass construction and 17-meter wingspan deliver a best glide ratio of approximately 34:1, allowing student pilots to stay aloft for extended periods while learning thermal soaring techniques and cross-country navigation. Unlike earlier training gliders with tandem seating, the ASK 21's side-by-side cockpit configuration improves instructor-student communication and makes it equally suitable for private owners seeking a rugged two-place sailplane. The type remains in production after more than four decades, with over 800 built, a testament to its enduring design. Its operating envelope spans from a minimum sink rate of about 2.1 feet per second at 46 knots to a never-exceed speed of 135 knots, with normal operations limited to 108 knots to preserve structural integrity during aerotow and thermaling flight. SkyMeter has tracked 42 flights across 15 airframes and 1 operators over routes, with the largest observed operator.