Slingsby Aviation
Slingsby T.21
The Slingsby T.21, known as the “Sedbergh” and later the “Swallow,” was a wooden two‑seat training glider that entered service with Slingsby Aviation in the late 1930s. Developed from the earlier T.20, the T.21 first flew in 1944 and quickly became the Royal Air Force’s primary elementary trainer, replacing older fabric‑covered models. Its high‑wing, strut‑braced design featured a 15‑metre (49‑ft) wingspan, a pronounced dihedral, and an open cockpit combination that allowed both instructor and pupil clear visibility. Constructed mainly of spruce and birch plywood, the glider’s simple, robust structure could endure the rigors of repeated take‑offs and landings on grass fields, and its low wing loading provided forgiving handling characteristics ideal for novice pilots.
Over 400 units were built, serving not only the UK but also Commonwealth air forces, and many were later sold to civilian clubs where they remained in operation well into the 1970s. The T.21’s longevity helped standardise basic glider instruction, contributing to the post‑war expansion of the sport and to the development of Britain’s aeronautical training curriculum. Its legacy endures today as a symbol of the transition from wartime necessity to peaceful aviation education.
Over 400 units were built, serving not only the UK but also Commonwealth air forces, and many were later sold to civilian clubs where they remained in operation well into the 1970s. The T.21’s longevity helped standardise basic glider instruction, contributing to the post‑war expansion of the sport and to the development of Britain’s aeronautical training curriculum. Its legacy endures today as a symbol of the transition from wartime necessity to peaceful aviation education.
