Letov Š-21

The Letov Š‑21 was a Czechoslovak single‑engine, low‑wing monoplane developed in the late 1920s by the aircraft works Letov Kbely. Designed by engineers Šimůnek and Vejvoda as a light utility and training aircraft, the Š‑21 first flew in spring 1929 and entered limited service with the Czechoslovak Air Force in 1930. The structure combined a wooden wing with a mixed steel‑tube and fabric fuselage, giving a relatively light airframe that could be built quickly in the modest facilities of the Kbely plant. Powered by a 120 hp Walter Vega radial engine, the Š‑21 reached a maximum speed of 185 km/h, a service ceiling of 5 500 m and a range of 600 km, while its simple fixed‑gear undercarriage and dual‑control cockpit made it ideal for basic pilot instruction and liaison duties. Although only a few dozen were produced before the type was superseded by more modern trainers, the Š‑21 demonstrated Letov’s ability to transition from wooden biplanes to all‑metal monoplanes and contributed to the development of Czechoslovakia’s interwar aeronautical industry. Its modest success helped lay the groundwork for later Letov designs that played a significant role in the country’s air defence during the 1930s.