#czechairforce

Initially developed for a Finnish requirement for a two seat biplane reconnaissance, the Letov S-28 first flew in 1929. Although not taken up by the Finish Air Force, Czechoslovakia bought 12 production Letov S-128s. These were followed by 4 S-228s for Estonia which were delivered in 1932. Production then shifted to the main S-328 version. A total of 470 of all versions were built.

Following the Sudetenland Crisis and the splitting of Czechoslovakia, the new state of Slovakia inherited a large number of S-328s while Germany took control of the rest. Some of these and new built machines were sold to Bulgaria.

Letov sent the Š-128 registered OK-VOT on a demonstration tour of the Baltic states in September 1931. Estonia expressed interest but required several modifications.

To meet the Estonia requirements, the Š-128 received a new landing gear with hydropneumatic shock absorbers and an increased vertical and horizontal tail area. The modified aircraft was redesignated the Š-228. Four Š-228E aircraft were then produced for the Estonian Air Force in 1932. The original prototype aircraft was left in the possession of Letov and in February 1932 now registered OK-VOU it was sent on another demonstration trip to the Baltics, focusing mainly on Finland. It crashed there a month later, but the interest it aroused in Finland gave rise to another version marked Š-328.

The Estonian Š-228s took no part in the Soviet invasion of Estonia in 1940.

Planned as a replacement for the successful Letov S-328, the S-528 was a reconnaissance and light bomber aircraft. The structure of the S-328 was strengthened and the powerplant was upgraded to a 800 hp (597 kW) Gnome-Rhône Mistral Major. Due to the German annexation of Czechoslovakia, only six were built.

Powered by an Avia VR-36 V-12 liquid-cooled inline piston engine of 740 hp, the Letov S-428 was a close support version of the Letov S-328. Only one prototype was built.

Developed from the underpowered Letov S-28, the S-128 had a strengthened forward airframe and more powerful Walter Jupiter VI engine of 330 kW. Although it failed to meet military requirements, it was ordered into production, primarily to keep the factory busy. A total of 12 production aircraft were built.

During the Second World War, the Slovak Air Force operated five Heinkel He 111 bombers. At least one of the He 111s survived and was used post war for aerial mapping by the Czechoslovak Air Force.