DAR 1 Peperuda

 

The DAR 1 Peperuda (Bulgarian for 'Butterfly') was a Bulgarian two-seater aircraft of the 1920s.

It was designed by the German engineer Hermann Winter who, after arriving in Bulgaria in the early 1920s, visited DAR's facilities at Bozhuriste (Sofia) and was convinced about the capabilities that such industries offered, specially employing pieces from remaining aircraft (that Bulgaria was forbidden from using) left-over from the Great War at the time, namely the German DFW C.V which was used by the Bulgarian Army Aviation Corps during the Great War.
Given that the DFW C.V was repaired in great numbers during wartime, DAR's (Bulgarian for 'State Aircraft Workshops') workers were familiar with the type so Winter picked a design which did not differ too much from the original C.V. The resulting design was named 'DAR Uzunov 1', Uzunov, in memory of Ivan Uzunov, a pilot who died in 1925 testing an Austrian advertising aircraft.

The DAR 1 was made entirely out of wood and was powered by a 60 hp Walter NZ radial engine, and flew for the first time on 16th November 1926 at the hands of Captain Marko Parvanov (a Bulgarian aviation hero who was the first Bulgarian to shoot down an enemy aircraft) with engineer Winter as a passenger. 
A further improved version was also made, this time with little to no design improvements, except that it was powered by a 85 hp Walter Vega engine, this was called 'DAR 1A'. 
Both variants were put into production in 1926 and a total of twelve DAR 1 and eight DAR 1A were manufactured between 1926 and 1928. They were assigned to the, then clandestine, flight school at Kazanlak and the Yato fighter squadron (another clandestine unit). The U-1 was well liked by the pilots who praised its good flying capabilities with its exceptional stability at lower speeds, making the type ideal for training duties. Many Bulgarian pilots learned to fly in an U-1, as well as some Soviet pilots such as Boris Ganev, Nikola Vatov and Zahari Zahariev, who would later be declared hero of the Soviet Union. 
It is also reported that the U-1 was used through the 1930s and the early 1940s by the Bulgarian Civil Air Service as glider tugs.

Sources:
1st https://en.wikipedia.org/wiki/DAR_1
2nd https://www.airwar.ru/enc/other1/daru1.html (translated)