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Dornier Do 11D Prilep
Twelve Do 11D twin-engined bombers donated by Csar Boris on 27 June 1937. Prilep = Bat. Used by 3 Yato of 5 Bomber Orliak initially for the bomber role, and then as a transport early 1940-44. Fuselage code 55 carried. Withdrawn from service in 1944? Two of the aircraft were previously D-AMIN and D-AQUR.

Way back in late 1920s and early 30s there was a world economic depression and most nations suffered severely because of the situation. Bulgaria was no exception and it was during this hard time that fresh links were established with Germany. In 1933 the new nazi government in Germany gave credits to Bulgaria following the collapse of her established trade with other European countries

In 1936 trade between the two countries increased substantially. That year Bulgaria imported no fewer than 42 aircraft of German origin comprising He51, Fw44, He72, He45 and Fw56 aircraft. It was in 1937 that Bulgaria received 12 of the largest aircraft ever to be used by her air force. These were the Dornier Do-11D.

The saga of the Do-11 in Germany goes back to 1934 when it had planned 372 Dornier Do-11for the Luftwaffe Air Force but delays and grossly unpleasant handling and structural qualities led to the substitution first to a short span Do-11D and then the Do-13 with 559 Kw BMW VI water cooled engines and fixed undercarriage (often spatted) landing gear. At least 77 Do-11 were delivered, and it was from this batch that some were passed on to other then clandestine Air Forces including that of Bulgaria. The Do-11 carried a crew of 4 and had a take off weight of 9 tons. The Do-11 flew in from Germany on 14th February 1937, almost to the date 70 years ago. These carried civil registration e.g. D-AMIN. The Do-11Ds were large twin-engine bombers and at the time were rendered as the first heavy bombers with a retractable undercarriage to be developed in Europe.

The Bulgarians has named the Do-11D, Prilep, which means “Bat” and these lumbered on in the Bulgarian Air Force service for the following three years until 1940 until these were replaced by 10 Do-17Ms . Thus the long overdue for the slow and clumsy Do-11D was in effect. All the 12 Do-11Ds were attached to one squadron, Orliak No5, meaning air regiment No5. Their main function was that of a medium bomber and were based at Plovdiv.

The Luftwaffe mission to Bulgaria had been established in Sofia before German Air Force units had entered the country. This organization was the Bulgarian Air Force and its first task was to bring the equipment, training and develop operational techniques of the Bulgarians in line with those of Germany. Still the Luftwaffe were in the beginning of their experience with twin engine large aircraft and one would shred doubts on the popularity that the Do-11 had with Luftwaffe pilots. The Do-11 was not the size that could be thrown about in the air without fear of structural failure. The nine cylinder radial engines were not yet fully developed and as mentioned earlier the undercarriage was giving problems.

This situation involved so many problems and was somewhat confusing, so much so there then evolved the Do-23. This re-design of the Dornier bomber, although still very closely resembling the original Do-11, had rectified every fault with the final design. This consisted of redesigned and strengthened wing spars, flap function, in-line engines in place of the radial ones and best of all a sturdy fixed undercarriage. The Do-11s were hastily removed from German service. The serious problems were not so much evident at the time when they were delivered to Bulgaria in 1937. Even so the German pilots dreaded this bomber outright. It said, the experienced and apparently more able and willing Bulgarian pilots at the time, in spite of all the difficulties attached to this bomber, have managed to take out three years of active service on this machine.

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