In 1936, the Czechoslovak government commissioned Frantisek Novotny, then chief engineer of Avia, a prototype light fighter for interception and border defense missions. Then, known as B.35, it was in the form of a single-seater single-engine monoplane. Of mixed construction wood covered and metal, the airplane was rather elegant despite its landing gear rigged fixed tricycle. Its engine, assured by a Hispano-Suiza in V, developed a power of 860 horses. As for its armament, it consisted of a 20 mm gun pulling through the pitch of the propeller and two 7.7mm machine guns in the wings. Thus rigged the Avia B.35 made its first flight on September 28, 1938.
At the time, the expansionist wills of the Third Reich, combined with a series of difficult tests, led Avia to review its copy and order a second prototype. However, it did not have time to fly before Bohemia Moravia was invaded by the German armies. A third prototype was then requested from Novotny, but this time by the RLM, the Nazi Air Ministry. Indeed, the B.35 was very interested in the Luftwaffe, which was looking for a light and modern single-seater destined for the operational transformation of its future fighter pilots. On this third prototype the 7.7mm English Vickers machine guns were simply replaced by German MGs of 7.92mm otherwise deemed more reliable in the long term. The fairing of the landing gear had also completely disappeared.
In the spring of 1939, this third B.35 was officially exhibited, under a puppet German livery, at the Brussels Air Show under the designation Avia Av-135.
In fact, the Luftwaffe asked Novotny to reconsider his copy but this time radically. Indeed, there was no longer any question of an advanced trainer or even of a frontier defense apparatus but simply of a classical fighter, like the main aircraft of this kind at the time as The Messerschmitt Bf 109 or the Morane Saulnier MS-406. However, the Av-135 was significantly lighter. Thus the Czechoslovak engineer developed B.135.
Externally, this one was clearly from the B.35 but more modern, finer, and more racy. It retained a propulsion based on the original Hispano-Suiza engine. His armament was revised with a 20 mm Oerlikon cannon in place of the original Hispano. The MG machine guns of 7.92mm were retained. Especially the landing gear became retractable, thus gaining to the airplane unmistakable kilometers in flight, not to mention its maneuverability that felt.
Soon the Bulgarian Royal Air Force announced that it was looking for a fighter similar to that of Novotny and ordered for twelve B.135 series built by Avia. The first of them left assembly lines at the beginning of 1942 and carried out his first operational mission in June of that year. The eleven other planes followed him quickly, although some were used by German propaganda in liveries sometimes more than fanciful.
Within the Bulgarian forces, the Avia B.135 received the designation DAR-11 and the name of baptism Ljastuvka, that is to say swallow in French. The DAR-11s are mainly dedicated to the air defense of the country's main school base. They were little used in the early years of the conflict, as their facilities were not considered a priority by the Allies. As a result, some Bulgarian officials planned to assemble fifty more copies of B.135 locally for reconnaissance missions and advanced training. However, since Bulgaria did not actually have any aeronautical industrial structure, coupled with the fact that Avia did not have enough French engines for this company, this did not lead to anything and the production of the DAR-11 remained there.
Despite their fragility and limited capabilities, the Bulgarian Avia B.135 experienced fire against Allied aviation. In the summer of 1944, a wave of bombers escorted by Republic P-47 Thunderbolt fighters attacked the small school base on which the light fighters were stationed. The latter took to the air and were, logically enough, decimated by the heavy American single engines. However, it seems that at least one bomber was shot down by Bulgarian B.135. A definitely collegiate victory. However, after this American attack, there were only three DAR-11s still in flight in Bulgaria. They awaited, along with their pilots, the end of the war.
Apparently of an interesting design in 1939, the B.135 was completely obsolete in 1944 when it had to face the US Army Air Force. It seems that the last three hunters of Frantisek Novotny were scrapped. Yet an aircraft, rebuilt from several others, is now on display in Sofia in the small national aeronautical museum.
For the record, the Czechoslovak engineer participated in the development of the Avia S.99 Turbina, a local version of the German battle roll Messerschmitt Me 262, copied for war damage.
Specifications :
Manufacturer Avia Akciová Společnost Pro Průmysl Letecký
Crew 1 pilotYear (s) 1938-39
Length 8.50 m
Wing span 10.25 m
Height 2.60 m
Wing area 17,23 m²
Drive a V-12 Avia HS 12 Ydrs (licensed Hispano-Suiza)
Maxspeed 495 km / h
Travel speed 435 km / h
Climbing power 13 m / s
Service height 8500 m
Maximum range of 500 km
Leermasse 1690 kg
Start weight maximum 2200 kg
Power 632.5 kW (860 hp)
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