Avia B - 534 The Avia B - 534 is a Czechoslovak biplane produced during the period between the Great War and World War II . Design and development . In 1932 , the Czechoslovak aircraft company flew a first prototype of a single - engined fighter biplane , the Avia B - 34 , designed by František Novotný . After modification , the Czechoslovak Ministry of Defence placed an order for B - 34s . A second prototype , the Avia B - 34 / 2 , was built , which was intended to be powered by a Avia Rr 29 radial engine instead of the Hispano - Suiza 12N V12 engine of the first prototype and the initial production series . This engine proved prone to overheating and vibration , however , and it was decided to re - engine the B . 34 / 2 before it flew , fitting it with a Hispano - Suiza 12Y brs V12 engine . The Avia B - 34 / 2 made its maiden flight on 25 May 1933 . The prototype was sent for testing in September and was redesignated as B - 534 . 1 . On 10 September , the B - 534 was displayed to the public for the first time at an Army Air Day . It was to compete against the Praga E - 44 and Letov Š - 231 . A second prototype , the B - 534 / 2 was completed in September 1933 . It differed from the first prototype in having an enclosed cockpit , a revised tail and undercarriage . On 14 April 1934 test pilot Václav Kočí successfully gained a Czechoslovak national speed record of . More testing followed and an initial order for 34 aircraft for the Czechoslovak Air Force , soon increasing to 147 , was placed on 17 July 1934 . At that time , the B - 534 was well ahead of its contemporaries . The United Kingdom was still dependent on Hawker Furies , with the first Gloster Gladiator s being produced at this time . The Soviet Union was placing its hope on its Polikarpov aircraft designs . The United States was still using descendants of the Curtiss Hawk series , with the Seversky P - 35 and Curtiss P - 36 just about to fly as prototypes . The B - 534 was designed as a single - engine biplane fighter with a license - built Hispano - Suiza inline powerplant , and fixed landing gear . The air forces of the 1930s were reluctant to abandon the maneuverability and climb rates of biplanes for the speed of monoplanes , even in the face of new and better technology . The success of the Soviet pilots with biplanes may have contributed to this reluctance ; they were known to strip their aircraft of sliding canopies , preferring to have the wind in their faces . Aircraft with two fabric - covered wings and fixed landing gear were also less expensive to manufacture . First deliveries of the B - 534 to the Czechoslovak air force began in October 1935 , and 666 or so had been completed by 1938 . The first 100 of these were of the first series . The second prototype was the blueprint for the I series , although it was built with an open cockpit . These early series aircraft were initially armed with four 7 . 92mm vz . 28 guns . Two were located in the nose either side of the engine in a similar manner to the Avia B - 34 and two were fitted in the wings . At an early stage of production it was however recognised that the wing mounted guns were troublesome . Aircraft from serial number B - 534 . 47 were completed without the wing guns , which were also removed from the earlier aircraft . The first to fourth series aircraft were fitted with the Avia licence built version of the Hispano - Suiza 12Y drs engine . This was a liquid cooled V12 cylinder engine with a capacity of 36 . 05 litres . On the ground its normal power rating was 650 hp , it could deliver 750 hp for two minutes . At an operational height of 4 , 000 m ( 13 , 123 ft ) , it could reach 860 hp . Total fuel was 347 litres ( 76 gal ) which was held in two fuselage fuel tanks of 90 and 257 litres . The II series completed the remainder of the first order from the Czechoslovak Government , These were forty - five aircraft numbered B - 534 . 102 to 147 . Like the I series these carried four guns . However the solution to the problems with the wing mounted guns was to move these guns , now upgraded to the vz . 30 to the fuselage with the others . The four 7 . 92 mm ( 0 . 312 in ) machine gun s were located in the sides of the fuselage , firing through the propeller . One very modern innovation was a bubble canopy . This was tested on a small number of the early series aircraft , although certainly not a standard fit . In 1936 a second order for 46 aircraft were issued by the government . The first 25 of these were the B - 534 / III version serial numbers B - 534 : 148 – 173 . Production took place in the second half of 1936 . It entered service between March and April 1937 . The III series had aerodynamic refinements which saw the streamlining of the front carburator air intake . Mudguard spats were also often added at the factory to the main gear . The remainder of the second order from 534 . 174 to 534 . 193 were the IV series . With later orders the fourth series would occupy the serial numbers . 174 and 445 and was therefore the most numerous of the types . The most important change to the earlier series was the enclosed cockpit . The IV series also enjoyed a metal light alloy Letov ( Hochfeld ) Hd - 43 propeller . The various refinements allowed the IV series to have an increased speed of over 200 mph , and this placed it on par with the best of its contemporary biplanes . A common alteration to the IV series was the replacement of the tail skid with a tail wheel . Operational experiences had shown that the spat on the main landing gear could become clogged with mud on grassy airfields and cause take - off and landing problems . The spats were then often removed . The superb performance of the aircraft was demonstrated at a flying exhibition in 1937 . The aircraft was tested against the best in the world at the IV International Air Meeting at Zurich ' s Dübendorf airport . The B - 534 entered three of the competitions . The first of these tested climbing and diving . A German Bf 109 took first place and a Henschel Hs 123 pilot pushed his biplane to claim second . The B - 534 took the next three positions . the 534 outflew every other fighter participating , bar the Messerschmitt Bf 109 – and even then , the Avia was only 11 kph slower than the German aircraft . The abrupt partition of Czechoslovakia in 1939 prevented the use of the B - 534 in combat by the nation that had produced it . By then , high performance monoplanes such as the Bf 109 and Britain ' s leading models – the Hawker Hurricane and Supermarine Spitfire – were raising the bar of fighter / interceptor standards . Four sub - types were produced during the B - 534 ' s production run , all with mostly minor improvements . One major variation was introduced in this production run . The Bk - 534 was designed to carry one 20 mm ( 0 . 79 in ) cannon firing through the nose and only two 7 . 92 mm ( 0 . 312 in ) machine guns to the sides . Developmental problems prevented the cannon from ever being used and , desperate to get more aircraft in the air , Avia decided to use a third machine gun in the nose only weeks before the German annexation of Czechoslovakia . Only three examples with this configuration were completed for the Czech air force , and the remaining production block was finished for the Germans . Operational history . On 1 September 1938 , less than a month before the Munich Agreement would cause Czechoslovakia to lose 30 % of its territory and 34 % of its population , 328 B - 534 and Bk - 534s equipped 21 fighter squadrons of the Czechoslovak Air Force , with other aircraft being assigned to reserve and training squadrons , and deliveries continuing of the final batch of fighters . On 14 March 1939 , Germany forced the partition of Czechoslovakia , with Slovakia being declared as the nominally independent Slovak Republic with Germany annexing the remaining " Czech " part of Czechoslovakia as the Protectorate of Bohemia and Moravia the next day . The " Slovenské vzdušné zbrane " ( Slovak Air Force ) was organised out of the units of the Czechoslovak Air Force that were based in Slovakia at the time of partition , and inherited about 71 B - 534s and Bk - 534s . Slovakia quickly had to use its new formed air force , weakened by the departure of Czech pilots , to defend itself when Hungary invaded on 23 March 1939 . Two B - 534s were shot down by Hungarian anti - aircraft fire with four more being shot down by Hungarian Fiat CR - 32 fighters and another Avia making a forced landing behind Hungarian lines , and being captured . In September 1939 , Slovakia participated in the German Invasion of Poland , with the aim of regaining territories lost to Poland at Munich . Two squadrons of B - 534s supported the attack , escorting " Luftwaffe " Junkers Ju 87 bombers on eight missions , losing two B - 534s while claiming a single Polish RWD - 8 liaison aircraft shot down . The same squadrons served with the Germans in Ukraine during summer 1941 , with one squadron returning in 1942 for anti - partisan duty . Obsolescence , lack of spare parts and the old Czechoslovak air force ’ s curious fuel mixture ( BiBoLi , or some other mix of alcohol , benzol and petrol ) finally relegated the surviving B - 534s to training duties . This would have been the last operational service of the B - 534s in Slovak colors if not for the Slovak National Uprising of September – October 1944 . The rest of the Slovak air assets did not turn - coat as expected and the leaders of the uprising were faced with using a rag - tag collection of leftover aircraft , including several B - 534s at Tri Duby airfield . On 2 September 1944 , Master Sergeant František Cyprich , just after testing a repaired B - 534 , downed a Junkers Ju 52 transport under Hungarian colors on its way to a base in occupied Poland . This was at once the first aerial victory for the Uprising and the last recorded biplane air - to - air victory . As the Slovak National Uprising was desperate for available aircraft , Sergeant Cyprich was derided by his colonel for not trying to force the Junkers Ju 52 to land and be captured instead . The last two B - 534s at Tri Duby were burned as the base was evacuated on 25 October 1944 . Bulgaria bought 78 B - 534s in 1939 , well after the partition . The last batch of these aircraft arrived in March 1942 . On 1 August 1943 , seven of these aircraft were able to make two passes at American Consolidated B - 24 Liberator bombers returning from the raid on Ploieşti . Hits were scored but no B - 24s were shot down and some of the B - 534s that received damage in the combat , cracked up on landing . After the anti - German coup of 9 September 1944 , Bulgaria switched sides overnight and its B - 534s were often used in ground attacks against German units . On 10 September 1944 , six B - 534s were involved in a brief melee with six German Bf 109s at low altitude . One B - 534 was lost , but the Germans quickly broke off , wary of the low altitude and the B - 534 ' s manoeuvrability . Survivors . There are no real surviving airframes , but a very convincing B - 534 replica is on display in the Prague Aviation Museum , Kbely , Czech Republic . A second very convincing replica , using ( like the Kbely example ) some original parts , is displayed at the Slovak Technical Museum at Košice International Airport , Slovakia .