The Avia B-534 is a Czechoslovak biplane fighter developed and manufactured by aviation company Avia. It was produced during the interwar period. The B-534 was perhaps one of the best-known Czechoslovak aircraft of the era.
During 1932, work had commenced on the development of a new single-engined biplane fighter aircraft, the Avia B-34, which had been designed by aeronautical engineer František Novotný. During its development, various alternative engines were considered and trialled before eventually settling upon the licence-built Hispano-Suiza 12Y engine. Other improvements during the prototype stage included the adoption of an enclosed cockpit along with a revised tail and undercarriage arrangement. On 14 April 1934, the second prototype, while flown by test pilot Václav Kočí, successfully attained a Czechoslovak national speed record of . Deliveries of aircraft to the Czechoslovak Air Force commenced in October 1935.
Partially as a result of its impressive maneuvrability, as well as some operators continuing to maintain a preference for the established biplane configuration over the incoming generation of monoplane fighters that would soon prove to outperform them, the B-534 stayed in production for considerable time (1933–1939). During the late 1930s, Czechoslovakia sought to expand production of the type in response to German claims over the Sudetenland (the western border area of Czechoslovakia). Large numbers of the type saw combat with multiple nations during the course of the Second World War. While relatively ineffective in combat during the later stages of war due to its obsolescence, the type formed a sizeable proportion of several countries' military aviation components.
Development Origins During 1932, the Czechoslovak aircraft company Avia flew the first prototype of a single-engined fighter biplane, the Avia B-34, designed by aeronautical engineer František Novotný. After modification, the Czechoslovak Ministry of Defence placed an order for B-34s.Air International July 1974, p. 26. 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 12Ybrs V12 engine.Air International July 1974, pp. 26–27.
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 the B-534.1.Air International July 1974, p. 27. 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.Krybus 1967, pp. 3–4.
A second prototype, the B-534.2, was completed in September 1933.Krybus 1967, p. 3. It differed from the first prototype by having an enclosed cockpit and a revised tail and undercarriage. On 14 April 1934, the second prototype, while flown by test pilot Václav Kočí, successfully attained a Czechoslovak national speed record of .
Initial production 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.Air International July 1974, pp. 27–28. 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 Gladiators 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 about to fly as prototypes.
The B-534 was designed as a single-engine biplane fighter with a licence-built Hispano-Suiza inline powerplant, and fixed landing gear. The air forces of the 1930s were reluctant to abandon the manoeuvrability and climb rates of biplanes for the speed of monoplanes, even in the face of new and better technology. The success of 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 568 had been completed by 1939. 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 on 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 12Ydrs 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 3,000 m (9,842 ft), it could deliver 850 hp for 30 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.
Further development
The II series completed the remainder of the first order from the Czechoslovak Government, These were 45 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 guns were located on the sides of the fuselage, firing through the propeller.Bílý, Miroslav and Jiří Vraný. Avia B-534: Cz. Fighter, 3rd and 4th Version, 2008, pp. 42–44, One very modern innovation was a bubble canopy; this had been tested on a small number of the early series aircraft, although it certainly was not a standard fit.
During 1936, a second order for 46 aircraft was 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 carburetor air intake. Mudguard spats were also often added at the factory to the main gear.Krybus 1967, p. 4.
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 tailskid with a tailwheel. Operational experiences had shown that the spat on the main landing gear could become clogged with mud on grassy airfields and cause takeoff and landing problems. The spats were then often removed.
During 1937, the superb performance of the B-534 was demonstrated at a flying exhibition. The aircraft was tested against the best in the world at the IV International Air Meeting at Zürich'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 km/h slower than the German aircraft.
Allegedly, problems were encountered with the redesign effort to adapt to installation of a newly installed cannon. These were not resolved in the summer of 1938; by this point, Czechoslovakia, sensing rising political tension amongst German claims to Czech-held territory, was eager to get more aircraft in the air, Avia decided to use a third machine gun in the nose. Judging by the size of the gun magazine, the nose machine gun was matched with an increased supply of ammunition. For the nation, time was running out and drew to Munich Diktat, at which point Germany commenced its occupation of the Sudetenland (the western border area of Czechoslovakia). Two series Bk-534 were produced, cn's 501 – 554 (63, for Czechoslovak air force), and cn's 555 – 620. Only three of the second batch were completed for the Czechoslovak air force, and the remaining 63 aeroplanes from this production block were finished for the Germans, after the German invasion of the remainder of Czechoslovakia on 15 March 1939.
Design
The Avia B-534 was a single-seat unequal-span biplane fighter aircraft.Krybus 1967, p. 5. The fuselage used a rectangular structure composed of steel tubes, which were attached together using a mixture of bolts and rivets and braced together using streamline wires. The wing, which had a riveted steel structure and fabric covering, was attached to the fuselage using N struts; similar struts were present in the outer section of the wings attaching the wings together. The forward section of the fuselage was covered with detachable metal panels, while the rear section had a fabric covering.
Production aircraft were exclusively powered by the Hispano-Suiza 12Y 12-cylinder water-cooled engine, rated to produce a maximum of 850 hp, which was built under licence by Avia. The total fuel capacity was 70 gallons (320 litres); a combined cooler and oil tank was installed beneath the fuselage, while a water-based radiator was also set below the engine. Engine ignition was provided via the cockpit, along with automated fire-fighting equipment. Other cockpit equipment included a radio set, oxygen provision, and an adjustable seat and cockpit cover. Early-built aircraft featured an open cockpit, while later-built examples were furnished with an enclosed cockpit.Krybus 1967, pp. 4–5.
The B-534 was furnished with a monoplane tailplane, composed of steel and covered by fabric; similar construction methods were used for the fin and rudder. Both the rudder and the elevator were statically and aerodynamically balanced. The undercarriage was of a split-type configuration, being oleo-sprung and equipped with Dunlop-built wheels. The wheels, which were housed within streamlined fairings, were fitted with brakes; for conducting operations under winter conditions, skis could also be fitted to the undercarriage. According to reports from pilots who flew the B-534, it possessed excellent handling characteristics for the era.
The Bk-534 was designed to carry one 20 mm (0.79 in) Oerlikon FFS-20 cannon firing through the nose, along with a pair of 7.92 mm (0.312 in) machine guns to the sides of the fuselage. By the summer of 1938, Czechoslovakia, sensing rising political tension caused by German claims to Czechoslovak border territory, was eager to get more aircraft in the service, thus Avia decided to use a third machine gun in the nose. However, there have been claims that the company had encountered substantial difficulties in adapting the aircraft to accommodate the additional weapon and these were not quickly resolved. Judging by the size of the gun magazine, the nose machine gun was matched with an increased supply of ammunition. Consequently, however, the fuel load was decreased
Operational history Czechoslovakia