Interwar Czechoslovak Air Force

Foreign aircraft types used by the Czechoslovak Air Force after World War I.

Avia aircrafts

Avia BH-1
The Avia BH-1 was a two-seat sports plane built in Czechoslovakia in 1920. It was the first product of the Avia company, and it was originally designated BH-1 exp. The BH-1 was a low-wing braced monoplane of wooden construction, with tailskid undercarriage. Power was provided by a Daimler engine, which proved inadequate to fly the aircraft with both seats occupied.
Soon after its first flight, it was exhibited at the inaugural International Aviation Exhibition in Prague. Its reception there was so enthusiastic that Czechoslovakian president Tomáš Masaryk awarded Avia with a 100,000 CSK development grant.

Avia BH-3
The Avia BH-3 was a fighter plane built in Czechoslovakia in 1921. Conceptually a descendant of the BH-1 sports plane, it was a braced, low-wing monoplane of conventional configuration and tailskid undercarriage. Following favourable trials in June 1921, ten examples were ordered by the Czechoslovakian Air Force. These were delivered in 1923 under the military designation B.3. The type proved temperamental in service and was soon relegated to training duties, where it served until 1927.

Avia BH-4
The Avia BH-4 was a prototype fighter aircraft built in Czechoslovakia in 1922. It was a development of the BH-3 fitted with a Hispano-Suiza 8 engine in an attempt to improve the aircraft's performance. To accommodate the new powerplant, the forward fuselage was considerably redesigned, and the structure in general and undercarriage in particular were strengthened. Performance was found to be only marginally better than the BH-3, and development was quickly abandoned.

Avia BH-5
The Avia BH-5 was a two-seat sport aircraft built in Czechoslovakia in 1923. It was based on the firm's experience with the BH-1 and shared that aircraft's basic design: a low-wing, braced monoplane. It received the nickname "Boska" due to its registration, L-BOSA, an appellation that was later transferred to the various Avia aircraft derived from this design. The BH-5 was flown competitively by Zdeněk Lhota at the Belgian Touring Aircraft Contest in Brussels in 1923 and won both the overall prize for the event and the King of Belgium Prize.

Avia BH-6
The Avia BH-6 was a prototype fighter aircraft built in Czechoslovakia in 1923. It was a single-bay biplane of unusual configuration developed in tandem with the BH-7, which shared its fuselage and tail design. The BH-6 crashed early in its test programme, and when the related BH-7 did as well, both implementations of this design were abandoned.

Avia BH-7
The Avia BH-7 was a prototype fighter aircraft built in Czechoslovakia in 1923. It was a parasol-wing monoplane developed in tandem with and as an alternative to the BH-6, which shared its fuselage and tail design. Like the BH-6, the BH-7 was involved in a number of serious crashes during its test programme, which led to its abandonment as a fighter. Undaunted, however, Avia used the design as the basis for a racing aircraft, shortening the wingspan by 1.4 m (4 ft 7 in) and fairing it directly into the top of the fuselage and dispensing with the cabane struts. This revised version was designated BH-7B and the fighter (retrospectively) as the BH-7A. When the design proved no more successful as a racer it was finally put to rest.

Avia BH-8
The Avia BH-8 was a prototype fighter aircraft built in Czechoslovakia in 1923. It was an unequal-span biplane developed on the basis of the ill-fated BH-6 design, in an attempt to address that type's problems. It shared the BH-6's unusual wing cellule design. When test-flown in late 1923, it did indeed display better flying characteristics than its predecessor, but was overtaken in development by another variation on the same design, the BH-17.

Avia BH-9
The Avia BH-9 was a one-seat sport aircraft built in Czechoslovakia in 1923, based on the BH-5. The BH-9 was a low-wing braced monoplane that accommodated the pilot and passenger in tandem, open cockpits. The BH-9's structure was strengthened to allow for the use of a higher-power engine than in its predecessors, and for the first time, this was a domestically-produced powerplant. The Czechoslovakian Army showed interest in it as a trainer and liaison aircraft, and ordered 10 examples under the designation B.9. A B.9 won the 1925 Coppa d'Italia air race, and the following year, one was flown on a 1,800 km (1,100 mi) circuit Prague-Paris-Prague with an average speed of 131.2 km/h (82 mph).

Avia BH-10
The Avia BH-10 was a single-seat aerobatic sports plane built in Czechoslovakia in 1924, based on the Avia BH-9. It was easily visually distinguished from the BH-9 by the tall anti-roll pylon added behind the open cockpit in order to protect the pilot in the event that the plane flipped over or crashed while inverted. At least 20 examples were bought by the Czechoslovakian Army as a training aircraft and operated under the designation B.10.

Avia BH-11
The Avia BH-11 was a two-seat sport aircraft built in Czechoslovakia in 1923, a further development of the Avia BH-9. The main changes in this version involved a redesign of the forward fuselage. 15 examples were ordered by the Czechoslovakian Army as trainers and general liaison aircraft and operated under the military designation B.11.

Avia BH-17
The Avia BH-17 was a biplane fighter aircraft built in Czechoslovakia in 1924. It was a development of the BH-6 and BH-8, and work on the latter aircraft was cut short in favour of this one. Operational trials in 1924 revealed performance good enough for the Czech Air Force to place an order for 24 examples. In actual service, however, the BH-17 proved unreliable and was soon withdrawn.

Avia BH-19
The Avia BH-19 was a fighter aircraft built in Czechoslovakia in 1924. It was a low-wing braced monoplane derived from the Avia BH-3 and reflected its designers' ongoing belief that the monoplane configuration was the most suitable for a fighter aircraft. Initial trials revealed excellent performance, but also displayed control problems and aileron flutter. Nevertheless, the Czechoslovak Army were sufficiently impressed to tell Avia that it would order the BH-19 if the problems could be rectified. The first prototype was destroyed in a crash during speed trials, and the second prototype revealed no better handling than its predecessor. At this point, the Czechoslovakian War Ministry stepped in and asked Avia to cease its attempts to develop a monoplane fighter.

Avia BH-21
The Avia BH-21, first built in 1925, was a robust biplane that served an important role in securing Czechoslovak national security during the period between World War I and World War II. As well as being a competent fighter, it was also an accomplished racer, winning several air races of its time. Both versions utilized 224 kW (300 hp) Hispano-Suiza 8fb engines built under license by Škoda. The BH-21 was put into production in 1925 and had a one-year production run which yielded 182 aircraft with 137 being produced by Avia for the Czechoslovak Air Force, one more was built by Avia for SABCA and another 44 were produced under license by the Belgian company, Société Anonyme Belge de Constructions Aéronautiques "SABCA" for the Belgian Air Force. There were also two experimental variants: BH-21J with Jupiter engine (predecessor of BH-33) and a race plane BH-21R with boosted HS-8Fb engine (298 kW/400 hp). While in service, the BH-21 saw no combat as it was retired before the outbreak of World War II. In spite of this, it served as an important stepping stone to the more advanced BH-33.

Avia BH-22
The Avia BH-22 was a trainer aircraft built in Czechoslovakia in 1925, based on the BH-21 fighter. The overall weight was reduced, while the structure was strengthened overall to allow for aerobatics. The weapons of the BH-21 were deleted and replaced by a camera gun. The type saw long service as a special aerobatic trainer and eventually several examples found their way into Czechoslovakia's aero clubs.

Avia BH-23
The Avia BH-23 was a prototype night fighter aircraft built in Czechoslovakia in 1926. The design was derived from the BH-21 day fighter, incorporating the structural changes made in the BH-22 trainer, and the type was originally designated BH-22N. Searchlights and other night-flying equipment were added, but the Czechoslovak Air Force were not interested in the project and no sale resulted.

Avia BH-25
The Avia BH-25 was a biplane airliner built in Czechoslovakia in 1926. Typical of airliners of its time, it seated five passengers within its fuselage, while the pilots sat in an open cockpit above. Of conventional configuration, it was a single-bay biplane of equal span and unstaggered wings, with fixed tailskid landing gear. Originally designed to use a Lorraine-Dietrich engine, this was changed to a Bristol Jupiter in service. After their withdrawal from airline use in 1936, some were used by the military for a while before ending their days as training targets.

Avia BH-26
The Avia BH-26 was a two-seat armed reconnaissance aircraft built in Czechoslovakia in 1927. It was a single-bay unstaggered biplane with equal-span wings and a fixed tail-skid undercarriage. Both upper and lower wings featured long-span ailerons, which were dynamically balanced by a small auxiliary airfoil mounted to the upper surface of the lower ailerons. Its design was typical of this type of aircraft built during World War I and the years following; pilot and observer in tandem open cockpits with the observer armed with a machine gun on a ring mount.

Avia BH-33
The Avia BH-33 was a biplane fighter aircraft built in Czechoslovakia in 1927. It was based on the BH-21J that demonstrated promising results by marrying the original BH-21 airframe with a licence-built Bristol Jupiter radial engine. Three examples were sold to Belgium, where there were plans to build the type under licence, but this did not eventuate. Licence production was undertaken, however, in Poland, where a single example was sold along with a licence to build 50 aircraft. These were designated PWS-A and put into service with the Polish Air Force in 1930. Development continued with an almost total redesign of the fuselage, replacing the wooden, slab-sided structure with one of oval cross-section built up from welded steel tubes. Designated BH-33E, this was at last a world-class fighter for its time. Nevertheless, the response from the Czechoslovakian military was lukewarm (although two were bought for the national aerobatics team), and Avia again looked abroad for customers, this time selling 20 aircraft to Kingdom of Yugoslavia, along with a licence to produce another 24. Two or three examples were also bought by Russia for evaluation.
In late 1929, a further development was flown as the BH-33L, featuring longer-span wings, and a Škoda L W-block engine. This version finally brought the company the domestic sales that it had been hoping for, with 80 aircraft ordered by the Czechoslovak Air Force. These became standard equipment with some air regiments up to the outbreak of World War II. A single, final variant with a BMW-built Pratt & Whitney Hornet engine was built as the BH-33H (later redesignation B-133) in 1930, but this did not lead to production.

Avia B-34
The Avia B-34 was a biplane fighter aircraft built in Czechoslovakia in the early 1930s. It was the first design of František Novotný for the Avia company and although built in only small numbers, it paved the way for the Avia B-534.The B-34 was an all-metal single-bay biplane of conventional configuration, with tailwheel undercarriage. The mainwheels of the prototype were fitted with large spats. The first prototype underwent testing from the 2nd February 1932, leading to a large number of modifications being made; in particular the tail and engine cowling designs were considerably revised. The resulting B-34.1 served as the prototype for the 12 production machines ordered by the Czechoslovakian Air Force. These had an even larger vertical tail, interplane struts of narrower chord, and no wheel spats.A second prototype, the B-34.2 was fitted with an Avia Rr 29 radial engine but never actually flown with it as the engine was not sufficiently developed. It was, however, offered to the Air Force under the redesignation B-234. The second prototype was then fitted with an inline Hispano-Suiza 12Ybrs piston engine, and later redesignated B-534.1.

Avia B-634
The B 634 represented the ultimate in the aerodynamic development of the basic B 34 single-seat fighter biplane design, and was to be numbered among the cleanes aircraft in its category to be flown. Tested in 1936, the B 634 was powered by an Avia-built HS 12Y crs endine mouting a 20-mm Oerlikon FFS cannon, two 7,7-mm Model 30 machine guns being installed in the upper fuselage decking. There was virtually no commonality of componets between the B 634 and the B 534. I from which it was derived. By comparison with the earlier fighter, the upper wing of the B 634 featured increased chord while the lower wing had reduced chord, the wingtips were redesigned, the ailerons were broader, the gap was reduced, increasing the splay of the interplane struts, the stagger was greatly increased, and cut-outs were introduced on the lower wings roots. Two prototypes were built, one with canopy.ilt, one with canopy.

Avia B-122
The Avia B.122 Vosa ("Wasp") was a Czechoslovak single-seat biplane trainer aircraft, which was developed in the mid-1930s. It saw some service in the first years of World War II. In the spring of 1934 the Czechoslovak Army Command decided that some Czechoslovak Air Force pilots would participate in the international aerobatic competition Coupe Mondial. For this purpose, the Czechoslovakian aircraft manufacturer Avia was given a task to design and construct an aircraft. The prototype, B.122 was presented after a mere six weeks time.The Czechoslovak pilots had only a few weeks to learn and master the aircraft as the competition was to be held in July 1934. Luckily, the design was quite successful and the Czechoslovak pilots managed to win the 4th and the 8th place in the competition. Afterwards, the aircraft was modified, based on the pilots' inputs, and this resulted in the improved version Ba 122. The Ba.122 was equipped with a larger rudder and had a more powerful engine. This version went into production and 35 aircraft were built. In the 1936 Summer Olympics in Berlin, Czechoslovak pilots took 2nd, 3rd and 8th place with their Avias. Some of these aircraft were equipped with 9-cylinder Walter Pollux engines instead of the 7-cylinder Castor. 1937 was also a successful year, as the Avias managed to take 1st and 3rd place at the International Flying Meeting in Zurich in July/August 1937. These successes led to export orders from the Soviet Union and Romania. The aircraft was later further developed into the prototypes Ba.222, Ba.322 and Ba.422. The Czech Ministry of Defence ordered 45 Bs.122 trainers. However, the outbreak of World War II put an end to further development. Some Avias ended up in the German Luftwaffe when parts of Czechoslovakia were absorbed into Germany in 1939. Other aircraft were sold to the Slovakian and Bulgarian air forces.

Avia tech tree

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