Avia BH-21 - Czechoslovak users

The Avia BH-21 was built first in 1925 and was a single-seat biplane fighter that served with the Czechoslovak Army Air Force in the interwar period. It wasn't just a competent fighter but also a good racing airplane too.

It was designed by the same team composed by the engineers Pavel Benes and Miroslav Hajn who designed the BH-17, it's most direct predecessor.
The BH-21 and the BH-17 share some design features, in fact it could be said that the final BH-21 version was a heavily revised and modified BH-17. It's most welcomed feature was the improvement of the pilot's field of view. It was powered by a 300hp Hispano-Suiza 8fb which were built by Skoda under license and was armed with two 0.303in Vickers machine guns placed in the frontern upper part of the fuselage. It was put into production in 1925 and in one year 182 airplanes were produced, 137 of them were assigned to the Czechoslovak Army Air Force and the rest were either sold to Belgium or produced under license by the Belgian SABCA.
Two experimental variants were also built. The BH-21J, which was a regular BH-21 powered by a Bristol Jupiter engine which served as the predecessor for the BH-33 and the BH-21R which was a racing variant and was powered by a boosted Hispano-Suiza 8fb engine delivering 400hp of power.

It wasn't proven as it was retired just before the beginning of the World War II, however it served as a pivotal point for the BH-33 and BH-34 which much more advanced fighter types. The BH-21R earned some renown as it was the winner of several racing competitions in 1925.

Sources:
1. https://en.wikipedia.org/wiki/Avia_BH-21
2. Salamander Books - The Complete Book of Fighers

Avia BH-21 - Belgian Users

Today it's the day to post about the Belgian users of this Czechoslovak fighter.

As the Belgian Aeronautique Militaire was greatly reinforced after the World War I, it was equipped with a mix amount of airplanes, ranging from British and French airplanes and even German ones, like the Fokker D.VII as war plunder. That situation created what today we would call a logistical nightmare as every type of aircraft had different engines, fuel types, spare parts... and so on.
That situation made obvious that a standarisation of their fighter fleet was needed which eventually would be completed in 1931 when they adquired the Fairey Firefly.

As, back in the mid 1920s when the standarisation/modernisation question was considered, the Nieuport-Delage NiD.29, a French fighter that entered service in 1918 was considered only as a minor improvements over their World War I counterparts, plus it was very hard to maneouver and weak.
In the meantime, in Czechoslovakia, the Avia Aviation Company, which was founded back in 1919 caught the attention of the Belgian authorities and achieved world prestige when their airplanes won various competitions all across Europe with their simple yet strong designs.
As the Avia BH-21 flew for the first time on January 1925 near Prague, by 1926 the Belgian authorities showed their interest for it. In order to evaluate them, the Belgian Defence Ministry bought one of them together with a French Dewoitine D.19 and a 420hp Bristol Jupiter powered Dewoitine D.9. Unlike later's standards, there wasn't a competing fly-off and the airplanes were delivered to the squadrons for them to evaluate.
As it was powered by the Hispano-Suiza engine that powered the NiD.29, spare parts weren't a problem and the BH-21 showed a good acrobatic performance so it was favoured by the Belgian Authorities. An order for 44 BH-21 was placed soon, five airplanes were to be constructed by Avia in Czechoslovakia and the 39 of them would be built in Belgium under license by the SABCA (Sociétés Anonyme Belge de Constructions Aéronautique - Belgian Aeronautical constructions Anonymous Society) company.
The first BH-21 arrived in Belgium on 1927 and the first Belgian built BH-21 rolled out from the factory on 14th September 1927. They served with the first group of the second regiment (I/2Aé) with base at Schaffen, close to the Belgian city of Diest.
Although the BH-21 was meant to replace the NiD.29, it served alongside with it both at Schaffen and Nivelles air bases until the early 1930s.
When the Fairey Firefly arrived on Belgium, both the NiD.29 and the BH-21 were gradually replaced and some BH-21 were transferred to the Belgian pilot school in Wevelgem where they served until 1934.
So, apparently, the bottom line is that it was intended to serve as an interim fighter between the obsolete NiD.29 and the Fairey Firefly in order to keep the SABCA's production lines active.

Sources:
1. http://www.belgian-wings.be/Webpages/Navigator/Photos/MilltaryPics/interbellum/Avia%20BH21/Avia%20BH21%20Frontpage.html
2. Salamander Books - The Complete Book of Fighters
3. https://en.wikipedia.org/wiki/Avia_BH-21