SFKB Kb-3/4/5 Chuchuliga

 

The SFKB Kb-3 was a Bulgarian biplane two-seater trainer that was built in 1937. It was designed by engineer Lazarov who also designed the previous Kb-2 and incorporated various improvements into the Kb-3 on the basis of flight tests. It was nicknamed as "Chuchuliga I" (Bulgarian word for Skylark) and only 20 were completed in 1937. 

It was powered by a single Walter-Castor II radial engine driving a two-bladed propeller. Wing system was identical to that of the Kb-2A, but hull chassis and tail section underwent significative changes to improve overall aerodynamics. 

It had a crew of two and served with the Royal Bulgarian Air Force as trainer until 1944. 

The SFKB Kb-4 was a development of the Kb-3 based around various improvements. Engineer Lazarov left Kaproni-Kazanlak (manufacturers of the type) for DAR-Bozurishte in 1938 so Kaproni-Kazanlak designed an improved variant of the Kb-3 called Kb-4 "Chuchuliga II". This was powered by an American Wright E1P-975 radial engine rated at 220 hp of power , covered in a Townend ring, driving a two-bladed propeller. The Wright engine turned to be very appreciated by the Bulgarians, however, when Bulgaria declared war on the United States, their supply was cut, so some of them were completed with the Czechoslovak Walter-Castor II. A total of 28 Chuchuliga II machines were completed.

The Chuchuliga II was the first in the series to feature defensive armament as it was equipped with a 7,7 mm FK-33 machine gun which was the Bulgarian copy of the British Vickers F machine gun. 

It served with the Royal Bulgarian Air Force in the trainer, liaison and reconnaissance roles until 1944.

The Kb-5 Chuchuliga III, was a further development of the type made in 1939. The first prototype was powered by the Walter-Castor II engine, covered in a NACA cowling, however, flight testing was not satisfactory so it was refitted with an Italian Piaggio R.VII C1 engine, driving a three-bladed propeller, achieving the desired performance rates, so it was decided to put it into production. A total of 45 machines of this type were manufactured (making a total of 93 Chuchuligas of every type), however, the production version of the Kb-5 differed from the modified prototype in being powered by a single Walter-Pollux engine rated at 444 hp of power, fitted in a Townend ring and driving a two-bladed propeller. 
The Chuchuliga III featured increased fuel capacity and was fitted with radio and photographic equipment. It was armed with a single 7.7 mm FK-33 machine gun mounted in the nose, synchronised to fire through the propeller. It was equipped with a second FK-33 placed in the observer's position and could carry up to 200 kg (441 lb) of underwing bombs, 100 kg (220 lb) under each lower wing. 

The Kb-5 was the most used variant of the Chuchuliga, as it served with 113, 123, 453 and 463 reconnaissance squadrons of the Royal Bulgarian Air Force. Three aircraft also served with the 5th Bomber Regiment, stationed at Plovdiv, equipped with the Dornier Do-17M and the Avia B-71. Some few machines were also employed in the liaison role by the Naval Squadron at Varna, equipped with the Arado Ar.196 and the Heinkel He.60. 

When the USSR entered Bulgaria, they were employed actively in combat and the type was kept in active as a trainer until the early 1950s.

 

Sources:

1st http://www.airwar.ru/enc/other2/kb3.html (translated)

2nd http://www.airwar.ru/enc/spyww2/kb4.html (translated)

3rd http://www.airwar.ru/enc/spyww2/kb5.html (translated)

4th https://www.armedconflicts.com/SFKB-KB-5-Chuchuliga-SFKB-KB-5-Chuchuliga-III-t167476

5th https://www.nevingtonwarmuseum.com/sfkb-kb-4.html

6th https://en.wikipedia.org/wiki/Caproni_Ca.113

Junkers Ju.52, some European users

 

The Junkers Ju.52/3m is a German cargo and passenger aircraft so successful that it was exported to many countries, among them, the following European ones:

• Austria: The ÖLAG (acronym for Österreichische Luftverkehrs AG - the main Austrian airline between the years 1923 and 1938) ordered a total of 7 Junkers Ju.52/3m between 1935 and 1938 as part of their joint venture with Deutsche Lufthansa (DLH). One aircraft, registered as OE-LAL was lost to an accident on 16th March 1936 and the remaining six machines were taken over by DLH when ÖLAG was bought by Lufthansa on 31st December 1938.
  The Österreichische Luftstreitkräfte (Austrian Air Force) had three Ju.52/3m in service. They formed the core of I. Nachtbomberstaffel (1st Night Bomber Flight) based in Vienna. After the Anschluss (the annexation of Austria into Germany) they were all pressed into the Luftwaffe.
• Belgium: The Belgian Société anonyme Belge d'Exploitation de la Navigation Aérienne (SABENA - Belgian national airline) bought five Junkers Ju.52/3m in the mid 1930s which constituted the backbone of their passenger fleet. One was assigned for operations in the Belgian Congo (as we saw in a previous post).
  They were used in most of their European routes which, using Brussels Haren airport as the main hub, went to Copenhagen, Malmö, Berlin and other European destinations. One of them, registerd as OO-AUB crashed close to the the town of Ostend, at the Belgian coast on 16th November 1937 killing all 12 people on board the airplane, some of which were members of the Hesse royal family. The airplane was on its way to London from Munich when, because of bad weather, it had to be diverted to Steene aerodrome to land. The airplane hit the chimney of a brick factory, crashed and bursted into flames. 
  
• Bulgaria: In 1938, the main Bulgarian airline, Bulgarski Vuzdushni Linii (BVL) acquired two Ju.52/3m, which after the outbreak of the World War 2, they were pressed into service with the Royal Bulgarian Air Force. Those were followed by two more during 1942 and by several captured ones at the end of the conflict (some sources claim that in January 1945 the Royal Bulgarian Air Force had up to 12 Ju.52/3m in inventory). 
  After the War, they were the backbone of the Air Communications Directorate, the forerunner of TABSO, the main Bulgarian Airline of the post-war, and served in various aerial routes until they were gradually replaced by the Russian Lisunov Li-2, with the last Ju.52/3m being replaced in 1950.

Sources:

1. https://en.wikipedia.org/wiki/List_of_Junkers_Ju_52_operators

2. https://en.wikipedia.org/wiki/Sabena

3. https://www.flugzeugforum.de/threads/erstes-oesterreichisches-bundesheer.60691/ (translated)

4. https://de.wikipedia.org/wiki/ÖLAG (translated)

5. https://rzjets.net/aircraft/?page=5&typeid=354

6. https://en.wikipedia.org/wiki/1937_Sabena_Junkers_Ju_52_Ostend_crash

7. http://www.airgroup2000.com/forum/viewtopic.php?t=3314

8. https://bg.wikipedia.org/wiki/Гражданска_авиация_в_България (trnaslated)

9. https://bg.wikipedia.org/wiki/Дирекция_„Въздушни_съобщения“ (translated)

10. https://en.wikipedia.org/wiki/Balkan_Bulgarian_Airlines

Arado Ar.65 - Bulgarian Users

Yes, that's the Luftwaffe's roundel over there.
Today we start covering the foreign users for the Arado Ar.65. As Bulgaria was the only non-German user of this fighter, it will be over in this post.

In 1937 Bulgaria bought some Arado Ar.65 (which by then they were already obsolete) in order to equip their training squadrons. Those airplanes were of the F sub-variant (which barely differed from the E variant) and nicknamed them as "Orel" (Eagle). They were assigned to the second fighter Orlyak (Wing) that was based in Kàrlovo, close to Plovdiv. The wing was composed by five Yato (Bulgarian word for Training Squadrons) and one acrobatic school. Those training squadrons were equipped with many types of airplanes, ranging from Avia B.534, Avia B.122, Heinkel He.51, Bücker Bü.131 and, of course, the 12 Arado Ar.65F. Obviously those training squadrons were just a cover-up for the rebuilt Bulgarian air force and they were purely fighter squadrons.

Officialy the rebirth of the Bulgarian air force was proclamed in 27th June 1937 at Bozhurishte airfield, close to Sofia when the king Boris III handed over to the Vazhdushnite na Negovo Velichestvo Voiski (VNVV - Royal Bulgarian Air Force) 12 Arado Ar.65 and another 12 Dornier Do.11 medium bombers that had been paid from his own pocket. Needless to say that the Ar.65 was intended to be used as a fighter (even if disguished in a training squadron) and the Do.11 was intended to be used in the bomber role. Due to the fact that those airplanes were paid from the king's own pocket, they displayed the king's Boris III own cipher, consisting in a yellow B inside a red shield located in the fuselage side and tail fin.

Despite the design of the Ar.65, it was never liked by the Bulgarian pilots who found the airplane hard to pilot, but they are famous for breaking the restrictions of the Neuilly-sur-Seine treaty that was officialy abolished by the Salonika Agreement of 1938 that allowed Bulgaria to stablish it's own air force.

They were used until well entered the war in the training role.

Sources:
1. http://histaviation.com/ar_65_bulgarian_service.html
2. https://en.wikipedia.org/wiki/Arado_Ar_65
3. Salamander Books - The Complete Book of Fighters