Tupolev SB in Spain. Part Two.

 

When the German Messerschmitt Bf.109B fighter made its appearance over Spain, with its experienced pilots, the losses of the SBs started to pile up. On 7th February 1938 four bombers were shot down, making it the worst loss rate in a single date, up to that date. By June 1938 only a handful of aircraft were serviceable, however, in July, thirty more SBs were delivered via France and were assembled at Figueres, Catalonia. This last delivery increased the total number of Tupolev SBs in Spain up to 93. 

During the conflict, one SB was captured by the Nationalist and received Aviación Nacional's (Nationalist Air Force) codes, was painted with Italian colours and camouflage pattern. It was shown at Tablada airfield (Seville) in October 1937.

One distinctive feature of the SBs assembled in Spain during the late-war period was the introduction of a fairing in front of the rear gunner's compartment. 

The code assigned by the Fuerza Aérea Republicana Española (FARE - Spanish Republican Air Force) to the SB was BK (which stands for Bombardero Katiuska - Katiuska Bomber) followed by a three-digit number, painted in black. Additionally, after a reform in FARE, some SBs received a two-digit number code painted in the tailfin.

The aerial superiority of the Nationalists, coupled with the inexperience of the Republican Katiuska's crews, quickly dropped the available number of SBs in the FARE. When the Spanish Civil War ended on 1st April 1939, a total of 73 SBs were lost, 40 of them to Nationalists actions. 

Shortly after the war, the reformed Spanish Ejército del Aire (Air Army - Spanish Air Force) created an unit with the captured and surrendered Katiuskas. This unit was called 13º Regimiento de Bombardeo (13th Bomber Regiment), based at Los Llanos airfield (Albacete - New Castile) and was composed of 19 Tupolev SBs. Some of these machines were re-engined with the Hispano-Suiza 12Ybrs engine, although the covering cowl was maintained, so, externally, there was no difference. This was done to ease maintenance, as they were still subject to spare shortages up to the point that, in April 1943, only three SBs were available. This forced Francoist authorities to ground the SBs and purchase some Junkers Ju.88A bombers from Germany which arrived in December 1943. The remaining Katiuskas were employed for occasional training flights until 1948, when they were scrapped.

Sources:

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/spanish/spanishrepublican.htm

4th http://elhangardetj.blogspot.com/2008/10/tablada.html (translated)

Tupolev SB in Spain. Part one.

 

In the early days of the Spanish Civil War, the Soviet freighter ship Komsomol shipped the first 31 Tupolev SB bombers from Odessa to the port of Cartagena, Murcia, south-eastern Spain. The Spanish Republican Government did pay  $110.000 US dollars per aircraft. Those SBs were part of one of the first production batches completed at GAZ-22 factory. They were unloaded on 15th October 1936 and assembles at Los Alcázares airfield, in the region of Murcia. 
The bombers were assigned to Grupo 12 (Group 12), which also operated the Polikarpov I-15 and I-16 fighters. Flying personnel, most of them, were Soviet, however, some Spanish and other international volunteers worked with the Grupo from its origin. Since the beginning of the conflict the SB was nicknamed as Katiuska by the Spaniards, after a popular character of a Spanish operetta, back at the time.

On 28th October 1936 the SBs flew their first combat mission when four Katiuskas belonging to 1ª Escuadrilla / Grupo 12 (1st Squadron / Group 12), under the command of the Swiss Ernst Schacht raided the Tablada airfield at Seville. After the attack, the SBs flew away at very high speeds, so Nationalists fighters couldn't intercept them, causing consternation among the Nationalists.

On 1st November 1936, three Katiuskas attacked the Gamonal airfield, in the city of Burgos, destroying six Fiat Cr.32 Italian fighters on the ground. The next day, two Cr.32 shot down one SB 2M-100 over Talavera, in new Castile. This loss showed its main flaw: the lack of both crew armour and self-sealing fuel tanks. 

On 6th November 1936 the SBs raided the airfield of Ávila, old Castile, destroying two Heinkel He.51 fighters of the German Condor Legion. These kind of raids, where a small group of Katiuskas targeted Nationalists airfields were very common in the months of November and December 1936. The first Spanish Nationalist pilot to claim a downed SB 2M-100 was Bermúdez de Castro. On 7th December he shot down a Soviet bomber over Castilblanco, Extremadura. By the end of the year 1936, Grupo 12 had lost a total of six out of 31 Katiuskas to various reasons.

In January 1937 the 1ª and 2ª Escuadrillas (1st and 2nd Squadrons) of Grupo 12, flew missions from Marbella, Andalusia, to try to stop the Nationalist advance on Málaga. On 20th January, some Nationalists strongpoints in Ceuta (Spanish Morocco) were bombed. During early March, the Katiuskas took part in the Battle of Guadalajara (old Castile) by bombing positions of the Italian Expeditionary Force. On 29th May 1937 two Katiuskas attacked the German Deutschland Panzerschiffe (Armoured Cruiser), off the coast of Ibiza, damaging moderately the cruiser in the attack.

The cargo freight SS Aldecoa arrived at the port of Cartagena on 24th June 1937 with 21 more Katiuskas, these were complemented with 10 additional ones shipped by the freighter SS Artea Mendi the next 1st July. This second batch was composed of the more powerful and improved SB 2M-100A model. The 31 new Katiuskas were assembled at San Javier, Murcia and Líria, in Valencia. They were assigned both to Grupo 12 and the newly formed Grupo 24. This new group flew its first combat mission on 3rd July when its two squadrons raided Talavera, Salamanca and Ávila. 

Both Grupos saw action during the Republican Offensive in Brunete (west of Madrid) on 6th July 1937. On 8th July a Katiuska was shot down by a Messerschmitt Bf.109B of the Condor Legion. Four days later, a Katiuska managed to shot down a Bf.109B that was attacking the formation of bombers.

In the Fall of 1937 Soviet crews were withdrawn and replaced by Spanish personnel, leading to the dissolution of Grupo 12 and assigning every Katiuska to Grupo 24. 

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/spanish/spanishrepublican.htm

Tupolev SB in Finnish service. Part two.

 

The Finnish Ilmavoimat (Finnish Air Force) assigned the 16 SB purchased from Germany (see our previous post for details) to the three flights of Lentolaivue 6 (Flying Squadron - LeLv.6) based at Nummela. Those SBs were employed in bomber, reconnaissance and anti-submarine patrols all over the Gulf of Finland. 

The Soviet coastal submarine M-95 was sunk by SB-1 flown by Lt. Virtanen east of Suursaari on 28th May 1942. On the next 14th July, many Finnish SBs attacked with depth charges a surfaced Soviet submarine off the Finnish town of Pellinki (east of Helsinki). Lelv.6 claimed it was a Shchuka-class submarine, Shch-317, to be more precise. On 14th October 1942, SB-1 destroyed Shch-302. 

The Ilmavoimat did not lose any of their SBs to Soviet fighters or anti-air fire, however six SB 2M-103s were destroyed in accidents or technical failures. During Continuation War, three Soviet submarines were sunk by SBs and many other were damaged. Additionally, one merchant ship and four other small vessels were also sunk by Finnish SBs.

Eventually when the Red Army launched an offensive against Karelia in June 1944, Finland was prompted to sign an armistice on 4th September 1944, giving way to the Lapland War (1944-1945) to drive out Germans from Finland. The Finnish overpainted the yellow identification bars on wing and fuselage. During this war a total of 84 anti-submarine sorties were flown by Lelv.6's SBs over the Gulf of Finland but they did not damage nor sink any German U-boat. No Finnish SB was lost during the Lapland War and, on 1st April 1945 the roundels were changed from the Finnish swastika to the white-blue-white roundel of the Ilmavoimat. Those markings were applied to any surviving SB. After the war they served either as trainers or were kept in storage depots until late 1940s when they were phased out.

Going back to the Winter War, among the eight SB 2M-103 captured by the Finns, there was a late production machine which, after being refurbished, received the code of SB-8. This bomber was selected to be converted into trainer, similar to the Tupolev USB. 

This SB-8 machine was different from other SBs in having the landing light in the right wing's leading edge. Its conversion was completed on 25th January 1943 and was assigned to Täydennyslentolaivue 17 (TLelv.17 - Advanced Training Squadron) at the town of Luonetjärvi, in Central Finland on 19th February. This trainer was later re-assigned to Pommituslentolaivue 46 (PLelv.46 - Bomber Squadron) based at Luonetjärvi too. It was later assigned to Lelv.45. On 24th February 1945 it was put in storage after having flown 268 hours with Ilmavoimat.

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/finnish/finnish-number.htm

4th https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/usb/usb.htm

Tupolev SB in Finnish service. Part one.

 

During the Winter War, which comprised from 30th November 1939 to 13th March 1940, the Finnish captured eight salvageable SB 2M-100A. Those were repaired and assigned to Ilmavoimat (Finnish Air Force), after the conflict, so they didn't see action with Ilmavoimat in the Winter War. However, eventually only one SB 2M-100A was in good enough conditions to be assigned to active service.

It was during that conflict that the Finnish managed to capture seven SB 2M-103, when many were forced to land in Finland.

The first SB 2M-103, registered as VP-10 by the Ilmavoimat, was overhauled at Valtion lentokonetehdas (State Aircraft Factory) at Tampere, Finland. On 13th August 1940 it was assigned to the Ilmavoimat and, on 15th October it was assigned to Lentolaivue 6 (LeLv - Flying Squadron) at Nummela. LeLv 6 was directly subordinated to Finnish Navy's Headquarters.

The Ilmavoimat re-registered the remaining SBs (among them the only SB 2M-100A which could be put into service) from VP-2 to VP-8. VP-10 was re-registered VP-1 in June 1941. During Continuation War, ranging from 25th June 1941 to 19th September 1944, LeLv 6 suffered its first casualty on 2nd August 1941 when VP-3 crash-landed at Nummela. The Finns changed the code for the remaining SBs in September 1941 but they didn't change the numerical suffix of each airplane. It was during this period that the SBs were repainted with yellow identification bands to identify them as Axis aircraft operating on the Eastern Front.

During the summer of 1941, the Germans captured several SBs in the context of Operation Barbarossa. Finland bought 16 SB 2M-103 from German war booty depots. On 5th November 1941 the six units arrived on Finland and were assigned codes SB-9 to SB-14. The following five were delivered in April 1942 and received codes SB-15 to SB-19. The last five ones reached Finland in August that same year. All those SB 2M-103 were refurbished at Valtion lentokonetehdas and some of them were equipped with additional carburetor intakes on the side of the engine cowling.

That made a total of 24 Tupolev SBs (23 SB 2-M103 and one SB 2M-100A) serving with the Ilmavoimat.

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/finnish/finnish-number.htm

Avia B-71

 

In May 1935 the First Czechoslovak Republic signed a non-aggression pact with the USSR, which included a mutual economic aid clause. That treaty also included that Czechoslovakia (one of the world's leading arms exporters at the time) granted license production rights for their 75mm Skoda C-5 mountain gun and 75mm Skoda R-3 anti-aircraft gun to the Soviets. In exchange, Czechoslovakia received a license to build the Tupolev SB.

In virtue of that agreement, a contract was signed between Technoexport (Soviet Union's external trade organization) and the Czechoslovak Ministry of National Defence on 15th April 1937. A total of 61 Tupolev SBs would be delivered straight from the USSR and Avia (subsidiary of Skoda) would build another 161 SBs at their Cakovice plant. The SB received the denomination of B-71 given by the Czechoslovenske Letectvo (CL - Czechoslovak Air Force) and was planned to serve both in the bomber and long-range reconnaissance roles.

The Soviet-supplied SBs were equipped with Czechoslovak-built engines, armament, radios and instruments. Those instruments were sent to Fili, Moscow, to be fitted to various airframes at GAZ 22 factory. It was estimated that the unit price for each of those SBs was set at $ 118.460 of the time, that's $ 2.519.362,55 adjusted for 2023 inflation. 

The Avia B-71 was powered by two Hispano-Suiza H.S.12 Ydrs engines, yielding 860 hp of power each and built under license by CKD-Praha. The original four 7,62mm ShKAS machine guns were replaced by three Czechoslovak 7,92mm ZB vz30 machine guns.

When compared to the SB 2M-100-A, it differed in various details. As we've just written, one vz30 machine gun was placed in the nose, instead of the origina two ShKAS. Two balance weights were added in the lower-right wing and the B-71s were equipped with radios, while the SB 2M-100As lacked any radio equipment. The B-71 had a retractable antenna fitted in the right rear fuselage. Those features were copied by the Soviets in the late-built SB 2M-100As. 

The first three Soviet-delivered machines were sent in March 1937. The first machine was assigned to the Vyzkummy a Skusební Letecky Ústav (VZLU - Research and Experimental Aviation Institute) at Prague-Letnany airport for trials on 17th April 1937. This first aircraft retained the cartridge case ejection tunnel present on every SB, but not in every subsequent B-71. The right nose step on these three initial aircraft, was mounted higher in production B-71s. The first three B-71 had front and back sights on the vz30 machine guns, however, those sights were not fitted in production aircraft.

The Soviet-built 61 B-71s were flown from Fili, Moscow to Kiev (Ukrainian SSR), where they were delivered to Czechoslovak pilots who flew the type from Kiev to Kocice (Czechoslovakia) via Romania. Once in Czechoslovak territory, the CL assigned the B-71 to their units. The first three were assigned to an operational squadron on 13th March 1938. Those B-71 intended for the bombardment role were assigned to the 5. Letecky Pluk (5.LP - Aviation Regiment) based at Brno-Turany airport and the 6.LP based at Prague. The B-71s intended for long-range reconnaissance were assigned to the 1.LP, at Prague and the 2.LP at Olomouc, Northern Moravia. 

The Germans invaded Czechoslovakia on 15th March 1939, so the B-71 was active with the CL for one year and two days, forming the Protectorate of Bohemia and Moravia. Avia had not begun license production of the B-71 yet, so every B-71 that fell into German hands was of Soviet production.

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/b-71/czech%2Bslovak/czech%2Bslovak.htm

Avia B-71 in use with Germany

 

When occupied Czechoslovakia on 15th March 1939, they seized a total of 59 serviceable B-71, all of them from Soviet production, stationed on various Czech airfields. 

The Germans hastily applied their markings on the bombers, disarmed them and deleted a circular window on both sides of the rear fuselage. Most B-71s were flown to Merseburg (Saxony-Anhalt), to be put in storage. During these flights, some Czechoslovak pilots assisted German ones carrying out ferry flights. Bohuslav Sikmund and Josef Navesnik were part of one of those flights. They flew from Hradec Králové but, instead of following the course to Merseburg, they defected to the USSR on 26th April 1939. 

One B-71 was sent to Rechlin Test Centre in April, where it was employed for various engine flight tests until June. 

As we've already covered in this post thirty-two B-71s were sold to Bulgaria in September 1939, for which they received civilian German codes in order to ferry them to Sofia. The Slovak Air Arm also received three B-71, as we already saw here.

Avia had already many plans for the B-71 in March 1939, however, the Germans found the B-71 ideal for the target-tug role, so they ordered 76 Avia B-71A (a target-tug variant) to Avia and Aero. 

A total of 41 B-71As were completed at Avia's factory in Cakovice, close to Prague, with the first machine taking off on 21st July 1939. In September that first machine was assigned to Erprobungstelle (Test Centre) at Tamewitz. The last Avia-built B-71A rolled out from the factory on 27th August 1940. 

Aero manufactured a total of 35 B-71As, however, it wasn't until 22nd May 1940 when the first Aero-built B-71A left the assembly line at Prague-Vysocany. It was assigned to Luftdienst Kommando 1/7 (1/7 Air Service Command) at Lechfeld airfield, in Bavaria. 

The B-71A differed in many ways from the Soviet-built B-71. They lacked armament and the central section of the nose glazing was covered by a metal sheet. The V-shaped step below the emergency roof hatch on starboard was also removed. It was also equipped with a fixed radio antenna placed on top of the fuselage and aft of the cockpit, replacing this way the retractable one on the lower part of the fuselage. A rear-view mirror was also installed on top of the canopy frame. As we've said, most of the B-71s had their rear circular small windows deleted and the B-71A was not an exception. On the left, a crew entry step was placed, just aft of the rear wing.
Both lower gun position and bomb bay were replaced with the target-towing equipment, which consisted of a winch, a drum with the 2,5 mm diameter cable and a 3 m  (9ft 10 in) long canvas target sleeve. The winch varied in length, ranging from 6 m (19 ft 8 in) to 9 m (29 ft 6 in). This equipment shifted aircraft's centre of gravity, so, in order to compensate, 240 Kg (529 pounds) of ballast were added to the navigator's compartment in the nose. 

Both production runs received Luftwaffe's colours, markings and insignias and most of them were assigned to Luftdienst Kommando 6 (Air Service Commando 6). They were employed both for target towing and meteorological flights. Some were also flown by the Ausbildungsgruppe 104 (Training Group 104), Jagdfliegerschule 4 (Fighter Pilot Training Unit 4) and even by the secret bomber wing Kampfgeschwader 200. 

The B-71A was widely used by the Luftwaffe thanks to its well-built all-metal structure and good performance. By March 31st 1944 there were still 57 B-71A in service with the Luftwaffe. That number was, however, reduced to just nine by September 30 1944 due to shortage of spare parts.

The B-71B was an improved variant of the B-71A that came out in late 1940. The target-towing cable was lengthened to 1.000 m (3281 ft). The tow-cable operator's canopy was moved forward to allow the additional space needed for the improved target-towing device. This new device was 70 kg (154 pounds) heavier than that of the B-71A. The rear cockpit's canopy was also moved forward.

The B-71B differed in many ways from its predecessor. Two triangular-shaped windows aft of the nose-glazing were deleted and a t-shaped boom was added on top of the antenna mast. A step was installed on top the port wing's rear extension and a holding boom was also mounted behind the rear canopy. Bomb bay doors were welded and the nose compartment exit hatch was relocated aft. Some late production machines were fitted with a windshield in front of the rear-aft sliding canopy. Winch compartment was replaced forward and the two stabilization booms on the housing's rear were deleted. The oval rear fuselage windows were also removed. Three additional pylons were installed under each wing. 

A total of 35 B-71Bs were built by both Aero and Avia. Aero built ten at Prague-Vysocany, the first of which left the assembly line on 18th October 1940 and was assigned to Luftwaffe's main test and evaluation centre at Rechlin. The last Aero-built B-71B was accepted by the Luftwaffe on 26th November 1940. 
Avia's factory at Cakovice manufactured 25 B-71B to the Luftwaffe, with the last aircraft being completed on 30th April 1941. Between July 1939 and April 1941 a total of 111 Avia B-71A and B-71Bs were manufactured by Avia and Aero for the Luftwaffe.

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/b-71/german/german.htm

Tupolev SB in service with China

 

On 7th July 1937 Japan invaded China sparkling the Second Sino-Japanese War. The Chinese Air Force (CAF) had, at that time just 284 aircraft and was commanded by General Moa Pang-chu who had learned to fly in the USSR. 

On 21st August both China and the USSR signed a non aggression pact, by virtue of which a secret clause was included to send military aid to China. This clause stressed on rebuilding the virtually destroyed Chinese Air Force. The Chinese negotiated a major loan with the USSR to provide China with war materials in exchange for cheap raw resources over the next five years.

During the course of October 1937,  four hundred fifty Soviet pilots and technicians were gathered at Alma Ata (Kazakh SSSR - nowadays Kazakhstan) from where they departed with a first batch of 185 aircraft (115 fighters, 62 bombers and 8 advanced trainers). These aircraft were transported by rail from Alma Ata to Lanzhou (province of Gansu) , where the Chinese railroad ended, following the trace of the old Silk Road. 

Chinese SB 2M-100-As (with old style cowlings) were all built at the GAZ factory No. 125 Imeni Stalina located at Irkutsk, in Siberia. Soviet pilots collected the first batch of bombers from the factory and ferried them from Irkutsk to Suzhou (in Gansu too) via Ulan Bator, Mongolia. Due to a sandstorm, the aircraft had to be grounded for a short time, before resuming the flight from Suzhou to Lanzhou. Many Soviet advisors began to train Chinese crews assigned to the 2nd Group of the CAF, on the SB 2M-100A. The first combat mission was led by Cpt. I.N. Kozlov on 2nd December 1937, when nine SBs attacked Japanese shipping in the East China Sea off the coast of Shanghai. 

A second batch of 31 SB 2M-100A was led by Cpt. Fiodor P. Polynin. These machines were ferried from Irkutsk to Hankou with stopovers at Ürümqi (Xinjiang), Hami (Xinjiang) and Lanzhou. The bombers were manned by Soviet crews until the Chinese were able to master the aircraft. A total of 150 sorties were flown by Soviet volunteers against Japanese airfields, riverine traffic and communications centers during the months of January and February 1938. One such mission took place on 25th January 1938 when 13 SB 2M-100A attacked the Japanese airfield at Nanjing (Jiangsu). 

On 23rd February Cpt. Polynin led a force composed of 28 SB 2M-100As to attack the airfield of Hsinchu, at north-western Formosa (Taiwan). The bombers were armed with ten bombs each and flew most of the distance from Lanzhou to Formosa across it straight at 5.500 m (18.045 ft) of altitude, causing headaches to crew members due to the lack of oxygen. In spite of this problem, the SBs approached Hsinchu from the north achieving total surprise when they dropped their bombs. Japanese anti-air fire proved ineffective and no Japanese fighters were put in the air to intercept the bombers. The SBs arrived back at Lanzhou without any incident after a seven-hour mission. Madame Chiang kai-shek, wife of the Chinese leader, rewarded the Soviet airmen with a banquet and decorations.

All those previously mentioned missions were flown without fighter escort, as the SB 2M-100A was the fastest bomber present on both sides of the Second Sino-Japanese War. These bombers suffered relatively low losses during combat and the biggest threat to them were Japanese raids on SB airfields.

A third Soviet bomber group (the exact number of flown aircraft is unknown) led by Georgy I. Tkhor left GAZ 125 at Irkutsk in late April 1938 and ferried to Lanzhou, this time via Ulan Bator and Dalanzadgad (Mongolia). This group took also part in many missions against the Japanese between the months of June and October 1938.

In late 1939 several SB 2M-103 were also supplied to the CAF. It was at this time when Soviet volunteer airmen began to leave China, as the Soviets became disillusioned and frustrated in spite of the fact that Soviet aid help to strength Chinese resistance against the Japanese. The Soviet aircraft were often misused and crashed when manned by Chinese crews as they lacked experience and therefore didn't follow (or didn't understand) Soviet instructions. The Chinese put the SBs in reserve, instead of flying them into combat.

On 27th December 1939 three SB M-103 of the last Soviet volunteer unit at Hengyang (province of Hunan) flew southwest to support Chinese ground troops at the Battle of Kunlun Pass. They were escorted by the last Gloster Gladiator fighters of 28th Squadron. After the Soviet withdrawal the remaining SB 2M-103s were assigned to the 1st and 2nd Groups of the CAF.

In 1940 a single Tupolev SB constituted the only offensive aircraft the Collaborationist Chinese Army Air Force (CCAAF - AKA Peacebuilding National Army) had. It was joined in September by another SB, piloted by Cpt. Zhang Diqin and manned by Lts. Tang Houlian and Liang Wenhua who defected to Nanjing, and were given substantial reward by the Japanese.

Chinese-manned SBs suffered heavy losses against experimented Japanese pilots. The USSR supplied 100 SB 2M-03 (including some SB 2M-105 -which was one of the last production variant-) in early 1941. These replaced some of the aircraft lost the previous years to accidents and combat. China became the largest foreign user of the SB with a total of 392 aircraft delivered straight from Soviet production lines. On 13th April 1941 Stalin and Japanese foreign minister Yosuke Matsuoka signed a neutrality pact. This resulted in a swift halt in the deliverance of Soviet war material to China, but the SBs were allowed to remain in CAF service. A formation of three SB 2M-103s made three attacks on Japanese troops crossing Dongting Lake (Hunan) and raided Yichang (province of Hubei) in September 1941. 

Chinese SB 2M-103 served well into 1943 and, in some missions, they were escorted by the Curtiss P-40 of the American Volunteer Group, the famous Flying Tigers.

Apparently some few SB survived World War 2 and took part, albeit in limited number and usage, in the last stage of the Chinese Civil War (1945-1949). 

Sources:

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/chinese/chinese.htm

Tupolev SB & Avia B-71 in service with Poland and Slovakia.

 

The Tupolev SB was a high-speed, twin-engined three-seat Soviet monoplane bomber which flew for the first time in 1934. It was also built under license in Czechoslovakia under the denomination of Avia B-71. It was mainly used by the USSR, but there were some foreign users as well, among them, the following ones:

• Poland: During World War 2 some Polish pilots in the USSR were trained with the Tupolev USB (the dual-control trainer variant). These pilots belonged to the 9th Group stationed at Buguruslan, in Chkalov oblast (nowadays Orenburg oblast). Just after the war, five USB trainers were delivered to the Aviation Officers School at Deblin, in the Lublin Voivodeship, to serve as trainers. In 1947 they were re-engined with M-105 engines. This change required a redesign of the exhaust collector system, while different propellers with more ogival spinners were also installed. Three of the five USB served with the Wojska Lotnicze (Polish Air Force)  at the Aviation Officers School until August 1949. This marked the longest use of the Tupolev USB outside the USSR, than any other country.
  
  
• Slovakia: When Germany invaded Czechoslovakia in March 1939, the state was split into the Protectorate of Bohemia and Moravia and the independent Slovak Republic. The Slovenské vzdusné zbrane ( SVZ - Slovak Air Force) had a total of 300 aircraft, among them three Avia B-71. 
  Just before the annexation, one B-71 had to perform a forced landing in the Slovakian part of Czechoslovakia, where it remained well after the split. Hungarian troops occupied the Carpatho-Ukraine region (Ruthenia) and looked to expand their borders in southern Slovakia. This soon led to various clashes which eventually escalated into the Slovak-Hungarian War of late March 1939 in the context of which, on 24th March ten Magyar Királyi Honvéd Legiero (MKHL - Royal Hungarian Air Force) Junkers Ju.86K-2 bombers attacked the airfield of Spisská Nová Ves, in the Kosicé region. This raid damaged one B-71 stationed there.
  The B-71 that force landed in Slovakia before the German occupation, was repaired during the spring of 1939 and received SVZ codes and the blue V3 registration. It was also fitted with German radio equipment, a direction finding loop antenna and an antenna mast mounted on the upper fuselage behind the cockpit. Two additional rack antennas were also fitted to the lower rear fuselage with the original retractable antenna being retained. Both balance weights were also removed from the lower right wing.
  On 18th April 1943 five Slovak airmen scaped to neutral Turkey in the blue V3 B-71. Sergeant Anton Vanko took off from Trencianske Biskupice airbase, close to the town of Trencin, in western Slovakia. Aboard the B-71 were Privates First Class J.Koman, J. Bzoch, L.Slezak and L.Pollak. The B-71 flew from Trencianske Biskupice to Kestanelik, in the Çanakkale province of Turkey, where they were interned for a brief period of time. The five Slovak airmen then travelled to England via North Africa, where they joined the various Czechoslovak Royal Air Force's (RAF) squadrons. Vanko became a Supermarine Spitfire pilot at the No. 312 (Czechoslovak) Squadron at RAF Bradwell Bay, in Essex. Unfortunately he was killed in a take off accident on 8th December 1944.

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB
3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/b-71/czech%2Bslovak/czech%2Bslovak.htm

Avia B-71 in service with Bulgaria

 

The Avia B-71 was a license-built Czechoslovak variant of the Tupolev SB. This variant saw service with Bulgaria.

In September 1939 Bulgaria bought 32 B-71 from Germany. Those machines were originally built at the GAZ 22 factory, in Fili, Moscow oblast, and were delivered to the Ceskoslovenské letecvo (CL - Czechoslovak Air Force) in March 1939, just before the German Occupation.

The Germans handed the B-71s to the Vazdushni Voyski (VV - Royal Bulgarian Air Force) at Merseburg, Germany and were not operational until early 1940, when they were assigned to the 5. Bombardirovochen Polk (5.BP - 5th Bomber Regiment), based at Plovdiv. The B-71 received the nickname of "Zherav" (crane) from Bulgarian pilots.

The Bulgarian B-71s saw combat for the first time in late September and early October 1941 when Greeks in the Bulgarian-occupied region of Thrace revolted. Three B-71s took off from Plovdiv and bombed the Greek town of Drama, in north-western Macedonia. This turned to be the only combat mission of the 5.BP during the period that Bulgaria was allied with Germany.

On 5th September 1944 the USSR declared war on Bulgaria (which, until then, had remained neutral in the Axis war against the USSR) and the Soviet Army invaded three days later. During this period, the pro-Soviet Bulgarian faction called "Democratic Party of the Patriotic Front" led by Kimon Georgiev, seized power and declared war on Germany on 9th September. 

In November 1944, the 2. Yato (Squadron) of the 5.BP had a total of 21 B-71 on strength. On 14th November the 5.BP was redeployed from Plovdiv to Vrazhdebna, close to Sofia, from where they took part in various bombing missions against the retreating Wehrmacht. On these missions, the B-71s had not a precise targets, but where instructed to take upon targets of opportunity in certain pre-defined areas where the VV thought German troops were concentrated. 

The Bulgarian B-71s were heavily employed over Yugoslavia. On 18th November three B-71s attacked a German train at the Vuchitran train station, causing heavy damage to the train. The next day four B-71s bombed the Zhitarica railroad station. Although they were meet with heavy anti-air fire, they returned safely to Vrazhdebna. 

Two days later, on 20th November, several B-71s flew a 'free hunting' mission against targets of opportunity in the regions of Mitrovica and Rashka, attacking a train north of Mitrovica at 12:30 hours. In this bomb run Zherav 4's bomb bay doors malfunctioned and couldn't release its bombs and Zherav 11, flew by Sgt. Manol Dojchev became disoriented and had to force-land at Staro Zhelezare, close to Plovdiv. 

The fourth and final bombing mission of the Bulgarian B-71s took place the next day, on 21st November when four B-71s joined a formation of approximately 15 Lockheed P-38 of the US 15th Air Force. The B-71s bombed a motorized German column near Kamenica while the P-38s attacked a railroad station near Mitrovica. This constituted the only joint Bulgarian-American action against Germany during World War 2. During this action Zherav 4 lost its bearings and had to force-land at Shtarklevei.

After this attack the front moved beyond the range of the B-71s. During their service period with Bulgaria, they made a total of 14 sorties during those four missions in which they destroyed a total of two railroad stations, three trains and one German motorized column, at the cost of no Bulgarian airman killed or wounded.

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/b-71/bulgarian/bulgarian.htm