Tupolev SB in Soviet Service. Part Eight.

 

The SB continued to serve during World War 2, specially during the siege of Leningrad and the Battle of Moscow, as we've already stated, but it was also, numerically speaking, the most important bomber the VVS had in the Stalingrad region when the Axis forces launched their offensive against the Caucasus in June 1942. 

The SB in all its variants served, in some sectors, in the night bomber role well until 1943, even if they were being replaced by either the Tupolev Tu-2 or the Petlyakov Pe-2 when they became available. The SBs were also used in other secondary roles by the VVS like supply-dropping, glider-towing, training and transport in the Far East until the end of the war in 1945.

Sources:

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

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

Tupolev SB in Soviet Service. Part Seven.

 

The SB continued to serve during World War 2, specially during the siege of Leningrad and the Battle of Moscow, as we've already stated, but it was also, numerically speaking, the most important bomber the VVS had in the Stalingrad region when the Axis forces launched their offensive against the Caucasus in June 1942. 

The SB in all its variants served, in some sectors, in the night bomber role well until 1943, even if they were being replaced by either the Tupolev Tu-2 or the Petlyakov Pe-2 when they became available. The SBs were also used in other secondary roles by the VVS like supply-dropping, glider-towing, training and transport in the Far East until the end of the war in 1945.

Sources:

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

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

Tupolev SB in Soviet Service. Part Six.

 

The SB continued to serve during World War 2, specially during the siege of Leningrad and the Battle of Moscow, as we've already stated, but it was also, numerically speaking, the most important bomber the VVS had in the Stalingrad region when the Axis forces launched their offensive against the Caucasus in June 1942. 

The SB in all its variants served, in some sectors, in the night bomber role well until 1943, even if they were being replaced by either the Tupolev Tu-2 or the Petlyakov Pe-2 when they became available. The SBs were also used in other secondary roles by the VVS like supply-dropping, glider-towing, training and transport in the Far East until the end of the war in 1945.

Sources:

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

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

Tupolev SB in Soviet Service. Part Five.

 

Germany launched Operation Barbarossa on 22nd June 1941, by invading the USSR. At that time the Tupolev SB was the most numerous bomber in the VVS, the SB 2M-100A, to be more precise. During the first day of the campaign alone, the Luftwaffe destroyed a total of 1811 Soviet aircraft, many of them SB bombers of all kind. In the year 1941, five years after its combat debut over Spain, the SB was completely obsolete and was an easy target for the Luftwaffe. On that same day, 22nd June, a whole Soviet Air Regiment took off to bomb the city of Königsberg, in East Prussia, but none of them managed to return home.
The SB was being replaced by the Petlyakov Pe-2 when available as it was faster and was much less vulnerable to the Luftwaffe, although it could carry 600 kg (1.323 lbs) less bomb load. Most Tupolev SBs flew at night, as it was harder for the Luftwaffe to intercept the SB. 
Although outdated, Soviets pilots praised flying characteristics of the SB to be far better than those of the Pe-2. During Operation Typhoon, the Battle of Moscow in late 1941 the VVS in Moscow had 28 SBs and only five Pe-2. 
It was during that winter, however, that the SB enjoyed a nimble advantage over German airplanes; thanks to the ski undercarriage many SBs were equipped with, they could operate from snow covered airfields, when Luftwaffe fighters were grounded because of the snowfall. 

 

Sources:

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

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

Tupolev SB in Soviet Service. Part Four.

 

The Tupolev PS-41 was a civilian version of the SB 2M-103. It was developed by Aeroflot in 1939 and by December 1940 forty-nine machines were in service. As civilianized as it was, every defensive armament, as well as armour plating and bomb release systems were deleted, with the exception of the cartridge case ejector tunnel, which remained in the nose. Many PS-41s had an additional antenna mast placed in front of the canopy frame. When serving with Aeroflot, most of them were left in bare metal with civil registration codes and Aeroflot's logo (albeit not always present), painted in black.

From early 1940 onwards, many PS-41s were assigned to Aviaarktika (Aeroflot's Polar Aviation Division). This organization served in the USSR's most northern region under extreme conditions, hence the non-retractable ski undercarriage the PS-41 were equipped with. Most of them were painted in orange or had their noses or engine cowlings painted red to increase their visibility. 

Shortly after the German Invasion of the USSR in June 1941, Aeroflot's PS-41 were pushed into service with the Civil Air Fleet (GVF in Russian acronym) under VVS (Soviet Air Force) command. Some PS-41s were assigned to liaison squadrons, operating from bases in Moscow and northern USSR. They were used for liaison duties between the Central Military Headquarter in Moscow and the Transcaucasian Front. They were also employed as liaison to link Moscow with the newly established industrial centers east of the Ural mountains. 

In combat, the PS-41 was also used, taking advantage of its high speed, to resupply beleaguered Soviet defenses in the Leningrad area, to supply the city with mail, medicines and military staff. 

As more modern Soviet bombers as the Tupolev Tu-2 or the Petlyakov Pe-2 became available, some former SB 2M-103 bombers were converted to PS-41 standard and assigned to GVF, to ease the acute shortage of transport planes the VVS suffered all along World War 2. 

Overall, the PS-41 served well and became VVS' main high speed transport during the war. It was kept on service for a short period of time after the conflict, until it was gradually replaced by more modern types like the Ilyushin Il-12 or the Lisunov Li-2.

There was an extended range sub-variant, called PS-41 bis designed for mail transport. It featured a pair of external wing mounted fuel depots in lieu of the bomb racks. Those depots allowed for an increased range of 1.180 km (733 miles). 

The Tupolev SB-RK was a regular SB 2M-100A fitted with two Klimov M-105R engines. This served as the initial prototype for the ground attack variant of the SB which eventually became the Arkhangelsky Ar-2. 
The Tupolev SBB was an attempt made by Arkhangelsky to modernize the SB design. It featured smaller wings and an almost complete new redesign with twin tail. The only prototype flew for the first time in September 1940. It was tested against the Pe-2 prototype and the Yakovlev Yak-4 and was discarded due to unsatisfactory performance. Some few attempts were made to attract VVS' attention on the type but the interest was lost.

There was another test aircraft based on the frame of the Tupolev SB. Igor P. Tolstikh an engineer from TsAGI (Central Aero and Hydrodynamics Institute) led a team to investigate a tricycle undercarriage (based on implanting a nose-wheel) in 1940. This landing gear configuration, however, wasn't new in the USSR as another aircraft, Kharkov KhAI-4 employed a nose-wheel back in 1934. 
A heavily modified SB 2M-103 was the basis for the nose-wheel arrangement. This experiment was never intended to be put into mass production, as it was just an study to improve future Soviet bombers.
The nose section was heavily modified to incorporate a large nose-wheel with two bracing struts. The main non-retractable undercarriage was repositioned to the rear.
It was test flown by the famous Soviet test pilot Marc L. Gallai on taxiing and landing flights, who praised the new arrangement as it made it much easier to take off and land, than the conventional tail-wheel bombers. 
TsAGI's prototype, nicknamed as 'Pterodactyl', was assigned to the NII (Flight Research Institute) located at Kratovo, near Moscow, in late 1940. Tests continued until 1941, when Germany launched Operation Barbarossa, invading the USSR in June. The first Soviet bombers with tricycle landing gear arrangement, didn't see the light until after the end of the war, namely the Tupolev Tu-12. 

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/prototypes/SBB.htm

Tupolev SB in Soviet Service. Part Three.

 

The Tupolev SB was Soviet's main bomber during the Winter War. During this conflict, ranging from late November 1939 until until mid March 1940, the VVS deployed more than 3.000 aircraft to defeat the Finns who had only 145 aircraft in their ranks.
As we said, the Tupolev SB was VVS' main bomber and it flew the first Soviet attack against Finnish soil, which was an attack against Helsinki, the Finnish capital city. As the winter was really harsh, many Tupolev SB 2M-100As were equipped with skis and some few of them were equipped with the, back then, experimental MV-3 rear turret. The RS-132 unguided rocket was also tested in this conflict as six Tupolev SB 2M-100As were fitted with rocket launching equipment on the wings. These rockets were mainly used against ground targets.
As the war progressed on, with a furious Finnish resistance, many Tupolev SB of various types were captured by the Finnish who repaired them and push them into service with the Ilmavoimat (Finnish Air Force). 
The war ended on 13th March 1940 with the Finnish agreeing to yield a buffer zone to the Soviets. However, casualties on the VVS side were enormous, estimated at a number between 700 and 900 aircraft, half of them bombers. 

The Tupolev USB was the trainer variant of the regular SB which came out almost two years after the first SB rolled out of the factory in 1936. It was based on a SB 2M-100A and was built at GAZ (State Aircraft Factory) 22 at Fili, Moscow. The whole nose section was remodelled to install a second open cockpit for the instructor. The step was relocated from the front to the rear of the starboard nose. A windshield was installed for the instructor's compartment but no canopy was provided. Instructor's cockpit had similar controls to those in the pupil's cockpit, however, they were automatically disconnected when the instructor took command. In spite of the importance of communication between the instructor and the pupil, the USB lacked an intercom. The instructor accessed his cockpit using a ladder placed through the open ventral hatch doors.
The USB prototype underwent State Acceptance Trials between 11 and 16 March 1938. During those tests it was equipped with non-retractable ski undercarriage. GAZ 22 at Fili completed just a few USB, as most of them were converted in the field from existing Tupolev SB of every kind. 

Sources:

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

2nd https://en.wikipedia.org/wiki/Tupolev_SB
3rd https://en.wikipedia.org/wiki/Winter_War

Tupolev SB in Soviet Service. Part Two.

 

The first combat usage of the Tupolev SB under VVS's (Soviet Air Force) Red Star was in the Battle of Lake Khasan. This battle was part of the many Soviet-Japanese border clashes in the eastern sector of the Sino-Soviet Manchurian region which took place between 29th July and 11th August 1938. One Tupolev SB was lost to Japanese fire. 

Tensions escalated in the region and fighting broke out again in the Khalkin Gol, eastern Mongolia, close to the border with China, in May 1939. At first there were two SBAP (Russian acronym for 'Fast Bomber Regiment') units present; 150 and 38 SBAP. 

In this battle, which lasted until 16th September and caused Soviet forces heavy losses, the SBs were not involved at first. However, due to the increasing Soviet casualties, two regiments of SB bombers were deployed in June, flying their first mission of the 26th. The SBs were employed thoroughly when the Japanese launched an attack in early July. 

Both 150 and 38 SBAPs were composed of a mixture of old and new models of the SB, so the differing speeds between bombers proved to be a serious problem when maintaining formation, specially when the Japanese Nakajima Ki-27 fighter attacked and the poor defensive arrangement of the SB could do little to defend, as the radio operator had to man both dorsal and ventral turrets. In order to minimise casualties against Japanese fighters, Soviets changed their tactics, so the SBs had to fly in altitudes over 6.100 m (20.000 ft), where it was difficult for the Japanese to intercept. In August a new regiment, 49 SBAP arrived in the battlefield and the SBs were employed in aerial raids against Japanese forces until Soviet and Mongolian forces lead by Georgy Zhukov carried out an offensive which ended with the cease-fire in 16th September 1939.

The SB was also employed by the VVS in the Soviet Invasion of Poland. At 6:00 am, on 17th September 1939 approximately 310.000 Soviet troops crossed the Polish border from the east and the SB was the backbone of the VVS during this campaign. Both Belarussian and Ukrainian fronts had a total of 637 SB 2M-100As available when the Polish-Soviet War broke out. They were assigned to 10th, 16th, 18th and 70th SBAPs. 

During the first days of the invasion, most of their missions were against strategical railroad stations and communication hubs, including the Stanislawow and Buczacz marshalling yards, as well as Polish airfields of Kowel, Dubno and Luzk, where they encountered resistance and Polish P-11 fighters shot down two SBs that day.

On 19th September, some of the remaining P-11s tried to attack a formation of SBs without any success at all. 

The SBs also raided one of the last Polish strongholds near Kamien Koszyrski on 22nd September. By that date the Polish Air Force had already collapsed and the VVS only flew some sporadic sorties over Poland. On 29th September a formation of various SB 2M-100As bombed the town of Nujno. 

VVS's bombing operations over Poland were limited until 6th October 1939, when the Polish campaign ended. This was because of the lack of suitable targets and only a handful of SBs were lost in the 20 days this campaign lasted.

The Tupolev PS-40 was a civilian transport variant, which we will cover in a future post. 

The Tupolev MMN was an version which featured several aerodynamical improvements. It was made on the basis of the SB 2M-103 and was powered by two 1.100 hp Klimov M-105 engines. Each engine, housed in an aerodynamically modified cowling was equipped with a centrifugal two-speed twin-stage supercharger driving a three-bladed propeller. 

The wingspan was reduced and the tail was redesigned and reduced in size. Nose section was also modified in order to have clearer portions. Armament consisted on two 7,62 mm ShKAS machine guns placed in a dorsal turret and a single ShKAS machine gun in the nose section. This reduced the defensive armament of the regular SB as they normally had two ShKAS in the nose.

The MMN also featured additional wing fuel tanks and a second landing light. It was also lighter than the SB 2M-013. 

It was accepted for state trials in September 1939 and achieved a top speed of 458 km/h (285 mph) flying at 4.200 m (13.780 ft). This was only 8 km/h (5 mph) faster than the standard SB 2M-103. As it had smaller wings, it also had smaller wing area, resulting in a faster landing speed of 160 km/h (99 mph), making it more dangerous. The MMN did not pass state trials because of its nimble defensive armament, its marginal faster speed and its high landing speed over the SB 2M-103. The only prototype was assigned to Aeroflot where it received the nickname of Shchuka (Pike).

Sources:

1st https://en.wikipedia.org/wiki/Tupolev_SB

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

3rd https://en.wikipedia.org/wiki/Battles_of_Khalkhin_Gol

4th https://j-aircraft.com/research/George_Mellinger/sovietorderofbattle.htm

5th Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

6th https://en.wikipedia.org/wiki/Soviet_invasion_of_Poland

7th http://www.airvectors.net/avtu2.html

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

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