The Tupolev SB-2 Katyushka

(Little Katie)

U.S.S.R.
U.S.S.R.

side view front view under view

The designation of this aircraft actually gives me headaches . Most sources designate this aircraft as the SB-2, while Russian/Soviet sources also refer to it as the SB. There was no other SB (Skorostnoy Bombardirovschik) as far as I know, and thus the -2 addition in western references to this aircraft will probably refer to Soviet habit of adding the engine types to different versions of the aircraft. In case of a double-engined aircraft this usually would be something like SB-2M100 for a SB with two M-100 engines. Since the language and audience of the website is more Western oriented, I decided for ease of reference to use the western designation. But let it be told that in the Soviet Union officially the bomber was known as the SB.

The SB-2 (Skorostnoy Bombardirovschik, or High Speed Bomber- 2-engine) was the Soviet Union's main light bomber at the start of Operation Barbarossa, the German assault on the Soviet Union. 71 Of the 82 Bomber Air Regiments operated the type, in one or the other version. However, all these version were obsolete since the design was already well dated.
Late 1920's and early 1930's the Tupolev Design Bureau made great strides in the field of all-metal aircraft. Especially the stressed-skin in stead of corrugated Duralumin skin helped in achieving aircraft with a lot less drag, hence a higher performance. So when in 1934 (?) a new request for proposal was received form the VVS, the Tupolev Design Bureau was ready to build a fast light bomber. The new aircraft would have to have a max level speed of 205 Mph (330 km/h) at 13,200 ft (4.000 m), a service ceiling of 26,250 ft (8.000 m), a range of 434 miles (700 km) and a bomb load of 1,102 lb (500 kg). For it's day, it was fast, and well defended with a double nose gun, and an upper turret and lower hatch mounting.
Design started on the first of january, 1934 (?). The result was an essentially all-metal cantilever monowing structure with a smooth metal skinning, very clean overall lines, enclosed accommodation and tailwheel landing gear with main units that retracted rearward into the underside of the nacelles for the two wing-mounted radial engines. Please note that the ID pictures above are actually of the Arkhangelsky Ar-2.

Version list:

Further pictures:

Tupolev SB-2 with M-103 engines and honeycomb radiators on an airfield
Tupolev SB-2 with M-103 engines and honeycomb radiators on an airfield

Arkhangelsky Ar-2, captured by the Germans
Arkhangelsky Ar-2, captured by the Germans

 

Technical data on the Tupolev SB-2M100A
Powerplant 2 × Klimov M-100A (Hispano-Suiza) Vee, rated at 860 hp (641.12 kW) each Role during war
  • Light Bomber
Length 66 ft 8.5 inch Height 10 ft 8 inch
Empty weight 8951 lb Operational weight 12407 lb max
Wing Span 66 ft 8.5 inch Wing Aspect ratio 7.29
Wing Area 610 sq ft Service ceiling 31400 ft
Maximum speed 244 mph at 13125 ft Cruising speed unknown
Initial climb rate Climb to 16,400 ft in 8 min 36 sec Range 777 miles max
Fuel capacity internal 367 Imp gal (441 US gal) Fuel capacity external -
Machine guns
  • 2 × 0.3 inch ShKAS trainable forward-firing in the nose, 1000 rounds each,
  • 1 × 0.3 inch ShKAS trainable rearward-firing in power-operated MV-2/3 dorsal turret, 1000 rounds,
  • 1 × 0.3 inch ShKAS trainable rearward-firing in ventral hatch, 500 rounds
Cannons -
Bomb load Up to 1,322 lb of disposable stores carried in a lower-fuselage weapons bay rated at 1,322 lb. General disposables load consisted of:
  • 1 × 1,102 lb bomb, or
  • up to 6 × 221 lb bombs
Torpedoes/rockets -
Crew 3: pilot, navigator/bombardier/gunner, radio operator/gunner Naval or ground based Ground
First flight (prototype) 7 October 1934 Operational Service Early 1936 - 1944
Manufacturer AGOS (department of Aviation, Seaplane and Experimental Construction) of the TsAGI (Central Aerodynamics and Hydrodynamics Institute) Number produced 6.656 total, unknown this version
Metric system
Length 20.33 m Height 3.25 m
Empty weight 4060 kg Operational weight 5628 kg max
Wing Span 20.33 m Wing Aspect ratio 7.29
Wing Area 56.67 m² Service ceiling 9571 m
Maximum speed 393 km/h at 4000 m Cruising speed unknown
Initial climb rate Climb to 5.000 m in 8 min 36 sec Range 1250 km max
Fuel capacity internal 1.670 liters Fuel capacity external -
Machine guns
  • 2 × 7,62 mm ShKAS trainable forward-firing in the nose, 1000 rounds each,
  • 1 × 7,62 mm ShKAS trainable rearward-firing in power-operated MV-2/3 dorsal turret, 1000 rounds,
  • 1 × 7,62 mm ShKAS trainable rearward-firing in ventral hatch, 500 rounds
Cannons -
Bomb load Up to 600 kg of disposable stores carried in a lower-fuselage weapons bay rated at 600 kg. General disposables load consisted of:
  • 1 × 500 kg bomb, or
  • up to 6 × 100 kg bombs
Torpedoes/rockets -

Here is a quick overview of all different versions, without the full technical specifications:

Different versions of the Tupolev SB-2  Katyushka
Tupolev ANT-40 This version was the prototype of the SB. ANT stands for the initials of the chief designer: Andrei Nikolayevitsch(?) Tupolev Designed and flown in 1934 the type was a major step forward for the Soviet aircraft industry. Several versions of this designation existed, mostly differing in the powerplant used:
  • 2 × Wright Cylcone radial, rated at 730 hp (544 kW) each, or
  • 2 × Hispano-Suiza 12Ybrs, rated at 780 hp (581 kW) each
Between these engines and license built versions thereof other changes ware tried, like greater wing -span and -area, wheeled or ski undercarriages, position of the engines, different propellers, more leading edge sweep of the outer wing panels, and mass balances fitted to ailerons. These last were installed after a crash, caused by wing-aileron fluttering resulting in the failing of the wing skin.
One of the prototypes was further used as a test aircraft to set a new world record for payload-to-height. With a 2,204 lb (1.000 kg) payload the Hispano-Suiza ANT-40 reached a respectable height of 41,650 ft (12.695 m) on 1 november 1936. In the end it was recorded only as a national record.
Number built: 2
Tupolev SB-2M100 This version was the first production version. It was powered by 2 × Klimov M-100 (Hispano-Suiza) radial engines, rated at 750 hp (559 kW) each, driving two-bladed fixed pitch propellers. It was very similar to the second prototype, but had increased wingspan and -area, as well as increased tailplane areas.
Number built: unknown out of 6.654
Tupolev SB-2M100A The simplification of the production process of the SB-2M100 meant that the aircraft became heavier (lightweight members from the contruction were replaced by heavier examples). Also the quality of the aircraft's skin diminished because of mass production and use of inferior materials. All these small weight- and drag-increasing changes meant the SB-2 was heavier than should be. The solution was found in an uprated engine, and the SB-2 became powered by 2 × Klimov M100A, rated at 860 hp (641 kW) each.
In the meantime the SB-2 had seen action in the Spanish Civil War (1936-1939), and experiances learned meant other changes as well. These changes included a new MV-3 gun mounting and a lower hatch mount with optical sight. The pilot's cockpit and the navigator's cockpit were joined by three shields, different instruments were installed, and a faired rear-view mirror was placed above the windshield of the pilot.
Number built: unknown out of 6.654
Tupolev SB-bis-2M103 In 1937 a new engine became available. This engine fitted nicely to the intended role of the SB-2, and thus became standard for subsequent aircraft built. Now the SB-2 was powered by 2 × Klimov M-103, rated at 960 hp (716 kW) each, driving three-bladed variable pitch propellers. because of this, new radiators had to be fitted, and the engine cowlings were adapted accordingly as well. Also the undercarriage, flaps, lower engine cowling control system and tailwheel received attention. Finally the navigator's cockpit was enlarged to accomodate dual controls. All these changes initially failed to increase the performance according to expectations, since aerodynamics had suffered as well. Once these were polished away, the new aircraft was able to set a new world record in payload-to-height, reaching 40,178 ft (12.246 m) with 2,204 lb (1.000 kg) of payload.
Number built: unknown out of 6.654
Tupolev SB-bis-2 2M103 Another designation for the Tupolev SB-bis-2M103. There may have been differences, but they are unclear to me at the moment. What is known is that different Aircraft plants (Plant 22 and Plant 156) received the order to build new M 103 powered SB-2 prototypes, and this designation may have been to distinguish between those prototypes.
Number built: unknown out of 6.654
Tupolev SB-bis-3 2M103 The SB-bis-3 was another M 103-powered prototype. This version had duct-type coolers instead of nose radiators. The water cooled oil radiators were replaced by air-cooled ones, reducing drag and increasing preformance. Tests showed that the increase of performance was promising, even though the reliability of the engines was a little less that that of the M-100.
Number built: unknown out of 6.654
Tupolev SB-2M103 Plant 22 received the order to take an M 103-powered SB-2 into production once more, based on the SB-bis-3 2M103. Thes resulting aircraft had the following changes applied: Increased bombload to 3,306 lb (1.500 kg) by installing Der-19 bomb-racks rated up to 1,102 lb (500 kg), An AFA-13 camera was fitted, the undercarriage was now operated electrico-hydraulically, a mechanical bomb-dropping system was fitted to the pilot's cockpit, a pilot's seat with 1/4 inch (6 mm) of armor was fitted.
Later, aircraft were also fitted with a capability for external fuel (drop-)tanks with a capacity of 84 Imp gal (100 US gal, 380 liters) each.
Even furhter in the production series, other changes were incorporated as well:new ducted water coolers with constant inlets were installed, the gap between the spinner and cowling was closed, fairings were fitted to inlet pipes and where the control surfaces were hinged to the flying surfaces, a separate water cooler cap control was installed, two coats of paint were applied and the wing and empennage leading edges were polished.
Number built: unknown out of 6.654
Tupolev USB USB stands for Uchebnyi Skorostnoy Borbardirovschik, or Trainer High Speed Bomber. This was exactly what it was, a high speed bomber trainer.
Plant 22 developed a trainer version to the SB-2 with an instructor's dual control cockpit in place of the navigator's cockpit. The new cockpit was designed in such a way that it could be fitted in stead of the navigator's cockpit in the field, enabling the units to chose whether or not, and how many of their SB-2's would be used for training. Initially only the cockpits were approved for production, but a small number of USB's were scratch-built nevertheless.
Number built: unknown out of 6.654
Tupolev MMN-2M105 Incresing demands in the field of performance necessitated not only increased engine output, but increased aerodynamics as well. The MMN (modified smaller lifting surface, no Russian explanation for the abbreviation) thus was powered by 2 × M 105, rated at 1,050 hp (783 kW) each. Also, wing area was reduced with 86 sq ft (8 m²). The outer wings' structure was simplified and fitted with 45 Imp gal (54 US gal, 205 liters) fuel tanks, the spars were replaced by shielded walls, and truss ribs were made of pressed parts. The nose of the fuselage became more streamlined, and one of the two ShKAS guns was dropped. The navigator's cockpit haoused dual controls, the lower gun mounting was closed by a hatch, and an MV-3 turret installed in the dorsal position. The areas of the ailerons and tail surfaces were changed as well, and the flap area increased significantly. the undercarriage could be extended by an emergency activator form the pilot's cockpit too.
All of these changes were in vain, and the new design was unable to meet the new demands set for high speed bombers. The MMN was thus never produced, but a number of changes were incorporated in production aircraft.
Number built: 0
Arkhangelsky SB-RK This version was an initiative of the Arkhangelsky Design Bureau. Originating as an uprated SB-2, during the (re-)design phase it became obsolete. However, it was felt that the type could still perform as a dive bomber.
The SB-RK was powered by 2 × M-105, rated at 1,050 hp (783 kW) each. These engines were fitted with two-stage superchargers, and drove three-blade VISh-22E variable pitch propellers. The radiators were relocated to the wing leading edges, greatly reducing drag. The engines were fitted more into the wings as well, which had besides reduced drag also the benefit of better view from the cockpit. The wingspan was reduced to 59 ft (18 m), and wing area to 518 sq ft (48,2 m²).
Number built: 0
Arkhangelsky Ar-2 When the SB-RK turned out to be obsolete, it was felt that the type could still perform as a dive bomber. After the decision was made to use it as a dive bomber further enhancements were made. The nose became more streamlined, the navigator's cockpit was redesigned including a movable seat, and dual controls were fitted to increase survivability. Fuel capacity was enlarged to 490 Imp gal (588 US gal, 2.230 liters) by adding two 81 Imp gal (97 US gal, 370 liters) external tanks.
The Ar-2 was able to enter a dive easily be setting elevator trim tabs. Recovery from a dive was automatic, after the bombs were dropped. Max level speed was 313 Mph (505 km/h), service ceiling rose to 32,800 ft (10.000 m). With a bombload of 1,102 lb (500 kg) max range was some 1,304 miles (2.100 km), and with a bombload of 2,204 lb (1.000 kg) it was 621 miles (1.000 km).
Number built: 200
Arkhangelsky SBB-1 'B' SBB stands for Skorostnoy Blizhniy Borbardirovshik, or Sort range High Speed Bomber. It was yet a further development of the SB-RK and Ar-2, this version was another attempt to increase speed, range and bombload of the basic SB-2 model. It was a three-seat midwing monoplane with twin fins and rudders, carrying a pilot, navigator and radio operator/gunner. Increased glazing meant that the crew had a better view from the cockpit. It was defended by two guns, one ShKAS defending the front of the aircraft operated by the navigator, one ShKAS operated by the radio operator defending the upper rear hemisphere fitted in a turret.
By reducing drag, and and fitting undercarriage fairings, ejector exhaust pipes and other modifications the bomber became real fast. A max level speed of 351 mph (560 km/h) was attainable at 16,000 ft (4.900 m) altitude. Climb to 16,400 ft (5.000 m) was 6 min 20 sec. This accounted for a performance more or less equal to production examples of the Messerschmitt Bf 109E. However, since the Petlyakov Pe-2 was already entering mass production there was no further development, nor was the SBB put into production.
Number built: 0
Tupolev PS-40 This version was the transport variant of the SB-2
Number converted: unknown
Tupolev PS-41 This version was the transport variant of the SB-2bis
Number converted: unknown
Avia B 71 Czechoslowakia had taken interrest in the SB-2, and ordered a number of the early aircraft. Later they secured a license to build them theirselves. Avia took up the production of the SB-2, and fitted them with Hispano-Suiza 12Ydrs engines, rated at 860 hp (641 kW) each. 161 were ordered, but only 111 were finnished at the time Germany annexated the major part of Czechoslowakia in 1939.
Number built: 111
Avia-Katusa M-8 Bulgary received a number of the B 71's after the annexation of Czechoslowakia. In the Bulgarian Air Force these were redesignated M-8.
Redesignated aircraft

Operational remarks:

When the War broke out for the Soviet Union, the SB-2 was already obsolete. As a consequence, it failed bitterly when it was most needed. This was not only because of outdated technology or lacking features (like protected fuel tanks), but also because of inadequate training of the aircrew, and the lack of fighter protection due to the very effective initial German attacks on Soviet airfields. Another factor to take into account was the fact that these aircraft were relatively short ranged or capable of a light load only. In order to carry a heavier load most units were situated very close to the border, which made them very vulnerable to the attacks of the German Luftwaffe. On the ground as well as in the air losses were heavy.
Not everything went wrong, however. In some instances the SB-2 crews were able to attack German infantry and armour while virtually unopposed in the air, and these strikes were most of the time reasonably effective. All that was needed in such cases were a little time without enemy fighters, and an experienced commander.
All in all, almost all SB-2's were destroyed on the ground or in the air during the first month of the hostilities between the Soviet Union and Germany. After this ordeal, the SB-2 began flying night missions, or with fighter escort only. The effectiveness of the SB-2's at night were good to excellent, but this could not prevend the staggering number of losses. From 22nd of July 1941 till the december counter-attack of the Soviets, the SB-2 force dwindled from about 1.250 to 60 airworthy SB-2's. This gives the the SB-2 the dubious reputation of being the aircraft which suffered the greatest losses of all.
The SB-2 was besides the Great Patriotic War (1941-1945) used in other wars as well: the Spanish Civil War (1936 - 1939), Second Sino-Japanese War, and Soviet-Finnish War (1939-1940). It was in use by the Finnish Air Force (24 captured), Chinese Air Force, Spanish Republican Air Force (200), and the Czech Air Force. After the SB-2 was withdrawn from front line service most surviving examples were used as transport, trainer or target tug.

Strengths:

Weaknesses:

 

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© by Frans Bonné, 2000
Last revision: 5/27/02