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Tupolev ANT-40 / SB-2 / AR-2 / PS-40 / PS-41
Avia B-71 Katyushkas



The two ANT-40 light bomber prototypes of Andrei N. Tupolev's design bureau first flew in October 1934. The all-metal construction, enclosed cockpit and retractable landing gear were then comparatively novel features. The ANT-40's maximum speed of 325km/h at operating height was faster than the biplane interceptor fighters that equipped most of the peacetime air forces.

Entering production in 1936, the initial production version as selected for export and service with the V-VS was based on the second prototype, and was known as the Tupolev SB-2 (skorostnoi bombardirovshchik, or fast bomber). The engines were two 830 hp / 619kW licence-built Hispano-Suiza 12Ybr, termed M-34 by Soviet industry, and initially they were fitted with two-bladed fixed-pitch propellers.
An aircraft of this type secured an official FAI recocd in 1937 for carrying a 1000 kg / 2200 lb payload to an altitude of 40,177 ft.


The first SB-2s were passed to the V-VS's bomber aviation regiments in February 1936, and in October of that year the first of 210 were transferred with Soviet crews to Spain to fight on the side of the Republican air force against the insurgent Nationalists.


The SB-2 was the first Soviet warplane delivered to the Republicans, arriving from October 1936 in an effort to provide an offensive type which could take the air war to the advancing Nationalists. The variant delivered was the initial SB-2 production model powered by M-100 or 641 kW (860-hp) M-100A inlines driving fixed or variable pitch propellers respectively. Estimates for the number of SB-2s delivered vary from 93 to 210, and these aircraft were amongst the best fielded by the Republicans: their performance and defensive firepower allowed most Nationalist fighters to be outrun or outfought. Some 19 operational SB-2 bombers fell into Nationalist hands at the end of the war, and claims on the type amounted to 14 by the Nationalists, a similar number by the Germans, and 48 by the Italians.

Over Spain the performance of the SB-2 caused considerable concern to the Nationalist fighter units which were equipped with Heinkel He-51 and Fiat CR.32 biplanes, and the urgent call went out for fighters of better speed and climb properties.

Tupolev SB-2


At the time SB-2s were passed to the Chinese Nationalist air force to fight aganst the Japanese, and to Czechoslovakia, where the type went into licensed manufacture as the B.71 bomber. Because all three Aeroplane Works within a range of German bombers were, a new plant was built at the village of Kunovice in South Moravia. Two batches of the B-71 bomber – 40 and 26 machines respectively. 30 SB-2s were purchased by the Czechoslovak Republic from the Soviet Union and in 1936 also their licence.
1934 Avia development was helped engineer A. A. Archangelskij from the ANT 40.2 SB - 2 ( Skorostnyj Bombardirovščik). The Czechoslovak Air Force had 60 of these aircraft and one at a research institute. Serial production started at Avia and by the German occupation not a single was finished, the unfinished aircraft were completed by the Germans.

Avia Works built forty-five that were used by Luftwaffe or sent to Bulgaria. The B-71 Katyushkas were powered by Czech-made 680 Avia-Hispano Suiza engines and were able to accommodate the bombload of 600 kg under their wings.

The Avia-built B-71 were fitted with a new tubular radiators and gained 15 kph. The idea was copied by the Soviets and brought into use in the SB-3. After the German occupation the B-71s were converted to target towing configuration.

Avia B-71
In general the SB-2 performed well until faced with sterner fighter opposition, which occurred over Spain in 1938 and in particular over Finland during the Winter War of 1939-40, when many were shot down. Steps were taken to improve performance by installing the 641kW M-100A engine with variable-pitch propellers. Increased fuel capacity and two 716kW M-103 engines were installed in the Tupolev SB-2bis, the performance of which was improved by three-bladed VISh-22 propellers.
The study of the 3-wheeled undercarriage on a twin-engined aircraft, nicknamed "pterodactyl", was carried out in 1940. Using a special frame under the center section the pilot, Mark Galley, repeatedly landed the aircraft with a vertical speed of up to 4.8 m / s. The landing gear was fully tested. For study of the "shimmy" phenomenon the ranover a log put across the runway. The original size of the front wheel was 470x210 mm, but changed to 600x250 mm.
SB "Pterodactyl"
The front wheel was 4.65 m from the center of gravity and the main struts moved back beyond the center of gravity 520 mm, the wheels remained the same - 900x300 mm.
SB "Pterodactyl"
A frame was used to rearrange the main undercarriage in order to determine their optimal location. The aircraft was tested with a flight weight of 6000 kg, the wing load was 106 kg/sq.m and flight speeds up to 220 - 230 km/hr. Landing speed with flaps was 140 - 150 km / h, without flaps 190 km/h.
SB "Pterodactyl"
Tests were summarized and published in February 1941, turned out to be very popular. It is believed that the research results were useful in developing a new generation of Soviet aircraft with a front support wheel.
The PS-41 was a transport variant with a ‘solid’ nose and gun positions eliminated.


In addition to the PS-40 and PS-41 transport versions the SB-RK (Arkhangelskii Ar-2) was a modified SB-2bis dive-bomber with reduced wing area and powered by two supercharged M-105R engines. The SB-2's record as a day bomber came to an abrupt end during the fierce fighting following the German invasion of the USSR on 22 June 1941. Those that were not destroyed on the ground ventured into the air on numerous missions over the front line, and paid a heavy price to the Luftwaffe's Messerschmitt Bf 109F fighters. Thereafter the SB-2 and SB-2bis bombers were relegated to night work with the V-VS and the Soviet naval air arm.

Production amounted to 6,967 of all marks.



Three-seat light/medium bomber
Span: 20.33m (66ft 8.5 in)
Length: 12.57m (41ft 2.75in)
Powerplant: 2 x Klimov M-100, 559kW (750 hp)
Armament: 4x7.62-mm (0.3-in) mg
Bombload: 1000 kg (2,205 lb)
Max T/O weight: 5628 kg (12,407 lb)
Max speed: 244 mph at 17,060 ft
Operational range: 777 miles

Engine: 2 x M-100
Max take-off weight: 5732 kg / 12637 lb
Empty weight: 4060 kg / 8951 lb
Wingspan: 20.3 m / 67 ft 7 in
Length: 12.7 m / 42 ft 8 in
Wing area: 52.0 sq.m / 559.72 sq ft
Max. speed: 420 km/h / 261 mph
Cruise speed: 360 km/h / 224 mph
Ceiling: 6600 m / 21650 ft
Range: 1600 km / 994 miles
Range w/max.payload: 1000 km / 621 miles
Crew: 3
Armament: 4 x 12.7mm machine-guns
Bombload: 1500kg

Engine: 2 x M-103, 990 hp
Wingspan: 70 ft 6 in
Length: 41 ft 6 in
Max take-off weight: 14,330 lb
Empty weight: 9436 lb
Max. speed: 280 mph at 16,400 ft
Cruise speed: 360 km/h / 224 mph
Service ceiling: 27,890 ft
Range: 1430 miles
Crew: 3
Armament: 4 x 7.62mm machine-guns
Bombload: 1320 lb


Tupolev ANT-40 / SB-2 / Ar-2




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