Tupolev TB-3 - WikiHQ

The Tupolev TB-3, OKB designation ANT-6, was a monoplane heavy bomber deployed by the Soviet Air Force in the 1930s and used during the early years of World War II. It was one of the world's first cantilever wing four-engine heavy bombers. Despite obsolescence and being officially withdrawn from service in 1939, the TB-3 performed bomber and transport duties throughout much of World War II. The TB-3 also saw combat as a Zveno project fighter mothership and as a light tank transport.

Development

In 1925, the Soviet Air Force approached TsAGI with a requirement for a heavy bomber with total engine output of and either wheeled or float landing gear. Tupolev OKB started design work in 1926 with the government operational requirements finalized in 1929. The Tupolev TB-1 was taken as the basis for the design and the aircraft was initially powered by Curtiss V-1570 "Conqueror" engines, with the intent of switching to Mikulin M-17s (modified BMW VIs) in production. The mock-up was approved on 21 March 1930 and the first prototype was completed on 31 October 1930.

The prototype was refitted with BMW VIz 500 engines, larger radiators, and wooden fixed-pitch propellers of TsAGI design. The single-wheel landing gear was deemed too weak and was replaced by tandem bogies with tires. The factories asked the workers for suggestions on reducing the weight, paying 100 roubles for each removed from the aircraft. In combination with OKB efforts, this resulted in weight savings of almost . Despite this, production aircraft could differ from each other by as much as several hundred kilograms.

In 1933, a single TB-3 4M-17F was streamlined with the removal of turrets and bomb shackles, covering all openings, and fitting wheel spats. This resulted in only a 4.5% increase in top speed and a similar increase in the range. Tupolev concluded that streamlining was minimally beneficial for large and slow aircraft. To study the effect of corrugated skin, in January–February 1935 a single TB-3 4AM-34R had the corrugations incrementally covered with fabric. This resulted in a 5.5% gain in top speed and a 27.5% increase in the ceiling. The same aircraft demonstrated a significant increase in climb rate when fitted with experimental four-blade propellers.

;Record flights

TB-3 4M-34R set a flight endurance record of 18 hours and 30 minutes.
TB-3 4AM-34FRN with Andrey Yumashev at the controls set a number of payload-to-altitude records:
11 September 1936 – to , improved to on 28 October.
16 September 1936 – to
20 September 1936 – to

Design

thumb|TB-3 after emergency landing during the [[Winter War in March 1940 ]]

The TB-3 was an all-metal aircraft of steel construction, as one of the designs from Andrei Tupolev's design bureau to be based on the 1918-onward all-metal aircraft design practices and technology pioneered by Hugo Junkers. The frame was composed of V-section beams covered with non-stressed corrugated skin ranging from to in thickness. The corrugations were deep and apart. The cantilever wing was supported by four tube-section spars. In 1934, thanks to the development of stronger steel alloys, the wingspan was increased from with a concurrent wing area increase from . Any part of the aircraft could be walked on in soft shoes without damaging the skin, and the leading edges of the wings swung down to form walkways for engine maintenance. Controls were cable-actuated with a variable-incidence tailplane and a trim compensation system in case of engine failures on one side. Fixed main landing gear was not fitted with brakes. The fuel tanks did not have fire or leak protection, although the engines had an internal fire-extinguishing system. The M-17 engines were tuned to provide a maximum theoretical range of without spark plug or carburetor fouling. Defensive armament consisted of light machine guns in five turrets — one in the nose, two on top of mid-fuselage, and one retractable "dustbin" under each wing between the engine nacelles. Later variants moved one of the top fuselage turrets aft of the tail fin. Stationed far from the USSR's western border, the ТB-3s avoided catastrophic losses during the first German air strikes, after which TB-3s from 3rd TBAP (Heavy Bomber Regiment) began flying night bombing missions on 23 June. A shortage of combat-ready aircraft also required daytime use of TB-3s without fighter escort and in this role the bombers, operating at low-to-medium altitudes, suffered heavy losses to enemy fighters and ground fire. By August 1941, TB-3s made up 25% of the Soviet bomber force and, operated by elite air force crews, were flying up to three combat missions per night. however the wreckage of what is believed to be a TB-3 is located at the Central Air Force Museum The wreckage of Tupolev TB-3 registration CCCP-N210 which crashed on approach at Bukhta Teplits in 1938 remains in much better condition as of 2006 with a mostly intact fuselage.

Variants

thumb|TB-3 4AM-34FRN in [[Zveno project|Zveno-SPB configuration with Polikarpov I-16 fighters armed with FAB-250 bombs]]

thumb|Paratroopers jumping from Tupolev TB-3

<small>Source: Shavrov

;14 March 1941

:An Aeroflot G-2 (CCCP-L1496) stalled and crashed near Begovat, Uzbekistan after the pilot attempted to climb following a loss of altitude caused by severe turbulence, killing the six crew. The aircraft was operating a Tashkent–Fergana cargo service.

;27 August 1941

:An Aeroflot G-2 (CCCP-L1996) struck a hill near Kizyl-Arvat, Turkmenistan while attempting to make a forced landing after the crew failed to locate their destination, killing six of nine on board. The aircraft was operating a Tashkent–Ashgabat cargo service.

;26 December 1941

:An Aeroflot G-2 (CCCP-L3043) crashed near Dmitriyevka (now Bayserke), Kazakhstan after the aircraft lost altitude while turning, killing 26 of 34 on board. The aircraft was operating an Alma-Ata (now Almaty)–Karaganda–Kazan passenger service with high-ranking Kazakh party and state officials. This crash is the deadliest involving the G-2.

;29 December 1941

:An Aeroflot G-2 (CCCP-L2010) crashed in the Amu Darya River near Chardzhou Airport after the aircraft rapidly lost altitude due to spatial disorientation of the pilot, killing seven of 36 on board. The aircraft was operating a Chardzhou–Urgench passenger service.

Specifications (TB-3 4M-17F, 1934 model)

thumb|Tupolev TB-3

References

Notes

Bibliography

Duffy, Paul and Andrei Kandalov. Tupolev: The Man and His Aircraft. Airlife Publishing, 1996. .
Gordon, Yefim and Vladimir Rigmant. OKB Tupolev: A History of the Design Bureau and its Aircraft. Midland Counties Publishing, 2005. .
Gunston, Bill. The Osprey Encyclopedia of Russian Aircraft from 1875 – 1995. Osprey Aerospace, 1995. .
Kulikov Victor and Michael C. Masslov. Les Bombardiers Quadrimoteurs Sovjetiques Tupolev TB3 & Petkyakov PE8 (in French). Lela Presse, 2001. .
Shavrov V.B. Istoriia konstruktskii samoletov v SSSR do 1938 g. (3 izd.). Mashinostroenie, 1985. .