page_title: Tupolev TB-3
section_title: Design
hierarchical_section_title: Tupolev TB-3 / Design
caption_attribution_description: English: Tupolev TB-3 bomber captured by Finnish troops after emergency landing. Suomi: Kuhmo-Saunajärvi. Venäl. lentokone. Pakkolaskun tehnyt ja kranaatinheittimellä tuhottu. Kuhmo 1940.03.14 Kyseessä Tupolev TB-3 pommikone, joka osunut laskeutuessaan puihin.
context_page_description: The Tupolev TB-3 was a heavy bomber aircraft which was deployed by the Soviet Air Force in the 1930s and during World War II. It was the world's first cantilever wing four-engine heavy bomber. Despite obsolescence and being officially withdrawn from service in 1939, the TB-3 performed bomber and transport duties throughout much of World War II.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.
context_section_description: 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 0.3 mm (¹⁄₆₄ in) to 0.8 mm (¹⁄₃₂ in) in thickness. The corrugations were 13 mm (0.51 in) deep and 50 mm (1.97 in) 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 39.5 to 41.85 metres (129.6 to 137.3 ft) with a concurrent wing area increase from 230 to 234.5 m² (2,476 to 2,524 sq ft). 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 3,250 kilometres (1,750 nmi; 2,020 mi) 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.
caption: TB-3 after emergency landing during the Winter War in March 1940
exif: {"Image ImageDescription": "Kuhmo-Saunaj\u00e4rvi. Ven\u00e4l.lentokone.Pakkolaskun tehnyt ja kranaatinheittimell\u00e4 tuhottu.", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "TouchRetouch", "Image DateTime": "2021:03:05 22:41:01", "Image ExifOffset": "238", "EXIF ExifVersion": "0210", "EXIF DateTimeOriginal": "2016:01:29 14:19:10", "EXIF DateTimeDigitized": "2016:01:29 14:19:10", "EXIF ComponentsConfiguration": "YCbCr", "EXIF FlashPixVersion": "0100", "EXIF ExifImageWidth": "1900", "EXIF ExifImageLength": "1388", "EXIF SceneCaptureType": "Standard"}