Tupolev TB-3

infobox Aircraft
name =TB-3 (ANT-6)
type =Heavy bomber
manufacturer =Tupolev



caption =TB-3-4M-17F
designer =Andrei Tupolev
first flight =22 December 1930
introduction =1932
retired =1939 Soviet Air Force (officially)
1945 Soviet Air Force ("de facto")
status =
primary user =Soviet Air Force
more users =Aeroflot as G-2
produced =1932-1934, 1935-1937
number built =
unit cost =
variants with their own articles =Tupolev TB-4

The Tupolev TB-3 (Russian: Тяжёлый Бомбардировщик, Tyazholy Bombardirovschik, Heavy Bomber, civilian designation ANT-6) 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.cite book|author=Shavrov V.B.|year=1985|title=Istoriia konstruktskii samoletov v SSSR do 1938 g. (3 izd.)|language=Russian|publisher=Mashinostroenie|id=ISBN 5-217-03112-3] Despite obsolescence and being officially withdrawn from service in 1939, TB-3 performed bomber and transport duties through much of WWII. The TB-3 also saw combat as a Zveno project fighter mothership and as a light tank transport.

Development

In 1925, Soviet Air Force approached TsAGI with a requisition for a heavy bomber with total engine output of 2,000 PS (1,970 hp) and either wheeled or float landing gear. Tupolev OKB started design work in 1926 with the government operational requirements finalized in 1929. Tupolev TB-1 was taken as the basis for the design and the aircraft was initially powered by Curtiss V-1570 "Conqueror" engines generating 600 PS (590 hp) each, 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 aircraft flew on 22 December 1930 with Mikhail Gromov at the controls and with ski landing gear. On 20 February 1931, Soviet Air Force approved mass production of ANT-6 with M-17 engines.

The prototype was refitted with BMW VIz 500 engines of 730 PS (720 hp) each, larger radiators, and wooden fixed-pitch propellers of TsAGI design. Single-wheel landing gear was deemed too weak and was replaced by tandem bogies with 1350×300 mm (53×12 in) tires. The first pre-production TB-3-4M-17 flew on 4 January 1932 with A. B. Yumashev and I. F. Petrov at the controls. Unexpectedly, subsequent mass-produced aircraft were found to be 10-12% heavier than the prototype which significantly hampered performance. The discrepancy was discovered to be due to high positive tolerances on raw materials which resulted in steel sheetmetal, pipes, and wires being much thicker than on the carefully constructed prototypes. The aircraft were also more crudely painted with a thick layer of camouflage and lacquer. The factories asked the workers for suggestions on reducing the weight, paying 100 roubles for each kilogram (2.2 lb) removed from the aircraft. In combination with OKB efforts, this resulted in weight savings of almost 800 kg (1,765 lb). 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 removal of turrets and bomb shackles, covering of all openings, and fitting of 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 A. B. Yumashev at the controls set a number of payload-to-altitude records:
** 11 September 1936 - 5000 kg (11,023 lb) to 8116 m (26,627 ft), improved to 8980 m (29,462 ft) on 28 October.
** 16 September 1936 - 10000 kg (22,046 lb) to 6605 m (21,670 ft)
** 20 September 1936 - 12000 kg (26,455 lb) to 2700 m (8,858 ft)

Design

TB-3 was an all-metal aircraft of steel construction. The frame was composed of V-section beams covered with non-stressed corrugated skin ranging from 0.3 to 0.8 mm (1/64 to 1/32 in) in thickness. The corrugations were 13 mm deep (0.5 in) and 50 mm (2 in) apart. The cantilever wing was supported by four tube-section spars. In 1934, thanks to development of stronger steel alloys, wingspan was increased from 39.5 to 41.85 meters (127 ft 7 in to 137 ft 4 in) with a concurrent wing area increase from 230 to 234.5 m² (2,475 to 2,524 ft²). 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 3250 km (1,760 NM, 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.

Operational history

The TB-3 was used operationally during the Battle of Khalkhin Gol and in the Winter War with Finland. Although it was officially withdrawn from service in 1939, at the start of the Great Patriotic War on 22 June 1941, Soviet Air Force had 516 operational aircraft, with an additional 25 operated by the Soviet Navy.cite web|url=http://www.tupolev.ru/Russian/Show.asp?SectionID=195|language=Russian|accessdate=2007-04-16 |title=TB-3 (ANT-6)|work=OAO "Tupolev"] The aircraft avoided destruction on the ground in the opening phases of the war and TB-3s from 3rd TBAP (Heavy Bombing Regiment) began flying night bombing missions on 23 June. 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. The aircraft participated in all major battles through 1943, including the first Battle of Smolensk, the Battle of Moscow, the Battle of Stalingrad, the Siege of Leningrad, and the Battle of Kursk. On 1 July 1945, 18th Air Army still had ten TB-3s on the active roster.

The TB-3 served extensively as a cargo and paratroop transport, carrying up to 35 soldiers in the latter role. In the first five months of the war, the aircraft transported 2,797 tons of cargo and 2,300 personnel.

The TB-3 was also used in several special projects as a fighter mothership in the Zveno project and for delivering light T-27, T-37. and T-38 tanks. On 1 August 1941, a pair of TB-3s in "Zveno-SPB" configuration, each with two Polikarpov I-16 fighters carrying a pair of 250 kg (550 lb) bombs, destroyed an oil depot with no losses. On 11 August and 13 August 1941, "Zveno-SPB" successfully damaged the King Carol I Bridge over Danube in Romania. Zveno operations ended in the fall of 1942 due to high vulnerability of the motherships.

In recognition of the role TB-3 played during the war, three aircraft were included in the first post-war air parade on 18 June 1945.

Variants

Source: Shavrov;TB-3-4M-17F:The first production version, comprised about half of all TB-3s built.;TB-3-4M-34:Mikulin AM-34 engines with revised radiators, added oil coolers, several dozen built.;TB-3-4M-34R:Mikulin AM-34R engines with reduction gearboxes providing significantly improved performance, additional turret aft of the tail fin, tail wheels with hydraulic brakes, aerodynamic refinements of the wing-fuselage join and radiators, retractable wind generators.;TB-3-4AM-34RD:A series of long-range demonstration aircraft with streamlined fuselages and wheel brakes. Some aircraft had single main gear wheels 2 meters (6 ft 7 in) in diameter and three-blade metal propellers. Used for flights to Warsaw, Paris, and Rome in 1933-1934.;TB-3-4AM-34RN:High-altitude version with AM-34RN engines, four-blade propellers on inboard engines and two-blade on outboard, 2-meter single main wheels, turrets upgraded to ShKAS machine guns, top speed 288 km/h (155 knots, 180 mph) at 4200 m (13,780 ft), service ceiling 7740 m (25,400 ft). Tested in August-October 1935 but did not enter production as the basic TB-3 design was becoming obsolete.;TB-3-4AM-34FRN/FRNV:AM-34FRN/FRNV engines with increased power output and four-blade propellers, aerodynamic refinements including streamlined turrets, 2-meter main wheels with brakes, top speed over 300 km/h (160 knots, 185 mph).;TB-3D:Proposed variant with Charomsky AN-1 diesel engines of 750 PS (740 hp) and projected range of 4280 km (2,310 nm, 2,660 mi), did not enter production as other performance characteristics were inferior to TB-3-4AM-34RN.;G-2:Retired TB-3s with M-17 and M-34 engines converted for freight duties with Aeroflot;ANT-6-4M-34R "Aviaarktika":TB-3 modified for the 1937 expedition to the North Pole with enclosed cockpit, single 2-meter main wheels, three-blade metal propellers.

Operators

;China as ROC
*Nationalist China Air Force;USSR
*Aeroflot
*Soviet Air Force

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

Aircraft specification

plane or copter?=plane
jet or prop?=prop

ref=Shavrov
crew=Four
length main=24.4 m
length alt=80 ft 1 in
span main=41.80 m
span alt=137 ft 2 in
height main=8.50 m
height alt=27 ft 11 in
area main=234.5 m²
area alt=2,524 ft²
empty weight main=11200 kg
empty weight alt=24,690 lb
loaded weight main=17200 kg
loaded weight alt=37,920 lb
max takeoff weight main=19300 kg
max takeoff weight alt=42,550 lb
more general=
engine (prop)=Mikulin M-17F
type of prop=V12 engines
number of props=4
power main=525 kW
power alt=705 hp
power original= [Originally measured as 715 PS]
max speed main=196 km/h
max speed alt=106 knots, 122 mph
max speed more=at 3000 m (9,840 ft)
range main=2,000 km
range alt=1,080 NM, 1,240 mi
ceiling main=4800 m
ceiling alt=15,750 ft
climb rate main=1.25 m/s
climb rate alt=246 ft/min
loading main=73 kg/m²
loading alt=15 lb/ft²
power/mass main=0.15 kW/kg
power/mass alt=0.09 hp/lb
more performance=
*Time to altitude: 5 min to 1000 m (3,280 ft), 29 min to 3000 m (9,840 ft)
*Best turn time: 40 seconds
*Takeoff roll: 300 m (985 ft)
*Landing roll: 330 m (1,085 ft)
armament=
* 5-8× 7.62 mm DA machine guns, 100 63-round magazines
* Up to 2,000 kg (4,410 lb) of bombs

ee also

aircontent
related=
similar aircraft=
see also=
Zveno project

References

*Cite book|author=Gunston, Bill
authorlink =Bill_Gunston|title=The Osprey Encyclopedia of Russian Aircraft from 1875 - 1995|publisher=Osprey Aerospace|year=1995|isbn= 1-85532-405-9