Friday, October 10, 2014

Soviet Tupolev TB-3

Soviet Tupolev TB-3 bomber
The first flight of the Tupolev TB-3 (ANT-6) bomber on December 12, 1930.
The Red Air Force does not get much good press about its World War II prowess, at least compared to the Luftwaffe and Western Allies. They had some awesome fighters and bombers after the war, but during the war - well, what they had worked, but they weren't exactly wowing very many observers, especially in the early stages of the conflict. Obsolete aircraft were used by all of the air forces at some point during the war, and they often proved quite useful and handy, so it is no insult to say that about the Soviets - their early aircraft stank.

One of the obsolete Soviet aircraft that helped craft the Red Air Force's reputation was the Tupolev ANT-6 aka Tupolev TB-3 bomber. We can say that it was obsolete without fear of contradiction because that was what the Soviets themselves decided before the war when they pulled it out of service in 1939. However, not wanting anything to go to waste, the Soviets simply shifted them to backwater airfields and kept their remaining obsolescent TB-3s in service regardless - and reaped benefits during the war from doing so.

Soviet Tupolev TB-3 bomber
The TB-3 looks quite impressive as a model.
The first TB-3 production version was delivered in 1931, and production lasted until 1937. It was the world's first cantilever wing four-engine heavy bomber and has the weird distinction of being perhaps the only unpressurized four-engine bomber with an open cockpit.

Soviet Tupolev TB-3 bomber
The gunners on the dorsal fuselage sat next to each other and could slide from side to side in a unique arrangement.
The prototype of the TB-3 performed reasonably well, but when the production model started rolling off the assembly line, it turned out to be 2,200lb/1,000kg heavier than planned. Poor machining and indifferent manufacture techniques were the culprits, with the precise construction of the prototype replaced with heavy tubing and metals along with heavy-handed painting techniques. Huge efforts were made to reduce the weight, but this remained an issue throughout the aircraft's lifetime.

Soviet Tupolev TB-3 bomber
Soviet paratroopers preparing for a mission aboard a TB-3.
The aircraft was made of corrugated metal, like the German Ju-52, which also hampered performance. However, speed was not an issue because the craft, with its immense wings, was designed for lifting capacity and range, not speed or altitude performance. Inevitably, the plane was very slow, with a top speed reported at 129 mph (and a cruising speed that naturally was much slower). Even for the early 1930s, that was plodding. On the bright side, the pilots found that adding all sorts of things to the aircraft did very little to degrade its performance, and this gave the designers some ideas.

Soviet Tupolev TB-3 bomber
Paratroopers rolling off the broad wings of the TB-3. This was only possible with a very slow airplane.
One of those ideas was the use of the TB-3 as a paratrooper transport. Unlike today, the paratroopers rode on the outside before dropping off with their parachutes. From their perspective, though, that was probably a vast improvement from earlier parachute experiments which involved the transport aircraft simply flying low over snow or soft ground, and the paratroopers dropping off while wearing heavy padding - and no parachutes. That didn't work out so well. The plane typically carried 35 paratroopers, which is fairly impressive and 15 more than the German Ju-52 - though in the Luftwaffe they all got to ride inside until the drop.

Soviet Tupolev TB-3 bomber
TB-3 docking with a Grigorovich I-Z under the fuselage.
The most interesting use of the TB-3, though, was as a mothership for parasite aircraft. While it looks odd to the modern eye, the TB-3 was used as a sort of flying aircraft carrier. Not only did it carry planes into the air and release them, it also docked and then refueled them while in flight. Somewhat incredibly, the TB-3's performance wasn't affected by this cumbersome arrangement at all. Of course, it flew so slowly in the first place that it couldn't afford to fly any slower or it never would have gotten off the ground. This arrangement was known as Zveno (Russian: Звено, Chain link or a military unit "Flight").

Soviet Tupolev TB-3 bomber
A three-plane Zveno line-up. To carry five, an additional two planes could be slung under the wings. The middle plane on the top was fixed in place to help provide lift with its own engine - plus it was too difficult to load it for each mission.
The Zveno project was developed by the Soviet Union in the 1930s and was used in some theatres during World War II. The project used the Tupolev TB-1 or TB-3 heavy bomber to carry fighter planes. There are stories of the TB-3s launching raids against Romania and strategic targets in Ukraine during the war. The bombs carried, however, could not possibly have been large enough to do more than nuisance damage. Various permutations were tried, varying from one to (incredibly) five parasite aircraft. While many photographs do show three parasite fighters in quite impressive fashion, in fact only two launched, while the middle fighter was a permanent addition that helped supply lifting power to the TB-3 itself. The definitive Zveno-SPB used a TB-3 and two Polikarpov I-16s, each armed with two 250 kg (550 lb) bombs.

Soviet Tupolev TB-3 bomber
Zveno SPB: a Tupolev TB3-A4M-34FRN mothership and two Polikarpov I 16 type 5 fighters. Each of the fighters being armed with a pair of 550 lbs FAB-250 high-explosive bombs. Photographs: ©V Kulikov.
The TB-3 was used fairly extensively right after the outbreak of the war. This was simply because they survived - its squadrons were based far behind the front lines (it being obsolescent and all) and thus, somewhat ironically, they were spared the combat that destroyed its less-obsolescent brethren in the first days of Operation Barbarossa, the German invasion of the Soviet Union. By August 1941, TB-3s comprised a full quarter of the Soviet bomber force, because the other (better) bombers had been decimated on the ground by the Luftwaffe.

Soviet Tupolev TB-3 bomber
The same set-up as in the picture above, from a bit further away.
TB-3s launched missions beginning on 23 June 1941, the day after the invasion, including a few rare offensive Zveno missions against Romanian territory (the initial Soviet plans called for an offensive, not a strategic retreat). It appears that the Zveno missions, though, petered out quickly during that first year. The bomber continued in service through the battle of Kursk in July 1943, and even after that several remained in service as transports through the end of the war. The TB-3 may not have been a high-performance aircraft, but it flew, and that was good enough.

Crew: Four
Length: 24.4 m (80 ft 1 in)
Wingspan: 41.80 m (137 ft 2 in)
Height: 8.50 m (27 ft 11 in)
Wing area: 234.5 m2 (2,524 ft2)
Empty weight: 11,200 kg (24,690 lb)
Loaded weight: 17,200 kg (37,920 lb)
Max. takeoff weight: 19,300 kg (42,550 lb)
Powerplant: 4 × Mikulin M-17F V12 engine, 525 kW (705 hp) each


No comments:

Post a Comment