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The Soviet Bomber That Was Reverse Engineered From Stolen American B-29s

Boeing B-29 Superfortress

Ask anyone, what won the war against Japan during the Second World War, and the answer would invariably be the ‘atomic bomb’, but truth be told, it was the Boeing B-29 Superfortress that broke Japan’s back. Months before Bockscar delivered the final payload of the war, hundreds of American B-29s had flown across the Pacific in thousands of sorties to destroy Japanese cities as well as their ability to fight.

The Boeing B-29 Superfortress was every nation’s envy. It was the most advanced aircraft of the time, with state-of-the-art technology, such as remote controlled guns, pressurized compartments, dual-wheeled, tricycle landing gear, and extraordinarily powerful engines. It could carry up to 20,000 pounds of bomb and drop them on targets 3,000 miles away. It could fly at 350 mph at an altitude of over 30,000 feet—comfortably out of reach of most Japanese planes and guns. The B-29 was a generation ahead of the Luftwaffe's Junkers Ju 290, and even Boeing’s own B-17 and B-24. Japan did not even have a heavy bomber, and the most advanced bomber in the Soviet inventory used fabric-covered ailerons, compared to the B-29’s all-aluminum marvel.

Several times Stalin asked President Roosevelt to supply the Soviet Union with B-29s under the US military aid program—an understanding among Allied nations to share food, oil, and materials among themselves. Under the program, the US sent Soviet $11 billion in materials, including over 400,000 jeeps and trucks, 12,000 armored vehicles, 11,400 aircraft, nearly 2,000 locomotives, 2.6 million tons of gasoline and oil, and 1.75 million tons of food. The only item they refused was heavy bombers.

Soviet Union was not exactly a friend. The only reason America and Britain were willing to fulfil Soviet’s demands was because they all faced a common enemy. Both America and Britain sent the Soviet Union massive amounts of military aid in order to shore them up. They needed Stalin’s troops to fight the Nazis on the Eastern Front, to draw them away from the fight along the English Channel and thwart a possible invasion of Britain. For this purpose America and Britain supplied Stalin with M3 Lees and M4 Shermans, as well as the American Airacobra fighter jets and British Hurricanes. But heavy bombers capable of flying over a continent and across an ocean, were a different matter. The US did not trust Stalin enough to equip him with a technology that might be used against them.

Boeing B-29 Superfortress

The B-29 Flight Deck. Photo: 900hp/Flickr

Luckily for Stalin, B-29 crews were instructed to land in Russia in case of emergencies, and in the summer of 1944, exactly such an emergency befell three B-29s during a bombing raid to Japan. The three aircrafts—General H.H. Arnold Special, Ding How, and Ramp Tramp—landed in Vladivostok, and at once, the Soviet whisked them away to a facility in Moscow. The crews were sent back home, but not after desperate pleas from the US. Demands for the return of the planes were ignored.

With these three aircrafts, Soviet engineers began one of the most complex and audacious reverse-engineering projects ever. Of the three, one was dismantled. To keep track of the growing mountain of parts, the second one was use as reference. The third was used for test flight.

Stalin ordered that the B-29 be copied exactly, down to the smallest detail. But that was easier said than done. The Soviet Union did not have the manufacturing ability to reproduce many parts. For instance, the B-29 used a 1/16″ aluminum skin, but the Soviets used the metric system, so sheet aluminium in that thicknesses was unavailable to them. The Soviet ended up using aluminium of a different thickness. Many alloys and other materials new to the Soviet Union had to be brought into production. Parts had to be re-engineered to compensate for the minor differences and then made sure they fitted and the entire aircraft worked as expected. Compromise had to be made. The .50 caliber machine guns used in the B-29 could not be sourced, and had to be replaced with cannons instead. For tires, agents scoured the western war surplus market.

The biggest challenge was duplicating the complicated central fire-control system. The B-29 used five General Electric analog computers to control the five gunsights located in the nose and tail positions of the airplane within Plexiglas blisters. These interconnected controls allowed a single gunner to remotely operate the B-29’s guns simultaneously. All weapons were aimed optically with targeting computed by the analog computers by taking into consideration the speed of the aircraft, gravity, temperature and humidity, among other things, allowing for increased weapons' accuracy. The system was so complicated, that even Andrei Tupolev, the lead engineer of the project, was surprised when his engineers pulled off the impossible.

Tupolev Tu-4

A surviving Tupolev Tu-4 at the Monino Central Air Force Museum, Moscow. Photo: Andrey Korchagin/Flickr

In less than two years, the Soviet Superfortress Tupolev Tu-4, was ready. Despite the many challenges, the prototype Tu-4 weighed only about 340 kg more than the B-29, a difference of less than 1 percent. It looked virtually identical to the B-29. It had the same wingspan and same fuselage length. It had the same speed, the same range, the same payload and a slightly higher service ceiling.

Tupolev and his team was so meticulous in their duplication effort that they copied every last detail including the fuselage patch and the color scheme. Some rumors circulated that even flak damage on the wings had been carefully copied, and that a misplaced typewriter within the B-29 was included as standard equipment on every Soviet copy of the plane.

While some of these stories were certainly exaggerated, there was an element of truth behind them. According to Leonid Kerber, an engineer who worked alongside Tupolev in the Tu-4 project, Tupolev was so scared of Stalin and Lavrentiy Beria, the chief of Stalin’s secret police, that he made sure that every minor detail was copied, lest he be accused of ignoring Stalin’s precise instructions.

The first batch of Tu-4s rolled off the assembly line on schedule in 1947. It flew for the first time on 19 May 1947.

On August 3, the same year, the Soviet Union held Aviation Day at the Tushino airfield northwest of Moscow. Representatives from all major air forces were present. As the American diplomats stood watching, they heard a familiar drone. Looking up they saw what appeared to be the three captured B-29s that the Soviets had refused to return years earlier. Only when a fourth aircraft appeared, that the world new that the Soviets had successfully copied the Superfortress.

The Tu-4 eventually went into mass production, and by 1952, when production ended, around 850 bombers had been made. The valuable experience gained during its design launched the Soviet strategic bomber program, and by the early 1960s, the Tu-4s were already withdrawn, replaced by more advanced aircrafts. A variant of the Tu-4, the Tu-4A, was used to carry and drop the first Soviet nuclear bomb.

References:
# Brian Benchoff, STOLEN TECH: THE SOVIET SUPERFORTRESS, https://hackaday.com/2016/03/10/stolen-tech-the-soviet-superfortress/
# Von Hardesty, Made in the U.S.S.R., https://www.airspacemag.com/military-aviation/made-in-the-ussr-38442437/?all
# Wayland Mayo, Russian B-29 Clone — The TU-4 Story, http://www.rb-29.net/HTML/03RelatedStories/03.03shortstories/03.03.10contss.htm
# Wikipedia, https://en.wikipedia.org/wiki/Tupolev_Tu-4

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