30 April 2007

Red Bulls: Of Replication, the B-29 and TU-4 Bull

One of the threads arising out of the F-22 "Raptor-ski" post was the practice of using foreign designs to advance indigenous efforts. All nations, at one time or another, have used this process. The US manned space program though Apollo, for example, is but an outgrowth of Werner von Braun's concepts and designs which in turn, were rooted in the V-2 project.

Perhaps, though, one of the more infamous examples was the development of the Soviet TU-4 Bull from the American Boeing B-29. In the process of duplication, the technology transfer to the Soviet heavy bomber industry was significant and when combined with a traditional evolutionary process, ultimately resulted in the highly successful TU-95 Bear series.

Until the Soviet Union declared war on Japan in the closing days of August, 1945 it maintained a state of neutrality towards combatants in that theater. During this period of neutrality, allied aircraft that diverted to the Soviet Union due to weather, mechanical or battle damage issues, were impounded and their crews eventually returned to their nations of origin, though not without attempted interrogation along the way. This practice began with the Doolittle B-25s that landed in Vladivostok in 1942 and in 1944, included three B-29's:
  • On July 29, 1944 Ramp Tramp, a B-29-5-BW serial number 42-6256 that was unable to return to its base after a raid in Manchuria (landed in Vladivostok);
  • On November 11, 1944 The General H.H. Arnold Special, serial number 42-6365, that was damaged during a raid against Omura on Kyushu was forced to divert to Vladivostok and;
  • On November 21, 1944 Ding How, serial number 42-6358, which also landed in Vladivostok.
The crews for these aircraft were eventually returned to the US (via Tehran) in January 1945, but Stalin, recognizing the possibility for jump-starting the technological capabilities of the Soviet heavy bomber industry, ordered exact duplicates made of the B-29s. Up to this point, the Soviet heavy bomber industry had provided mediocre products that were notable more for their size than any nascent operational capabilities. The only bomber of note, the ANT-40, could only be categorized as a medium bomber (similar to the A-20 Havoc) and was obsolete by 1941. And the Petlyakov Pe-8 fell woefully short in all areas as a heavy bomber. It was clear to Stalin that the US intended to exploit its advantgage in long-range heavy bombers post-war and the development of atomic weapons heightened the urgency on the Soviets' part to close that vulnerability.


Petlyakov Pe-8

A.N. Tupelov eventually took charge of the replication process and immediately confronted the enormous challenge that they faced. The B-29 represented the ultimate of technological refinement in the US aircraft industry - using lightweight metallic alloys (including magnesium alloys) and the latest in electronic capabilities for self defense and all weather bombing, the B-29 was a veritable lodestone of information - if it could be decoded. Under normal circumstances, this would be a many year effort, but with Stalin's interest and imperative, the project assumed the urgency of America's Manhattan Project, except with Stalin's well known propensity to brutally punish failure. To that end, when he demanded an exact copy, as close as was possible, an exact duplicate was generated. How exact? Here is one story (as related by Victor Suvarev (pen name for a critical post-war writer who had extensive experience with this effort):

"A little hole was found on the left wing of the [first] aircraft. No aerodynamics or durability expert had the slightest idead what the hell it was there for. There was no tube or wire attached to it, and there was no equivalent to it on the right wing. The opinion of a commission of experts was that the hole had been bored by a factory drill at the same time as the other holes for the rivets. So what to do? Most probably, the hole had been drilled by mistake, and later no one had bothered to fill it in as it was much too small. The chief designer was aked his opinion. 'Do the Amercans have it?' 'Yes.' 'So why the hell are you asking me? Weren't we ordered to make them identical! Alike as two peas?' So, for that reason, a very small hole indeed, made with the thinnest possible drill, appeared on the left wing of all Tu-4 strategic bombers...'"
and a better known variant regarding interior paint:

"The scroll tunnel connecting cockpit and rear parts of the bomber was half green and half white, because Boeing run out of one of the color when painting this particular specimen. On the copied aircraft, two thirds was painted chromate green, the aft portion left in white primer. 'Later, this ratio was included in all the instruction books on how to paint the interior of the bomber'."
Finally, this measure of the paranoia present in Stalinist Russia :

"'What kind of stars should be put on the mass-produced aircraft - white American stars of red Soviet ones? If you put white stars, you risked being shot as an enemy of the people. If you put red, first, it will not be a copy, and second maybe Stalin is planning to use the bombers against America, England or China, and therefore keep the American markings.' The question went all the way up to Stalin himself: Beria (NKVD chief, in charge of B-29 duplication project) 'told Stalin about the stars as if it were a funny story and that by the way in which Stalin laughed at the joke, Beria knew unerringly which stars should be used. The last problem was solved and mass-production started...'"
Of the three B-29's, the General H.H. Arnold Special was disassembled at the Central Aerodrome in Moscow. Ding How was grounded as a reference aircraft and Ramp Tramp remained flyable. Ramp Tramp's engines were replaced with ASh-73TK's to make the aircraft more maintainable and it remained in-service for nine years.

To perform the replication, everything, right down to bolts and fasteners, had to be converted from English to metric units. Some immediate problems were addressed, the chief one being the thickness of the aluminum skin. The B-29's was 1/16th inch which r
equired an impractical 1.5875 millimeter thickness in order to be an exact duplicate, therefore a skin of varying thickness between .8 and 1.8 millimeters was used instead.

Disassembly of the General H. Hap Arnold.

Period cutaway of the Tu-4.

However, as closely as everything else was copied, the bugs were copied as well, to include problems with the engines and props that US crews experienced (including an unfortuante tendancy to catch fire and for the electric prop governor to runaway) and other probelms with the landing gear. Crews complained about visibility and distortion problems from the extensive glazing in the nose and the centralized self defense system also proved especially problematic.

The first public display of the TU-4 was Aviation Day, 3 August 1947 when 3 were flown in addition to the TU-70 airliner variant. By 1949 the bugs were pretty well worked out and eventually production of 850 units completed. In toto, 0ver 900 factories and research bureaus were part of the effort, all coordinated with a radio-linked production tracking process instittued by Tupelov. The production processes and technology unlocked combined with indigenous industry effrots (e.g., engines) began a process of evolutionary change that led directly to the TU-95 Bear and in part, the Tu-6 Badger (see illustration below).

From Soviet Military Aircraft Design and Procurement - 2nd Edition. (General Dynamics)



In addition to serving in Soviet Long Range Aviation forces, the TU-4 was also put in service with China in both bomber and AEW variant form:

China's AEW variant (developmental).

TU-70 Production.

As mentioned and like the Stratocruiser in the US, the TU-4 was also converted to a 70 passenger airliner. The impact of the TU-4 went far beyond its actual capabilties, forcing the USAF into development of a wide-ranging early warning and interceptor system.

Ramp Tramp
, like her sister B-29s in USAF markings, served as an airborne launch platform for the Soviet Union's rocket powered supersonic research aircraft, the Samolet 346. This was the product of a German experimental project called DFS 346. The Soviets reportedly captured the DFS 346 in 1945 and built the Samolet 346 using German scientists and a German test pilot. Reportedly, Ramp Tramp was eventually scrapped sometime in the early 1990's.


  • Soviet Military Aircraft Design and Procurement, 2nd edition. General Dynamics (Ft Worth division), 1983.