The TB-7 bomber is perhaps one of the few Soviet warplanes built before the war whose history clearly reflects all the distinctive features of aircraft development under the onerous totalitarian Soviet regime of the 1930s and 1940s. The fact that even its designation changed twice (fromANT-42 to TB-7 and then Pe-8) gives food for thought, not to mention that it was twice withdrawn from production.
Preparation for series production had begun as early as 1937, but was not completed until 1939. It was a long time before a plant was found to build the supercharger units, and this caused great anxiety. When series production started, Plant No. 124 obtained ATsNs for the first four aircraft only, and the TsIAM refused to manufacture any more. This was a sad blow, as without the ATsN the bomber’s service ceiling was greatly reduced, along with other performance parameters. The advisability of TB-7 production became questionable.
Delivery problems with the AM-34FRNV main engines arose in the second half of 1939, and TB-7 production was halted. The plant had managed to complete only the first two production bombers, and several more were in various stages of construction. Only two of these featured the ATsN superchargers.
At the beginning of 1940 the People’s Commissariat of the Aircraft Industry (Aviaprom) gave aircraft Plant No. 124 directions and construction of the TB-7 was finally halted, but the Aviaprom authorities realised the need to supply the WS with the new bombers. At the same time a number of aero-engine design bureaux proposed alternative powerplants for the TB-7.
The newly-appointed director of aircraft Plant No. 124, Mikhail Kaganovich, brother of Lazar Kaganovich, one of Stalin’s high-ranking officials, also paid great attention to the bomber, and obtained enough of the new 1,200hp (895kW) AM-35A engines to equip the six aircraft then under construction. At the same time a powerplant using- Aleksei Dmitriyevich Charomskii’s M-30 and M-40 diesel engines was designed.
In the spring of 1941 the first TB-7 powered by M-40s, with a nominal power of 1,000hp (746kW) and a take-off power of 1,500hp (1, 119kW) was rolled out. Kaganovich invited Georgy Baydukov, well-known throughout the USSR as a crew member on Valery Chkalov’s record-breaking long range flights, to act as its test pilot.
Simultaneously another aircraft powered by M-30s, subsequently redesignated ACh30B after Charomskii, was constructed. The M-30 and M-40 were essentially the same, but differed in turbo-supercharger dimensions and number. However, in the process of running the diesels it was found that they were unreliable. They were liable to cut out at high altitude because the manually-controlled fuel feed depended on a certain rate of revolutions per minute being maintained, and they could only be restarted at about 1,500m. The M-30 was more reliable in this respect because it had a centrifugal supercharger.
By the end of 1940 Plant No. 124 had completed 18 aircraft and delivered them to the WS, despite constant production stoppages. After the outbreak of war the plant began production of Pe-2s, which drew heavily on the factory’s resources, but TB-7 production continued. Complicated and skilful work was undertaken to ensure the aircraft’s efficiency. In August 1941 TB-7 formations were organised, one of them led by the well-known Arctic flyer M Vodopyanov. On 9th August the first air raid by these bombers was made on Berlin.
Most of the TB-7s built in 1942 had AM-35As, which were considered more reliable, but engine deliveries suffered frequent hold-ups. It was therefore proposed that Shvetsov designed 1,850hp (1 ,380kW) air-cooled M-82s be fitted, though their installation posed problems because wing and engine nacelles needed to be reconstructed and complicated exhaust collectors had to be fitted. Nevertheless, these more powerful engines were installed, and were provided with’ two-speed superchargers to increase their altitude capability. At first the M-82s ran irregularly because of the turbo-superchargers, but this problem was later eliminated. Adoption of the M-82 meant that Plant No. 124 was not short of engines in 1943, and steady production began. In the middle of the war the bomber was redesignated Pe-8 in acknowledgement of Vladimir Petlyakov, who led the team that designed it. He later became leader of the design collective. The bomber’s development was controlled by the chief designer at Plant No. 124, Joseph Nezval, one of A Tupolev’s best assistants, who had taken a most active part in its design.
Production of the M-82-powered Pe-8 continued in 1944. It was believed at the plant that the versions with M-30s and M-40s would no longer be built, but another four aircraft were constructed with modified M-30s. However, the performance was not greatly improved.
With a 4,4091b (2,000kg) bomb load and full fuel tanks the Pe-8 powered by AM-35As had a maximum range of 2,236 miles (3,600km). With M-30 or M-40s its range increased to 3,392 miles (5,460km), and with M-82s it was 3,604 miles (5,800km). Most production TB-7s (Pe-8s) had AM-35As, which were the most reliable. Unlike the first prototypes, aircraft powered by M-30s, M-40s, AM-35As and M-82s had no ATsN to enhance their altitude capabilities. In total, 93 aircraft were built (96 according to some sources).
Practically all of the available TB-7 heavy bombers were delivered to the 14th Heavy Bomber Air Regiment, which was non-operational at the beginning of the war. Most of its four-engined giants were awaiting planned modernisation of their engines and replacement of their defensive armament.