TB-1, ANT-4 prototype by A.N.Tupolev

20k b/w ANT-4 prototype with mockup torpedo, "History of aircraft construction in the USSR", Vol.1 p.371

The first in the World all-metal cantilever twin-engine bomber. Layout of the ANT-4 was reproduced all over the World since 1930, after the first international appearance. All following multi-engine bombers added no radical layout changes to this aircraft of 1925, except airdynamic and structural refinement, number of engines and guns, different levels of equipment sophistication.

It is interesting that this (mostly) land-based aircraft has a naval pre-history. In 1923- 1929 the Special Technical of military inventions (Ostechbureau at Leningrad, headed by V.I.Bekauri) badly needed a heavy bomber aircraft for their research (naval torpedoes). Plans to buy some in the Great Britain did not materialize. As a result, A.N.Tupolev at the TsAGI started to work on this project (November 11, 1924). Timeline was only 9 months. Aircraft was assembled on the second floor in non-industrial building! In addition to this A.N.Tupolev had not enough skilled workers.

Despite all odds, ANT-4 was ready in time. It was 'extracted' from the second floor, through removed building wall on August 11, 1925. In October 1925 assembly was finished on the Moscow Central Airfield. On 26 November, 1925 first flight was performed by pilot A.I.Tomashevskij. It took 7min to carry out preliminary evaluation.

Following the flight, some changes were introduced into design. Next flight (35min, 15 February, 1926) was a complete success, and on March 26 ANT-4 fulfilled factory trials. Special representatives from Ostechbureau, TsAGI and NOA were present. Pilots A.I.Tomashevskij and N.N.Morozov suggested some minor modifications, and on June 11 State Acceptance Trials started. On July 2 unanimous conclusion: 'First Class Aircraft' lit green light to production of ANT-4/TB-1.

On June 10, 1926 A.I.Tomashevskij on the first ANT-4 performed 12 hours flight (and landing) with 1075kg load.

It took some time before series manufacturing started. Prototype had single set of controls, carried no defensive weapons, no radio, no navigation (and photo) equipment. Original Lorraine-Dietrich engines were replaced by BMW-VI. Following replacement by license built copy M-17 was scheduled.