A.N.Tupolev

20k b/w drawing of ANT-40.2 (by I.G.Sultanov) from History of aircraft construction in the USSR V.B.Shavrov Vol.2 p.13

he first version of the SB bomber. It was slightly smaller than following series aircraft and was powered with Wright 'Cyclone' radials.

Rolled out of factory in October 1934. When restored after crush-landing on October 31 ANT-40.1 became a testbed for new technologies, including retractable ski gear. It did not became a series aircraft because the ANT-40.2 with Hispano-Suiza 12Y was considered more promising.

ANT-40.2 was finished at the very end of 1934, and during flight tests in January 1935 speed 430km/h was demonstrated.

It was the first Soviet aircraft to be equipped with weight-compensated elevones. After minor changes (engines moved forward by 10cm, wing leading edge sweep increased from 4.5⁰ to 9⁰) aircraft was adopted as a base for mass production series.

The SB series became a major bomber of the Red Army Airforce for next 5 years, used in several wars: clashes with Japanese on Mongolian border, Spanish War, Winter War, Great Patriotic War (WWII).