The work on the plane that became the SB (Skorostnoi Bombardirovshchik, Fast Bomber) started at the beginning of 1934. The plane was called ANT-40 (from Andrei Nikolayevich Tupolev, the leader of the OKB). The principal designer was A.A. Archangelsky, while V.M. Petlyalov designed the wings and control system.

The first prototype, ANT-40-1, made its first flight on 7 October 1934, flown bty the test pilot I.S. Zukhov.

The first prototype in its first configuration. The plane was powered by two nine-cylinders radial engines Wright Cyclone SGR-1820 F-3, that drew two Hamilton three-blades propellers.

The plane looks finished in light grey, perhaps with the cowling of another light color. The rivet heads were flushed, a characteristic that was lost on production planes for industrial reasons.

Its wingspan was 19 m only, with a wing area of 46.3 m2.

Note the shape of the stabilizer and rudder, thinner than the one of the successive production planes and with a very large trim tab.

Note that the tail wheel had a bracing strut on its front.

The second prototype ANT-40-2 was powered by two Hispano Suiza 12 Ybrs , easily recognizable for the new engine cowl with frontal cooler.

On this prototype, the radiator shutters were horizontal, and the opening for the spinner was hexagonal. On these photos, the front windows have a temporarily cover.

The plane was finished in natural metal, perhaps with te engine rings painted with a different color. thev wheel disks appear dark, possibly dark green.

TsAGI is painted, probably in black, on the fuselage sides.

The wing span and area were larger than the first prototype, passing to 20.3 m and 52 m2 respectively.

Both the drop-shaped cover on the tail wheel and its bracing strut, seen on the first prototype, weren't preserved on the second one.

The ANT-46 was a fighter derivative of the SB conceived as an heavy escort fighter, experimented in November 1935. It was moved by two Gnome- Rhone 14 Kdrs engines covered by shutters.

Its armament included:

two APK-4 76 mm recoilles guns in the wing leading edge;

two rearward-firing ShKAS 7.62 machine guns in the wings;

a ShWAK 12.7 mm gun in the navigator's position;

two ShKAS for the rear gunner, as on standard bombers.

It was projected to abandon the recoilless guns and to install for SHWAK 20 mm guns under the fuselage.