The SPB (D) closely resembled the
Polikarpov VIT-2, which had been recommended for production as a dive bomber, but the former actually was an entirely new design. It was smaller than the VIT-2 and had a
monocoque fuselage. The main gears of the
conventional undercarriage retracted aft into the rear of the engine nacelles and the tail wheel retracted into the rear fuselage. Two liquid-cooled
Klimov M-105 V12 engines were slung underneath the wings. It retained its predecessor's prominent canopy and nose glazing, but reduced the armament to a single
ShKAS machine gun for the bombardier/navigator while the rear gunner had a retractable
Berezin UB dorsal gun and a ventral ShKAS to protect the aircraft's underside. The
bomb bay could carry up to 800 kg (1,764 lbs) internally and an additional 700 kg (1,543 lbs) of bombs could be carried underneath the wings. In addition to the SPB (D) prototype, five pre-production machines were ordered even before the prototype made its first flight. This flight, piloted by Boris Kudrin, occurred safely on 18 February 1940, but on 27 April 1940 the first prototype crashed for unknown causes, killing test pilot
Pavel Golovin. ==Specifications ==