Viktor Nikolayevich Belyayev had an illustrious early career with TsAGI, AVIAVnito, Aeroflot, OMOS, AGOS, KOSOS and the Tupolev OKB.

Each fuselage pod carried a single M-88 engine in a long chord cowling, driving a three-bladed VISh-23D propeller, as well as a pilot/navigator cockpit and radio operator/gunner station in each of the extensively glazed tail-cones.

The retractable undercarriage consisted of single main legs in the fuselage pods aft of the engines and a tail-wheel in the base of the fin.

Nyukhtikov, carried out many fast taxis to assess the handling of the unconventional DB-LK, one of which ended in an undercarriage collapse.

Flight trials eventually got under way early in 1940 revealing an excellent performance, but with a high sensitivity to centre of gravity changes.