 It made its first flight on 30 April 1930 and was fitted with an imported supercharged 450-horsepower (340 kW) Jupiter VII. It was painted in silver with a red cheat line; a red "VT" was superimposed on the red star on the rudder. The second prototype, known as the VT-12, had a Jupiter VI engine, and took to the air on 22 May, bearing the name "Klim Voroshilov." The two prototypes also differed in minor details regarding the shape of the tail and the construction of the landing gear. All this meant a slight difference in weight and performance between the two prototypes was present, with the second being slightly heavier and faster, while the first had a slight range advantage and a higher service ceiling. The third prototype, designated as the VT-13 and inscribed with "A Gift for the XVIth Congress of the Party", was powered by a 600-horsepower (450 kW) Soviet-built M-15 engine with a NACA cowling, but this proved to be unreliable and was not put into production.
