The fast and sleek Tupolev SB-2 light bomber had already drawn blood in Spanish skies when Czechoslovakia came to terms with the Soviet Union in 1937 to purchase 60 examples of the aircraft direct from the manufacturer, and secured a license to produce more. Under the terms of the deal, the planes were delivered with Avia-built Hispano-Suiza 12-Ydrs liquid-cooled 12-cylinder engines turning Letov Hd-43 two-bladed metal propellers. For defense, Czech 7.92mm vz.30 machine guns replaced the Soviet 7.62mm ShKAS originals. Six 220-pound bombs could be carried. In Czechoslovak service the bomber was designated B-71 and had a maximum speed of 267 mph. With a 423-gallon fuel tank capacity, the 850hp engine managed a maximum range of 621 miles.