Complex sentence: From 1931, Soviet Vladimir Vakhmistrov conducted experiments on the Zveno project; up to five fighters of various types were carried by Polikarpov TB-2 and Tupolev TB-3 bombers.
Split into simpler sentences: From 1931, Soviet Vladimir Vakhmistrov conducted experiments on the Zveno project. Up to five fighters of various types were carried by Polikarpov TB-2 and Tupolev TB-3 bombers.