Tupolev ANT-16

The Tupolev ANT-16, also known as the TB-4 (Tyazhely Bombardirovshchik, heavy bomber), was an experimental Soviet heavy bomber designed and tested in the early 1930s as an evolution of the TB-3. It was built on the doctrine that size and payload mattered more in a bomber than speed, since heavy defensive armament would protect it. Its twin bomb bays, each 5 by 1.8 by 1.8 metres, were the largest in the world at the time and posed many design challenges for the rigidity of the airframe. Six Mikulin AM-34 V-12 engines powered it, two of them mounted on top of the wing. The sole prototype first flew on 3 July 1933 with M. M. Gromov at the controls, and the test programme ended on 29 September 1933 with disappointing results. A second prototype was never finished, and some of its parts were used in the ANT-20.