Tupolev Vakhmistrov Zveno

Some of the weirdest aircraft ever to have flown, the Vakhmistrov's series of composite bomber/fighter designs was an experimental product of the 1930s. Using the biggest bomber of the day, the Tupolev TB-3, different combinations of fighters or light dive bombers were attached to the fuselage and/or wings, providing the aircraft with it's own self-defense capability. One squadron of these strange Zveno aircraft saw service in World War II.

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Zveno configurations

Tupolev TB-1 and two Tupolev I-4 on top of the wings. The normally sesquiplane I-4s had the bottom wings removed (with no ill effect on flight characteristics) due to clearance problems with TB-1 propellers. First flight December 3 1931. The TB-1 was piloted by A. I. Zalevskiy and A. R. Sharapov, the I-4s were piloted by V. P. Chkalov and A. F. Anisimov. Vakhmistrov himself flew in the front gunner's turret.
TB-1 and two Polikarpov I-5 on of the wings, first flight September 1933. The TB-1 was piloted by Stefanovskiy, the I-5s were piloted by Kokkinaki and Grozd.
Tupolev TB-3 and three I-5, the third aircraft was attached over the fuselage. First flight August 1934. The TB-3 was piloted by Zalevskiy, the I-5s were piloted by Altynov, Suprun, and Suzi.
TB-3 and two Grigorovich I-Z under the wings.
TB-3 and a single I-Z under the fuselage which attached and detached in the air as there was not enough ground clearance for the fighter. On March 23 1935, TB-3 piloted by Stefanovskiy and I-Z with Stepanchenok at the controls performed the world's first mid-air docking between two aircraft.
TB-3 and two Polikarpov I-16 which were attached on the ground with the landing gear retracted. First flight August 1935, with the TB-3 piloted by Stefanovskiy, and the I-16s piloted by Budakov and Nikashin. I-16s could only detach, not re-attach, in flight
TB-3 and two I-16s, all docked in the air. First flight November 1939, pilots Stefanovskiy, Nyukhtikov, and Suprun. Fighters could re-attach in flight due to two retractable trapezes, one under each wing. Docking, while possible, was deemed too difficult to be practical.
Aviamatka (Airborne mothership)
TB-3 with two I-16s under the wings, two I-5s on top of the wings, and one I-Z attached under the fuselage in mid-air. First flight November 20 1935. The TB-3 was piloted by Zalevskiy, the fighters piloted by Stefanovskiy, Nikashin, Altynov, Suprun, and Stepanchenok. Vakhmistrov also worked on a larger Aviamatka with eight I-16s. In this scheme, the TB-3 would get airborne with two I-16s under the wings and the remaining six would attach in the air. Not all eight would attach at one time, but would rotate in and out during the flight, detaching and re-attaching as needed. These six aircraft could also refuel from the mothership. Although a few successful mid-air dockings and fuel transfers were performed in 1938 (Zveno 6 and 7), the eight-fighter configuration was never completed.
SPB (Sostavnoi Pikiruyuschiy Bombardirovschik - Combined Dive Bomber)
TB-3-4AM-34FRN and two I-16s under the wings, each armed with a pair of 250 kg (550 lb) FAB-250 bombs. Used operationally by the Black Sea Naval Air Force from 1938, one unit operating in the Ukraine nead Odessa in World War II against targets in Romania and the Chernovodsky bridge over the Danube in 1941, and against other pinpoint targets into 1942 with good success.
