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The Vakhmistrov Zveno
A Very Strange Airplane
by Raul Colon
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The Zveno composite bomber/fighter designed by Vladimir Vakhmistrov.
    One of the most strange and bizarre looking aircraft that ever took to the air has to be the Zveno composite bomber/fighter designed by Vladimir Vakhmistrov. The concept first took shape in the mid-1920s, when the Soviet Air Force was looking at ways to both, shoot down incoming enemy bombers and to supplement ground troops in the field. Many new concepts and designs came forward, but the most intriguing idea presented to the Tupolev Bureau of Aircraft Design was the Zveno. The concept was fairly straight forward—utilizing the largest bomber of its day, the massive TB-3 with different combinations of fighters and dive-bombers attached to its fuselage and wings, would provide the bomber with defensive capabilities.

    After experiments were conducted with gliders attached to the "mother ship", Vakhmistrov (the designer of the Polikarpov R-1), proposed a radical new concept that eventually developed into one of the world's first "parasite" configurations. In the late-1920s, Vakhmistrov persuaded the infant Soviet Air Force, that a heavy bomber can carry fighters for its own protection and release them when necessary and also provide ground attack capability.

    The first of these combinations, designated the Zveno 1 or Z-1, involved carrying two modified I-4 fighters above each wing. The fighters were placed in position by using wooden ramps and ropes to haul them onto the wing. The initial trials proved successful and after the design had been adapted to carry larger I-5 fighters, the bomber designation changed to Z-1a. The Z-2 consisted of a TB-3 with three I-5s mounted on the wings and fuselage. The TB-3 proved to be an excellent carrier platform and the next model, the Z-5, was even more ambitious and featured a Grigorovich I-Z suspended beneath the TB-3 on a steel trapeze. The airplane could then be recovered after their release using a system similar to that used by the Curtiss F9C.

The Z-2 employed ramps to load Polikarpov I-5 fighters onto the wings.


    The TB-3 was powered by four 819 hp (610 kW) Mikulin AM-34-RN engines and had a maximum speed of 152 mph (245 km/h)—a major feat for this kind of unorthodox aircraft. The climb rate was 410 fpm (2.08 m/s) to 3,280 ft (1,000 m), the range was some 622 miles (1,000 km) and the service ceiling was 25,400 ft (7,742 m). The maximum takeoff weight was 41,529 lb (18,837 kg) with a wing span of 137 ft, 1 in (41.78 m), length of 82 ft 4 in (25 m) and a wing area of 2,523 ft² (769 m²). Armament consisted of (apart from its parasite fighters) four 7.62 mm machine guns—one mounted on the nose, one in the tail and one each in the dorsal and ventral positions. The original Zveno Z-1 made its inaugural flight, with Vakhmistrov onboard, on December 3rd, 1931 at Monino—the first successful in-flight release of all five units occurred in November 1935.

The Z-7, carried two Polikarpov I-16SPB fighters below the wings.


    The pilot of the TB-3 bomber had the difficult task of keeping the "mother ship" steady as possible during the extremely difficult release sequence. The fighters above the wing, had to be released simultaneously, to prevent a dangerous asymmetrical situation of having an aircraft on one wing, but not on the other. The aircraft was extremely unmaneuverable when all aircraft were attached. The copilot was assigned the task of releasing the main axle attachment on the I-5 fighter, once the pilot had released the rear fixture. The fighter above each wing of the Zveno was the Polikarpov I-5 model, secured by a hold-down undercarriage and a steel tripod fixture attached to the Zveno's wing. An I-16 fighter plane was attached beneath each wing. Each of one was held in position by a two large V-struts made from aluminum tubing.

    Suspended beneath the bomber's fuselage, on a steel tube trapeze, was the I-Z fighter. This was the only aircraft that could be recovered after it had been launched from the "mother ship". The I-Z had a steel structure with a sprung hook in the front of the pilot's cockpit, which the pilot guided into the trapeze.

    The culmination of the design process was the still incredible Aviamatka Z-6, which carried two planes I-5 fighters above the wings, two I-16s below the wings and an I-Z on the trapeze. Unexpectedly, the final combination, the Z-7, saw service during the early years of the Great Patriotic War (WW II), carrying two I-16SPB dive-bombers—it made one famous bombing mission and destroyed a bridge at the Danube in Chyernovod, Romania. After the TB-3, other major aircraft companies tried composite aircraft designs. One of the most famous designs was the Curtiss F9C Sparrowhawk that was attached to the airships USS Macon and USS Akron and were recovered by the "mother ship" utilizing a trapeze system.

    Another design was the late 1945 Luftwaffe experimental Ju 88 Mistel using a bomb carrying Junkers Ju 88 guided by an attached fighter—the experiment was never carried out on major scale. The last attempt to use a composite system was the use of the US Air Force Convair B-36 Peace-Maker bomber as a "mother ship" with a YF-84F reconnaissance aircraft under the fuselage, or joined at the wingtips. Again, as in the other programs, they never make it to the operational stage.

The Z-5 carried a Grigorovich I-Z beneath the TB-3 on a steel trapeze.


Sources

* Concept Aircrafts: Prototypes, X-Planes, and Experimental Aircrafts. Editor Jim Winchester. ThunderBay Press 2005
* Soviet X-Planes. Yefim Gordon and Bill Guston. Midland Publishing 2000
* Russian Aviation and Air Power in the Twentieth Century. Edited Robin Higman, John Greenwood, and Von Hardesty, Frank Cass 1998
* Axis Aircraft of World War II. David Mondey. Smithmark Publishers, 1996.
* German Military Aircraft. Bryan Philpott. Crescent Books, 1981.
* The History of Soviet Aircraft from 1918. Vaclev Nemecek. Willow Books, 1986.
* World Aircraft 1918-1935. Enzo Angelucci and Paolo Matricardi. Rand Mcnally, 1976.
* Polikarpov Fighters in Action Part I. Hans-Heiri Stapfer, Don Greer and Joe Sewell. Squadron Signal Publications, 1995.
* Polikarpov Fighters in Action Part II. Hans-Heiri Stapfer, Don Greer, Ernesto Cumpian and Joe Sewell. Squadron Signal Publications, 1995.
* Russian Fighter Aircraft 1920-1941. Heinz J. Nowarra. Schiffer Military History, 1997.


The author Paul Colon is a freelance writer who resides in San Juan Puerto Rico. rcolonfrias@yahoo.com

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©Raul Colon. The Aviation History On-Line Museum. All rights reserved.
Created October 21, 2007. Updated November 24, 2013.