Zveno (

Russian Russian(s) may refer to: *Russians (), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *A citizen of Russia *Russian language, the most widely spoken of the Slavic languages *''The Russians'', a b ...

: Звено, a military unit "

Flight Flight or flying is the motion (physics), motion of an Physical object, object through an atmosphere, or through the vacuum of Outer space, space, without contacting any planetary surface. This can be achieved by generating aerodynamic lift ass ...

") was a

parasite aircraft A parasite aircraft is a component of a composite aircraft which is carried aloft and air launched by a larger carrier aircraft or mother ship to support the primary mission of the carrier. The carrier craft may or may not be able to later recove ...

developed in the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

during the 1930s. It was the brainchild of the aviation engineer Vladimir Vakhmistrov. It consisted of a

Tupolev TB-1 The Tupolev TB-1 (development name ANT-4) was a Soviet Union, Soviet bomber aircraft, an angular monoplane that served as the backbone of the Soviet bomber force for many years, and was the first large all-metal aircraft built in the Soviet Unio ...

or a

Tupolev TB-3 The Tupolev TB-3, OKB designation ANT-6, was a monoplane heavy bomber deployed by the Soviet Air Force in the 1930s and used during the early years of World War II. It was one of the world's first cantilever wing four-engine heavy bombers. Des ...

heavy bomber mothership and two to five fighters. Depending on the variant, the fighters either launched with the mothership or docked in flight, and they could refuel from the bomber. The definitive Zveno-SPB using a TB-3 and two

Polikarpov I-16 The Polikarpov I-16 () is a Soviet single-engine single-seat fighter aircraft of revolutionary design; it is a low-wing cantilever monoplane fighter with retractable landing gear, and the first such aircraft to attain operational status. It "in ...

s, each armed with two bombs, was used operationally as a strategic weapon system with good results against targets in

Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...

during the opening stages of the

German-Soviet War The Eastern Front, also known as the Great Patriotic War (term), Great Patriotic War in the Soviet Union and its successor states, and the German–Soviet War in modern Germany and Ukraine, was a Theater (warfare), theatre of World War II ...

. The same squadron later carried out an attack against a bridge on the River Dnieper that had been captured by German forces.

Development

In June 1931, Vladimir Vakhmistrov of the ''Nauchno-Issledovatel'skiy Institut Voyenno-Vozdushnykh Sil'' (NII VVS, the "scientific test institute of the air force") started work on combinations of fighters rigidly attached to heavy bomber aircraft. The system was envisioned to serve several purposes: # Delivery of fighters beyond their conventional range # Provision of bombers with escort fighters # Use of fighters for dive bombing with heavier bombs than they would be able to take off with on their own # Using the added thrust of parasite aircraft to get a heavily laden bomber airborne. In all ''Zveno'' configurations, all aircraft were piloted and all had their engines running — it was expected that the combined thrust would more than offset the weight and actually improve the performance of the mothership compared to conventional bombers. The fighters were rigidly attached via pyramid-shaped metal frames, with both latches controlled by the fighter pilots. On Zveno-1, the front latches were controlled by the bomber crew, while the back latch was controlled by the fighter pilot; this was changed to all-fighter-pilot control in the next version. The original design included umbilical fuel lines which allowed the fighters to use fuel from the bomber while attached, although this was not fully implemented in practice. The first successful flight of ''Zveno-1'', using a

mothership and two

Tupolev I-4 The Tupolev I-4 was a Soviet sesquiplane single-seat fighter. It was conceived in 1927 by Pavel Sukhoi as his first aircraft design for the Tupolev design bureau, and was the first Soviet all-metal fighter. Design and development After the fi ...

fighters mounted on top of the wings, took place on 3 December 1931. An error in the sequence of opening the latches by the bomber crew resulted in one of the fighters prematurely separating, but the TB-1 -with an I-4 still attached to one of the wings - remained in controlled flight and the second fighter was soon uneventfully deployed. After latch control was fully moved onto the fighters, the normal launch procedure consisted of fighter pilots opening the tail lock and then pulling on the control stick to open the front locks and separate from the bomber. As predicted, the presence of docked fighters had a minimal impact on performance of the mothership, and ''Zveno-2''

carrying three Polikarpov I-5 fighters handled the same as an ordinary bomber. To mount the aircraft on the wings, they were pushed up special ramps but the centerline aircraft had to be lifted on top of the fuselage by hand. This was so cumbersome that the centerline I-5 became a permanent fixture on top of the Zveno-2 TB-3 and never started in the air. At one point, the centerline I-5, still with a pilot at the controls to operate the engine, had the wings and the tail surfaces removed and was used purely as a fifth powerplant for the bomber mothership. The ''Zveno-3'' in which a TB-3 carried two Grigorovich I-Z fighters under the wings presented a different challenge — the I-Z was a monoplane with fixed landing gear which touched the ground while it was suspended under the mothership. To accommodate uneven ground during takeoffs, the fighters were attached via a floating frame that permitted vertical movement relative to the TB-3. However, immediately after takeoff the I-Z pilots had to push forward on the control sticks to lock the frame in the fixed bottom position — if the fighter-bomber was not held rigid in flight, the bomber became extremely difficult to control. During one of the test flights, one I-Z pilot, Korotkov, incorrectly timed the locking maneuver and the lift generated by his fighter broke the docking frame and he crashed him into the underside of the mothership's wing. The bomber then attempted an emergency landing with both fighters still attached. At the relatively slow landing speed of the TB-3 there was a loss of lift for the I-Z which fell away, killing Korotkov. This was the most serious accident of the entire Zveno program despite the inherent complexity of carrying as many as five aircraft, performing mid-air launches and dockings, and damage to the motherships by propellers and landing gear of the fighters. Tests with various combinations of aircraft determined that top-mounted configurations presented the most difficulty in docking due to turbulent airflow coming off the mothership's wings. The problem of safe underwing attachment was solved with the introduction of the

fighter with retractable landing gear, permitting the use of the same rigid mounting frames as for the top-mounted aircraft. The mothership and its fighters were unofficially nicknamed the "Vakhmistrov's Circus" (Цирк Вахмистрова). The military ordered 40 carriers to be split between the navy and army, but the Soviets were worried of an invasion by the Germans, and production was shifted toward proven weapons. Only five carriers were ever delivered.

Configurations

;Zveno-1 :

and two

on top of the wings. The normally

sesquiplane A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While a ...

I-4s had the bottom wings removed (with no ill effect on flight characteristics) due to clearance problems with TB-1 propellers. First flight 3 December 1931. The TB-1 was piloted by A. I. Zalevskiy and A. R. Sharapov, the I-4s were piloted by

Valery Chkalov Valery Pavlovich Chkalov (; ; – 15 December 1938) was a test pilot awarded the title Hero of the Soviet Union (1936). Early life Chkalov was born to a Russian family in 1904 in the upper Volga region, the town of Chkalovsk, Russia, Vasi ...

and A. F. Anisimov. Vakhmistrov himself flew in the front gunner's turret. ;Zveno-1a :TB-1 and two Polikarpov I-5 on the wings, first flight September 1933. The TB-1 was piloted by Stefanovskiy, the I-5s were piloted by Kokkinaki and Grozd. ;Zveno-2 :

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. ;Zveno-3 :TB-3 and two Grigorovich I-Z under the wings. ;Zveno-5 :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 23 March 1935, TB-3 piloted by Stefanovskiy and I-Z with Stepanchenok at the controls performed the world's first mid-air docking between two fixed wing aircraft. ;Zveno-6 :TB-3 and two

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 ;Zveno-7 :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 20 November 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 in World War II with good success.

Operational history

In 1938, Vakhmistrov devised the Zveno''-SPB (''Sostavnoi Pikiruyuschiy Bombardirovschik'', "Combined Dive Bomber") which consisted of a Tupolev TB-3-4AM-34FRN mothership and two Polikarpov I-16 Type 5 fighters. Each of the fighters was armed with a pair of FAB-250 high-explosive bombs. Although an I-16 Type 5 could get airborne on its own with no more than 100 kg (220 lb) of bombs, once hoisted in the air by the TB-3 it could reach 410 km/h (220 knots, 255 mph) at 2500 m (8,200 ft), had a service ceiling of , and could dive at up to 650 km/h (350 knots, 405 mph). Once the bombs were dropped, the SPB-launched I-16s performed like conventional Type 5s. The three-aircraft Zveno-SPB had a total takeoff weight of , a top speed of 268 km/h (145 knots, 165 mph), and a range of 2,500 km (1,350 NM, 1,550 mi). The use of a mothership increased the range of the I-16s by 80%. The SPB first flew in July 1937. Following the successful test program in 1938, the Zveno-SPB was accepted into service. By 1 February 1940, the

Soviet Air Force The Soviet Air Forces (, VVS SSSR; literally "Military Air Forces of the Union of Soviet Socialist Republics"; initialism VVS, sometimes referred to as the "Red Air Force") were one of the air forces of the Soviet Union. The other was the Sovie ...

was supposed to receive 20 TB-3s and 40 I-16s, with the same number going to the

Soviet Navy The Soviet Navy was the naval warfare Military, uniform service branch of the Soviet Armed Forces. Often referred to as the Red Fleet, the Soviet Navy made up a large part of the Soviet Union's strategic planning in the event of a conflict with t ...

. Vakhmistrov was also asked to investigate the possibility of using Tupolev TB-7, Tupolev MTB-2, and the GST (a transport version of the American

Consolidated PBY Catalina The Consolidated Model 28, more commonly known as the PBY Catalina (U.S. Navy designation), is a flying boat and amphibious aircraft designed by Consolidated Aircraft in the 1930s and 1940s. In U.S. Army service, it was designated as the OA- ...

flying boat) as the motherships, as well as arming I-16s with 500 kg (1,100 lb) bombs. By 1939, government support for the project had waned, the Navy canceled all of its orders, and the Air Force reduced the number of fighters from 40 to 12. However, Soviet military observers noted the success of the German Junkers Ju 87 Stuka dive bombers in the opening stages of

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. As the Soviet Union had no dive bombers, it was decided to resume low-scale work on the Zveno-SPB. Testing of the first production Zveno began in June 1940. It differed from the prototype in using the much more powerful I-16 Type 24 fighters. Six mothership-fighter combinations (six TB-3s and twelve modified I-16 Type 24s) were completed. All were attached to the 2nd Special Squadron of the 32nd Fighter Regiment of the 62nd Aviation Brigade of the

Black Sea Fleet The Black Sea Fleet () is the Naval fleet, fleet of the Russian Navy in the Black Sea, the Sea of Azov and the Mediterranean Sea. The Black Sea Fleet, along with other Russian ground and air forces on the Crimea, Crimean Peninsula, are subordin ...

Air Force stationed in

Yevpatoria Yevpatoria (; ; ; ) is a city in western Crimea, north of Kalamita Bay. Yevpatoria serves as the administrative center of Yevpatoria Municipality, one of the districts (''raions'') into which Crimea is divided. It had a population of His ...

, western

Crimea Crimea ( ) is a peninsula in Eastern Europe, on the northern coast of the Black Sea, almost entirely surrounded by the Black Sea and the smaller Sea of Azov. The Isthmus of Perekop connects the peninsula to Kherson Oblast in mainland Ukrain ...

. Mirroring the nickname of the Zveno experiments, the squadron was dubbed 'Shubikov's Circus' (Цирк Шубикова) after its commander Arseniy Shubikov. Zveno-SPB saw limited but successful combat use on the Eastern Front of World War II. In the opening stages, the Black Sea Fleet Air Force was tasked with destroying industrial targets in

Nazi Germany Nazi Germany, officially known as the German Reich and later the Greater German Reich, was the German Reich, German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a Totalit ...

-allied

. The most important of these was the

King Carol I Bridge The Anghel Saligny Bridge (), formerly King Carol I Bridge, is a complex of two railroad truss bridges in Romania, across the Danube River and the Borcea branch of the Danube, connecting the regions of Muntenia and Dobruja. The bridge is listed ...

over the

Danube The Danube ( ; see also #Names and etymology, other names) is the List of rivers of Europe#Longest rivers, second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest sou ...

which carried the Ploieşti-

Constanța Constanța (, , ) is a city in the Dobruja Historical regions of Romania, historical region of Romania. A port city, it is the capital of Constanța County and the country's Cities in Romania, fourth largest city and principal port on the Black ...

oil

pipeline A pipeline is a system of Pipe (fluid conveyance), pipes for long-distance transportation of a liquid or gas, typically to a market area for consumption. The latest data from 2014 gives a total of slightly less than of pipeline in 120 countries ...

. After several failed attempts to destroy the heavily protected bridge with conventional bombers, the task was given to the Zveno squadron. As a combat test, it was decided to first attack the Constanţa

oil depot An oil terminal (also called a tank farm, tankfarm, oil installation or oil depot) is an industrial facility for the storage of oil, petroleum and petrochemical products, and from which these products are transported to end users or other stor ...

. On 26 July 1941, two Zveno-SPB aircraft performed a successful attack on the depot in broad daylight with no losses. The fighters disconnected 40 km (22 NM, 25 mi) from the target and returned to the home airfield under their own power. The first of the two bridge raids took place on 10 August 1941. For this mission, the I-16s were fitted with additional 95-liter (25 US gal) underwing fuel tanks for an additional 35 minutes of flight time. Of the three Zveno-SPBs, one had to turn back due to mechanical problems. The other two launched their fighters from the Romanian coastline. The fighters successfully dive-bombed from the altitude of and returned home with no losses despite heavy anti-aircraft fire. The second raid took place on 13 August 1941. This time, all three Zveno-SPBs reached the target. The six fighters scored five direct hits on the bridge and completely destroyed one of the spans. On the way back, the fighters strafed Romanian infantry near Sulina and returned to Eupatoria with no losses. Following the successful sorties, two additional Zveno-SPB were brought to operational status, bringing the total to five. The main limiting factor was the lack of high-output Mikulin AM-34FRN engines, as the other versions were not powerful enough to get the aircraft airborne. On 16 August 1941, Admiral Nikolai Kuznetsov asked

Joseph Stalin Joseph Vissarionovich Stalin (born Dzhugashvili; 5 March 1953) was a Soviet politician and revolutionary who led the Soviet Union from 1924 until Death and state funeral of Joseph Stalin, his death in 1953. He held power as General Secret ...

for additional AM-34FRN-engined TB-3s from the Air Force so they could be converted to Zveno-SPB carriers, but the request was denied as the Air Force had suffered heavy losses in the opening days of the war. In the meantime, the five aircraft continued flying operational sorties, destroying a

dry dock A dry dock (sometimes drydock or dry-dock) is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction, maintenance, ...

in Constanţa on 17 August and a bridge across the

Dnieper River The Dnieper or Dnepr ( ), also called Dnipro ( ), is one of the major transboundary rivers of Europe, rising in the Valdai Hills near Smolensk, Russia, before flowing through Belarus and Ukraine to the Black Sea. Approximately long, with ...

on 28 August, losing one I-16 in the process. During the repeat attack the next day, four Zveno-launched I-16s engaged several

Messerschmitt Bf 109 The Messerschmitt Bf 109 is a monoplane fighter aircraft that was designed and initially produced by the Nazi Germany, German aircraft manufacturer Messerschmitt#History, Bayerische Flugzeugwerke (BFW). Together with the Focke-Wulf Fw 190, the ...

s, shooting down two. Despite the high success rate, Zveno missions ended by 1942 due to high vulnerability of the obsolete TB-3s and I-16s in the face of enemy air superiority. It is estimated that Zveno-SPB flew at least 30 combat missions.

References

Bibliography

* {{WWIIUSSRAF Airborne aircraft carriers Science and technology in the Soviet Union Soviet Air Force Abandoned military aircraft projects of the Soviet Union Parasite aircraft Vehicles introduced in 1931 Composite aircraft

Development

Configurations

Operational history

See also

References

Bibliography