Zveno project
Encyclopedia
Zveno was a parasite aircraft
concept developed in the Soviet Union
during the 1930s. It consisted of a Tupolev TB-1
or a Tupolev TB-3
heavy bomber acting as a mothership for between two and five fighters. Depending on the Zveno 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
s, each armed with two 250 kg (550 lb) bombs, was used operationally with good results against strategic targets in Romania
during the opening stages of the German-Soviet War. The same squadron afterwards also carried out a tactical attack against a bridge over the River Dneiper that had been captured by advancing German forces.
In June 1931, Vladimir Sergeyevich Vakhmistrov
of the NII VVS (Nauchno-Issledovatel'skiy Institut Voyenno-Vozdushnykh Sil – 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:
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 bomb 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 pilot, this was changed to all-pilot control in the next version). The original design included umbilical fuel lines which permitted 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 Tupolev TB-1
mothership and two Tupolev I-4
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 attached to one of the wings remained in controlled flight and the second fighter was soon uneventfully deployed. After latch control was fully moved into the fighters, the normal launch procedure consisted of 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 Tupolev TB-3
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 fifth powerplant for the bomber mothership.
The Zveno-3 in which 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 the 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 rigid in flight, the bomber became extremely difficult to control. During one of the test flights, I-Z pilot Korotkov incorrectly timed the locking maneuver and the lift generated by his fighter broke the docking frame and crashed him into the bottom of the mothership's wing. As the bomber came in for an emergency landing with both fighters still attached, the slow landing speed of the TB-3 resulted in 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 appearance of the Polikarpov I-16
fighter with retractable landing gear. This permitted 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).
Source: Shavrov
Zveno-1
Zveno-1a
Zveno-2
Zveno-3
Zveno-5
Zveno-6
Zveno-7
Aviamatka (Airborne mothership)
SPB (Sostavnoi Pikiruyuschiy Bombardirovschik - Combined Dive Bomber)
In 1938, Vakhmistrov devised Zveno-SPB (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 250 kg (550 lb) 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 6800 m (22,310 ft), 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 22000 kg (48,500 lb), a top speed of 268 km/h (145 knots, 165 mph), and a range of 2500 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, with TB-3 piloted by Stefanovskiy, and I-16s piloted by Nikolayev and Taborovskiy. Following the successful test program in 1938, Zveno-SPB was accepted into service. By 1 February 1940, Soviet Air Force
was supposed to receive 20 TB-3s and 40 I-16s, with the same number going to the Soviet Navy
. Vakhmistrov was also asked to investigate the possibility of using Tupolev TB-7
, Tupolev MTB-2
, and GST (PBY Catalina)
as the motherships, as well as arming I-16s with 500 kg (1,100 lb) bombs. By 1939, the 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 Luftwaffe
Junkers Ju 87
dive bomber
s in the opening stages of World War II
. 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. A total of 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 IAP (Fighter Regiment) of the 62nd Aviation Brigade of the Black Sea Fleet
Air Force stationed in Eupatoria
. 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 during the German-Soviet War. In the opening stages, the Black Sea Fleet Air Force was tasked with destroying industrial targets in Nazi Germany
-allied Romania
. The most important of these was the King Carol I Bridge
over Danube
which carried the Ploieşti
-Constanţa
oil pipeline
. 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
. 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 15 km (8 NM, 9 mi) from the Romanian coastline. The fighters successfully dive-bombed from the altitude of 1800 m (5,900 ft) 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-34
FRN engines, as the other versions were not powerful enough to get the aircraft airborne. On 16 August 1941, Admiral Kuznetsov
asked Joseph Stalin
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
in Constanţa on 17 August and a bridge across the Dnieper River
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
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.
Parasite aircraft
A parasite aircraft is a component of a composite aircraft which is carried, and air launched by, a mother ship aircraft.The first use for parasite aircraft was in 1916, when the British used a Bristol Scout, flying from a Felixstowe Porte Baby, a giant flying boat of its time. This eventually...
concept developed in the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
during the 1930s. It consisted of a Tupolev TB-1
Tupolev TB-1
-See also:-References:* Duffy, Paul and Andrei Kandalov. Tupolev: The Man and His Aircraft. Shrewsbury, UK:Airlife Publishing, 1996. ISBN 1 85310 728 X....
or a Tupolev TB-3
Tupolev TB-3
The Tupolev TB-3 was a heavy bomber aircraft which was deployed by the Soviet Air Force in the 1930s and during World War II. It was the world's first cantilever wing four-engine heavy bomber. Despite obsolescence and being officially withdrawn from service in 1939, TB-3 performed bomber and...
heavy bomber acting as a mothership for between two and five fighters. Depending on the Zveno 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
Polikarpov I-16
The Polikarpov I-16 was a Soviet fighter aircraft of revolutionary design; it was the world's first cantilever-winged monoplane fighter with retractable landing gear. The I-16 was introduced in the mid-1930s and formed the backbone of the Soviet Air Force at the beginning of World War II...
s, each armed with two 250 kg (550 lb) bombs, was used operationally with good results against strategic targets in Romania
Romania
Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...
during the opening stages of the German-Soviet War. The same squadron afterwards also carried out a tactical attack against a bridge over the River Dneiper that had been captured by advancing German forces.
Development
Vladimir Sergeyevich Vakhmistrov
Vladimir Sergeyevich Vakhmistrov was a Soviet aviation engineer. He is most famous for creating a series of parasite aircraft projects under the common name Zveno....
of the NII VVS (Nauchno-Issledovatel'skiy Institut Voyenno-Vozdushnykh Sil – 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 bomb 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 pilot, this was changed to all-pilot control in the next version). The original design included umbilical fuel lines which permitted 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 Tupolev TB-1
Tupolev TB-1
-See also:-References:* Duffy, Paul and Andrei Kandalov. Tupolev: The Man and His Aircraft. Shrewsbury, UK:Airlife Publishing, 1996. ISBN 1 85310 728 X....
mothership and two Tupolev I-4
Tupolev I-4
-External links:*http://www.aviation.ru/Tu/#ANT-5...
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 attached to one of the wings remained in controlled flight and the second fighter was soon uneventfully deployed. After latch control was fully moved into the fighters, the normal launch procedure consisted of 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 Tupolev TB-3
Tupolev TB-3
The Tupolev TB-3 was a heavy bomber aircraft which was deployed by the Soviet Air Force in the 1930s and during World War II. It was the world's first cantilever wing four-engine heavy bomber. Despite obsolescence and being officially withdrawn from service in 1939, TB-3 performed bomber and...
carrying three Polikarpov I-5
Polikarpov I-5
The Polikarpov I-5 was a single-seat biplane which became the primary Soviet fighter between its introduction in 1931 through 1936, after which it became the standard advanced trainer...
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 fifth powerplant for the bomber mothership.
The Zveno-3 in which TB-3 carried two Grigorovich I-Z
Grigorovich I-Z
-References:...
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 the 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 rigid in flight, the bomber became extremely difficult to control. During one of the test flights, I-Z pilot Korotkov incorrectly timed the locking maneuver and the lift generated by his fighter broke the docking frame and crashed him into the bottom of the mothership's wing. As the bomber came in for an emergency landing with both fighters still attached, the slow landing speed of the TB-3 resulted in 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 appearance of the Polikarpov I-16
Polikarpov I-16
The Polikarpov I-16 was a Soviet fighter aircraft of revolutionary design; it was the world's first cantilever-winged monoplane fighter with retractable landing gear. The I-16 was introduced in the mid-1930s and formed the backbone of the Soviet Air Force at the beginning of World War II...
fighter with retractable landing gear. This permitted 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).
Zveno configurations
Zveno-1
- Tupolev TB-1Tupolev TB-1-See also:-References:* Duffy, Paul and Andrei Kandalov. Tupolev: The Man and His Aircraft. Shrewsbury, UK:Airlife Publishing, 1996. ISBN 1 85310 728 X....
and two Tupolev I-4Tupolev I-4-External links:*http://www.aviation.ru/Tu/#ANT-5...
on top of the wings. The normally sesquiplaneBiplaneA biplane is a fixed-wing aircraft with two superimposed main wings. The Wright brothers' Wright Flyer used a biplane design, as did most aircraft in the early years of aviation. While a biplane wing structure has a structural advantage, it produces more drag than a similar monoplane wing...
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 V. P. ChkalovValery ChkalovValery Pavlovich Chkalov was a Russian aircraft test pilot and a Hero of the Soviet Union .-Early life:...
and A. F. Anisimov. Vakhmistrov himself flew in the front gunner's turret.
Zveno-1a
- TB-1 and two Polikarpov I-5Polikarpov I-5The Polikarpov I-5 was a single-seat biplane which became the primary Soviet fighter between its introduction in 1931 through 1936, after which it became the standard advanced trainer...
on of the wings, first flight September 1933. The TB-1 was piloted by StefanovskiyPetr Mikhailovich StefanovskiyPetr Mikhailovich Stefanovskiy was a Soviet test pilot. During the German-Soviet War, he was in charge of forming special fighter squadrons composed of Soviet test pilots and flew combat missions protecting the airspace above Moscow. He was promoted to Major General in 1944 and was awarded the...
, the I-5s were piloted by Kokkinaki and Grozd.
Zveno-2
- Tupolev TB-3Tupolev TB-3The Tupolev TB-3 was a heavy bomber aircraft which was deployed by the Soviet Air Force in the 1930s and during World War II. It was the world's first cantilever wing four-engine heavy bomber. Despite obsolescence and being officially withdrawn from service in 1939, TB-3 performed bomber and...
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-ZGrigorovich I-Z-References:...
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 aircraft.
Zveno-6
- TB-3 and two Polikarpov I-16Polikarpov I-16The Polikarpov I-16 was a Soviet fighter aircraft of revolutionary design; it was the world's first cantilever-winged monoplane fighter with retractable landing gear. The I-16 was introduced in the mid-1930s and formed the backbone of the Soviet Air Force at the beginning of World War II...
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
Tupolev TB-3
The Tupolev TB-3 was a heavy bomber aircraft which was deployed by the Soviet Air Force in the 1930s and during World War II. It was the world's first cantilever wing four-engine heavy bomber. Despite obsolescence and being officially withdrawn from service in 1939, TB-3 performed bomber and...
mothership and two Polikarpov I-16 Type 5
Polikarpov I-16
The Polikarpov I-16 was a Soviet fighter aircraft of revolutionary design; it was the world's first cantilever-winged monoplane fighter with retractable landing gear. The I-16 was introduced in the mid-1930s and formed the backbone of the Soviet Air Force at the beginning of World War II...
fighters. Each of the fighters was armed with a pair of 250 kg (550 lb) 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 6800 m (22,310 ft), 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 22000 kg (48,500 lb), a top speed of 268 km/h (145 knots, 165 mph), and a range of 2500 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, with TB-3 piloted by Stefanovskiy, and I-16s piloted by Nikolayev and Taborovskiy. Following the successful test program in 1938, Zveno-SPB was accepted into service. By 1 February 1940, Soviet Air Force
Soviet Air Force
The Soviet Air Force, officially known in Russian as Военно-воздушные силы or Voenno-Vozdushnye Sily and often abbreviated VVS was the official designation of one of the air forces of the Soviet Union. The other was the Soviet Air Defence Forces...
was supposed to receive 20 TB-3s and 40 I-16s, with the same number going to the Soviet Navy
Soviet Navy
The Soviet Navy was the naval arm of the Soviet Armed Forces. Often referred to as the Red Fleet, the Soviet Navy would have played an instrumental role in a Warsaw Pact war with NATO, where it would have attempted to prevent naval convoys from bringing reinforcements across the Atlantic Ocean...
. Vakhmistrov was also asked to investigate the possibility of using Tupolev TB-7
Petlyakov Pe-8
The Petlyakov Pe-8 was a Soviet heavy bomber designed before World War II, and the only four-engine bomber the USSR built during the war. Produced in limited numbers, it was used to bomb Berlin in August 1941. It was also used for so-called "morale raids" designed to raise the spirit of the Soviet...
, Tupolev MTB-2
Tupolev MTB-2
Tupolev MTB-2 , also known as ANT-44, was a four-engine flying boat designed in the Soviet Union in 1935.-Design and development:The ANT-44 was designed as a long range maritime reconnaissance/bomber flying boat...
, and GST (PBY Catalina)
PBY Catalina
The Consolidated PBY Catalina was an American flying boat of the 1930s and 1940s produced by Consolidated Aircraft. It was one of the most widely used multi-role aircraft of World War II. PBYs served with every branch of the United States Armed Forces and in the air forces and navies of many other...
as the motherships, as well as arming I-16s with 500 kg (1,100 lb) bombs. By 1939, the 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 Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
Junkers Ju 87
Junkers Ju 87
The Junkers Ju 87 or Stuka was a two-man German ground-attack aircraft...
dive bomber
Dive bomber
A dive bomber is a bomber aircraft that dives directly at its targets in order to provide greater accuracy for the bomb it drops. Diving towards the target reduces the distance the bomb has to fall, which is the primary factor in determining the accuracy of the drop...
s in the opening stages of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. 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. A total of 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 IAP (Fighter Regiment) of the 62nd Aviation Brigade of the Black Sea Fleet
Black Sea Fleet
The Black Sea Fleet is a large operational-strategic sub-unit of the Russian Navy, operating in the Black Sea and the Mediterranean Sea since the late 18th century. It is based in various harbors of the Black Sea and the Sea of Azov....
Air Force stationed in Eupatoria
Eupatoria
Yevpatoria or Eupatoria is a city in Crimea, Ukraine.-History:The first recorded settlement in the area, called Kerkinitis , was built by Greek colonists around 500 BC...
. 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 during the German-Soviet War. In the opening stages, the Black Sea Fleet Air Force was tasked with destroying industrial targets in Nazi Germany
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...
-allied Romania
Romania
Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...
. The most important of these was the King Carol I Bridge
King Carol I Bridge
The Anghel Saligny Bridge was built between 1890 and 1895 in Romania over the Danube and Borcea branch of the Danube, and when it was completed it then became the longest bridge in Europe and the third longest in the world...
over Danube
Danube
The Danube is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway....
which carried the Ploieşti
Ploiesti
Ploiești is the county seat of Prahova County and lies in the historical region of Wallachia in Romania. The city is located north of Bucharest....
-Constanţa
Constanta
Constanța is the oldest extant city in Romania, founded around 600 BC. The city is located in the Dobruja region of Romania, on the Black Sea coast. It is the capital of Constanța County and the largest city in the region....
oil pipeline
Pipeline transport
Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....
. 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
Oil depot
An oil depot is an industrial facility for the storage of oil and/or petrochemical products and from which these products are usually transported to end users or further storage facilities...
. 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 15 km (8 NM, 9 mi) from the Romanian coastline. The fighters successfully dive-bombed from the altitude of 1800 m (5,900 ft) 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
Span (architecture)
Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge.A span can be closed by a solid beam or of a rope...
. On the way back, the fighters strafed Romanian infantry near Sulina
Sulina
Sulina is a town and free port in Tulcea County, Romania, at the mouth of the Sulina branch of the Danube. It is the easternmost point of Romania and of the continental European Union.-History:...
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-34
Mikulin AM-34
The Mikulin AM-34 was the Soviet Union’s first indigenous mass-produced, liquid-cooled, aircraft engine. Its initial development was troubled, but it eventually became one of the most successful Soviet aircraft engines of the 1930s...
FRN engines, as the other versions were not powerful enough to get the aircraft airborne. On 16 August 1941, Admiral Kuznetsov
Nikolai Gerasimovich Kuznetsov
Nikolay Gerasimovich Kuznetsov was a Soviet naval officer who achieved the rank of Admiral of the Fleet of the Soviet Union and served as People's Commissar of the Navy during The Second World War....
asked Joseph Stalin
Joseph Stalin
Joseph Vissarionovich Stalin was the Premier of the Soviet Union from 6 May 1941 to 5 March 1953. He was among the Bolshevik revolutionaries who brought about the October Revolution and had held the position of first General Secretary of the Communist Party of the Soviet Union's Central Committee...
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
Dry dock
A drydock 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...
in Constanţa on 17 August and a bridge across the Dnieper River
Dnieper River
The Dnieper River is one of the major rivers of Europe that flows from Russia, through Belarus and Ukraine, to the Black Sea.The total length is and has a drainage basin of .The river is noted for its dams and hydroelectric stations...
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
Messerschmitt Bf 109
The Messerschmitt Bf 109, often called Me 109, was a German World War II fighter aircraft designed by Willy Messerschmitt and Robert Lusser during the early to mid 1930s...
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.
See also
- Short Mayo CompositeShort Mayo CompositeThe Short Mayo Composite was a piggy-back long-range seaplane/flying boat combination produced by Short Brothers to provide a reliable long-range air transport service to the United States and the far reaches of the British Empire and the Commonwealth....
- long-range air transport combination of two seaplanes operated by Imperial AirwaysImperial AirwaysImperial Airways was the early British commercial long range air transport company, operating from 1924 to 1939 and serving parts of Europe but especially the Empire routes to South Africa, India and the Far East...
in the late 1930s. - MistelMistelThe Mistel , also known as Beethoven-Gerät and Vati und Sohn , was a Luftwaffe composite aircraft type of bomber, that appeared late in World War II....
- various fighter-bomber combinations used by LuftwaffeLuftwaffeLuftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
during World War II for attacking large heavily-defended targets. - FICON projectFICON projectThe FICON program was conducted by the United States Air Force in the 1950s to test the feasibility of a Convair B-36 Peacemaker bomber carrying an Republic RF-84K Thunderflash parasite fighter in its bomb bay. Earlier wingtip coupling experiments including Tip Tow which were attempts at carrying...
- Convair B-36Convair B-36The Convair B-36 "Peacemaker" was a strategic bomber built by Convair and operated solely by the United States Air Force from 1949 to 1959. The B-36 was the largest mass-produced piston engine aircraft ever made. It had the longest wingspan of any combat aircraft ever built , although there have...
— F-84F ThunderstreakF-84F ThunderstreakThe Republic F-84F Thunderstreak was an American-built swept-wing turbojet fighter-bomber. While an evolutionary development of the straight-wing F-84 Thunderjet, the F-84F was a new design. The RF-84F Thunderflash was a photo reconnaissance version....
combination for fighter escort and long-range reconnaissance used by the United States Air ForceUnited States Air ForceThe United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
during the Cold WarCold WarThe Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
.