Category Archives: Soviet

ANT-1

Soviet, WW2, , ,

 USSR (1921)
Experimental Single-seat light aircraft – 1 Prototype Built

While the Russian Civil War was raging on, there were early attempts to rebuild its shattered aviation industry.  Aviation engineers and enthusiasts attempted, despite the chaos around them, to build small experimental aircraft to test their ideas and concepts. One such young individual was Andrei Nikolayevich Tupolev. His ANT-1 was a specialized design to test the concept of using metal alloys in aircraft construction.

The ANT-1 experimental aircraft. Source: www.globalsecurity.org/military

History

Tupolev began his career as an aircraft engineer in 1909, when he was admitted to the Moscow Higher Technical School. There he met Professor Nikolai Yagorovich who greatly influenced Tupolev’s interest in aviation. In the following years, he spent time developing and testing various glider designs. When the First World War broke out Tupolev managed to get a job at the Russian Dux Automotive factory in Moscow, which produced a variety of goods, including aircraft. There he gained valuable experience of aircraft manufacturing.

Andrei Nikolayevich Tupolev was one of the greatest Russian/Soviet aviation engineers and designers. Source: Wiki

In 1917, the October Revolution plunged the disintegrating Russian Empire into total chaos. The few aircraft manufacturing centers were either abandoned or destroyed. All work on the design and construction of new aircraft was essentially stopped. The Dux was one exception and continued to work at a limited capacity. It was renamed to Gosudarstvennyi aviatsionnyi zavod (Eng. State aircraft factory) or simply GAZ No.1. Given that he was one of few aviation engineers left, with most skilled either being killed or fled the country, Tupolev remained working for the GAZ No.1. He spent a few years working on various projects such as designs improving weapon mounts for older aircraft that were still in service.

In 1921, Tupolev was elected as the deputy of the Aviatsii i Gidrodinamiki AGO (Eng. Aviation and Hydrodynamics Department). This department was tasked with developing various aircraft designs but also including torpedo boats. In 1921 he and his team from AGO began working on a new aircraft design that was to test new concepts. Two new innovative features were that it should be a monoplane, and be built using mainly metal alloy. Its primary purpose was not to gain any production orders, but instead to serve as a test bed for new ideas and concepts. The aircraft was named ANT-1, where ANT stands for the initials of  Andrei Nikolayevich Tupovlev.  This designation should not be confused with a snowmobile developed by  Tupolev, which shared its name.

During this period, Soviet aviation officials and the German Junkers company spent years negotiating the possibility of producing a Duralumin alloy that could be used for aviation construction. Junkers proved the validity of this concept on the J.I saw service during the First World War. The German company wanted to avoid sanctions on arms and aviation development imposed by the Allies, while the Soviets wanted the technology for themselves, not wanting to depend on the Germans entirely. The Soviet Union in 1922, managed to produce their own copy of Duralumin known as Kol’schugaluminiyem alloy. The name was related to a small village Kol’chugino where this factory was located. Limited production of this alloy began in 1923.

Due to problems with the production of the new alloy, Tupolev was forced to postpone the development of his new aircraft until 1922. At that time the alloy was not yet available, so Tupovlev decided to go on with a standard all-wood design. The benefit of using wood was that it was an easily available material, with almost unlimited supply in Russia. It was cheap and there were plenty of skilled woodworkers. However, there were also numerous flaws in using wooden materials. The greatest issue was a generally short service life in harsh climates as in Russia, in addition, standardization of spare parts is almost impossible to do.

Tupolev himself preferred the new metal technology believing that it would offer many benefits to the aircraft industry,  giving new aircraft a lighter and stronger overall construction. Tupolev eventually decided to go for a mixed-construction solution. His decision was based on a few factors, such as the general lack of this new material, and he wanted to be on the safe side as using metal in aircraft construction was still a new and not yet fully proven concept. In addition, he wanted to be sure about the Aluminum alloy material’s quality before proceeding to design a fully metal aircraft.

Once the choice for the construction material was solved the next step was to decide whether it was to be a single or two-seat configuration. The wing design was also greatly considered. After some time spent in calculations and small wind testing, the choice was made to proceed with a single engine and low-wing monoplane.

For the engine, three different types were proposed including 14hp and 18 hp Harley-Davidson and a 20 hp Blackburn Tomtit. Despite Tupovlev’s attempts, he failed to acquire any one of these three. It was not until early 1923 that he managed to get his hands on an old 35hp Anzani engine which was over 10 years old by that point. Despite its poor mechanical state, Tupovlev knowing that nothing else was available decided to try salvage it.

Testing and the Final Fate

The construction of this aircraft took over a year to complete. Given the general chaos at that time, this should not be surprising. It was finally completed in October 1923, and the first test flight was carried out on the 21st of October of the same year. Despite using the older engine, the flight proved successful. It was piloted by Yevgeni Pogosski.

The completed ANT-1 test aircraft. Source: www.globalsecurity.org

Following this, the ANT-1 was used mainly for various testing and evaluation. It would see service in this manner for the next two years. In 1925 the aging engine finally gave up, and this made the aircraft unflyable. Tupovlev tried to find a factory that could potentially refurbish it. He ultimately failed, as the engine was simply beyond repair by that point.

The aircraft was for some time stored at Factory No.156.  The fate of this aircraft is not clear in the sources, however, there are few theories about what happened to it. After Tupovlev’s imprisonment by Josef Stalin, his plans and documentation were confiscated. The aircraft was believed to be also confiscated and scrapped in the late 1930s. Another possibility is that it was moved to another storage facility where it was eventually lost during the Axis Invasion of the Soviet Union in 1941.

Specification

The ANT-1 was designed as a cantilever low-wing monoplane aircraft of mixed construction. The fuselage consisted of four spruce longerons. The lower two were connected to the wing spars and  were held in place with four bolts. The parts of the fuselage starting with the pilot cockpit to the engine were covered in the metal alloy. This alloy was also used to provide additional strength of some internal wooden components of the aircraft fuselage. The pilot Pilot cockpit was provided with a small windscreen. Inboard equipment was spartan consisting only of an rpm counter, oil pressure indicator, and ignition switch.

The cantilever wings were made of single pieces. At the end of the two tips  (on each side of the wings) large wooden spars were installed. Some parts of the wing were built using metal parts such as the wing ribs,  The rest of the wing was mainly covered in fabric. The tail unit was made of wood, its surfaces were covered with a metal-fabric cover.

The fixed landing gear consisted of two large wheels. These were connected to a metal frame which itself was connected to the aircraft fuselage. Small rubber bungees acted as primitive shock absorbers.

Given that nothing else was available, the ANT-1 was powered by an old, refurbished 35-hp strong Bristol Anzani engine.

A good view of the ANT-1 internal wing and fuselage construction. Source: www.globalsecurity.org
The cantilever wings received on each side one large wooden spar. Source: Wiki
The pilot cockpit received only a few basic instruments and a small windshield. Source:www.globalsecurity.org

Conclusion

The ANT-1 despite its simplicity, and being built a single, cobbled-together prototype, could be considered a great success for Tupolev. Through this experimental aircraft, Tupovlev gained valuable experience in designing an aircraft by using metal alloy. This success emboldened Tupovlev to go even further and design and build the Soviet first all-metal construction aircraft known as ANT-2. The ANT-1 was Tupovlev’s first stepping stone in a long and successful career as an aircraft designer in the following decades.

ANT-1 Specifications
Wingspans 7.2 m / 23ft 7 in
Length 5.4 m / 17 ft 8 in
Height 1.7 m / 5 ft 7 in
Wing Area 10 m²  / 108 ft²
Engine One 35 hp Bristol Anzani engine
Empty Weight 230 kg / 5,070 lb
Maximum Takeoff Weight 360 kg / 7,940 lb
Maximum Speed 125 km/h / 78 mp/h
Range 400 km / 250 miles
Maximum Service Ceiling 600 m /  1,970 ft
Maximum Theoretical Service Ceiling 4,000 m / 13,120 ft
Crew 1 pilot
Armament
  • None

 

Gallery

 

 

Credits

  • Article written by Marko P.
  • Edited by  Henry H.
  • Illustration by Godzilla

Sources:

  • Duško N. (2008)  Naoružanje Drugog Svetsko Rata-SSSR. Beograd.
  • Y. Gordon and V. Rigmant (2005) OKB Tupolev, Midland
  • P. Duffy and A. Kandalov (1996) Tupolev The Man and His Aircraft, SAE International
  • B. Gunston () Tupolev Aircraft Since 1922, Naval Institute press

 

Belyayev DB-LK

Soviet, WW2, , ,

USSR flag USSR (1938-1940)
Experimental Long-Range Bomber – 1 Prototype Built

The Belyayev DB-LK [airwar.ru]
In the late thirties and early forties, the Soviet aviation industry had developed and tested a variety of aircraft design concepts, some quite peculiar. While generally unknown around the world, a number of these strange aircraft would represent a serious departure from anything resembling their contemporaries. Such is the case with Victor Nikolayevich Belyayev’s DB-LK experimental long-range bomber.

History

Victor Nikolayevich Belyayev, March 1896 – July 1953, began working for the Department of the Marine Experimental Aircraft Construction, OMOS, in 1925, where he gained his first experience in aircraft design. In the following years, he worked for the Central Aerohydrodynamic Institute, TsAGl, and Tupolev. During this time, he became an advocate for tailless aircraft designs. He also argued that the so-called “batwing”  or “butterfly”, offered better performance, due to their reduced drag and better stability, than regular wing designs.

The “batwing” design possessed a slightly forward-swept wing with back curved tips. Belyayev managed to construct a glider, designated BP-2, which was equipped with this kind of wing design in 1933, on which he tested this concept. During its test flight, it was successfully towed in the air from Crimea to Moscow, where it proved to have good stability and control during flight.

The BP-2 glider in flight. [airwar.ru]
The next year, Belyayev participated in the competition for a new Soviet military transport plane design. His design was unusual, as it consisted of a large wing and two nacelles,  powered by Tumanskii M-87B 950 hp (708 kW) engines. His design was not approved nor did he build a working prototype. However, four years later, he would reuse this project and adapt it for the role of a long-range bomber. In 1938, he designed the DB-LK long-range flying wing bomber, which the TsAGl approved and ordered the construction of a fully operational prototype. The prototype was built the following year by factory No.156 and by November 1939 it was ready for testing.

Technical Characteristics

The DB-LK had an unusual overall design with no classical fuselage. Instead, the crew, armament, and other equipment were located in the two extended engine nacelles that ended in glazed tail cones (gondolas), somewhat similar to the later German Fw 189. The two extended engine nacelles were, technically speaking, the plane’s fuselage. The semi-monocoque fuselages were constructed by using a combination of metal frames and longerons covered with a duralumin sheet. The DB-LK was designed in this unusual configuration in the hope of reducing the overall drag and weight and thus increasing its speed and range.

The DB-LK’s wings had a unique design, where beside the “batwings” there was an additional center wing section between the two fuselages. Also, the wings were slightly swept to the front with back curved tips. The wings consisted of an airframe covered with light metal stressed-skin. The outer wings had a Gottingen 387 profile, while the center section had a CAHI (TsAGI) MV-6bis profile. The wing edges were curved at an angle of -5° 42′.

A side view of the DB-LK. The strange wing design can be seen. [elpoderdelasgalaxias.wordpress.com]
The rear tail was located on the middle section wing between the two fuselages. The tail consists of one fin and a large 20 ft2 (1.9 m2) rudder. Above the rudder, a smaller tailplane with two, one on each side, large elevators was placed.

A rear view where the large tail and the left glazed rear cone can be seen. [airwar.ru]
One Tumansky M-87B 950 hp (708 kW) 14-cylinder radial engine was installed at the front of both nacelles. For these engines, three-bladed propellers with variable pitch were used. It was planned to upgrade these two with much stronger 1,100 hp (820 kW) M-88 engines, or even the 1.700 hp M-71, but this was never implemented. The fuel was stored in the wing and fuselage tanks, with a total fuel load of 3.444 l.

The landing gear retracted rearwards, with one wheel (900 x 300 mm) in each fuselage. During later testing, the landing gear design was changed with a forward retractable one. This whole landing gear system was operated hydraulically. There was a small fixed rear wheel (450 x 150 mm) located at the bottom of the tail unit.

The DB-LK was to be operated by a crew of four: the pilot, navigator, and the two rear gunners. The pilot position was in the left cockpit and the navigator in the right. The gunners were positioned in both rear glazed cones. One of the two gunners was also the radio operator. The crews entered their positions through roof hatch doors. The two glazed cones could be mechanically rotated 360° by using a small electric engine located at the fuselage top, but the sources do not specify why this was done.

Inside the pilot cockpit [авиару.рф]
The interior of one of the two fuselages. In the picture on the right, the rear machine gun mount can be seen. On the left, the radio and the mechanism that rotated the whole glazed cone can be seen. [авиару.рф]
Both rear glazed tail cones had a recess where a twin  7.62 mm (.30 caliber) ShKAS machine gun mount was installed. These machine guns had a -10 to +10 field of fire in all directions.  Besides these four machine guns, there were two additional ones forward mounted in the leading edge of the center section. These two machine guns were operated by the pilot. In total, around 4,500 rounds of ammunition were provided for these machine guns. The bomb bays were located behind the landing gear doors in each of the two nacelles.

Depending on the sources, the load capacity of the bomb carried is different. The authors Yefim G. and Dimitri K. note that the bomb load was 1000 kg (2,200 lb) with another 1000 kg that could be carried on external racks. According to Bill G., the capacity of each bomb bay (in each fuselage) was one 1000 kg (2.200 lb), two 500 kg (1.100 lb), or smaller bombs with a total of 1000 kg (2.200 lb) weight.

 

Both front and rear views of the DB-LK’s unusual design. [авиару.рф]

Flight Tests

While being completed in November 1939, the first extensive flight test would only begin the following year. This was due to the unwillingness of the test pilot to fly this plane. He did not believe that it was safe to fly due to its unorthodox design. During this time, the plane received the nickname “Kурица” (chicken).

In order to move the entire project testing through this roadblock, the Soviet Direction of the Air Force Scientific test institute, GK Nil WS, appointed M. Nyuikhtikov as the main test pilot, supported by aircraft engineer and test pilot T. T. Samarin and N. I. Shaurov. Under the new leadership, the tests were carried out in the spring of 1940. During the new leadership, the DB-LK was extensively tested in over 100 flights.

During these flights, the pilots managed to reach speeds of 245 mph (395 km/h) at sea level and 300 mph (490 km/h) at an altitude of 16,400 ft (5,000 m). The DB-LK needed a 2,030 ft (620 m) long airfield for landing and taking off. However, the  DB-LK was never truly trialed with a fully loaded payload. The numbers presented above would have likely been different with a full payload of equipment.

The test pilot Nyuikhtikov, after flying on the DB-LK, pointed out some issues with the plane’s design. The main problems were the inadequate overall flight-control system, poor visibility for the pilot and the navigator, especially on the ground. He also noted the poor construction of the landing gear. These reports were examined by the Nil WS Commission led by A. I. Filin. They agreed that the control system should be improved, but Filin had a positive opinion on the landing gear construction. Ironically, during a test flight, where Filin was the pilot, there was a landing gear malfunction during the landing when one of the front wheels broke free, after a possible collision with a treetop. The aircraft was only lightly damaged and the testing continued, but this led to a change in the landing gear design.

There were also other problems mentioned during the tests, like uncomfortable cockpits, low-level of fire protection, structural problems, a limited firing arc of the rear-mounted defense machineguns, and the tendency for the crew compartments to be filled with exhaust fumes from the engines. To solve these issues, there were plans for the DB-LK improvements, with stronger engines, wings, and various other modifications, to be completed by late 1940 but they were probably never implemented.

Rearview of the accident. [авиару.рф]

Conclusion

Despite plans for more testing and improvements, unfortunately for the DB-LK design team, they never got a chance to do so. In late 1940, the Nil WS Commission gave orders for the cancellation of the DB-LK program. The main reason for this was the decision for the production of the Il-4 as the main Soviet long-range bomber.

 

Belyayev DB-LK specifications
Wingspan 70 ft 10 in / 21.6 m
Length 32 ft  1 in /  9.8 m
Wing Area 612 ft² / 65.9 m²
Engine 2x Tumanskii M-87B 950 hp (708 kW) 14 cylinder radial engines
Empty Weight 13,230 lbs / 6,000 kg
Maximum Takeoff Weight 23,530 lbs / 10,670 kg
Fuel Capacity 3.444 l
Maximum Speed 300 mph / 490 km/h
Cruising Speed 245 mph / 395  km/h
Range 790 mi /  1.270 km
Maximum Service Ceiling 27,890 ft / 8,500 m
Climb speed Climb to 3,000 m in  8 minutes
Crew Pilot, navigator, gunner and radio operator/gunner
Armament
  • Six 7.62 mm ShKAS machine gun
  • Two 1,000 kg bombs or Four 500 kg bombs

Gallery

Illustration by Godzilla

Credits

  • Article written by Marko P.
  • Edited by Stan L. & Henry H.
  • Illustration by Godzilla

Sources

  • Y. Gordon, D, Khazanov (1999), Soviet Combat Aircraft Of The Second World War, Midland Publishing
  • Yefim G. and Bill G (2000), Soviet X-Planes, Midland Publishing
  • Peter G. D. (2015), Soviet Aircraft Industry, Fonthill Media
  • D. Nešić (2008), Naoružanje Drugog Svetskog Rata SSSR, Beograd.
  • Aviamuseum

 

 

 

Yakovlev Yak-4

Soviet, WW2, ,

USSR flag USSR (1939)
Light Bomber – 90 to 100 Built

The Yak-4. [Wiki]
Following the failure of the Yak-2, Yakovlev attempted to salvage the project. One of the attempts that saw limited production was the Yak-4. While it would be powered by a somewhat stronger engine, it too would prove to be a failure and only some 100 aircraft would be built by 1941.

The Yak-2 Failure

While the Yak-2 prototype initially had excellent flying characteristics, once it was actually fully equipped with its military equipment, its performance dropped dangerously. A large number of issues, like overheating, poor flight stability, and problems with its hydraulics, were also noted during the development phase. Despite this, some 100 aircraft would be built and some were even issued for operational use.

Yak-2 side view. [Gordon & Khazanov, Soviet Combat Aircraft]
One of the many weak points of the Yak-2 was its problematic Klimov M-103 engine. The Soviet designers decided to replace this with the more powerfulr M-105 engine. Two basic designs emerged, one for a dive bomber and one for a short-range bomber. During its first test flight, the dive bomber variant proved to be so disappointing that the project was canceled. The bomber version, however, showed to be somewhat promising and the green light for its development was given.

Development History

The development of the BB-22bis (also known as Izdeliye 70bis) prototype was given to Factory No.1, and the Yak-4 designation was officially adopted only in December 1940. Engineers at Factory No. 1 started to build the prototype in early 1940 and it was completed by March the same year. This was not a new aircraft, but a modified Yak-2,serial number 1002) . That same month, Factory No.1 was instructed to produce additional prototypes for testing the aircraft’s performance by the Army, which had to be completed by the start of July 1940. The Army requested a maximum speed of 590 km/h (366 mph) at 5,000 m (16.400 ft)be , an operational range of 1,200 km (745 miles), and a service ceiling of 11,000 m (36,090 ft).

The modified Yak-2 (serial number 1002) aircraft that served as the base for the BB-22bis prototype. [Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev ]
Following the completion of the first prototype, a series of test flights were carried out. During one of the test flights, carried out on the 12th May, a maximum speed of 574 km/h (356 mph) was achieved. On 23rd May, however, there was an accident and the pilot was forced to crash land at a nearby airfield, damaging two other bombers and the prototype’s wing in the process. Given the extensive damage to the aircraft’s wing, the prototype had to be written off. Due to this and delays in production, the first two trial aircraft could not be completed before the end of 1940. Interestingly enough, these were actually produced by the Moscow Aircraft Factory No.81, which started the production of the Yak-4 during October and November 1940. At that time, the type had not yet received official approval from the Soviet Army.

The damage suffered by the first prototype during its hard landing was so severe that it had to be scrapped. [Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev]

The two trial aircraft were given to the Army for testing on 10th December 1940. These tests were held at the end of January 1941. The results were once again disappointing, as these aircraft had worse performance than the prototype. With the added weight of equipment and fuel, the maximum speed was reduced from 574 km/h (357 mph) to 535 km/h (332 mph). The cockpit was described as being too cramped, and with the full bomb load, the plane proved to be difficult to control even by experienced pilots. The commission that examined the two aircraft insisted that the Yak-4 should not be accepted for service. In late February 1941, the Director of Factory No.81 gave a report to the Soviet People’s Commissar of the Aircraft Industry, A. Shakhoorin, that the production of the Yak-4 was to be stopped and replaced with the Yak-3. Interestingly enough, while the Yak-2 was developed by Alexander Sergeyevich Yakovlev, he did not direct the design process of the Yak-4.

Technical Characteristics

The Yak-4 was an overall copy of its predecessor, the Yak-2, but there were still some differences. The most obvious change was the introduction of new engines. The older M-103 ,960 hp, was replaced with a stronger M-105 1050 hp engine. The installation of the two new engines also introduced a number of internal improvements to the ventilation and fuel systems. New 3.1 m (122 in) long VISh-22Ye type propellers were also used on this model. The landing gear retracted to the rear into the engine nacelles, but was not fully enclosed. These consisted of two pairs of 700×150 mm wheels.

The rear parts of the fuselage were lengthened and redesigned, and it was less bulkier than the Yak-2. The cockpit was improved in order to provide the crew with a slightly better overall view. The rear gunner received a completely new pivoting canopy. He operated the TSS-1 mount armed with two 7.62 mm (.30 caliber) ShKAS types machine guns.

Rear view of the Yak-4. [Wiki]
The maximum bomb load was increased to 900 kg (1,980 lbs). In addition, there was an option of mounting two 90 (20 gallons) or one 250 liter (54 gallons) auxiliary fuel tanks under each wing. There were six fuel tanks placed in the wings. These had a total capacity of 1,120 litres (244 gallons) of fuel.

A front view of the Yak-4 with its new and stronger M-105 engines. [Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev]

In Combat

The Yak-4, together with the Yak-2, was allocated to the 314th and 316th Reconnaissance Regiments in the western district. Some were given to the 10th, 44th, 48th, 53rd, 136th and 225th short to medium range Bomber Regiments. The main problem for the units that operated the Yak-2 and Yak-4 was the slow delivery of these aircraft. For example, only a few pilots from the reconnaissance units had a chance to fly on these new aircraft. By 10th June 1941, only limited numbers of Yak-4s were available for service. A shipment of some 10 new aircraft was meant to arrive but did not due to the war’s outbreak.

Pilots from the 314th Reconnaissance Regiment performed several flights over the border with Germany just prior to the Invasion of the Soviet Union while flying Yak-4s. The Germans responded by sending the Bf 109E to intercept them, but they failed to do so. However, once the war started, the German Luftwaffe destroyed many Soviet aircraft on the ground. This was also the case with the Yak-4, with the majority lost this way. Some did survive though and offered limited resistance to the Germans. By September 1941, on the Northern front, there were still fewer than 10 operational Yak-4s. To the South, there were still some 30 or so Yak-4s which were still operational by October 1941. There is no information of the use or losses of the Yak-4 after 1942. According to Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev , at least one Yak-4 was still operational and used by the 118th Reconnaissance Regiment in 1945.

Most of the Yak-4s were destroyed on the ground by the advancing Germans. [Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev]
The advancing Hungarians, who were supporting the Germans during the Invasion of the Soviet Union, managed to capture at least one Yak-4 aircraft during 1941. The use of this aircraft by them would be limited at best, due to the scarcity of spare parts and general poor performance.

Production

The production of the Yak-4 was only carried out at Factory No.81. The production lasted from November 1940 to April 1941. Around 90 to 100 aircraft would be built, with the last 22 Yak-4s being delivered for use by late April 1941.

Operators

  • Soviet Union – Operated some 90 aircraft
  • Hungary – Managed to capture at least one Yak-4 aircraft

Conclusion

Despite attempts to resolve a number of issues noted on the previous version, the Yak-4 in general failed to do so. The problem was the overall poor design of the original Yak-2 which offered little room for improvement. The inability to improve the aircraft to the satisfaction of the Soviet Air Force led to the cancelation of the Yak-4 project after only a small number of aircraft was built.

Yak-4 Specifications
Wingspans 45 ft 11 in / 14 m
Length 33 ft 4 in / 10.18 m
Wing Area 316.4 ft² / 29.4 m²
Engine Two M-105  hp engines
Empty Weight 10,050  lbs / 4,560 kg
Maximum Takeoff Weight 13,481 lbs / 6,115 kg
Climb Rate to 5 km In  6.5 minutes 
Fuel load 1,120 litres (244 gallons)
Maximum Speed  332 mph / 535 km/h
Cruising speed 284 mph  / 458 km/h
Range 460  miles / 740 km
Maximum Service Ceiling 31,824 ft / 9,700 m
Crew Pilot and the rear gunner. 
Armament
  • Two 7.92 mm (.30 caliber) machine guns 
  • 400 to 900 kg (880 to 1.980 lbs) bombs

Gallery

Illustrations by Ed Jackson

Yak-4, 118th Independent Reconnaissance Aviation Regiment, Northern Fleet, 1943
Yak-4, Riga, Latvia, June 1941
Yak-4, 314th Reconnaissance Aviation Regiment, 1941
Yak-4, Grodno, Belarus, June 1941
Yak-4 from the 314th Reconnaissance Aviation Regiment, Babruysk, Belarus, June 1941

Credits

  • Written by: Marko P.
  • Edited by: Stan L. & Henry H.
  • Illustrations by Ed Jackson

Sources

  • D. Nešić (2008), Naoružanje Drugog Svetskog Rata SSSR, Beograd
  • B. Gunston and Y. Gordon (1977)Yakovlev Aircraft Since 1924, Putnam Aeronautical Books.
  • Y. Gordon, D, Khazanov (1999) Soviet Combat Aircraft, Midland Publishing
  • Y. Gordon, D, Khazanov and S. Komissarov (2005) OKB Yakovlev, Midland
  • G. Sarhidai, H. Punka and V. Kozlik. (1996) Hungarian Air Forces 1920-1945, Hikoki Publisher

 

Yakovlev Yak-2

Soviet, WW2

USSR flag USSR (1939)
Ground attack bomber – 100 Built

The Yak-2. Source: Y. Gordon, D, Khazanov Soviet Combat Aircraft

During his career, Alexander Sergeyevich Yakovlev designed a number of successful aircraft, his most famous being his single engine fighters. But his first proper military aircraft project, the Yak-2, would be so poorly designed that it was practically useless. Nevertheless, thanks to Yakovlev’s good standing with Stalin, this aircraft would be put into production, albeit in small numbers, and would see limited action during World War Two.

The No-22 and BB-22 projects

While being involved in civil aviation, Yakovlev wished to pursue military contracts., Yakovlev actually wanted to gain a proper military contract. He estimated that the best way to do this was to impress Stalin himself. To do so, he set on designing the fastest plane in the Soviet Union. Having no previous experience in designing military aircraft, this was no easy task. Nevertheless, he soon began working on a two-engined mixed construction aircraft named simply the No.22 (but also known as the Ya-22). When the prototype was complete and flight tested it reached a maximum speed of 567 km/h (352 mph). This design would first be presented to the Soviet Spanish Civil War hero Yakov Smushkeviche, who was also the Chief of the Soviet Air Force. Yakov was highly impressed with this aircraft and informed Stalin about its performance. Stalin agreed and gave a green light for its future development.

In May of 1939, for further testing and evaluation, this prototype would be given to the Nauchno Issledovatelysii Institut (NII VVS). There, the aircraft was evaluated by a commission consisting of Chief engineer Holopov, test pilot Shevarev, and navigator Tretyakov. They managed to reach a maximum speed of 567 km/h (352 mph) without any problems. The commission also suggested that, with an improved cooling system and with new propellers, the maximum speed could be increased up to 600 km/h (372 mph).

When Yakovlev began working on the No.22, he did not seriously consider in which role it should be used. Military officials would decide the aircraft would be used as a light bomber, a use that both Yakovlev and Stalin would agree with. The plane would be renamed BB-22  (Blizhnii Bombardirovshchik, short range bomber) to fit its new role.

 

The BB-22 prototype, Source: Source: Y. Gordon, D, Khazanov Soviet Combat Aircraft

While at first glance the BB-22 showed to be capable of racing at high speeds, its use in military aviation would prove to be highly problematic. The core of this problem lay in the fact that this aircraft was designed with the main purpose of reaching the highest possible speed, with little thought for military adaptation. Very shortly, the BB-22 began showing the first signs of being an inadequate design. While being tested, it was noted that the engine was prone to overheating. During one test flight, the pilot attempted to reach 7,000 m (23,000 ft) which the designers claimed that it could reach in 8 minutes. In reality, the pilot needed more than half an hour due to constant engine overheating problems. Other issues were also noted, like the inadequate fuel system and wheel brakes.

In the meantime, Air Force officials were discussing the BB-22’s performance and if it should have been put into production. Nearly two months earlier, Yakovlev had already made first steps for the BB-22’s production without their knowledge, despite no official order being given. While military officials were still discussing the BB-22, he had already given copies of the design to GAZ’s Plant No.1. In June 1939, the Council of Soviet People’s Commissars officially gave orders to put the BB-22 into production. The first production aircraft was completed by the end of 1939, and thanks to the political machinations of its designer, made its first flight in February 1940. Production of the aircraft was subsequently delayed. By the end of 1939, of the planned 50, only one was built. Despite these problems, the Soviet Defence Committee issued orders for 580 new aircraft to be built.

 

Work on the Yak-2

Despite the best attempts of Soviet Air Force officials to cancel the BB-22 project, they were hindered by two facts. First was the fact that Stalin personally showed significant interest in its development. Secondly, Yakovlev was appointed as the Deputy People’s Commissar for aircraft production. As a result, the aircraft’s production could not be interrupted. In November 1940, the name of the aircraft was changed to Yak-2, as it was common practice in the Soviet Union to name the aircraft after their designers

By March 1940, after numerous tests and attempts to improve this aircraft, it simply proved to be unusable due to many mechanical flaws. These included the engine overheating, poor flight stability, problems with hydraulics, insufficient quality of bolts that held the wings etc. In total, over 180 faults were reported. The situation was so bad that the Directorate of the Soviet Army Land-based Aviation actually demanded the cancellation of any further work on the Yak-2. On the other side, GAZ No.1 plant officials (who were responsible for the production of this aircraft), along with their test pilots who had flown on this plane, urged its production in order to stay in Yakovlev’s graces. There were plans to produce the first series of 21 aircraft that would be ready by May 1940. After numerous complaints about the Yak-2’s performance, Stalin ordered that the whole situation be investigated. To avoid any kind of guilt, Yakovlev simply blamed the GAZ No.1 production plant for the Yak-2’s poor quality. Ultimately, only 100 Yak-2s would be built and given to the Air Force for operational use.

 

Yak-2 side view. Source: Pinterest

Technical characteristics

The Yak-2 was designed as a twin-engined, mixed-construction low-wing light bomber. The frontal part of the fuselage was made of duralumin. The central part of the fuselage, which was integrated into the wings, was made of wood. The rear part of the fuselage consisted of a welded steel tube frame that was covered with fabric. This rear part could be, if needed (for repairs for example), be separated from the remainder of the aircraft.

The Yak-2 was powered by two Klimov M-103 960 hp liquid cooled engines. The two engines were placed in wing nacelles, on each side of the central fuselage.

op view of the Yak-2. The two engines could be clearly seen. Source: Wiki

The Yak-2 had standard retractable landing gear units, which consisted of two larger frontal wheels and one smaller to the rear. All three retracted to the rear, with the frontal two retracting into the engine nacelles. While, initially, the aircraft had only one large frontal landing wheel on each side, the majority would be built with twin-wheels on each side.

Unusually, the wings were built using only a single large piece. This greatly limited the possibility of transporting this plane by rail. The wings were built using two metal spar structures which were covered with plywood skin. At the rear of the fuselage, the twin-finned tail was positioned.

While it was based on the BB-22, unlike it, the Yak-2 received a modified canopy with both crew members being placed in it. The pilot was placed in front, while the navigator/rear gunner was placed behind him. This arrangement provided easier crew communication.

The Yak-2 had a crew of two, with the pilot placed to the front and the navigator/machine gunner to the rear. Source: Pinterest

The armament of this aircraft consisted of two rear positioned 7.62 mm (0.3 in) machine guns. These were placed in a small cupola that could be raised higher up to provide better covering fire. There was a provision for an internal bombing bay that could hold 400 kg (880 lbs) of bombs. In addition, the aircraft could carry up to 100 kg (210 lbs) bombs in external bomb racks

In combat

Despite its obvious mechanical unreliability, the Yak-2 would be allocated for operational service. The first group of 25 aircraft were initially allocated to the Kharkov Military District. Due to many mechanical problems, they could not be used for flying. Even at this time, there were still attempts to somehow improve the Yak-2’s overall performance, with minimal results. When the aircraft was fully equipped with military equipment, such as radio, weapons, and full fuel load, the flight performance dropped dramatically. For example, the maximum speed was reduced to 399 km/h (247 mph). In addition, the Yak-2 struggled to reach heights of 8,100 m (26,500 ft), which were some 2,800 m (8.800 ft) lower than those reached during prototype testing.

When the war with the Germans broke out, some 75 Yak-2s were allocated to the 136th Bomber Regiment located in Kiev and the 316th Reconnaissance Regiment in the western district. Their use was quite limited, as most were destroyed on the ground by the German Air Force. At least one was shot down by friendly aircraft fighters.

 

The majority of Yak-2s were destroyed on the ground by the German Air bomb raids. Source Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev, Midland
Some did survive the initial German Air raids but would be lost in the following weeks. Here, a group of three Yak-2s on their way to bomb German positions can be seen. Source: Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev, Midland

Proposed versions

Despite its generally poor performance of the Yak-2, there were some attempts to reuse this aircraft for other purposes. These included the BPB-22 short-range bomber, R-12 reconnaissance, I-29 escort fighter, Yak-2KABB ground attack aircraft, and a trainer version.

The BPB-22

The GAZ. No.81 production plant, on its own initiative, tried to develop a short-range dive bomber based on the BB-22. For this proposal, they equipped one aircraft with the newly developed M-105 engines and added dive brakes. The first flight test made in October 1940 was disappointing and the project was canceled.

R-12 reconnaissance

Based on elements from No-22 and the Yak-2, a reconnaissance aircraft named R-12 was to be developed. This aircraft was to be powered by 960 hp M-103 engines. In the end, nothing came of this project.

Yak-2KABB

This was a ground attack prototype equipped with bombs, two 20 mm (0.78 in) cannons, and two machine guns placed under the fuselage. It also received a new modified cockpit design. The aircraft was tested in a series of evaluation flights and was generally considered to be a good design. The outbreak of the war stopped any further work on this aircraft.

The experimental Yak-2KABB. Source: Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev, Midland

I-29

The I-29 was a heavy escort fighter that was to be armed with two 20 mm (0.78 in) cannons. While work on this aircraft continued up to 1942, it would ultimately be canceled.

A trainer version

One Yak-2 was built as a dual-control trainer aircraft. While it was tested in March 1941, nothing came from this project. It is not known if this version ever received any official designation.

Production

Being an unsuccessful design, the actual production run was limited. The Yak-2 was produced by the GAZ No.1 production plant, which built around 25 aircraft. The Moscow Aircraft factory No.81 produced some 75 Yak-2s which were slightly improved in quality but, otherwise, were the same. By the time production ended, only around 100 aircraft were built.

  • No-22/BB-22 Prototype – The first prototype built during the summer of 1939, which served as a base for the Yak-2
  • Yak-2 – Main production version
  • Yak-2KABB – A ground attack prototype
  • BPB-22 – Short-range bomber, one prototype built
  • R-12 – Reconnaissance version proposal
  • I-12 – Escort fighter proposal
  • Trainer Aircraft – One prototype of a dual-control trainer version was built but was not accepted for service

Conclusion

While it managed to achieve extraordinary speed during the prototype phase, in the military role, the Yak-2 proved to be a disappointing design. Once it was fitted with armament and other equipment, its performance dropped dramatically. This, together with other design problems, ultimately led to the cancelation of this project after only 100 built aircraft.

Specifications –  Yak-2 Specifications
Wingspan 45 ft 11 in / 14 m
Length 30 ft 7 in / 14 m
Wing Area 316.4 ft² / 29.4 m²
Engine Two M-103 960 hp engines
Empty Weight 9,390 lb / 4,260 kg
Maximum Takeoff Weight 12,410 lb / 5,630 kg
Fuel Capacity 600 liters
Maximum Speed 310 mph / 500 km/h
Cruising Speed 255 mph / 410 km/h
Range 560 mi / 900 km
Maximum Service Ceiling 28,545 ft / 8,700 m
Crew One pilot and one navigator/gunner
Armament
  • Two 7.92 mm (0.3 in) machine guns
  • 400 to 500 kg (880 to 1100 lbs) bombs

Gallery

Yak-2 (BB-22) – 316th RAP Lt.I.M.Agarkov. South-West Front – July-August 1941
Illustration by Ed Jackson

 

  • D. Nešić (2008), Naoružanje Drugog Svetskog Rata SSSR, Beograd.
  • B. Gunston and Y. Gordon (1977)Yakovlev Aircraft Since 1924, Putnam Aeronautical Books.
  • Y. Gordon, D, Khazanov (1999) Soviet Combat Aircraft, Midland Publishing.
  • Y. Gordon, D, Khazanov, and S. Komissarov (2005) OKB Yakovlev, Midland.

Yermolayev Yer-2ON

Soviet, WW2, ,

USSR flag USSR (1944)
VIP Transport – 3 Converted

A 1/4 view of the Yer-2ON. (AviaDejaVu)

The Yer-2ON was a VIP passenger transport aircraft designed in 1944 by Vladimir Grigoryevich Yermolayev and his Yermolayev OKB (design bureau). Based off of the firm’s preexisting Yer-2 bomber, the Yer-2ON was meant to fulfill the role of a government VIP transport aircraft which would carry government members to and from meetings in or out of the Soviet Union. Shortly after Vladimir Yermolayev died on December 31st of 1944 from a typhoid infection, the Yermolayev OKB firm was integrated into Pavel Sukhoi’s Sukhoi OKB firm where the project continued. Despite showing relatively promising performance, the Yer-2ON would eventually be cancelled due to the conclusion of the Second World War and the Sukhoi OKB’s need to concentrate resources on other projects. Thus, the three produced Yer-2ON would never be used for their intended purpose and were presumably scrapped some time post-war.

History

Diplomacy between the Allied countries during the Second World War was an essential step in defeating the Axis powers. With the increasing successes of the Allies during the war, meetings between representatives from the United States, Soviet Union and United Kingdom were held to discuss the future of Europe along with battle plans. In order to attend these meetings, the Soviet government became aware of the need for a long-range VIP passenger transport aircraft capable of carrying 10 to 12 people while maintaining comfort, reliability, cruising abilities at 13,000 ft to 16,400 ft (4,000 m to 5,000 m) and range of 2,500 mi to 3,100 mi (4,000 km to 5,000 km). After Joseph Stalin himself made a request for an aircraft meeting these requirements in January of 1944, a meeting was held between government and Soviet Air Force officials discussing the feasibility of converting existing bomber aircraft to meet this need. Not only would this save time, but also had the benefit of sharing the same airframe as aircraft already in production. In the end, the Yermolayev OKB’s liquid-cooled Charomskiy ACh-30B V-12 diesel engine powered Yer-2 bomber was chosen for conversion. Curiously enough, Yer-2 being used as a transport aircraft is quite ironic, as it reflects on Roberto L. Bartini’s 1937 Stal-7 transport aircraft, from which the Yer-2 bomber was originally developed from.

A frontal view of the passenger compartment. (AviaDejaVu)

Shortly after the NKAP (People’s Commissariat for Aviation Industry) approved Order 351 on May 23, 1944, the head designer of the Yermolayev OKB firm, Vladimir Grigoryevich Yermolayev, began work on converting the Yer-2 into a VIP passenger transport aircraft. In his address to the NKAP on that day, he promised that a completed example would be converted by Factory No.39 and be ready for tests by November 15th. This new variant would be designated Yer-2ON (Osoboye Naznachenie – Special Purpose). With most of the groundwork already completed, Yermolayev was able to complete the conversion blueprints by August. An inspection was conducted on the Yer-2ON’s plans on August 28th and was approved for production. The difference between the Yer-2ON and the standard bomber variant was the removal of all armament and replacement of the bomb bay with a passenger compartment. The passenger compartment would have been able to hold 9 passengers, as well as a flight attendant. All relevant technical drawings were sent to Factory No.39 in the Irkutsk Oblast. A total of four Yer-2 bombers were ordered for conversion, but standard Yer-2 production would run into difficulties as the diesel powered Charomskiy ACh-30B engines manufactured at Factory No.500 were found to have defects and needed to be addressed. As such, the project was put on hold for a considerable amount of time.

A rear view of the Yer-2ON. (Одноклассники)

On December 31st, Vladimir Grigoryevich Yermolayev passed away due to a typhoid infection. As a result, the Yermolayev OKB and its assets were integrated into Pavlov Sukhoi’s Sukhoi OKB firm. It would appear that N.V. Sinelnikov took over as head designer once the project was integrated into Sukhoi OKB. Once the issue with the engines was resolved, three Yer-2 bombers were set aside and were prepared to be converted into the Yer-2ON. Due to the relatively poor documentation of the Yer-2ON’s development, it is unknown when precisely the first Yer-2ON was completed, but most sources allege it was completed at the end of December. The manufacturer’s flight tests and maiden flight appeared to have taken place sometime in February of 1945. Through these tests it was revealed that the Yer-2ON was capable of covering a distance of 3,230 mi / 5,200 km while maintaining a flight ceiling of 19,700 ft / 6,000 m and a top speed of 270 mph / 435 kmh.

On April 16th, the first Yer-2ON made a record non-stop flight from the Irkutsk Aviation Plant’s airfield in Eastern Siberia to Moscow. This flight was accomplished by Heroes of the Soviet Union M. Alekseev and Korostylev over a flight time of 15 hours and 30 minutes and covered a distance of approximately 2,611 mi / 4,202 km. It would appear that a second flight would be conducted sometime near the end of April with the second converted aircraft once it was ready. The second flight had identical circumstances as the first flight (same pilots, destination, fuel load, etc). Interestingly enough, both flights concluded with enough fuel for four more hours of flight, attesting to the Yer-2’s long-range capabilities. A third Yer-2ON was converted at an unspecified time, but details of its tests (if it performed any at all) are unknown. Some internet sources claim that a fourth example was completed on May 10th of 1945, but this cannot be confirmed and disagrees with most publications.

One of the passenger seats of the Yer-2ON. (AviaDejaVu)

Despite the Yer-2ON performing relatively well and passing the manufacturer’s flight tests, the aircraft was never used for its intended role of government VIP passenger transportation. This was likely the result of the project being deemed as low priority within the Sukhoi OKB firm. At the time, Sukhoi was invested in other more pressing projects which led to the Yer-2ON being eventually canceled. Joseph Stalin himself was reputed to have aviophobia (a fear of flying) and the Yer-2ON not entering service did not appear to have consequences for the Sukhoi OKB. Nonetheless, the Yer-2ON project was dropped some time post-war and the three manufactured prototypes were likely scrapped as a result.

Design

A cutout drawing of the Yer-2ON’s interior. (AviaDejaVu)

The Yermolayev Yer-2ON was a two engine VIP passenger transport aircraft based on the Yermolayev Yer-2 bomber aircraft, powered by two liquid-cooled Charomskiy ACh-30B V-12 diesel engines capable of producing 1,500 hp each. The Yer-2ON was identical to the standard Yer-2 bomber in most respects, though armaments and turrets were removed and the bomb bay was converted to a passenger compartment with seats for 9 passengers and 1 flight attendant. The crew would have consisted of a commander pilot, a co-pilot, a navigator, a radio operator, and a flight attendant. In the passenger compartment, the left side (aircraft facing forward) had 5 seats while the right side had 4. The flight attendant’s seat was located behind the last seat on the right side, and was retractable. A luggage compartment was also provided. Another notable feature was the addition of a toilet compartment, as the aircraft’s long-distance travel routes required such a feature. Several windows were installed on the side of the fuselage for the passengers.

Operators

  • Soviet Union – The Yer-2ON was intended to be used as a passenger transport aircraft for government VIPs traveling in and out of the country to attend meetings.

Yermolayev Yer-2ON*

* – Statistics taken from “OKB Sukhoi: A History of the Design Bureau and its Aircraft” by Dmitriy Komissarov, Sergey Komissarov, and Yefim Gordon
Wingspan 75 ft 5.51 in / 23 m
Length 53 ft 7.31 in / 16.34 m
Height 15 ft 9.76 in / 4.82 m
Wing Area 850.35 ft² / 79 m²
Engine 2x liquid-cooled Charomskiy ACh-30B V-12 diesel engines
Engine Ratings 1,500 hp (1,120 kW) – Maximum at Sea Level

1,250 hp (930 kW) – Regular
Empty Weight 38,800 lb / 17,600 kg
Takeoff Gross Weight 41,890 lb / 19,000 kg
Maximum Speed 270 mph / 435 kmh at 19,680 ft / 6,000 m
Ranges 3,040 mi / 4,900 km – Standard

3,230 mi / 5,200 km – Maximum
Maximum Service Ceiling 19,700 ft / 6,000 m
Takeoff Run 3,445 ft / 1,050 m
Landing Run 3,346 ft / 1,020 m
Crew Pilot / Commander

Co-Pilot

Navigator

Radio Operator

Flight Attendant
Accomodation 9 Passengers

Gallery

Yermolayev Yer-2ON Side View Illustration
A side view of the Yer-2ON. (AviaDejaVu)
The entrance to the passenger section. (AviaDejaVu)
This photo shows what appears to be a retractable seat in the rear of the passenger compartment. This seat most certainly would be for the flight attendant. (AviaDejaVu)
Toilet compartment of the Yer-2ON. (AviaDejaVu)

Sources

 

Bolkhovitinov S-2M-103

Soviet, WW2

USSR flag USSR (1936)
Experimental Light Bomber – One Prototype Built

Bolkhovitinov’s light bomber was a truly unusual design, with two engines mounted in the same fuselage.

Prior to the German invasion, the Soviet air industry was in the process of developing a series of new experimental ideas and concepts. While generally unknown around the world, some of these were interesting designs, such as the Bolkhovitinov “S” experimental twin-engine fast attack bomber. Due to the German advance and the need for immediately operational planes, the development of this model was terminated.

An Unusual Idea

The leader of the whole S-2M-103 project, aircraft engineer Viktor Federovich Bolkhovitinov.

The S-2M-103 was designed and developed by a Soviet aircraft engineer team led by Viktor Federovich Bolkhovitinov (Ви́ктор Фёдорович Болхови́тинов). Bolkhovitinov (February 1899 – 29 January 1970) was a Soviet professor at the Zhukovsky Air Force Academy in Moscow, and also an aircraft engineer. One of his best known designs was the four-engined Bolkhovitinov DB-A bomber that was intended to replace to aging TB-3 bomber.

During 1936, Bolkhovitinov and his team were looking for a solution for the lack of a high-speed light bomber in the Soviet Air Force. Their answer would be an unusual twin-engine aircraft with a peculiar wing configuration. Instead of a conventional wing placement, the wings were mounted very low on the fuselage, and the tail was a twin fin design.

When they began working on the first calculations and drawings, their greatest concern was how to reduce drag. Usual bomber designs with wing-mounted engines slowed down the plane due to excessive drag. Fighters, on the other hand, had much better aerodynamic properties as they were designed to achieve the highest possible speeds. Bolkhovitinov and his team decided that, for their purposes, they would reuse elements from other bombers (two engines, bomb-carrying capacities, defensive armament) and a one-part fuselage.

The problem was how to position the two engines in order to reduce the drag as much as possible. They quickly came up with the idea of putting them both on the same line (one behind the other) and in the same fighter-like fuselage. While this configuration would make the new plane longer, it could be designed with much better aerodynamic properties.

The development and design of the unusual twin-engine system began in 1936, while work on the aircraft design itself began the next year. By 1938, the design was completed and preparations for the construction of a fully operational prototype began in July that year. The prototype was completed in 1939 and flight tests were scheduled to begin in July 1939 (or in early 1940 according to some sources).

Designation

This was the single-engined version tested during the winter of 1940/41.

The aircraft’s original designation was simply “Bolkhovitinov S” or “Sparka/Cпаренный”, which means twin. Today it is generally known under the “S-2M-103” designation, where the “2” stands for twin-engine configuration and “M-103” is the name of the engine. There were other designations used for this plane, such as “BBS-1” (Ближний бомбардировщик скоростной, fast short-range bomber), “LB-S“ (легкий бомбардировщик спаренный, light twin-engined bomber) оr “BB“ (Болхови́тинов Бомбардировщик, Bolkhovitinov Bomber). As the plane is best known as the the S-2M-103, this article will use this designation.

Technical Characteristics

The S-2M-103 was designed as a low wing, all-metal construction, two-seater, two-engined fast attack bomber. The S-2M-103’s main fuselage had an elliptical cross-section. The fuselage consisted of four (bottom, top and left and right side) panels that were held in place by using four strong angled-section longerons. The S-2M-103’s structure was covered with a modern light alloy stressed-skin.

The wings were constructed using a structural box with flanged lightening holes (to save weight). The wings’ interior sheet ribs were covered on both sides (upper and lower) by metal skin and held in place by flush riveting.

The two three-bladed propellers turned in the opposite directions in order to provide better stability during flight.

The rear twin-finned tail was covered with duralumin skin. For better stability, the rudders were equipped with inset balanced hinges. For the tailplanes’ movement, an irreversible trimming motor was used. The elevator had trim tabs with a variable geared drive.

The S-2M-103 had a completely retractable landing gear that was operated electrically. The front wheels and the smaller rear tail wheel was able to retract backward 90 degrees. During the winter of 1940/41, the wheeled landing gear was replaced with fixed skis.

Drawing of the twin-engined configuration.

This aircraft had an unusual two tandem engine arrangement, placed in the same mounting in the fuselage. The rear-mounted engine’s shaft passed through the front engine’s cylinder blocks. Both engines were connected to the two propellers (with six blades in total) which, when powered, turned in opposite directions, which provided better stability during flight (at least in theory). The S-2M-103 was powered by two 960 hp (716 kW) Klimov M-103’s V-12 liquid cooled engines. This engine was based on the French Hispano-Suiza 12Y which was produced under license by the Soviet Union as the M-100.

The water radiators were placed under the fuselage and had controllable exit flaps. Two oil coolers were located on the ducts on both sides of the two engines. The fuel was stored in four fuel tanks that were placed in the wings (between the wing spars). Unfortunately, there is no information available about the capacity of these tanks.

The two crew members were positioned in an unusually large cockpit fully enclosed with a plexiglass canopy. The crew consisted of the pilot and the navigator. The navigator was also provided with a bombsight. The navigator’s position was covered with plexiglas on all sides, which provided him with an excellent all-around view, including under the plane. His additional role was to operate the rear-mounted machine gun.

The S-2M-103 lacked any forward-firing offensive armament. While it was planned to equip it with weapons mounted in the wings, this was never accomplished. For self-defense, one 0.3 in (7.62 mm) ShKAS machine gun was provided for the navigator/gunner. Due to its tail design, the rear machine gun had a wide firing arc. Later, it was planned to replace the single 7.62 mm rear gun with heavier twin 0.5 in (12.7 mm) UBT machine guns. There were also alleged plans to equip the S-2M-103 with a rear-mounted remotely controlled ShKAS machine gun. Whether this was ever implemented is unknown, as there no photographs or precise information are available. The bomb bay, which could carry 880 lb (400 kg) of bombs, was located under the pilot cockpit. The bomb bay opening doors were opened electrically.

Operational Tests

Side view of the S-2M-103.

The S-2M-103, piloted by D.N. Kudrin, made its first test flight in late 1939. More tests were carried out by the Army from March to July 1940, the plane being piloted by D.N. Kudrin and A.I. Kabanov. During these flight tests, the S-2M-103 proved to be able to achieve a maximum speed of 354 mph (570 km/h) at 15,400 ft (4,700 m). The tests also proved that the concept of installing two engines in the same fuselage had some advantages over the wing-mounted configuration. The most obvious was the reduced drag, which lead to increased speed and improved flight performance.

There were also some problems with the design. Immediately noticeable were the poor take-off and landing performance during these tests trials. Due to its high weight of 12,460 lb (5,650 kg), the S-2M-103 needed a 3,430 ft (1,045 m) long airfield. More tests were carried out by removing any extra weight. With the weight being reduced by some 1,100 lb (500 kg), the S-2M-103 now only needed a 2,800 ft (860 m) long airfield. During landing at speeds of 103 mph (165 km/h) the aircraft needed a 2,130 ft (650 m) long airfield. Some problems with the twin propellers were also noted. The rear-mounted propeller drive shaft was damaged due to strong vibrations. Unfortunately, there are no records of cruising speed, climbing speed, or maximum service ceiling.

The Single-Engine Version

For testing during the winter of 1940/41, instead of the standard landing gear, fixed skies were provided.

In the following months of 1940 and 1941, the S-2M-103 received a number of modifications in the hope of solving the issues observed during preliminary testing. The twin-engine configuration was replaced with a single M-105P engine with a power of 960 hp (or 1,050 hp depending on the source). The area where the second engine was previously located was filled in order to maintain the stability of the aircraft. Due to the removal the second engine, the second contra-rotating propeller was no longer needed. The new engine’s oil coolers were placed in the main radiator duct. The designers had a dilemma about what to do with the extra interior space left by the removal of the second engine, but this was never solved completely. With these modifications, the weight was reduced from 12,460 lb (5,650 kg) to 8,820 lb (4,000 kg).

The wing design was also changed to one done by Z.I. Iskovich by increasing its size and using a new aerofoil shape. The previous wing design had an area of 246.5 ft² (22.9 m²), while the new one had 252 ft² (23.4 m²). The last change was made to ease testing during winter, replacing the landing gear with fixed skis.

It appears that no official designation for this version existed but, using the same logic as for the two-engine version, it could be called S-M-105, but this is only speculation at best. According to some sources, the single-engined variant was marked as the S-1.

There were plans to improve the performance of the projected fighter version by mounting two M-107 engines. The new fighter was to be designated simply as the “I” or “I-1”. Due to the later cancellation of the S-2M-103 project, the I-1 was also abandoned.

The Fate of the S-2M-103 Project

More flight tests were carried out during the first half of 1941. While there is no precise information, the newly modified single-engined version of the S-2M-103 allegedly had poor performance. Despite the modifications, the new single-engined version managed to achieve a much lower top speed of 248 mph (400 km/h) at 14,440 ft (4,400 m). The poor performance, preparation for Pe-2 production at the factory where it was built, and the German Invasion of the Soviet Union led to the cancellation of the S-2M-103 project.

Operators

  • The Soviet Union – A single prototype was tested in 1940/41, but was not adopted for production.

Variants

  • S-2M-103 – Twin engine fast bomber
  • S-2M-103 (possibly S-M-105) – Single-engine version
  • I-1 – Improved fighter version equipped with two M-107 engines, due to cancelation of the S-2M-103 none were built.

Conclusion

The concept of installing two engines in the same fuselage had some advantages over the wing mounted configuration. It reduced drag, which lead to increased speed and flight performance. The S-2M-103 proved this by achieving speeds of up to 350 mph (570 km/h). However, its design had issues that were never resolved. Given enough time, those might have been solved. Alas, in 1941, the German Invasion and the need to increase production of already existing aircraft stopped all unimportant projects.

Bolkhovitinov S-2M-103 (original twin-engine configuration) specifications
Wingspan 37 ft 5 in / 11.4 m
Length 43 ft 4 in / 13.2 m
Wing Area 246.5 ft ² / 22.9 m²
Engine Two 960 hp (716 kW) Klimov M-103
Maximum Takeoff Weight 12,460 lb / 5,650 kg
Maximum Speed at 4.6 km 354 mph / 570 km/h
Range 435 mi / 700 km
Crew The pilot and the navigator
Armament
  • One 0.3 in (7.62 mm) ShKAS machine gun
  • Bomb load of 880 lb/400 kg

Gallery

Illustrations by Haryo Panji https://www.deviantart.com/haryopanji

Drawing of the S-2M-103.
View of the engine compartment interior.
Rear view of the S-2M-103.

Credits