Leonard Bonney, an aviation pioneer and one-time First World War US Army and Navy flying instructor became obsessed with the shape of a gull’s wing, which he believed to be the most efficient and capable wing form in nature. The Bonney Gull was the result.
A single-seat secondary glider was designed by a Mr Bolton of the Kent Gliding Club, UK. It first flew on 3 April 1932.
The Bolkhovitinov AVF-6 Favzayat single-seater training glider was developed by Victor Fiodorovich Bolkhovitinov, a student of the Air Fleet Academy, in 1924.
Structurally it was a sesquiplane with ailerons on the upper wing and a rear fuselage with a flexible structure. The pilot was located in a small nacelle attached to the lower wing. The landing gear was made up of skis. The tail unit was of the conventional type.
The construction of the glider was carried out at the Duks factory.
In 1924, the AVF-6 participated, together with the AVF-18 “Pioner” in the national competitions in Koktebel.
Only the one was built.
Upper wingspan: 11.5 m
Lower wingspan: 6.2 m
Length: 6.6 m
Height: 2.22 m
Wing area: 25 m²
Empty weight: 68 kg
Seats: 1
The Bolkhovitinov AVF-18 Pioner single-seater training glider was built in 1924 at Factory No.1, by Victor F. Bolkhovitinov during his student years at the Air Fleet Academy.
This glider participated in the National Sailing Competitions held in Koktebel together with the AVF-6 “Fazvayat”.
Only the one was built.
Wingspan: 5.64 m
Length: 3.0 m
Wing area: 14.6 sq.m
Empty weight: 24 kg
Accommodation: 1
In 1936 Bolkhovitinov considered the problem of high-speed military aircraft. He choose a layout with two M-103 engines, installed one after the other (tandem) with the transmission on coaxial propellers.
He constructs a paired set of engines, followed by bench testd. Bench tests were promising, so in 1937 under the leadership of Bolkhovitinov a high-speed short-range bomber was conceived, indexed “C” (there were several options for decoding the index: “Stalin,” “Spark,” “Spartacus”).
In parallel with the construction of short-range bomber DB, Bolkhovitinov began the design of another aircraft, equipped with a similar twin powerplant. This a project of high-speed long-range fighter-1 twin engine M-107. This was designated “I”. The development was carried out until the spring of 1941 however, an unexpected obstacle has stopped development of the machine. April 25, 1941 Bolkhovitinov was summoned to a meeting of Deputy People’s Commissar Balandin aviation industry. Present at the meeting, Director Motor Works Lavrent’ev and chief designer of engines Klimov reported the impossibility of creating a two-seat trainer M-107P engines.
The main cause of failure was it was thought that in this engine the elongated shaft at working speeds could have resonance problems. Bolkhovitinov were asked to choose any other type of engine available in the country and to convert it for the project. The designer chose the diesel M-40, and while it was heavy, but consumed half as much fuel.
Change the engine caused change for the whole project. Preliminary survey was conducted during May – June 1941, returning to the designation “C”.
I-1 was then included in the plan of an experimental aircraft in 1941, due to the large similarity of the scheme and design of aircraft with “C”, 2M-103 and “C-2”, equipped with one engine M-103 (front-engine was left in place, but its transmission has been disabled from the second propeller.
In general, the draft I-1 was tested by repeating the “C”, but with a much more powerful Klimov M-107 engines. Different from the prototype were vertical stabilizer and skid. The stabilizer was 4.5 m without end plate.
This fighter was never completed due to the refocusing of the bureau.
The draft I-1 had been identified, many new technological approaches for assembly, riveting and bonding aircraft components, in-flight pilot’s ejection, corresponding to speed range 600-750 km / h.
Around mid-1941 TsAGI study of was co-axial propellers completed, with the following conclusions:
During the war, however, put into practice the results of the research was not possible.
With the intention of creating a high speed light bomber, Viktor Bolkhovitinov designed what is commonly referred to as the Bolkhovitinov S or Sparka. During flight trials the Soviet Air Force (VVS) referred to the aircraft as S-2M-103, for skorostnoy (high speed) with two M-103 engines; however, a number of other designations have been applied over the years. The common “Sparka” designation means twin—because the aircraft had two engines mounted in tandem. Other designations are BBS-1 for blizhniy bombardirovshchik skorostnoy (short range bomber, high-speed), BB for blizhniy bombardovshchik (short range bomber), and LB-S for lyohkiy bombardirovshchik-sparka (light bomber-paired).
The Sparka was a low-wing aircraft of all-aluminum construction with stressed skin. The aircraft had a twin fin tail to increase the rear gunner’s field of fire. The undercarriage was fully retractable; the main gear retracted toward the rear, and the wheels rotated 90 degrees to lie flat within the wings. The pilot and navigator/bombardier/gunner sat in tandem under a long canopy. Between the pilot and second crew member was a small bomb bay for 882 lb (400 kg) of bombs. A plexiglass section on the bottom of the aircraft just aft of the bomb bay provided the bombardier a view of the ground. The aircraft was 43 ft 4 in (13.2 m) long and had a relatively short wingspan of 37 ft 4 in (11.38 m). The Sparka weighed 12,460 lb (5,652 kg).
The Sparka was powered by two Klimov M-103 engines positioned in tandem in the aircraft’s nose. Each engine drove half of the aircraft’s six-blade, coaxial contra-rotating propeller unit. This engine and propeller arrangement was similar to the FIAT AS.6 installed in the Italian MC.72 and the Hispano-Suiza 12Y installed in the French Arsenal VB 10. With this engine arrangement, the front engine drove the rear propeller, and the rear engine drove the front propeller via a drive shaft that ran through the Vee of the front engine.
The Klimov M-103 engine was derived from the M-100, which was a licensed copy of the Hispano-Suiza 12Ybrs. The M-103 had a 5.91 in (150 mm) bore and 6.70 in (170 mm stroke). Total displacement was 2,200 cu in (36.05 L). The engine produced 960 hp (716 kW). A radiator was installed in a large duct just below the rear engine, and it cooled both of the Sparka’s engines.
Bolkhovitinov started design work on the Sparka in 1937, and prototype construction began in July 1938. The aircraft made its first flight in January 1940 (some say late 1939) with B. N. Kudrin at the controls. VVS testing took place from March through July 1940. The Sparka showed good speed, reaching 354 mph (570 km/h). However, the take-off run was excessive, landing speeds were high, and visibility over the nose was impaired. In addition, some trouble was encountered with the rear engine’s propeller drive shaft breaking due to excessive vibrations. Even so, the aircraft received a positive assessment, noting that the installation of the tandem engines eliminated a considerable amount of drag over two separate nacelles.
A new wing was designed with a NACA-230 airfoil section to improve take-off and landing performance. The aircraft was tested with this new wing from September to December 1940, and it did improve the aircraft’s take-off and landing characteristics.
Some say the single engine version was really a separate aircraft (known as S-1) that flew in January 1940 to test the airframe configuration. This seems unlikely because of the time frame involved. The twin-engine Sparka (S-2) would have been nearly complete by the time the single engine airframe test ship first took to the air, making major changes impossible and minor changes difficult. Official trials took place in March 1940.
The Sparka was reconfigured for a single 960 hp (716 kW) Klimov M-105P (some say 103P) engine, which was installed in the forward engine bay. The M-105P was a development of the M-103P; both had a smaller bore of 5.83 in (148 mm), but the stroke was unchanged, and could be fitted with a cannon to fire through the engine’s Vee. The aircraft was tested on skis in early 1942 but was underpowered with the single M-105P, attaining a top speed of 249 mph (400 km/h).
Development on the Sparka was abandoned in mid-1941, partially a result of the German invasion. In addition, the factory where the Sparka was built was needed to produce the Petlyakov Pe-2 attack bomber.
I-1 Modification
Engine Type 2 PD-107 AM
Power,
maximal 2 x 1400 HP
rated at 2 x 1250 HP
Wingspan: 13.80 m
Length: 12.96 m
Wing area: 22.90 sq.m
Empty weight: 2560 kg
Maximum take-off weight: 4810 kg
Maximum speed SL: 640 km / h
Maximum speed: 750 km / h
Range: 2000 km
Rate of climb: 1000 m / min
Service ceiling: 10,000 m
Crew: 2
Armament:
two 23-mm cannon and four BR 12.7-mm machine gun BS
two to four bombs caliber from 100 kg to 250 kg.
S-2M-103 Sparka
Engines: two Klimov M-103, 960 hp (716 kW)
Prop: six-blade, coaxial contra-rotating
Wingspan: 37 ft 4 in (11.38 m)
Length: 43 ft 4 in (13.2 m)
Weight: 12,460 lb (5,652 kg)
Bomb load: 882 lb (400 kg)
At the beginning of 1933 it became necessary to find a replacement for the aging Túpolev TB-3 bomber, which formed the basis of the long-range bomber aviation of the RKKA VVS. At the same time it became known that a group of professors and assistants from the Zhukovski Military Aeronautical Academy had been working on the conception of a new giant 12-engine bomber known as “Gigant”. By 1934 the need for an aircraft of these proportions had waned, so the financing of the project was cancelled. It was proposed to this group to develop a capital reconstruction project for TB-3.
Viktor Fedorovich Bolkhovitinov became the head of the VVIA design group at the VVA Žukovskij (VVS academy Žukovskij ) tasked with the design of a replacement for the Tupolev TB-3 heavy bomber. It was decided to study in depth the limitations of TB-3 and propose solutions to improve them. To this end, consultation work was started directly with the builders of Factory No.22 in Fili , where the Túpolev bomber was produced.
The new aircraft was designed as a Long Range Bomber or BDD (Russian: бомбардировщик дальнего действия – БДД). The technical tasks approved by the VVS for the new bomber in December 1934 included a speed of 320 km / h, a landing speed of 90-95 km / h, a flight ceiling of 6000 – 7000 m and a transport capacity of 1000 kg of bombs at a distance of 4000 km (with a total load capacity of 5000 kg). For its projection, a Joint Projection Bureau (OPB) was created, made up of technologists and builders from the factory and designers from the Zhukovski Academy.
The proposals put forward by the Academy were supported by RKKA chief of armament M. N. Tukhachevsky.
The Academy’s group of specialists conceived that, maintaining the tooling of Factory No.22, it was entirely possible to create an aircraft capable of meeting the specifications of the VVS and even in some cases exceeding them.
Soon Bolkhovitinov’s brigade was transferred to Factory No.22 in Fili, where the KB-22 was organized. Already participated in the projection of the new model. M. Kuritskies, IF Florov, BE Chertok, MM Shishmariov, among others.
The factory name for the new model was “A”. The Commission analysis of the model met on 14 January 1935, leaving some constructive recommendations for changes, the composition of the weaponry and equipment. By this time it was clear that even when the dimensions and composition were maintained constructively, it was a new aircraft. Despite this, it is remarkable that many official documents of the time refer to the new model as “the last modification of the TB-3 ” or “the TB-3 of 1935 “.
The resulting Bolkhovitinov DB-a (Russian: Болховитинов ДБ-А. Its acronym comes from the term Long Distance Bomber – Academy, Russian: Дальний Бомбардировщик – Академия) was advanced for its day with stressed skin aluminium alloy construction throughout with clean lines, neatly cowled engines and trousered main undercarriage legs, with fully retracting main-wheels and tail-wheel. The split flaps, undercarriage, nose turret and bomb-bay doors were all operated by a pneumatic system re-charged by engine driven compressors.
Upgraded bombs with 6 x 2 m hatches, mechanized and armoured Tur-8 turret and closed cockpits for the crew (with the exception of the tail gunner).
The new fuselage with a monocoque structure made it possible to significantly increase the interior volume of the aircraft. In the lower part of the center was located the bomb bay with a capacity for 3000 kg of bombs in the following configurations:
8 bombs of 250 kg;
6 bombs of 500 kg;
2 bombs of 1000 kg;
or 24 bombs of 100 kg.
The ability to install VAP-500 and VAP-1000 external supports, as well as a rotary launching system for RRAB pumps, was envisaged.
In the nose there was a Tur-8 turret with a ShKAS machine gun, which rotated with the help of a pressurized air system and in the central area of the fuselage a Tur-Aldis turret, designed in the TsAGI, with a ShVAK 20mm cannon. To defend the belly area, a ShKAS machine gun was installed firing through a hatch. In the tail area, the installation of a TUR-8 turret with another ShKAS machine gun was planned. The cannon had 250 rounds, while the total ammunition load for the machine guns reached 3,000 units.
The wing had a structure with three spars and a TsAGI – 620 profile. It was made up of the centrewing and two wing consoles. Nine fuel tanks accommodated 14,600 liters and two 460-liter oil tanks were located in the wing between the engines. In the intrados the underwing supports were located with a total capacity of 2000 kg of pumps. Both the flaps and the ailerons had a metallic structure and textile covering. The use of these flaps, capable of operating at 60º, allowed the landing speed to be reduced to 80 km / h.
The operation of the flaps, the retraction and extension of the wheels, the turning of the bow turret and the opening and closing of the hold gates were carried out by means of a pneumatic system.
The DB-A incorporated an APR-3 radio-rangefinder. The project also included the addition of an AVP-10 autopilot system. Both crew members communicated with the help of an intercom system. For night landings, the placement of headlights under the wings was foreseen.
The power plant consisted of four M-34RN engines. The project was calculated for the turboed version M-34FRN, but this model became available later.
The landing gear was designed as a conventional type with a tail wheel. The main units featured 2000x450mm wheels that partially retracted into large ‘pant’ type fairings. To allow the exploitation of the aircraft in winter operations, the use of special skis was envisaged, but these were never built, so for the factory tests the skis of a TB-3 were used. The main landers used telescopic, hydro-pneumatic shock absorbers.
The DB-A crew of nine were two pilots, a navigator, two engineers, a radio operator – gunner and three other gunners, but in different configurations it varied between 6 and 9 people.
In November 1934 the construction of the first copy of the DB-A (Dalni Bombardirovchik – Akademia or Long-range Bombardment of the Academy) was completed. Instead of the M-34FRN engines required by the project, four M-34RNs with a lower power were installed in the new prototype.
Flight trials began on 2 May 1935 at Khodinka piloted by factory pilots N.G. Kastanyev and Ya.N. Moseyev, Later, due to Moiseyev’s illness, he was replaced by AK Tumansky, brother of the aircraft engine manufacturer Sergei Konstantinovich Tumansky . The crew also included engineers Godovikov, Florov, Konkin and Osipienko.The first flight of the new “22A” factory index bomber lasted barely half an hour, but it demonstrated the value of the technical solutions applied to the “Annushka” (Anita) as the workers of Factory No.22 where it was developed called it.
Initially, the DB-A engines had wooden propellers with two blades and a diameter of 4.35 m, similar to those used in the TB-3, but this brought about a noticeable decrease in performance in relation to those calculated, therefore It was decided to replace them with one of three 4.1 meter blades, similar to those used in the Túpolev ANT-25.
Factory tests were completed by April 1934 and NII testing was carried out in May and June 1935. In them it was shown that the DB-A out-performed not only the TB-3, but even the Farman-222 with a similar mission. Despite presenting an empty weight 15.4 tonnes higher than that of the TB-3, the DB-A showed an increase in speed of 40 – 50 km / h. This increase in performance was mainly due to the aerodynamic improvement of the model. With retraction of the landing gear, 18-20 km / h were gained at sea level and 25-28 km / h at 2000 meters. The performance demonstrated included, sustained flight at an altitude of 2,500m (8,202 ft) with two engines shut down, and 4,500 km range.
The aircraft assessment report only included poor visibility from the cockpit as a defect. However subsequent investigations have shown that the report was not objective. There is evidence of contradictions between Kastanayev and Tumanski, as the former eliminated the defects from the reports in order to get the plane to be chosen for the long-haul flight to the United States proposed by the polar pilot SA Levanevski.
The aircraft was shown to Levanevski and government approval was soon received to prepare the first factory specimen No.22-A1 for flight, assigning it the USSR-N-209 polar aviation index.
In 1936 the DB-A was shown in the parade commemorating the first of May, causing a sensation among national and foreign guests.
A decision was made to fly non-stop from Moscow to the USA and the DB-A was modified to fly, at an overload weight of 34,700 kg (76,500 lb), carry enough fuel to fly 8,440 km (5,244 miles). While the state tests were being carried out, the first DB-A was modified and prepared for the record flight on the Moscow – North Pole – Fairbanks route. The plane was lightened. All weapons were removed; the glazing of the forward cabin in which the navigator and radio operator were located was modified; an astrological dome was installed over the pilot’s seat, the position of the tail gunner was removed. The weight saved went to a new fuel tank and commercial cargo.
During the preparation of the flight, a test flight was carried out on the Shelkovo – Baku – Shelkovo route and a test takeoff with a weight of 32,300 kg.
The flight across the North Pole on the red painted DB-A prototype USSR-N-209 began on August 12, 1937 from Moscow Shchyelkovo airport on an attempt to fly to Fairbanks, Alaska. The crew consisted of SA Levanevski as pilot and captain, NG Kastanayev as second pilot, VI Lievchenko as navigator, mechanics GT Pobratimov and NN Godovikov and radio operator N. Ya. Galkovski.
Although the weather conditions on the route were extremely difficult, it was decided to continue the flight. On August 13 at 1:40 p.m. Moscow time, the crossing over the North Pole was reported. At 14:32 the last radio communication was received informing that an engine had stopped. Then the link was lost. The plane was never found, despite intensive searches carried out for almost a year. In more recent times, attempts have been made to continue searching using more advanced search techniques, without obtaining any results.
In order to verify the performance obtained during the prototype factory tests, it was decided to deliver the second prototype, known as DB-2A, to the NII VVS to carry out the state tests, which began on March 14, 1936. This model was equipped with a more powerful version of the M-34RN engine rated at 1000 hp and a new radiator.
The main pilot for the tests was MA Nyuxtikov and the principal engineer Losiukov. The flight results set in these tests were:
Maximum speed at sea level: 280 km / h
Maximum speed at 3000 meters: 323.5 km / h
Maximum speed 4200 meters: 330 km / h
Landing speed: 80 – 85 km / h
Practical ceiling with weight of 21,600 kg: 7,220 m
Take-off run: 300 – 350 m
The evaluation report of the state tests, signed by the head of the VVS Ya. I. Alksnis on June 1, 1936 concluded: “Compared to the TB-3 4M-34RN aircraft, the DB-2A prototype presents the following improvements: 1 – Considerable increase in horizontal speed. With the use of M-34FRN engines for which it was calculated, the speed should be increased until reaching 360 – 370 km / h. 2 – The large capacity of the fuel and oil tanks, at the overloads for which the aircraft was calculated, guarantee a great range. ” But there were a series of defects whose enumeration reached 38 points. Among them:
1 – Unsatisfactory stability and handling;
2 – Low effectiveness of the ailerons and great pressure on the lever during its operation;
3 – Low effectiveness of the rudder and great pressure on the lever during its operation;
4 – In flight regime between atmospheric turbulence, the effectiveness of the tail decreases significantly with rolling. A prolonged flight in these conditions is made impossible by the pilot’s fatigue.
5 – Appearance of strong vibrations in the tail unit in some flight regimes.
Despite not being included in the official report, Tumansky had highlighted other defects, including the impossibility of completing the oil capacity in flight, the inability to use the last 60 kg of oil in the tanks, due to the location of the system nozzles. Piloting the plane required great physical strength and there was no oxygen system for the crew.
Several improvements were made to the aircraft that included modifications to the aileron and rudder control systems. The appearance of strong vibrations in the tail section forced a flight weight limit of 21,800 kg to be established. Upon learning of this, Boljovitinov himself together with the test pilot MA Nyuxtikov conducted a test flight, managing to find a weak point in the aircraft’s structure, which was soon reinforced. With this it was possible to raise the takeoff weight to more than 30,000 kg.
The DB-A was flight tested with only three engines. In this case the maximum speed decreased to 292 km / h, the ceiling with 21,500 kg of weight reached 5100 meters. It is noteworthy that in the tests an engine was never really disconnected, but the power was reduced to the maximum. With two engines working, the plane was unable to exceed 2,500 meters in height.
In the flight tests there were several mishaps that luckily did not end in disasters:
On March 11, at an altitude of 2000 m, due to a power failure during the climb, the four engines stopped and only the quick action of the pilots who managed to stabilize the horizontal flight, guaranteeing the necessary flow of fuel to the engines. was able to avoid an accident.
On May 21, 1936, during landing 67 and due to a manufacturing defect, the left leg of the landing gear broke.
In June 1936, installation tests were carried out on the DB-2A of the M-34FRN engines with take-off power of 1220 – 1240 hp and new metal propellers. It was decided to develop a new test suite on the NII VVS. These tests were developed by the third rank military engineer MA Lipkin and had MA Nyuxtikov as the main pilot.
The M-34FRN engines (with factory numbers № 436, 437, 4311, 4314) were experimental and did not pass the test because they were considered unreliable. Compared to the M-34RN they had a power increase of only 50 – 70 hp. It was impossible to install them on the plane until its completion by Factory No.24.
In the report of the test results with the new powerplant signed by the head of the VVS Ya. I. Alksnis on November 2, 1936 it is found that:
“… The installation of the M-34FRN engines in the DB-A aircraft, due to its low working height and lack of completion, negatively influenced the flight data of the aircraft, excluding the speed performance (maximum speed grew at 10 km / h)”.
In the conclusions of the state tests Alksnis also wrote:
“Taking into account that the DB-A significantly surpasses the TB-3-4M-34RN in performance and that the defects indicated in the state tests can be solved during the construction of the field series, consider it essential to begin preparation for production series of these aircraft based on the results of field tests”.
In 1936 itself, the process of preparation for serial production began. At that time a contradiction was created between Bolkhovitinov and the director of Factory No.22, Tarasievich. The factory had been instructed to restore production of the TB-3 and a large production plan for SB bombers. On the other hand, Túpolev had begun to propagandize the series production of his TB-7. For this reason, Tarasievich submitted to Glavaviaprom (of which Tupolev was deputy chief engineer) the request to develop the production of DB-A in Kazan, at Factory No.124. This request soon became a decision sanctioned by the Commissariat for Heavy Industry.
This decision directly affected the group. Bolkhovitinov could not refuse to move, as this meant refusing to produce the bomber. KB members received the documents for a lengthy service commission. Several specialists were unable to transfer and others simply did not want to do so, for example Kuritskies and Shishmariov, who taught at the Academy, decided not to leave the VVA.
Only two complete copies had been built at Factory No.22: the DB-A prototype and the second DB-2A. A third uncompleted specimen was sent to Factory No.124 in Kazan for completion. As a basis for serial production it would be necessary to build 4 or 5 aircraft, which were to be produced at Factory No.22.
Although initially it was planned to have the first copy ready for December 1936, the construction of the plane was delayed. At the beginning of 1937 all the forces of Factory No.22 focused on the first copy in order to be able to deliver it for testing on February 8.
In April 1937, joint tests began with the contractor of the first specimen intended for field tests, produced at Factory No.22. This aircraft was a modified DB-2A. Among the main differences was the fully retractable landing gear. Initially 1350×300 mm wheels were selected but it was shown that they did not support the maximum flying weight of the aircraft, so other 1600×500 mm wheels were chosen. The cockpits for the pilots, navigator and mechanics had been totally modified and raised to improve visibility. This caused the deck to protrude from the fuselage, ending in a fall in which it was thought to locate a ShKAS machine gun.
On the nose was the two machine gun system used in the SB. In the central region there was a turret with a ShVAK cannon that rotated with the help of an electric motor. The initial turret, now equipped with a PMP-2 collimator, was kept in the tail.
This new specimen received the name DBA-37 or simply DB. The test brigade was made up of the test pilot MA Nyuxtikov, the second pilot and engineer Antojin, the armament engineer Stvietkov and the chief engineer of Factory No.124 Volkov.
As a result of the second stage of testing, the surface and trim area of the rudder was increased. Later, the construction of the cellar hatch opening system was changed, the engine exhaust system was modified, the trimmers and the aileron and rudder compensation system were modified, among other minor changes. For crew communication, a new intercom system SPU-1 was adopted and RSTB-1 and RSB radios were added. The crew grew to 11 people. The changes continued until the end of 1937.
The first modernized DB-A copy was completed only for the month of May. Factory tests with M-34RNV engines took place between May 11, 1937 and March 22, 1938. The test brigade in this case consisted of the test pilot MA Nyuxtikov, the second pilot and engineer Antojin, the chief engineer of Factory No.22 Frolov and the engineer of Factory No.124 Garanovich.
Compared to the first copy, the handling worsened. With respect to the first prototype, the take-off weight had increased by 2000 kg and the maximum speed to 3000 meters was increased by only 8 km / h, so the modifications had been insignificant.
The long duration of the tests was due to the fact that, after the disappearance of Levianevski, the works in the DB-A were stopped and only continued in early 1938.
The first stage of state testing of the modernized DB-A took place between October 21 and December 20, 1937. After several modifications to the aircraft, the tests were continued at the NII VVS between April 14 and June 24, 1938. The final result of the tests was generally positive, for which the series production of 16 copies was authorized.
Between August 26 and September 28, tests were carried out with the M-34FRN engines with turbochargers and VISH-3B propellers of 3.9 m diameter. The tests were carried out in conjunction with the NII VVS. A total of 13 flights were carried out, of which 6 were carried out at altitudes of more than 9000 meters. They aspired to reach 11,000 meters, but the poor work of the compressors did not allow this result to be achieved. With this new power plant, the empty weight of the aircraft grew by 910 kg, reaching 17,722 kg. The takeoff weight was close to 24 tons.
Only 12 copies had been built by the end of 1939, when production was halted in favour of the Túpolev TB-7. The built specimens were destined for the 5th Long Range Bomber Aviation Corps of the RKKA VVS in the Far East. In 1940 there were 6 DB-A bombers in service there. At the beginning of the war these aircraft were not transferred to the European region of the USSR, serving basically as transports until the end of their useful life.
In 1940 the problems presented with the production of the TB-7 brought to the table for discussions the issue of restoring the production of the DB-A, but from there it did not happen.
Among the possible development variants to eliminate the problems of the use of a lower performance powertrain than the projected one, the use of Charomsky AN-1 diesel engines was valued.
Records:
The 10 November of 1935 pilots MA Nyuxtikov and MA Lipkin set a new world record for the lifting 10 tons of weight to 7,032 meters high.
On 20 November 1935 these pilots set a new record holder for the lifting 13 tons to 4,535 meters.
The 14 May 1937 pilots GF Baydukov. NG Kashtanayev and LL Kerber flew in a DB-A on the Moscow – Melitopol – Moscow route covering 2002.6 km in 7 hours 2 minutes and 11 seconds with a payload of 5 tons. Two world records were set on this flight:
Speed of 280 km / h in distance of 1000 km with 5 tons of load.
Speed of 246 km / h in distance of 2000 km with 5 tons of load.
Variants:
DB-A – The initial prototype aircraft, with M-34RN engines, lost on a non stop flight Moscow to Fairbanks, Alaska.
DB-2A – The second prototype with many detail improvements and M-34RNV engines.
DBA – Production aircraft ordered in 1937. Sixteen aircraft ordered, but only twelve completed, with M-34FRN engines plus turbo-chargers, rearwards retracting main undercarriage, gunners cockpits in the rear of the inner engine nacelles, and other modificatoions.
TK-1 TK ( – heavy cruiser) – Projected escort bomber with 11 crew, 3xShVAK + 3,000 rounds, 5xShKAS + 11,000 rounds and underwing rockets.
Specifications:
DBA
Engines: 4 × M-34FRN + turbo-chargers, 970 hp
Wingspan: 39.5 m (129 ft 7 in)
Wing area: 230 sq.m (2,476 sq.ft)
Length: 24.4 m (80 ft 0-5/8 in)
Stabilizer wingspan: 12.5 m
Height: 8.50 m
Wheelbase: 7,690 m
Empty weight: 16,150 kg (35,605 lb)
Gross weight: 22,000 kg (48,500 lb)
Power load: 5.7kg / hp
Wing loading: 95 kg / m²
Maximum speed: 316 km/h (196.4 mph)
Maximum speed at 4000 m: 330 km / h
Cruising speed: 260 km / h
Range: 4500 km (2,796 miles)
Service ceiling: 7,730 m (25,360 ft)
ROC: 135 m / min
Climb to 1000 m: 5 min
Climb to 7000 m: 56 min
Crew: 6 – 9
Armament:
2 x ShKAS 7.62mm machine-guns in each of the inner nacelle gun positions.
1 x ShKAS 7.62mm machine-guns in nose and tail positions.
1 x ShVAK 20mm cannon in the dorsal turret.
5,000 kg of bombs in internal bomb-bay.
Victor Fiodorovich Bolkhovitinov (Russian: Виктор Фёдорович Болховитинов) was born on January 23 (February 4 according to the new calendar), 1899 in the city of Saratov, in the Soviet Union.
In Saratov Boljovitinov finished elementary studies with a gold medal and entered the medical school of the University of Saratov, but after a semester he understood that medicine was not his profession and requested a transfer to the physical-mathematical faculty. In 1918 he moved to Moscow, joining the MVTU.
In this institution, he listened to various lectures given by Nikolai Egórovich Zhukovski and fell in love with aviation. In 1921 he entered the Institute of Engineers of the Red Air Fleet, which would later become the Zhukovski Military Aeronautical Academy.
As a student, In 1924 he created the AVF-6 Favzayat and AVF-18 Pioner gliders, which participated in the national competitions at Koebel. Later he was part of a group of enthusiasts who designed a small plane.
In 1926 he finished his studies at the Zhukovski Air Fleet Academy and began working as an aviation mechanic at the Sevastopol Military Aviation School. Sometime later, he returned to the Academy, beginning his work as a teacher. From 1931 he was in charge of the projection work of the KB VVIA. From 1933 he directed the OKO de la Fábica No.22 and in 1937 he was appointed head of the Department of Aeronautical Construction.
Between 1934 and 1936 Bolkhovitinov led the work on the long-range heavy bomber DB-A, created as a development of the Tupolev TB-3 and in which between 1936 and 1937 Soviet pilots set 4 world records. The DB-A was produced in small series until 1940, being used as a transport.
Starting in 1936, Bolkhovitinov’s KB-22 was transferred to Kazan. In 1937 he was appointed main builder and entry into the ranks of the Communist Party of the USSR.
In 1939 he was appointed chief of the OKB-293, located in the factory of the same name in Khimki. In that year Bolkhovitinov directed the construction of the original “S” high-speed bomber with two counter-rotating propellers, which reached a speed of 570 km / h during testing. At the beginning of the 1940s, a ramjet took part in the installation tests on this aircraft, but development was abandoned at the beginning of the war.
Between 1941 and 1945 under his direction, engineers A. Ya Bereznyak and A. M Isayev developed the BI reactive engine interceptor fighter. In October 1941 the KB was evacuated to the outskirts of Sverdlovsk.
In 1944 AG Kostikov, head of the NII-3 reactive engine research institute, was arrested and Bolkhovitinov’s OKB-293 was unified with NII-1, a new reactive research institute.
Bolkhovitinov was appointed chief of investigations at NII-1 . In 1946 his OKB became part of the group led by M. Bisnovat, at Factory 293. As head of NII-1, Mstislav Keldish was appointed.
From 1947 Bolkhovitinov returned to work as a professor and chair at the Zhukovsky Military Aeronautical Academy, where he remained until his retirement.
Author of several books and publications related to aeronautical science.
He died on January 29, 1970 in Moscow and is buried in the Vvedienski cemetery.
Awards:
Twice Order of Lenin
Twice Order of the Red Banner
Order of the Red Banner of Labor Medals
By the 1930s the euphoria of record flights had reached pilots and political leaders alike in the world’s most developed countries. In 1937, after making their flights across the pole, Valeri Pavlovich Chkalov’s crew sent a letter to Stalin where they wrote:
“We understand your claims to allow us to fly outside the borders of the USSR in 1939. There is not so much time left for 1939, for this reason we are writing to you with the request to build an airplane with a range of 15 – 20 thousand kilometers with diesel engines and capable of flying at 8 – 10 thousand meters … “
In response in October 1938 a resolution was issued by the Commissioner of the aviation industry MM Kaganovich, establishing development in the BOK led by Chizhevski of the long – range aircraft, the BOK-15.
The BOK-15 aircraft design began in Smolensk and the BOK-7 was taken as the basis for development. The main directions of work were aimed at improving aerodynamics and increasing fuel capacity. Initially, the works were carried out slowly and only on July 9, 1938 did the commission to analyze the model meet, made up of the pilots Gromov, Yumashiev, Danilin and Petrov.
The fuselage was of the monocoque type with the pressurized cabin forming an integral part of it.
The BOK-15 wing featured traditional double spar construction, similar to that used on earlier BOK stratospheric aircraft. This scheme led to the wing spars going through the pressurized cabin. Each wing spar consisted of two steel tubes joined by duralumin walls. The space between the spar and the wing leading edge housed 12 tanks capable of holding 7.5 tons of fuel. The wing coating on the BOK-15 was smooth, using 0.6 to 1.5 mm thick duralumin sheets.
The tail unit was practically the same one used in the BOK-7 and BOK-11.
The landing gear was similar to that of the ANT-25, semi-retractable in the fuselage. The exposed parts were covered with fairing. The oleo-pneumatic system was calculated for the landing with the maximum weight of flight. The tail wheel did not retract.
The selected powerplant was the Charomsky AN-1RTK capable of developing 1,100 hp, driving a three-bladed propeller.
The BOK-15, for the first time in the USSR, featured a sealed ventilated cabin. Although this new cabin, calculated for three people, presented a number of new technological challenges, it was lighter by 300 – 500 kg than the regenerative type cabin used in the BOK-1.
Access to the cabin was through two doors, one at the top, for emergencies and the other at the bottom of the plane. The crew consisted of three: two pilots and a navigator. The two pilots sat side by side and had dual flight control. On the left seat, intended for the captain of the aircraft, a transparent drop-shaped cover was installed. The other pilot had only side visibility. The navigator was located in the back of the cabin, where the radio station and equipment for route calculations were located. In order to avoid the use of thermostats for the motor oil, the oil tanks were located inside the sealed cabin. On one of these tanks, on the right side of the cabin, there was a bed for the rest of the crew.
Due to the transfer of the BOK to KB-29 in 1939, the development of record-setting aircraft was slow. The decision to build two BOK-15 was finally made by the NKAP on 10 February 1939. However, construction had started some time before at the facilities of Factory No. 35 in Smolensk, after some discussions between Chizhevski and the NKAP commissioner Kaganovcih.
The first of the two were 10-12% ready by January 1, 1939. The tail unit, flight control mechanisms, power bank and landing gear were built on the KB-29 at Podlipki. The most technologically complex aggregates were ordered from Factory No.156.
The requirements for the new wing structure grew as the project continued to develop. Initially, keeping dimensions similar to those of the BOK-7 wing, emphasis was placed on strengthening the wing structure only in the area where the fuel tanks were located. After a few months, the TsAGI was tasked with selecting a more effective wing profile for the BOK-15. The factory was forced to develop a smooth, polished coated wing with a better finish quality.
Several very long-range flights were planned to be carried out with these two aircraft. According to initial calculations, the BOK-15 was to reach a distance of 24,000 kilometers without stops. This would make it possible to go around the world without stops and thus surpass the results of the North American pilots William Post and Howard Hughes. Even more spectacular flights were planned, such as the one around the world flying over the poles.
The calculated cruising speed was 240 km / h (about 70 km / h more than the ANT-25). To achieve these results it was necessary to use a diesel engine. The only candidate with these features was the AN-1RTK engine, developed in 1931. By 1935 the AN-1 had passed state tests in which at an altitude of 3000 meters it had been possible to set a nominal power of 850 hp with a fuel consumption of 170 – 180 liters per flight hour. A series production of 20 of these engines had been ordered at Factory No.24 in Moscow. The AN-1RTK version was turbocharged and weighing 1100 kg, developing a maximum power of 1250 hp (for about 5 minutes) and a rated power of 1000 hp at 5500 meters. Only this engine was capable of working in the air between 50 and 100 hours to reach the requested 18 – 24 km. The calculations showed a consumption of only 0.43 kg of fuel per kilometer of flight at the cruising speed of the BOK-15.
The data were only theoretical and were not proven. In practice the BOK-15 turbochargers were constantly failing. The oil losses were so great that the pilots were forced to carry a large additional tank with oil on board. All this had a negative influence on the engine’s consumption. It was necessary to make changes to the projected flight routes, since the aircraft’s range guarantee did not exceed 15,000 kilometers. Manufacturers even proposed to replace diesel engines with the carburetted AM-35TK designed by Alexander Alexandrovich Mikulin.
Preparation for flights began in 1939, long before the appearance of airplanes on the airfield. According to the order issued by No.0018 VVS on 21 January 1939 for the realization of long – haul flights were prepared two crews with the following composition:
All of these pilots, with the exception of navigators Spirin and Danilin, were released from their duty responsibilities and began preparation for the flight. This group of pilots received on January 25 DB-3, SB and R-5 aircraft for training, being located at the central airfield.
Preparation of the BOK-15s for flight was slow. The fault of the engine again, but the commissioner of the aeronautical industry MM Kaganovich, instead of giving his support to the KB-29 began to look for a culprit. The “enemy of the people” this time was VA Chizhevski.
In a letter Kaganovich wrote to Stalin of 28 January of 1938 he wrote:
“ The state of the construction and work apparatus of Chizhevski’s KB-29 is such that it does not allow to trust in the accomplishment of the great task that has been assigned to them in the construction of the BOK-15 plane … to be able to build this plane without Chizhevski it is necessary to assign this work to a large group of qualified builders and move their production to a more qualified factory … In the coming months it will be necessary to strengthen and clean the group of harmful people … With Chizhevski, act without delay ”.
Four days later, a commission report reviewing the BOK-15 technical documentation found an error in the number of the overload coefficient. In the opinion of the commission, the coefficient should be calculated not at 3, but at 3.5 to avoid the destruction of the aircraft in the event of extreme overloads. The argument that the ANT-25, capable of performing two flights across the North Pole to the United States, was also calculated using a coefficient of 3. On February 1, 1939 VA Chizhevski was arrested.
As of January 24, the TsIAM began the revision of the AN-1RTK engines for the BOK-15, receiving the task of delivering two units with BISh-34D propellers to the KB-29, but without a compressor, by March 15.
The first BOK-15 with AN-1RTK engine and 4.75 m propeller was completed on October 9, 1939. The first flight took place on October 17. Even before completing the tests, it was decided to install better quality wings on both aircraft that should allow for a greater range. This decision brought about great changes and for this reason as of 1 June 1940 the first example was only 80% ready and the second 50%. In Europe the war had already started so the decision to make the flight was rejected. The Soviet leadership decided to abandon all developments of the stratospheric BOK.
However, the development of the BOK-15 continued. Originally it was decided to change the engine to a turbocharged M-40F diesel engine TK-E88, which had completed 100 hours of testing in September 1940. Despite the fact that the engine showed lack of completion, it was decided to install this engine and start the flight tests. The M-40F developed 1500 hp at takeoff with a rated power of 1200 hp and had a weight of 1200 kg. As fuel it used kerosene.
Another engine that successfully passed the tests was the M-30 diesel, which was a version of the M-40. The main difference was the installation of a turbocharger on each side of the engine. In relation to weight and power, both engines were similar. The manufacturer Tulipov promised to have the M-30F ready with a maximum power of 1700 hp in the near future. This proposal led to the decision to prepare the second BOK-15 to install the M-30 engine. The beginning of the war did not allow these changes to be made. In 1941 the second of the BOK-15 was evacuated to Kazan.
In the summer of 1940 the first BOK-15 flown by Gromov was based at Department 8 TsAGI airfield in Ramenskoye, along with other stratospheric BOKs. On this date the plane was used for the filming of the movie “Valeri Chkalov”, painted with the colors and serials of the ANT-25. The remains of this aircraft were long in the Ramenskoye aircraft graveyard. At the end of the war the fuselage was still preserved there with the name “Stalinsky Marshrut” (Stalinian Route) painted on the side.
BOK-15
Powerplant: 1 Charomsky AN-1RTK 1200 hp diesel
Wingspan: 32.0 m
Wing area: 81.4 m²
Length: 15.75 m
Height: 5.77 m
Empty weight: 4679 kg
Fuel weight: 7500 kg
Maximum takeoff weight: 13.57 kg
Wing loading: 166 kg / m²
Maximum speed: 333 km / h
Cruising speed: 266 km / h
Maximum speed at 8000 m: 328 km / h
7500 kg weight ceiling: 11300 m
Range at 256 km / h: 13,500 – 15,000 km
Accommodation: 3
The BOK-11 was conceived as a development of the BOK-8 concept, in turn an armed military version of the BOK-7, but in this case with a new Charomsky ACh-40 diesel powerplant with mechanical supercharger and turbocharger. Initially the set of remotely controlled weapons was called BOK-11, but later the name was used for the armed aircraft, which was also sometimes named in the documents as SB (Stratospheric Bomber according to the Russian acronym for “Стратосферный Бомбардировщик »(СБ)).
Construction of the BOK-11 began in Smolensk in 1937 from specifications delivered by the VVS and confirmed on February 28, 1937. Completion of the aircraft was developed on the KB-29 in Podlipki in mid-1939.
As a difference, the pressurized cabin of the BOK-11 was designed for three people. The main task in the development of the BOK-11 was the fine-tuning of the weapon system and its remote fire control system, developed by Factory No.213. For the defense of the upper hemisphere, a synchronized installation with an electric drive was created. A remote control turret with periscope collimator was located in the lower part. The BOK-11 could carry between 500 and 1000 kg of bombs on external supports. The installation of photographic equipment in different combinations was also planned.
At the beginning of 1939 the BOK-11, with the AM-34FRN power plant, was delivered to Department 7 of the TsAGI for the installation and fine-tuning of the armament, but on May 24, together with the BOK-7, it was delivered for development. training of crews for long-haul flights. In practice, it was never equipped with weapons.
BOK-11
Powerplant: 1 Mikulin M-34FRN 890hp
Wingspan: 32.40 m
Wing area: 81.4 m²
Length: 16.00 m
Empty weight: 3900 kg
Maximum takeoff weight: 6564 kg
Speed at sea level: 240 km / h
Maximum speed at 10,000 m: 354 km / h
Landing speed: 90 km / h
Ceiling: 3800 m
Range: 2000 km
Accommodation: 3
The high-altitude experimental aircraft project began in 1935. The BOK-7 or SR (from the Russian acronym for Stratospheric Reconnaissance Plane – Стратосферный Разведчик – СР) was designed based on experience gained with the BOK-1 and was generally similar to the BOK-1.
Originally conceived as a stratospheric reconnaissance aircraft, it ended up being developed as a record-setting aircraft. It began to be projected in 1935 as a development of the BOK-1.
The BOK-7 was designed as a stratospheric reconnaissance aircraft, hence its name SR (Стратосферный Разведчик), capable of photographic reconnaissance at heights of 14 – 16 km. Because it was designed as an airplane for military use, it was decided to equip it with weapons. The BOK-7 was designed with two ShKAS machine guns in the wings and two other machine guns defending the rear hemisphere. The possibility of transporting 400 kg of bombs was also envisaged.
In 1937 these original plans were modified. It was decided to build two copies as a development of the BOK-7, the first intended to establish a world height record and the second in the military version, originally known as BOK-8.
The BOK-7 from the structural point of view was designed similar to the BOK-1. The main difference was that in this new model the airtight cabin was designed as an integral part of the aircraft structure. Two domes with several skylights protruded above the fuselage, one located over the pilot’s station and the other over the observer’s position.
The initial project envisaged the use of a fixed landing gear with trouser-type fairings, but during development a similar gear was returned to that used in the BOK-1, with drop-type fairings on the wheels.
Until mid-1938 the construction of the BOK-7 was developed at Factory No.35 in Smolensk. Then, with the decision to transfer the BOK to KB-29, the unfinished plane was transferred to the Moscow suburb of Podlipki. In September 1938 Alexander Alexandrovich Mikulin delivered the AM-34FRN engine with two turbochargers requested for its structure, with which the assembly of the aircraft was completed. On December 20, the construction work on BOK-7 was completed and on the 28th of that month a first short-duration straight-line flight took place.
There is no data about the first test flight of the BOK-7, but it is known that for its successful completion the KB-29 collective was awarded and its main constructor NN Kashtanov received a cash prize.
The BOK-7 was tested at the end of 1938 and presented performances not very different from those of the BOK-1, therefore the tests were not concluded. The test pilots were IF Petrov and PM Stefanovski. The fundamental reason for abandoning the tests was due to the fact that they failed to exceed expectations of setting new world height records. Again, the blame fell on the power plants.
In the spring of 1939, it was decided to use the BOK-7 and BOK-11 airplanes to prepare the crews for long-haul flights. For this reason, on 24 May 1939 the aircraft was delivered to pilot Gromov. Various crews that included Gromov, Yumashiev, Spirin, Baidukov, Beliakov, among others; They lived for several days in the airtight cabin of the plane, based on the ground, checking the feasibility of executing the complete life cycle. This served as training for the projected long-haul flights on the BOK-15.
During these tests everything worked without problems. The cabin proved its ability to be airtight. The air losses due to the few holes for the cables and control systems were compensated by the delivery of the oxygen system. However, it was decided to add an additional compressor in the future that worked powered by the engine.
The BOK-8 was designed as an armed development of the BOK-7. The conception of a military aircraft operating in the stratosphere brought with it the impossibility of using defensive systems of the traditional type. The weaponry was made impossible to handle in the thick pressurized suits and diving suits. It was necessary to develop a defensive weapons control system that could be operated from the pressurized cabin. This task was successfully solved in 1938 with the design and laboratory testing of the first remote weapon control system.
The new armament control set consisted of a synchronized electro-automatic sighting system with collimator designed by Riezunov and located in the second turret above the navigator’s cockpit and a system capable of controlling fire from the sealed cockpit designed by the engineers. VS Kostishkin and KB Zhbanov, who operated a machine gun located on the fuselage, outside the cockpit.
The installation of this system was carried out on the BOK-7. It is noteworthy that this remote fire control system was developed long before the appearance of similar systems in the United States on Boeing B-29 Superfortress bombers. The development was materialized in the BOK-11.
Later, on the basis of the BOK-7, the BOK-10 projects were developed for a high-altitude reconnaissance plane, BOK-12, an atmosphere research plane and the BOK-13 as a passenger plane. All these variants did not go beyond the project table.
BOK-7
Powerplant: 1 M-34FRN 890hp
Wingspan: 32.40 m
Length: 14.85 m
Wing area: 81.4 m²
Empty weight: 3400 – 3600 kg
Takeoff weight: 4814 kg
Maximum speed at 9000 m: 350 km / h
Landing speed: 86 km / h
Practical ceiling: 15,200 m
Accommodation: 2
All Aero 