Józef Borzęcki choose Olesno Śląskie as his place of residence. There, he designed and built the fourth ultra-light structure called JB-4 “Skowronek”.
In the fall of October 29, 1989, in the presence of Elżbieta’s daughter, “Skowronek” made several successfully completed take-offs and landings. A year later, on October 14, 1990, he made his last flight. From a height of 200 m, while descending to land, the left wing girder was broken. On this day, Józef Borzęcki died.
In late 1960s Józef Borzęcki undertook a rebuilding of his Stratus motor glider. The aircraft was fitted with wings from Komar (mosquito) glider, lighter and providing better glide ratio and flat two-stroke four-cylinder RB2 engine, designed by J. Borzęcki out of two connected Riedel starter engines from German Junkers Jumo 004 turbojet engine from World War II.
After this rebuilding the motor glider was named Altostratus and first flew in 1972. It remained in use until 1982.
Since 1994, “Altostratus”, as the only surviving structure of Józef Borzęcki, was transferred to the Polish Aviation Museum in Krakow.
Engine: RB2 Four-cylinder two-stroke, 18 kW (24 hp)
Span: 10 m (32.8 ft)
Length: 5.5 m (18 ft)
Empty weight: 90 kg (198 lb)
Take-off weight: 160 kg (353 lb)
Glide ratio: 20
Sink rate: 0.9 m / s
Maximum speed: 100 km / h (54 kt)
Minimum speed: 48 km / h (30 kt)
In the autumn of 1967, Józef Borzęcki began preparations for the construction of the “Cirrus” motor glider (“Salamandra moto”). In its construction, he used the experience gained while working on the “Stratus” motor glider. In the airframe, the designer used a number of wooden construction details from the school glider IS-A “Salamandra 53” (SP-1161) Kiibelwagen. He used a Volkswagen Kübelwagen car engine that he converted. A technical curiosity was the so-called elastic chassis, made of special shock-absorbing steel. The chassis on a single spring shank in the shape resembling the letter M was made of railway spring steel. This type of chassis designed and constructed by Borzęcki was the first of its kind in Poland to be used for light aircraft. The plane had, like “Stratus”, coupled control only by means of a joystick.
Looking for new solutions and constructional improvements, he used, among others double engine speed control system. It consisted in the fact that the aircraft also had a gas throttle mounted on the inside of the pilot’s cabin (as in a normal plane), and a car-type foot pedal, whose pressure increased the engine speed. These two control systems operated independently. The builder of Cirrus took the propeller-engine assembly very seriously. He took an exhaust gas analyzer, connected to the engine exhaust system, to the cabin. Flying at different heights, the amateur designer and pilot simultaneously selected the optimal composition of the gas-air mixture. The end result of these efforts was a significant engine economy with good performance of power.
“Cirrus” was flown on October 22, 1967. It had the characteristics of an ordinary glider after switching off the engine in flight. The powered glider carried out many flights in different weather conditions and seasons. Some of them on the ceiling 3000-4000 m and sometimes lasted 2-3 hours, with the engine turned on and off, circling in the thermals, enjoying a slow flight. For several years of using Cirrus, there were no accidents. The constructor flew about 2000 hours on it.
The constructor’s activities were revealed by a press article in 1968 and in 1969, unknown perpetrators destroy the motor glider, which, however, was rebuilt and flown. From 1971, the motor glider was hangar in the hangar of the Wroclaw Aeroclub, where in 1972 unknown perpetrators destroy Cirrus again, this time completely.
Engine: Volkswagen, 21 kW (28 HP).
Span: 12.5 m
Length: 6.5 m
Height: 1.95 m
Wing area: 16.8 sq.m
Empty weight: 200 kg
Total weight: approx. 300 kg.
Permissible speed: 140 km / h
Max speed: 120 km / h
Landing speed: 45 km / h
Minimum speed: 42 km / h
Rate of climb – 1.4 m / s
Glide: 12 / 1.3-1.5 m/s
Theoretical ceiling: 5000 m
Range: 400 km
The ‘D’ design was started in 1941 by Alexei Andreeyevich Borovkov & Ilya Florenteyevich Florov as a mixed power fighter with a piston engine and Merkulin ramjet booster. A 1,500 kW (2,000 hp) Shvetsov M-71 engine was intended to be the main powerplant but it is unclear how the thermodynamic cycles of the two engines were to be linked. Similar aircraft were built later in the German-Soviet War using the main engine to drive a propeller and a compressor to supply air to a ramjet/afterburner booster, both the Su-5 and MiG-13 were produced in limited numbers but the performance gains were limited and soon eclipsed by turbo-jet engines.
The ‘D’ was to have been a gull- winged monoplane with high set wing, of stressed skin construction with exceptionally smooth skin stabilised by underlying corrugated structure. The cockpit featured a pneumatic ejection system which rotated the seat downwards and fired it clear of the propeller arc.
A heavy armament of two 37 mm (1.457 in) Nudelman-Suranov NS-37 cannon and two 20 mm (0.787 in) ShVAK cannon was included, but all work was abandoned with the German invasion of 1941.
Powerplant: 1 × Shvetsov M-71, 1,600 kW (2,200 hp)
Powerplant: 1 × Merkulov DM-12 ramjet
Wingspan: 14.8 m (48 ft 7 in)
Length: 11.67m
Wing area: 35m²
Top Speed: 837km/h (with ramjets)
Max. Cruise Speed: 600km/h (without ramjets)
Crew: 1
Armament:
2x 37 mm (1.457 in) Nudelman-Suranov NS-37 cannon
2x 20 mm (0.787 in) ShVAK cannon
After eight months from the destruction of the “7211”, Borovkov and Florov were called to Moscow, where it was proposed to them to continue the development of the original biplane. On 13 September 1938 both builders presented a new preliminary draft of its Object 7 changed this time with a Tumansky M-88 1000 hp engine and sealed cabin.
The project was reviewed and approved, but soon the director of Factory No.21 reported that building a new experimental model in his factory would be impossible due to the lack of productive capacities and requested that the new model be removed from his development plan. In this situation Borovkov and Florov were instructed by GUAP to gather as few personnel as possible and move to the territory of Factory No. 207 located in the city of Dolgoprudni, near Moscow. In this new facility these engineers continued their developments, building several biplanes that became known as I-207.
Factory No.207 was created with the objective of producing airships, which is why it was commonly known as “Dirizhablestroi” and at that time it presented a lot of problems. The construction of the military airship DP-16, conceived for the air defense of Leningrad, was progressing with difficulties, for which the factory managers received constant reprimands and sanctions. By early 1938 the arrests had begun, which included the factory manager and several workers. The new principal Gorin had too many problems to solve and therefore paid too little attention to the new builders.
It was practically not until April 1939 that work began on Borovkov and Florov’s new fighter. Initially, two copies were built, both under the name I-207 (Factory Hunting No.207). The first specimen had an M-62 engine and was named “Object 7” No. 1 (I-207/1).
The three prototypes delivery date were set as September, October and November 1938.
Borovkov served as head of the factory’s building and drawing department (ChKO) (sometimes also called series monitoring department or CKO) and Florov headed a group of builders directly subordinate to NN Polikarpov, so in fact he could be considered main factory builder. The position of NN Polikarpov towards the new fighter was known.
In the summer of 1938, the advances in the new fighters of Borovkov and Florov were little. Kaganovich decided to appoint Mikhail Pashinin as the main builder of Factory No.21, who came to Gorky not only with the task of directing, but with the idea of building his own fighter model here.
Under these conditions, Borovkov and Florov were given the option of setting up their own production base at Factory No. 207 located in the city of Dolgoprudni, on the outskirts of Moscow. They were allowed to take only 12 collaborators with them. After a visit by Yakov Vladimirovich Smushkievich, it was decided to start work on the new fighter prototypes.
The first example, with a Shvietsov M-62 engine, was designated at the factory “Object 7 No.1” or I-207/1.
The I-207/1 was generally similar to the “7211” prototype. It kept the fixed landing gear and fairing, but introduced a somewhat longer fuselage, the windshield was fixed in the open cockpit, and a number of constructive improvements.
The fuselage featured mixed construction. The central part, which connected to the engine, was designed of welded steel tubes (30JGSA), covered with easily removable thin metal sheets, which facilitated maintenance and repair actions. In this central section the wings were fixed. The tail section was constructed of wood with a monocoque structure built with birch veneers on a lightweight skeleton, similar to that used on the I-16.
The wings were 14% thick at the wing and 6% at the ends and featured an all-metal construction with a smooth coating and great aerodynamic cleanliness.
Both wings had the same dimensions. The structure was covered with corrugated metal in layers to which smooth 0.5 mm duralumin sheets were attached, forming a honeycomb-like structure. The wing upper surface had two layers of corrugated metal, one 1 mm and the other 0.8 mm. Only a 0.8 mm thick corrugated duralumin layer was used on the soffit.
By using the coating as a structural component, the resistance was considerably increased, while achieving a noticeable reduction in weight. This also allowed the stringers to be eliminated, preserving only the metal ribs obtained by pressing. The wing weight on the NII VVS returned a relative weight of only 13.6 kg / m².
The upper wing featured flaps and was fixed to the fuselage structure by 4 short supports reinforced with steel turnbuckles. The lower wing contained the ailerons and braking surfaces.
The 850-hp, air-cooled M-62 radial engine was selected as the power plant, covered by a hood that highlighted the fairings for the cylinder heads and lacked the side gates. An air intake was added in the upper part. A VISh-26 propeller with 2 blades and 2.8 m in diameter was selected. The small size of the aircraft did not allow for a larger propeller.
The I-207/1 kept the cockpit moved rearward in order to improve the pilot’s visibility. This lacked protection, although it was considered that the radial engine should guarantee adequate protection in frontal encounters.
The landing gear was designed as a fixed type with the wheels and the landings fairings, introducing a tail wheel at the base of the rudder to replace the original 7221 skid.
The armament consisted of four ShKAS 7.62 mm machine guns with 2,200 rounds.
I-207/1 was taken to the airfield in June 1939. On the 29th of June, the test pilot LM Maximov made the first flight. Joint testing (factory and acceptance) at the NII VVS lasted until October 2nd. Apart from LM Maximov, the prototype was also flown by PM Stefanovski. The document with the conclusions was signed by MM Kaganovich and AD Loktionov on October 5.
The expected top speed of 490 km / h could not be reached. The I-207/1 reached only 437 km / h at a height of 4750 meters. In general, in all its aspects the I-207/1 was comparable to the Polikarpov I-153 and against it it was compared. Using the same Shvietsov M-62 engine, the I-207 was heavier at 213 kg. The turn time was 19 – 20 seconds against the 13 – 14 reached by the I-153, while in relation to the ascent speed the I-207 reached 5000 meters in 6.2 minutes (0.5 minutes less than the Polikarpov fighter).
The I-207/1 was found to have no advantages over Polikarpov’s biplane and maneuverable fighters and the I-153 was already in series production. It was also noted that the fixed landing gear was obsolete and affected performance. The small dimensions of the plane made it necessary to use a very small diameter propeller, which could only be solved with a reducer that allowed to increase the revolutions.
Despite this, the excellent flight and operating characteristics of the I-207 were recorded and it was recommended to develop a small series with the aim of achieving a reduction in weight, installing retractable landing gear and increasing maximum speed. With a retractable undercarriage, the I-207 was predicted to be similar to or superior to the Polikarpov I-153.
The purpose of the I-207/2 was to serve as a backup to the I-207/1 evidence, which is why in the documents of the time it was called “dublior” or duplicate.
The second example, called “Object 7” No. 2 (I-207/2) was built with an M-63 engine. Both examples were characterized by having fixed landing gear and were fundamentally different from the 7211 prototype in presenting an elongated fuselage and constructive improvements. One of the main characteristics of the model was its high technological level, designed to facilitate the production process.
The I-207/2 was generally similar to the I-207/1. It kept the fixed landing gear and fairing and the windshield was fixed in the open cockpit, but with small differences in its construction.
The fuselage featured mixed construction. The central part, which connected to the engine, was conceived of welded steel tubes (30JGSA), covered with easily removable thin metal sheets, which facilitated maintenance and repair actions. In this central section the wings were fixed. The tail section was constructed of wood with a monocoque structure built with birch veneers on a lightweight skeleton, similar to that used on the I-16.
The wings were 14% thick at the wing and 6% at the ends and featured an all-metal construction with a smooth coating and great aerodynamic cleanliness.
Both wings had the same dimensions. The structure was covered with corrugated metal in layers to which the smooth sheets of duralumin were fixed, forming a honeycomb-like structure. Unlike the I-207/1, the coating was made with 0.8 mm sheets. The wing upper surface had two layers of corrugated metal, one 1 mm and the other 0.8 mm.
Only a 0.8 mm thick corrugated duralumin layer was used on the soffit. By using the coating as a structural component, the resistance was considerably increased, while achieving a noticeable reduction in weight. This also allowed the stringers to be eliminated, preserving only the metal ribs obtained by pressing. The wing weight on the NII VVS returned a relative weight of only 13.6 kg / m².
The upper wing featured flaps and was fixed to the fuselage structure by 4 short supports reinforced with steel turnbuckles. The lower wing contained the ailerons and braking surfaces.
The M-63 air-cooled radial engine with a nominal 930 hp, covered by a NACA hood with skirt-type side gates, was selected as the powerplant. The installation further ahead of the M-64 and M-65 engines, obtained as a development of the M-63, was also envisaged. The fuel system in this specimen was modified, since by increasing the wing drag it was possible to place the initially projected fuel tank in the upper wing.
The I-207/2 kept the cockpit moved rearward in order to improve the pilot’s visibility. This lacked protection, although it was considered that the radial engine should guarantee adequate protection in frontal encounters.
The landing gear was designed as a fixed type with fairings and wheels. The tail wheel was also faired.
The armament consisted of four ShKAS 7.62 mm machine guns with 2,200 rounds.
State testing of this model took place between 17 September 1939 and 22 May 1940. Nikolayev (for the NII VVS), Maximov (for Factory No.207), Kubyshkin and Stefanovski were selected as test pilots. A total of 22 flights were flown with a total of 12 hours. The tests showed that the manoeuvrability of the aircraft was not satisfactory. The turn time at 1000 meters was 18 – 18.8 seconds instead of the requested 12 seconds. The ascent time to 8000 meters was 15 minutes against the 8 established in the requirements. Top speed only reached 422.5 km / h. With these terrible results, the rest of the benefits were not even tested.
The test report found that despite the increase in power from the new engine the results were generally lower than those obtained with the I-207/1, so the result was unsatisfactory and soon the interest in this prototype disappeared. It was dismantled shortly before the war.
Only shortly after starting the construction of the two “Object 7” at Factory No.207 began construction of an improved model which was designated “Object 8 No.3” and later I-207/3. This prototype introduced a significant number of improvements, among which the retractable landing gear and a motor with reducer stood out (which could not be installed because it was not available). The I-207/3 was generally similar to the I-207/2.
The fuselage featured mixed construction. The central part, which connected to the engine, was conceived of welded steel tubes (30JGSA), covered with easily removable thin metal sheets, which facilitated maintenance and repair actions. In this central section the wings were fixed. The tail section was constructed of wood with a monocoque structure built with birch veneers on a lightweight skeleton, similar to that used on the I-16.
The wings were 14% thick at the wing and 6% at the ends and featured an all-metal construction with a smooth coating and great aerodynamic cleanliness.
Both wings had the same dimensions. The structure was covered with corrugated metal in layers to which the smooth sheets of 0.8 mm duralumin were fixed, forming a honeycomb-like structure. The wing upper surface had two layers of corrugated metal, one 1 mm and the other 0.8 mm.
Only a 0.8 mm thick corrugated duralumin layer was used on the soffit. By using the coating as a structural component, the resistance was considerably increased, while achieving a noticeable reduction in weight. This also allowed the stringers to be eliminated, preserving only the metal ribs obtained by pressing. The wing weight on the NII VVS returned a relative weight of only 13.6 kg / m².
The upper wing featured flaps and was fixed to the fuselage structure by 4 short supports reinforced with steel turnbuckles. The lower wing contained the ailerons and braking surfaces.
As a power plant, it maintains the M-63 radial engine with air cooling and nominal 930 hp, covered by a NACA hood with inlet regulation windows and skirt-type side doors. The selected propeller was the 2.8 m AV-1 two-blade automatic.
The landing gear was designed of the retractable type, maintaining the conventional design with a faired tail wheel. The main landers were constructed of chrome-plated steel tubes. The retraction system was novel, or at least unusual, because instead of retracting into the wing or fuselage by pivoting over a point, these landers did so by rising vertically until they were covered inside the fuselage. Once the undercarriage retracted, the opening was covered with a fairing. The tail wheel was fixed.
The I-207/3 kept the cockpit open and moved rearward in order to improve the pilot’s visibility. The armament consisted of four ShKAS 7.62 mm machine guns with 2,200 rounds.
I-207/3 was built between June 1939 and April 1940. In compliance with NKAP order No. 124 of April 22, 1940, the state tests of this model were started. These tests took place between April 22 and June 7 at the NII VVS and comprised 30 flights with a total duration of 13 hours and 20 minutes. These flights were executed by pilot LM Maximov.
During the tests, the excellent speed of 486 km / h at 5000 meters was reached and the turning time decreased to 17 seconds (still higher than the 12 requested). These values were already interesting. Due to its results, the I-207/3 surpassed the I-16 of the latest versions in all its characteristics. It was considered that with the installation of the new M-64 or M-65 engines, the maximum speed could be brought to 550 km / h.
The I-207/3 demonstrated excellent stability and a very good response to controls at all speed ranges. Take-off and landing operations were straightforward and the plane kept the course smoothly. The chopping was carried out with great stability and it was easy to get out of the augers. The aircraft was undemanding to maintenance and steps had been taken to facilitate service.
On the other hand, the introduction of the retractable undercarriage decreased the weight of the aircraft, solving an old model problem. This made it possible to use the aircraft for other tasks by being able to increase the payload capacity with fuel or bombs.
The Winter War with Finland demonstrated the importance of having punctual bombing planes, capable of attacking specific objectives such as bridges, railway junctions, buildings and military objectives. The VVS launched a call to urgently develop dive bombers capable of accomplishing these tasks.
Borovkov and Florov, realizing that the biplane design had lost its moment as a fighter, decided to seize this opportunity. Vaxmistrov had developed a version of his Zvenó that used two Polikarpov I-16 fighters under the wings armed with two FAB-250 bombs. Modifications to these attack I-16s were made at Factory No.207 itself. With the new changes, the I-207 presented the ability to carry the same armament, overcoming some of the limitations of the monoplane fighter.
The I-207/3 was urgently modified, providing it with underwing supports for two FAB-250 bombs. The tests of the airplane took place between September and October 1940 and in them it was possible to demonstrate the feasibility of the model for this task.
Unlike the I-16, which lacked the power to take flight with the two bombs, the I-207 could take off with this load without difficulty, maintaining stable flight and good control. The dive for the bombardment was carried out at angles of 70º. It was proposed to increase the firepower by replacing the ShKAS machine guns with others of greater caliber without affecting the weight, as well as to assess the possibility of using non-directed rockets.
During the development of the tests, the NII VVS was visited by Kliment E. Voroshilov, who positively assessed the aircraft and promised to obtain authorizations to build a series of 200 copies.
Despite Voroshilov’s promise, it was not mass-produced due to its poor range, which at that time was considered essential for a bomber.
Despite the gain in benefits, “Object 8” was already unable to meet the demands of 1940. Although its speed could already be considered superior to the latest modifications of the Polikarpov I-16, it was surpassed by almost 100 km by the new Yak, MiG and LaGG monoplane fighters.
For this reason, and in order to increase performance, the I-207/3 was used as a test bed for the DM-4 ramjet designed by IA Merkulov. This auxiliary power plant used the same fuel as the piston engine. Two units were installed under the lower wing, in the position of the supports.
During the tests it was found that with these engines turned off, the speed of the aircraft decreased by 12 km / h, due to the increase in aerodynamic resistance. With the engines running, the increase achieved was about 24 km / h. it was not really much, but calculations showed that this gain increased if the aircraft was accelerated before turning on the auxiliary engines. Around 20 flights were made without any accident occurring.
Taking into account the experience of the I-207/3 tests, between the end of 1940 and the beginning of 1941 at Factory No.207 a new version of the I-207 known as “Object 9” or “Deviatka” was built. Shortly afterwards it received the denomination I-207/4 and in some literature it has been named I-209, although this name was never official.
This model was designed to use the M-65 engine and was to serve in manoeuvrable fighter and dive bomber roles. The use of the M-64 and M-65 engines should allow achieving the desired speed of 550 km / h.
The “Object 9” project was essentially completed by May 1, 1940, but its construction ran into a number of problems. The I-207 fighter was removed from the aircraft industry’s experimental construction plan for 1940. The financing was cancelled and the workers assigned to its construction were redirected to other activities.
Borovkov and Florov were forced to go to the headquarters, achieving a meeting with the new Commissioner Shajurin. The introduction of the model as a dive attack aircraft sealed its fate and approval was soon obtained for further development.
The I-207/4 attack was designed in two versions; with fixed gear and with retractable gear. The fundamental reason for this decision was given by the results of the calculations depending on the load. The retractable train provided better performance and could guarantee the dive bombardment of two 250 kg or four 100 kg bombs, but in order to transport a 500 kg bomb in the center of the fuselage it was considered necessary to keep the train fixed. The armament also included two 12.7 mm machine guns.
According to the calculations, the version with the retractable train had to develop about 470 km / h at 6500 – 7000 meters and 405 at sea level. The 7000 meters could be reached in 9.5 minutes.
The fixed undercarriage version with a 500 kg bomb delivered a calculated speed of 396 km / h at altitude and 350 km / ha at sea level. The ascent time to 7000 meters was calculated to be 19 minutes.
Eventually neither the M-64 nor the M-65 were produced, so the manufacturers were forced to settle for the Shvietsov M-63R (M-63AR) engine with an elongated shaft and a reducer. This made it possible to modify the shape of the nose, thereby improving aerodynamics.
The I-207/4 was fitted with a three-meter diameter VISh three-blade propeller. The cabin of this version was conceived closed with the cover opening to one side. The landing gear remained retractable type.
Under the wings it could carry two FAB-250 or four FAB-100 bombs. The conceived armament included two 12.7 mm BS machine guns, although it is not known that they could have been installed.
The I-207/4 was finally built in the spring of 1941 and made several flights, but by this time the interest in the biplane configuration had disappeared and with the start of the war the tests were never finished. The last prototype of the I-207 fighter built.
The fate of the prototype fighters built was as follows: The I-207/2 ended up serving as an experimental aircraft in the TsAGI’s T-104 wind tunnel tests. The I-207/3 with retractable undercarriage was for some time based at the LII airfield in Ramenskoye until it was damaged. After repairs, this plane received a ramjet engine designed by Merkulov, making about twenty flights.
It was proposed to deliver the first two airplanes (with fixed train) to the Moscow air club of the MAI, but the director of the LII, MM Gromov categorically opposed it, considering that the I-207 was too complex a plane to be used in sports flights. Finally in the autumn of 1940 the substitute of the commissioner of the aeronautical industry for experimental aviation, AS Yakovlev, decided to deliver these two copies as a static exhibition at the MAI. At the beginning of the war, it was decided to dismantle the exhibited specimens and all their useful elements to donate them to the industry. This was the final destination of the I-207.
I-207/1 / Object 7
Powerplant: Shvietsov M-62, 800 hp and 930 hp at takeoff
Wingspan: 7.00 m
Wing area: 18.00 m²
Length: 6.34 m
Empty weight: 1622 kg
Loaded weight: 1950 kg
Flying weight: 1975 kg
Wing loading: 109.7 kg / m²
Power load: 2.0 kg / hp
Maximum speed at sea level: 387 km / h
Maximum speed at 4000 m: 436 km / h
Landing speed: 115 km / h
Ascent time to 5000 m: 6.2 min
Practical ceiling: 9150 m
Spin time: 19.2 sec
Range: 700 km
Take-off run: 196 m
Armament: 4 ShKAS machine guns with 220 rounds
Accommodation: 1
I-207/2 / Object 7
Powerplant: M-63, 930 hp and 1100 hp at takeoff
Wingspan: 7.0 m
Wing area: 18.0 m²
Length: 6.34 m
Empty weight: 1590 kg
Flying weight: 1951 kg
Wing loading: 108.7 kg / m²
Power load: 1.8kg / hp
Maximum speed at sea level: 397 km / h
Maximum speed at 4000 m: 422 km / h
Landing speed: 115 km / h
Ascent time at 5000 m: 6.7 min
Practical ceiling: 9200 m
Spin time: 18.1 sec
Endurance: 2h
Armament: 4 ShKAS machine guns
Accommodation: 1
I-207/3 / Object 8
Powerplant: M-63, 930 hp and 1100 hp at takeoff
Wingspan: 6.98 m
Wing area: 18.00 m²
Length: 6.34 m
Height: 3.46 m
Empty weight: 1521 kg
Flying weight: 1879 kg
Wing loading: 102.7 kg / m²
Power load: 1.7kg / hp
Maximum speed at sea level: 437 km / h
Maximum speed at 2000 m: 453 km / h
Maximum speed at 5300 m: 486 km / h
Cruising speed: 405 km / h
Landing speed: 110 km / h
Ascent speed: 1087 m / min
Ascent speed at sea level: 18.9 m / sec
Ascent speed at 2000 meters: 20.4 m / sec
Ascent time at 5000 m: 4.6 min
Turn time at 1000 m: 17 sec
Practical ceiling: 10,200 m
Practical range at 90% of maximum speed: 500 km
Take-off run: 165 m
Landing run with brakes: 200 m
Armament: 4 ShKAS machine guns with 2200 rounds
Accommodation: 1
I-207/4 / Object 9
Powerplant: M-63R, 930 nominal hp gearbox and 1100 hp at takeoff
Wingspan: 7.0 m
Wing area: 18 m²
Length: 6.98 m
Flying weight: 2215 kg
Wing loading: 123 kg / m²
Power load: 2.0kg / hp
Maximum speed at sea level: 489 km / h
Maximum speed at 5000 m: 583 km / h
Landing speed: 115 km / h
Ascent time to 5000 m: 4.4 min
Practical ceiling: 10,500 m
Range: 640 km
Armament: 4 ShKAS machine guns with 550 rounds per weapon
Accommodation: 1
The head of the VVS, Alksnis determined that the Air Force would need both fast monoplane and manoeuvrable biplane, which should complement each other in battle.
To solve these contradictory requirements Florov and Borovkov proposed a biplane wing structure with thin profile wings and totally free of braces or struts. The basis for this idea was supported by the work carried out by IV Ostoslavski which demonstrated the improvement of the lift capacities of the wing by using the air flow generated by the propeller and the work of the German scientist L. Prandtlya on drag.
Based on this reasoning, the idea of two young engineers who proposed to achieve in a single model an airplane capable of combining both potentialities seemed quite attractive and Alksnis decided to support the project. It is noteworthy that in this case there was no governmental or aeronautical industry resolution. Nor did the factory manager, Miroshnikov, have any information on the development.
The new model was designed with some influence from the Polikarpov I-16 fighter. This was seen mainly in the profile view of the fuselage, but the similarity between the two planes did not go beyond there. The new aircraft featured the cockpit moved rearward in order to improve pilot visibility. Another notable difference was the smooth coated metal wings and great aerodynamic cleanliness.
These wings, with a wingspan of only 6.98 meters, had a corrugated metal structure to which the smooth sheets of the coating were fixed, forming a honeycomb-like structure, which contributed considerably to the increase in resistance and allowed a significant decrease in weight (the wing weighed only 110 kg and the relative weight was 12.23 kg / m²).
The upper wing was fixed to the fuselage structure by four short supports reinforced with steel tensioners.
The fuselage featured mixed construction. The central part, which connected to the engine, was conceived of welded steel tubes (30JGSA), covered with easily removable thin metal sheets, which facilitated maintenance and repair actions.
In this central section the wings were fixed. The tail section was constructed of wood with a monocoque structure built with birch veneers on a lightweight skeleton, similar to that used on the I-16.
As the power plant, the Tumansky M-85 14-cylinder double-row air-cooled engine was selected, with a power of 800 hp at 3850 meters of altitude. The power plant included a NACA-type hood and a three-bladed propeller.
The cockpit lacked protection, although the radial engine was considered to provide adequate protection against frontal encounters. The windshield was moved forward through rails located on the sides of the fuselage. The aircraft envisioned an armament of four 7.62mm ShKAS machine guns with 2,200 rounds, but was never installed.
The landing gear was designed as a fixed type with fairings and wheels. The tail skid was also faired with the particularity that it was conceived as a continuation of the rudder and could be retracted by compressing the shock absorber.
At the beginning of 1936, a life-size wooden model of the new model was ready. On one of its plywood sides was written in ink in large handwritten letters “Accepted. Alksnis”.
From this moment the production of the prototype began. Its creators called it “Object No.7”, but in official documents the plane was named 7.21.1 (seventh type of Factory No.21, first copy). The process of projection, construction and preparation of the new plane took a few months and only by the end of the year was the prototype ready.
Despite Alksnis’s signature, Object 7 was something “illegal” in the production process and for this reason it was worked on whenever possible and on weekends at Factory No.21, Gorky.
The civil war that began in Spain in 1936 demonstrated the potentialities of the I-15 biplane in combat and soon the interest towards this scheme strengthened. At the end of 1936, Polikarpov was asked for an accelerated upgrade of its biplane with the aim of relaunching its production. The creators of “Object 7” were also pressured, especially considering that the plane was practically finished.
The 7211 was taken to the airfield in March 1937, when the snow began to give way. Between 17 and 19 the first runs were held, but the flights were postponed to May, waiting for the runway to dry out. On 6 May 1937 LM Maximov made the first flight of 15 minutes around the airfield.
Over a month of test flights, the plane accumulated 22 flights. On June 1, 1937, the 7211 was flown by PM Stefanovski, who made a positive assessment of the plane. The ease of piloting, the simplicity of take-off and landing and the excellent stability in all flight regimes were highly valued, which allowed the model to be flown by pilots without great preparation. The rearward shift of the cockpit improved visibility.
In terms of manoeuvrability, the “7211” occupied an intermediate position between the I-15 and the I-16. The turning time at 2000 meters was 14 seconds and the ascent time at 5000 meters was 4 minutes and 37 seconds (for the Polikarpov I-15 it was 6 minutes and for the I-16 it was 7 minutes).
The maximum speed reached at 4000 meters was 416 km / h and was considered insufficient, especially since the calculations were 480 – 500 km / h. However, it was considered that with better construction completion and selection of the propellor the expected results could be achieved.
The Head of the Republican Aviation and the Madrid Air Defense, Yakov Vladimirovich Smushkievich, recently arrived from Spain, was also interested in the model. It was urgently decided to develop state tests and send the aircraft to the NII VVS Shelkovo airfield, outside Moscow. Experienced test pilot Edgar Yuganovich Prieman was selected for this flight.
On June 22, Prieman made the first familiarization flight in the “7211”. This flight was the 24th flight on the plane and ended in catastrophe. After making a first circuit, Prieman had to land, but at the last minute he changed his mind and put power on to make a second circuit. When accelerating, the engine suddenly failed.
The pilot decided to make a sharp turn and the plane, lacking power, ended up crashing into the railway embankment. The nose of the plane was destroyed and the pilot, thrown from his seat, died when his head hit the rails.
The causes of the accident was an obstruction in the carburettor. Despite the fact that it was a known and frequent cause, times were too turbulent and it was necessary to find culprits. The director of Factory No.21, Miroshnikov and the main builder of Factory No.29 of engines in Zaparozhie, AS Sakharov were arrested. Reprisals were also expected towards Borovkov and Florov for their direct relationship with a failed model and, on the other hand, the fate of the model was hanging by a thread.
Several specialists were asked to assess the model. Among them was NN Polikarpov, who harshly criticized the work of the young specialists. A conclusive report of September 28 is preserved with his signature and addressed to AN Túpolev, who at that time was temporarily in charge of the People’s Commissariat for the Defense Industry (NKOP). This report specified:
These conclusions by Polikarpov about a disgraced plane could have several interpretations, but scholars agree that the success of “Object 7”, which was built in a factory that produced its models and was preparing to introduce new versions of the I -16 and your new “Ivanov” monoplane, could affect your interests. On the other hand, there may be other personal reasons as the “7211” was developed without your authorization.
Despite these evaluations, towards the end of September the government decision to mass-produce the model 7211 was issued. Unfortunately, and for unknown reasons this authorization never reached Factory No.21 in Gorky. The young builders weren’t in a position to be pushy either, as the project’s main mentor, Alksnis, was arrested in November, making it even better not to create too much noise.
Powerplant: 800 hp Tumansky M-85
Wingspan: 6.98 m
Wing area: 18 m²
Length: 5.88 m
Empty weight: 1,355 kg
Flying weight: 1745 kg
Wing loading: 97 kg / m²
Power load: 2.1kg / hp
Maximum speed at sea level: 365 km / h
Maximum speed at 5000 m: 416 km / h
Landing speed: 110 km / h
Ascent time at 5000 m: 4.37 min
Practical ceiling: 6,880 m
Range: 700 km
Endurance: 2 h
Take-off run: 175 m
Accommodation: 1
The Lurko is reported as a light side-by-side seating trainer project in Hungary in the 1950s. Engine was said to be a Hirth HM504A and the Lurko is described as a low wing and wooden construction monoplane.
Very strong airplane, steel tube fuselage aluminum covered, with all metal wings and empennage. Equipped with a ballistic parachute. 2009 Price: 20000 USD
Stall: 32 kt – 37 mph / 60 kmh
Cruise: 67 kt – 78 mph / 125 kmh
VNE: 84 kt – 97 mph / 156 kmh
Empty Weight: 370 kg / 816 lbs
MTOW Weight: 570 kg / 1257 lbs
Climb Ratio: 1000 ft/min / 5 m/s
Glide Ratio: 7.2
Take-off distance (50ft obstacle): 520 ft / 160 m
Landing distance (50ft obstacle): 460 ft / 140 m
The German car manufacturer, Borgward set up a helicopter division in 1956 under the leadership of Prof. Heinrich Focke, whose Focke-Wulf Fw.61 aircraft of 1937 was one of the earliest successful helicopters. The Kolibri I is the first helicopter of German design to have flown since the war.
A light three-seat helicopter, the Kolibri I, was designed with a three-blade main rotor. Blades have steel-tube spar, with plastic-bonded plywood covering. Fully-articulated hub with adjustable friction dampers. Main rotor drive is via two-stage cam-wheel. Tail rotor drive via hollow steel-tube shaft and two bevel-gears. Two tail rotors, inclined at 45° to horizontal, at extremities of tail stabilisers. Tail rotor blades of plastic-bonded plywood.
The uncovered steel-tube girder fuselage had a conventional tail boom and a tricycle type landing gear. Shock-absorption by torsion spring and Borgward hydraulic damper. Fuel tank aft of rear fire-wall.
Normal seating for three persons, with a central seat behind and on a higher level than front two seats, with a forward cockpit enclosed with bubble canopy. Alternative loads can include up to 300kg of freight slung from an under-fuselage hook.
The prototype had a 260hp Lycoming VO-435-A1B engine in the centre section.
The prototype made its first free flight on July 8, 1958, piloted by Herr Ewald Rohlfs, who set up several international helicopter records in the pioneer Fw.61 in 1937. Airworthiness trials were progressing satisfactorily in the Spring of 1959, and plans are being made to put the Kolibri in production.
Kolibri I
Engine: 1 x Lycoming YO-435-A1B, 260hp
Main rotor diameter: 9.40m
Main rotor blade area (each) 1.28 sq.m
Main rotor disc area 70 sq.m
Length of fuselage: 8.30m
Height to top of main rotor head: 3.05m
Weight empty: 800kg
Weight loaded: 1200kg
Fuel capacity: 180 litre
Wheel track 1.93m
Wheel base 1.80m
Tail rotor diameter: 1.66m
Tail rotor disc area (total) 4.3 sq.m.
Main rotor/engine r.p.m. ratio 1 : 10
Tail rotor/engine r.p.m. ratio 1 : 6.75.
Max speed (est.): 160km/h
Cruising speed (est.): 140km/h
Rate of climb at sea level (est.): 240m/min
Vertical rate of climb at sea level (est.): 60m/min
Absolute ceiling (est.): 4500m
Hovering ceiling OGE (est.): 600m
Endurance: 3.0h
The Borgnis-Desbordes et de Savignon Triplane, also known as the Borgnis de Savignon et de Desbordes, was named after its designers/financier, Achille and Paul Borgnis, and Desbordes de Savignon. A development of the second Bousson-Borgnis, it was of all-metal construction, built at Gennevilliers. There were no rear tail surfaces: steering was done with ailerons set on forward outriggers, and a forward elevator was set low ahead of the 4-wheel undercarriage.
According to reports this triplane actually left the ground several times in Gennevilliers on January 31, 1909.
The first version was later modified. In the modification the elevator was brought to the rear of the machine and with new undercarriage, it was driven to Yffiniac on the northern coast of Brittany, where it flew and made a “memorable crash”. Repaired, this machine was destroyed in a collision at the end of 1910, ending the aviation related careers of the Borgnis brothers.
Engine: 6-cylinder, 28 hp
Span: 14.5 m / 47′ 7″
Wing area: 80 sq.m
Gross weight: 570 kg / 1250 lb
