Building the SB2 was started in 1994 by S Boshoff, before the KR2S concept gained momentum. Looking for an aircraft that had better aerodynamic characteristics than the KR2, and the simplicity of the KR2, the SA-CAA granted permission to build an aircraft that was based on the KR2, but they would not allow it to be register as a KR2. Hence the SB2 which has the same wing as the KR2 with a lengthened fuselage and bigger tail areas.
The aircraft had its maiden flight on 23 November 2001.
SN: 1 Engine: Turbo charged VW 2.0 l t Wing Span: 6150 mm Length: 5050 mm Empty weight: 310 kg MAUw: 545 kg Vstall: <50 mph Vcruise: 155 mph Vne: 190 mph U/C: Fixed Composite MLG, Steerable NLG
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
Józef Borzęcki was absorbed in the idea of building a simple, amateur glider for everyone. It was created under the influence of information about the pre-war Polish glider Bąk, designed by Adam Kocjan. His interest in aviation matters grew. He collected aerial books and magazines. He visited libraries and private collections. Despite many classes at work and family responsibilities, he devoted every spare moment to design work on his dream glider. Independently acquired the knowledge necessary to carry out the construction project.
During 1952–1961 Józef Borzęcki designed and built a motor glider called Stratus. He even built his own dyno to choose the right engine. He made this engine himself, based on a Czech circular saw engine. He designed and made the propeller himself, then he began making parts and assembling the airframe. He made all parts, from the smallest ones (e.g. he tapped several thousand rivets!) By himself. The construction of the powered sailplane was carried out in extremely difficult conditions – an apartment and a garage served as a workshop. The designer believed that all parts should be made perfectly, because flight safety depends on them. At the same time, he strived for its construction to be characterized by simplicity of operation and reliability of operation.
It was initially powered by an engine from a Czech chainsaw and wings from Żuraw (crane) glider. It initially featured classic flight control system with a control stick and rudder pedals, subsequently replaced by a “coupled” control system, designed by Borzęcki, in which the stick was used to control the aircraft in all axes (pitch, roll and yaw). It was aimed at facilitating flight training and increasing comfort in non-professional conditions.
The construction of the powered sailplane was completed in 1960 and J. Borzęcki began the first tests. During an attempt to take off, during Easter 1962, the wing was seriously damaged. Failures broke the constructor’s stubbornness. He no longer wanted to repair the glider, but he returned to work on it. He used in it (later used in all its constructions) so-called coupled control, i.e. only with a joystick that deflects the rudders and provides longitudinal and transverse control. Control of this kind, which he developed and developed completely independently, took him two years of hard work. Coupled control system of J. Borzecki’s idea had a number of advantages, especially significant in the case of little experience of amateur pilot. He again began the tests, which showed the correct flight properties of the powered sailplane. Over the next few months, he often performed test flights, which slowly turned into flying for pleasure. During 1961–66 the Stratus was flown illegally and in secrecy.
In July 1966, the designer invited the pilot of the flight and the editor of the newspaper Polish Word – editor Andrzej Macko to perform a test flight. He made several test flights, issuing a very favorable opinion about him. Articles by A. Macko published in Kulisach and the Polish Word about Józef Borzęcki’s motor glider started a nationwide discussion on amateur aviation in Poland.
In May 1967, an extensive article on amateur aviation was published in Winged Poland, a lot of space was devoted to the glider “Stratus”. In the press and everywhere where there were people interested in aviation, from aeroclubs to the Department of Aviation, there was a discussion about the future of amateur aviation in Poland.
In late 1960s the constructor undertook a rebuilding process. After this rebuilding the motor glider became the Altostratus.
Józef Borzęcki was born on March 19, 1928 in Olszany near Stary Sącz, as a son of Jan and Wiktoria. It was the Father who awakened the five-year-old boy’s imagination and interest in flying, telling about the famous flight of Stanisław Skarżyński across the Atlantic in 1933. The pre-war atmosphere of worship for aviation reached every corner of reborn Poland. The pilots were the heroes of meetings and legends.
Just before the outbreak of World War II, Józek, as a high school student, received a state guardian for his clearly targeted abilities. However, the outbreak of war changed the path of life for all Poles. Instead of studying at his dream school in Austria, 14-year-old Józef spent four years under German occupation, experiencing hunger, hard work in the factory, inhuman humiliation, fear and rebellion.
In 1945, after liberation of the country from the Nazi occupation, he went to Wrocław and began his education at the Technical Secondary School of Mechanical Engineering, obtaining a diploma as a technician in the design of internal combustion engines. In 1947 he completed glider training at the Aero Club of Wroclaw (at that time he performed flights on SG-38 and Grunau “Baby II” gliders). In a sense of lost youth and the desire to fly, he gives up his technical studies, however, the politicised atmosphere of the Aero Club once again turned his thought to independent aviation constructions. In 1951, he began the first calculations and made experimental models.
In the library, reaching for Russian-language textbooks on aviation technology, he meets his future wife – Aniela Plucinska, born in Nieśniew, who knows Russian. In December 1952 he married Aniela. In 1953, her daughter Elżbieta was born. The young couple are moved, together with the wife’s parents, to a new apartment. This is where the first construction begins to appear. In 1954, daughter Barbara was born.
In 1960, the trial take-off of the first glider “Stratus” took place. There are years of balancing passion with family responsibilities.
In July 1966, the designer invited the pilot of the flight and the editor of the newspaper Polish Word – editor Andrzej Macko to perform a test flight in the Stratus. He made several test flights, issuing a very favorable opinion about him. Articles by A. Macko published in Kulisach and the Polish Word about Józef Borzęcki’s motor glider started a nationwide discussion on amateur aviation in Poland. The construction and piloting of own aircraft were strictly prohibited in Poland at that time. In September 1966, J. Borzęcki wrote a letter to the well-known Soviet designer Oleg K. Antonov, who was a great enthusiast of amateur aircraft and glider construction. After two months, he received an answer, Antonov warmly congratulated him on the achievements in construction and encouraged him to continue working.
In May 1967, an extensive article on amateur aviation was published in Winged Poland, a lot of space was devoted to the glider “Stratus”. In the press and everywhere where there were people interested in aviation, from aeroclubs to the Department of Aviation, there was a discussion about the future of amateur aviation in Poland. Some spoke in favor of amateur aviation, others against him. There were moderate voices, but there were also those aimed at causing sensation. Most opinions, however, were evidence of a thorough reflection on the substance, seeing Stratus as a precedent. In Winged Poland of May 21, 1967 there was an article sharp in tone. It expressed views that the development of amateur aviation in Poland has no justification and is not simply needed, and the amateur construction of gliders, airplanes or even helicopters is today an archaic obsolete, economically unjustified and socially unnecessary. Not only with us. And therefore there will be no green light for this movement. J. Borzęcki received a lot of letters from supporters of amateur aviation that came from home and abroad. Everyone wanted to build a small amateur plane that made their innermost dreams come true. They wrote warmly, friendly. He became an example for them. It was the greatest payment for the designer for many years of effort. The letters confirmed his belief that there were many like him and that it was worth working for them.
In 1967, the second motor glider “Cirrus” was completed and flown, and Józef Borzęcki receives the honorable distinction “Blue Wings” from the editorial team of the weekly Skrzydlata Polska for his aviation activities. Until now it was awarded only for outstanding achievements, for his creative contribution to the development of Polish aviation in the professional and sport fields. Awarding them to an amateur, who was often embarrassing, set a precedent for those who had dreamed of their own wings for years. In the press competition for “Good Work” he was selected by the inhabitants of Wrocław to be “Big Twenty Winners”. In 1969, the motor glider “Cirrus” was recognized as the “Wrocław Work” this year. The Wroclaw Aviation Senior Club also awarded J. Borzęcki.
In 1972, the success of the next, third glider – “Altostratus” – is mixed with the sadness of the designer after losing both his parents. In 1974, Polish Television Wroclaw broadcast a film titled Cirrus. At that time, Józef Borzęcki becomes the initiator of the Amateur Constructors’ Club and a co-organizer of amateur air rallies. Domestic press and foreign magazines have published dozens of interviews as well as problem-technical and adventure articles of his authorship.
Borzęcki kept in touch with the Soviet designer Antonov and translated the diary of Antonow into Polish. Ten times from the beginning. An album published in 1976 in West Germany 50 Moderne Motorsegler, which was a kind of review of the world technique in the field of motor-sailing, contained photographs and technical descriptions of Cirrus and Altostratus. Also, the West German airline with international reach, Der Flieger from 1976, posted an extensive article about J. Borzęcki’s micro-planes and a 24 HP 2 RB engine.
In 1980, the Ossolineum Publishing House of Wrocław published his autobiographical book titled On own Wings. He chooses Olesno Śląskie as his place of residence. There, he also designs and builds the fourth ultra-light structure called JB-4 “Skowronek”.
Józef Borzęcki was a co-designer (next to Tadeusz Dobrociński) of the first “Pterodaktyl 1” soft-wing in Poland. In the 1980s, Józef Borzęcki received from the Amateur Club of Constructors (Aeroclub Opole) glider SZD-10 “Czapla” registered SP-2187. It was a thank you for help in constructing and building amateur aerial constructions. J. Borzęcki wanted to motorize “Heron”. For this purpose, he wanted to use his own drive, based on two MZ-250 engines. The project has not been implemented.
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. Grandfather of Magdalena and Samantha.
Borucki, an engineer from Kielce built in 1912 two aircraft, one modelled after Bleriot and another after Farman airplane. Because of his wife’s serious illness he didn’t made any flight attempts on these but the “Farman” plane was purchased my Russian military, thereby suggesting that flights on it were made;
After the “Object 10” project, the Borovkov and Florov working group got to work on a new version known as “Object 11” or simply No.11. In some literature it has also been called I-207/6. This new project owed its origin to the intention to comply with the requirements issued by BN Yuriev during the review of the “Object 10” project as a way to achieve its serial production.
This new project returns to the conception of pure fighter with high manoeuvrability and to the conventional type landing gear. The armament included two 12.7 mm machine guns and two 7.62 mm ShKAS, but the possibility of carrying two FAB-250 250 kg bombs or instead two detachable containers with PTB-23 23 mm cannons remained.
It was smaller and lighter derivative of the “10”. Maintaining the same wing configuration of gull and inverted gull, the new model included two Merkulov DM ramjets in its metallic tail section, located side by side and with side gates for the air intakes. Instead of one large DM ramjet, it has two smaller ones placed side-by-side. This arrangement made it possible to install the tail wheel between them.
The project kept the Shvietsov M-71 engine, but in this case a variant with an elongated shaft was used, which made it possible to improve the aerodynamics of the forward section of the fuselage.
All efforts in the design of this new version were directed to obtain the lowest possible weight. The calculated speed of the project in fighter configuration at 5830 meters and without the auxiliary engines gave 654 km / h. With the bomb load the speed decreased to 611 km / h. The ascent time to 5000 meters was 3.7 and 4.5 minutes respectively.
The conceptual project for “Object 11” was presented in the fall of 1940. The evaluation commission considered that the calculated speed was a bit high and recalculated it to 630 km / h, leaving the speed with bombs at 585 km / h. The commission proposed to include the model in the plan of experimental works for the next year, obtaining the approval of AS Yakovlev.
In October 1940 the project was presented at the NII VVS and the conclusions of its evaluation were signed by PV Rychagov on December 9 1940. In general, the evaluation was positive and it was again recommended to include the fighter in the experimental construction plan for 1941 with the condition of increasing its range to 1000 km in normal version and 1400 km with auxiliary fuel (taking into account that “Object 11” it was not foreseen as an escort fighter, such range value was exaggerated and forced to considerably increase the weight of the aircraft in fuel).
The position of the GUAP, together with the negative perception of the industry and the air forces towards the biplane wing structure, resulted in the work on the project being closed. The deputy commissioner for experimental aviation AS Yakovlev, in a meeting informed the constructors of the decision not to include new proposals for two-plane configurations in the future work plans of the Narkomat.
Borovkov-Florov Object 11 Powerplant: One Shvietsov M-71 (1700/2000 hp) and two Merkulov DM ramjet Wingspan: 8.5 m Wing area: 22.0 m² Length: 7.85 m Flying weight: 3250 kg Wing loading: 148 kg / m² Maximum speed: 790 – 800 km / h Ascent time at 8000 m: 6 – 7 min Range: 800 km Accommodation: 1
Florov and Borovkov continued with the “Object 10” project airplane that had a clear influence of the I-207 fighter, which is why the literature has sometimes named it I-207/5.
The project for this aircraft was ready for 1940 and envisaged the use of a Shvietsov M-71 engine. The fundamental objective of this new project was to achieve a design capable of eliminating all the difficulties encountered during the I-207 tests.
The aim was to demonstrate the possibility of creating a highly maneuverable biplane fighter with minimal resistance to advance, capable of competing with the best monoplane fighters of the time. The selection of a biplane wing box, according to its creators, should guarantee a more compact aircraft with better visibility for the pilot.
On this occasion and in order to achieve a wing as thin as possible, the builders decided to use a gull-type wing configuration for the upper wing and inverted gull for the lower wing. As in the I-207, the use of any type of bracing or upright was not foreseen. According to calculations the “Object 10” should reach a speed of 650 km / h with a turn time of 14 – 16 seconds.
In an attempt to achieve the highest possible speed, the builders designed from the beginning of the design stage, the use of reactive engines.
As early as July 1939 the engine manufacturer Merkulov had proposed the use of auxiliary ramjets in piston-engined aircraft. These ramjets were characterized by using the same jet fuel as the main power plant. These motors were called DM, acronym for Dopolnitielni Motor or auxiliary motor.
DM motors were designed as short-term supports for those moments in combat when additional speed was required. The first tests of these auxiliary engines were developed on a Polikarpov I-15bis in late 1939. The results were promising and for this reason in 1940 the constructors Borovkov and Florov installed these engines on the I-207/3. The test pilot of Factory No.207, LM Maximov, carried out about twenty flights without difficulties on this plane.
In the “Object 10” project the DM was installed inside the rear fuselage, behind the cockpit. In this way, its installation did not affect performance during the flight under normal conditions. The DM could be switched on by the pilot. For this, some side doors were opened that allowed air access to the engine and it was turned on. An increase in speed was calculated to about 840 km / h.
Unlike the previous models, the tail section was designed as a monocoque duralumin structure with a structure similar to that used in the wing. This was due to the need to reinforce the tail for the installation of the DM engine and to the need to avoid possible fires caused by the hot exhaust gases from the ramjet.
The armament was designed in such a way that it could be added or removed depending on the mission. The initial version was armed with two ShKAS 7.62 mm machine guns and a BS 12.7 mm machine gun, which could be replaced in field conditions by two 23 mm guns in the ground attack version. The armament had to include the possibility of transporting 250 – 500 kg bombs and dropping them accurately during dive on the target.
In the design, 350 – 400 kg were estimated for the armor and the installation of the guns. The cockpit and vital organs of the plane had to be protected. In the fighter version, the pilot’s back was protected by 8.5 mm thick concrete armor capable of defending the pilot from the firing of normal caliber weapons. The frontal armor was provided by the radial motor. This, together with the small dimensions of the plane, guaranteed an important level of safety to the pilot. The fuselage fuel tank was also protected.
A feature was the retractable type tricycle undercarriage. This configuration had been successfully tested by the TsAGI on an SB bomber. As early as 1940, several Soviet models included this type of landing gear in their design. In the case of “Object 10” this decision was forced by the fact that the tail was occupied by Merkulov’s engine.
The “Object 10” project was handed over to the NKAP in the summer of 1940. This project envisaged the use of a Shvietsov M-71 engine and a maximum armament capacity of 1000 kilograms. The armament could be made up of 250 or 100 kilogram bombs, although the possibility of using eight RS-82 reactive rockets under the wings was envisaged. The armament was also composed of two 12.7 mm and two 7.62 mm machine guns.
The cockpit armor comprised a 4 – 4.5mm armored seat plus an 8.5mm cement plate at the rear of the seat.
The project data showed a speed of 658 km / h without the auxiliary engine in the fighter version. The ground attack model had to fly at a speed of 550 km / h.
The project was reviewed by a directed commission for academic BN Yuriev on 3 August 1940, which considered objective the construction of the aircraft in its hunting version high manoeuvrability and in its version with two FAB-250 or four FAB- 100. The commission noted that the actual speed to be reached without the auxiliary engine would be only 605 km / h.
With these results, this variant in general could become an excellent ground attack aircraft. The possibility of using the M-82 engine was also evaluated.
With the start of the war, neither this model nor its development known as “Object 11” were built.
Object 10 Engine: 1x Shvetsov M-71 (1700/2000 hp); 1x Merkulov DM ramjet Wing span: 9.5 m Wing area: 24.0 sq.m Length: 8.35 m Takeoff weight: 3500 kg Wing loading: 146 kg/sq.m Max speed w/out ramjet: 650 km/h Max speed with ramjet: 750-800 km/h Climb to 8000 m (with ramjet active): 8.0 min Flight range: 800 km Armament: 1x 12.7 mm Berezin BS, 2x 7.62 mm ShKAS or 2x 23 mm cannons. Crew: 1
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.
