The G-102 Astir is a single seat glassfibre Standard Class sailplane, designed by Burkhart Grob. It was the first Grob-designed sailplane.
Construction of the prototype Astir CS began in March 1974. It features composite (fiberglass/resin) construction, a large wing area, a T-tail and water ballast. A Standard Class Sailplane, the large wing area gives good low speed handling characteristics. The main gear retracts. It first flew on 19 December 1974 and it went into production in July 1975 and soon proved to be popular, a total of 534 being delivered.
The cantilever mid wings have glassfibre roving main spars and a glassfibre/epoxy resin sandwich skin except for the ailerons, which are of glassfibre sandwich. There are Schempp-Hirth aluminium air brakes in the wing upper surfaces, but no flaps, and up to 220lb of water ballast can be carried in tanks in the wings, being jettisoned via a dump valve in the fuselage. Rigging is carried out without any separate removable parts as the wings and the tailplane are attached by a system of ‘snaplock’ connectors. The glassfibre semi-monocoque fuselage has a towing/launching hook, and the large one-piece cockpit canopy opens sideways to starboard. Construction of the T-tail unit is the same as that of the wings.
This was followed by the Club II with similar fixed gear. A slightly improved version, the CS-77, was introduced in 1977. The CS-77 has a different rudder profile fuselage similar to that of the Speed Astir. The Astir CS 77 made its first flight on 26 March 1977; nearly 400 of the CS 77 and Club Astir had been built by the end of 1978.
The Club Astir II and the Standard Astir II featured the new fuselage of the Speed Astir II. with a one piece canopy, as well as the elasticated flaps of the Speed version and a new wing tip profile.
The Astir CS 77 has a retractable monowheel with an internally-expanding drum brake located ahead of the center of gravity, which folds up behind closed doors, and there is also a rubber-sprung tail wheel. The Astir CSM was a powered version under development in mid-1976 with a 25hp Fichtel & Sachs Wankel KM24 rotating piston engine on a retractable pylon aft of the pilot, driving a two-blade Hoffman tractor propeller. A 6.6 gal fuel tank is fitted.
G-102 Astir
The Astir CS Jeans was of similar configuration to the CS 77, but with fixed wheel, and a tailskid.
The Standard III followed in the early 1980’s reverting to the higher profile fuselage and with reduced empty weight and increased payload. The Club III has a fixed main gear ahead of the center of gravity, and a tailwheel. The Club IIIB has a cockpit almost identical to the front seat of the two-place G 103 Twin II with a fixed main gear aft of the center of gravity and a nosewheel. Air Transport Certified (except Club II which is EXP). One, flown by R.R. Harris of the U.S., won the world absolute altitude record at 14.938 m/ 49.009 ft in 1986.
Production variants were the Club Astir III, IIIB and Standard Astir III, which have a roomier cockpit and reduced empty weight.
Grob G-102 Astir CS77 ZK-GMA
Grob 102 Wingspan: 15.00 m (49 ft 3 in) Wing area: 12.4 sq.m (133 sq.ft) Water ballast: 50 kg (110 lb) Aspect ratio: 18.2 Empty weight: 255 kg (561 lb) Gross weight: 450 kg (990 lb) Maximum glide ratio: 38 Glide Ratio: 36 at 50 kt (92 km/h) / 5.9 nm (10.97 km) per 1000 ft Sink rate: 141 ft/min (0.71 m/s) at 50 kt Glide Ratio: 34 at 41 kt (76 km/h) / 5.6 nm (10.36 km) per 1000 ft Sink rate: 122 ft/min (0.62 m/s) at 41 kt At 90 knots (166 km/h) Glide Ratio: 23 at 90 kt (166 km/h) / 3.8 nm (7.01 km) per 1000 ft Sink rate: 393 ft/min (2.00 m/s) at 90 kt Stall: (without airbrakes) 32 knots (60 km/h) Stall: (with airbrakes) 35 knots (65 km/h) Never Exceed: 135 knots (250 km/h) In Rough Air: 135 knots (250 km/h) Manoeuvering: 92 knots (170 km/h) On Aerotow: 92 knots (170 km/h) On Winch: 64 knots (120 km/h) Airbrakes: 135 knots (250 km/h) Gear Down: 135 knots (250 km/h) Minimum Payload: 70 kg Maximum Payload: 110 kg Crew: One pilot
Grob G-102 Astir CS77 Span: 49 ft 2.5 in / 15.0 m Length: 21 ft 11.25 in / 6.69 m Height: 4 ft 7 in / 1.4 m Wing area: 133.5 sq.ft / 12.4 sq.m Aspect ratio: 18.2 Wing section: Eppler E603 Empty weight: 595 lb / 270 kg Max weight: 992 lb / 450 kg Water ballast: (220 lb / 100 kg Max wing loading: 7.43 lb/sq ft /36.3 kg/sq.m Max speed: 155 mph / 135 kt / 250 km/h Stalling speed: 32.5 kt / 60 km/h Max aero-tow speed: 105 mph Max rough air speed: 135 kt / 250 km/h Min sinking speed: 0.6 m/sec / 1.97 ft/sec at 47 mph / 40.5 kt / 75 km/h Best glide ratio: 38:1 at 65 mph / 56.5 kt / 105 km/h
1926: Company foundation in Munich Aviation work began in 1971 and has since built many thousands of motorgliders, lightplanes and other aircraft. 1974: Foundation of aircraft plant in Mattsies Burkhart Grob Flugzeugbau GmbH built the Schempp-Hirth Standard Cirrus under licence during 1972-75. Recent aircraft include the G 103 Twin III and G 109 series of gliders/motorgliders, piston-engined G 115 two-seat lightplane (some versions suited to training and aerobatics; first flown November 1985), GF 200 pusher piston-engined and pressurised 4/5-seat lightplane (first flown November 1991, turboprop-powered G-520 Egrett and Strato 1 high-altitude and long-duration research platforms capable of carrying different electronic payloads in 12 separate compartments (first flown June 1987 in G-500 Egrett form), and the most recent G-850 Strato 2C high-altitude and long-duration atmospheric/ stratospheric/ climatic research aircraft with a unique compound propulsion system using two turbocharged piston engines and two gas generators (first flown March 1995).
France Orion four-seat composites monoplane, with pusher propeller aft of tail, produced by Jean Grinvalds 1982. Plans and access to moulds later made available from Club Orion.
In New Zealand, Gavin Grimmer’s own design, the Grimmer Skylux (c/n 1005-2) is a single seat glider towplane powered by a converted Lexus V 8 engine. It was registered on 10/12/12, at Hastings, New Zealand, as an Amateur Built Aircraft. Gavin has had a lot of experience with automotive engine conversions in homebuilt aircraft with his Maranda ZK-JGR (which has the c/n 1005-1).
The bases of this project go back to an idea presented by Fleet Senior Lieutenant II Golenischev-Kutuzov, who proposed to build a special hovercraft capable of carrying out torpedo attacks on enemy ships. Little by little the idea of the hovercraft was derived from a specialized seaplane. This idea of Golenischev-Kutuzov was presented to PRTV for its implementation.
The plane began to be designed and built in 1916 at the Shchetinin Society. Co – engineered by Mikhail Mikhailovich Shishmariov, who headed the construction department at the Shchetinin factory. Shishmariov developed the entire technical project for the new aircraft, while Grigorovich was in charge only of the general conception of the model and the general direction during the preparation of the plans and technical documentation.
The GASN was designed as a huge twin-engine sesquiplane with a pair of floats and capable of carrying a 450-hp torpedo designed at the “Novi Lessner” factory in Petrograd. The power plant consisted of two 220 hp Renault engines located between both planes on steel tube supports and moving large four-blade propellers.
The initials GASN (Григорович/Шишмарев ГАСН) correspond to G idro Aeroplan S petsialnovo N aznachenia (Special Missions Hydroplane), although the model was also known as SON ( Samoliot O sobovo N aznachenia ) and in either of the two names it was considered to create an aircraft capable of carry and launch a naval torpedo, making this model the world’s first naval torpedo boat. We must add that this subject was considered highly secret, so in fleet documents references to the project are made as Type K.
The floats had a traditional construction similar to that used for the hull of submarines at the time and were fixed to the lower wing by means of uprights in an inverted V made of steel tubes with rubber attachment points.
The fuselage had a rectangular cross section secured by cables and covered with fabric.
The tail was of the biplane type with three rudders and a small keel on the central empennage.
The large-span wing featured traditional wood-frame construction with fabric covering. The structure had three auxiliary spars to be able to fix the large ailerons. The shape in the plane of the wing was rectangular with a constant chord, but instead of being straight it presented a slight sagging.
The leading edge of the upper wing had indentations in the area of the propellers. The interplane supports were built with steel tubes on which they installed fabric-covered aerodynamic fairings and cable tensioners.
The GASN crew consisted of 3-4 people. In the bow area there was a position reinforced with sheets of plywood for an observer-gunner in charge of defending the forward hemisphere. Behind this position was the cockpit for two pilots and behind the wing box a third position for a gunner.
Even without completing the assembly of the first example, a request for the construction of 10 examples had been sent to Shchetinin.
The first flight of the prototype took place on August 24, 1917 in Petrograd under the leadership of Senior Lieutenant A. Ye. Gruzinov. The first tests showed that the GASN had good behaviour in the water and was easily controllable, but it was necessary to modify the trim and improve the response of the rudders. It was proposed to advance the engines, locate certain weights and increase the wing’s rake angle to advance the center of gravity of the airplane. It was also proposed to increase the surface of the rudders.
The GASN on Krestovsky Island in Saint Petersburg in 1920.
On September 24, during one of the flights, one of the floats was damaged, showing the need to reinforce its structure. After the repairs the plane began to fly again. These flights produced another series of problems, which is why the possibility of the Navy not continuing development and adapting the “Ilya Muromets” bomber or the Jioni twin-tailed plane for this role was considered.
The events of the revolution in Petrograd and the chaotic situation of the first years of the revolution prevented further development. Despite these factors, the GASN and an important set of construction elements of the started series of 10 copies were preserved intact, initially at the Shchetinin factory, which had changed its name to “Gamayún” and later at the “Krasni Liotchik” Factory.
The intention to continue the works would arrive in 1920. In that year Grigorovich traveled to Moscow and received an engineering post in Glavnoavia. His first task consisted of trying to continue the development of the projects stopped in the period 1917-1918. Grigorovich proposed to restore the work on the GASN torpedo bomber, knowing the state of conservation of the prototype and a good number of parts and components to assemble various aircraft of this type.
In November 1920 the GASN was made airworthy and the pilot LI Giks began carrying out the tests. Dmitri Pavolvich was on the shore supervising the process. On the 4th of that month, after long checks on the state of the engines, the mechanic Ozolin told Giks that the plane was ready for flight. The pilot stood in the cockpit and gave instructions to release the seaplane into the water.
During takeoff runs, tabs of fire began to come out of the exhaust pipes of one of the engines. Fearing a fire Giks decided to interrupt the test.
The engines were once more overhauled and the plane was finally cleared to take off, despite the fact that the weather conditions had deteriorated with a southerly wind that made take off difficult and the appearance of floating ice in the bay.
Steering the plane in the direction of Volni Island, Giks turned the plane upwind and took off. The plane was beginning to climb without difficulty when suddenly the engine on the right stopped working. The pilot turned for a landing near Krestovski Island. After gliding, the pilot managed to land and tried to steer the seaplane with a single engine. It was found that the seaplane’s rudder was ineffective and the aircraft only rotated around one axis. Giks directed the mechanic to go to the wing to try to compensate by sinking the float, but that didn’t help either. Waiting for help Giks switched off the engines. The plane began to drift freely.
The crew members removed the cushions from the seats, sprayed them with gasoline and lit them, throwing them near the plane as a signal for help, but help did not appear anyway.
For a whole day the plane drifted. At dawn the crew confirmed that they were about three kilometers from the shore and that the entire plane was surrounded by sheets of ice that made rescue difficult. Finally it was possible to bring the plane to the shore. The analysis of the accident showed that during the preparation of the flight, instead of oil, it was poured into the diluent tank.
With this the development came to an end.
GASN Power plant: 2 x Renault, 220 hp Upper plane wingspan: 28.0 m Wing area: 150.0 m² Length: 14.50m Payload: 1450kg Speed at sea level: 110-120 km/h Accommodation: 3 – 4 Armament: two machine guns Bombload: 450 kg torpedo or 480 kg of bombs
Between 1915 and 1916 at the Shchetinin Factory and based on a Grigorovich project, two “land” models were designed (in Russian Sujoputnie and hence the S in the name as opposed to the M for Morskoi or naval). The objetive of these models was to increase the performance of the Farman biplanes that the factory built under license.
The first of these projects, known as S-1 (Григоровича С-1), was designed as a conventional biplane heavily influenced by Farman’s designs and equipped with a rotary engine. Construction was abandoned before the prototype was finished.
A second model, called S-2, was designed as a two-seater aerial observation and reconnaissance aircraft and generally repeated the successful scheme of the Farman biplanes with a central nacelle and a rotary engine. As a “novelty” it is worth noting the use of double tail cones that ended in individual empennages joined by the stabilizer with the elevators.
The selected powerplant was the 100 hp French Gnôme Monosoupape.
The entire construction was made of wood, covered with fabric. The wings had an Eifel-36 profile and were characterized by a large difference in span between both planes and the use of parallel uprights with cable tensioners.
The S-2 was built and its assembly was completed in January 1916. During flight tests, conducted by pilot Ya. I. Siedov, an accident occurred and the plane was not restored as it was considered that there was no point in trying to improve the outdated Farman designs
As early as 1915, a group of naval pilots had asked the Fleet for a long-range aircraft capable of carrying out long patrols, covering the entire Baltic Sea area. The start of the war increased the requests and increased when the conflicts with Turkey began.
On August 12, 1915, a meeting of the Aviation Committee of the Baltic Sea Liaison Service took place, in which once again the issue of the need for the provision of large seaplanes with a 6-hour patrol capacity was discussed. Based on these requirements, the builder DP Grigorovich proposed to build such a device.
The Marine Cruiser (Mosrkoi Kreiser or MK (Russian: Григорович МК-1 “Морской крейсер”)) was designed in 1916 to meet the requirements of the Naval General Staff (MGSh) and was conceived to serve with the Baltic and Black Sea fleets in long-range reconnaissance and bomber functions.
The MK-1 was the largest Russian seaplane ever designed and it only yielded to the Ilya Muromets bomber with floats.
The MK-1 featured a center float, biplane configuration, three engines, and a four-crew capacity. From the technological and constructive point of view, the model maintained the characteristics of the designs developed in the Schetinin Factory.
A feature was that the float and fuselage were merged into a single structure, resulting in a general outline of combined features. This float had such dimensions that it could generally be considered a hull. In its lower region it presented a redentient with concave and lateral sides similar to those used in Grigorovich’s M flying boats. The construction of the internal structure of the float was made of ash with plywood covering.
In the forward region of the fuselage the closed cockpit was located, built with plywood and with good frontal glazing. At the rear, the fuselage appeared as a wooden frame braced by cables and covered with fabric.
The wing box was of the conventional type with three pairs of struts in each half plane and a certain offset. The upper plane was slightly larger than the lower plane and had trapezoidal-shaped ailerons. The wing structure was conventional, with two wooden spars and a rather slim profile. It should be noted that this wing box was fixed to the upper part of the float body by means of rubber shock absorbers with a travel of 180 mm.
In the tail section there was a wide triangular keel on which the horizontal planes were fixed, braced by uprights and the large-area rudder.
Originally it was thought to equip the MK-1 with only two 220 hp Renault engines located between the planes. Later, when construction began, the designers realized that the weight of the model exceeded that calculated and the center of gravity was located a little behind, so it was decided to locate on the upper plane and on the line of the longitudinal axis a third engine. A 150 hp Sunbeam motor was first tested, but was later replaced by a 140 hp Hispano-Suiza V-cylinder motor, which was found at the factory. In this way the MK-1 became the world’s first three-engined seaplane.
The cockpit of the pilots in the MK-1 was characterized by being very spacious and located high above the hull. In the bow section a gunner was located operating a 76 mm gun.
The MK-1 was completed in the middle of 1917 and only late in the fall was it ready for testing. In November the pilot Ya. I. Siedov-Sierov attempted to make the first flight in Petrograd Bay, taking several people on board. The weather was not the most propitious, the cold wind had created waves. At the beginning of the take-off and giving full throttle to the upper engine, the nose sank and the water swept over the bow, filling a large part of the first watertight compartment of the hull. The “Cruise” was stuck on its nose and ended up sinking. All the crew members were able to be evacuated.
The flying boat was pulled out of the water with significant damage. The cause of the problem was considered to lie in design problems of the bow section of the float, which needed to be lengthened. The need was also seen to eliminate the upper engine and increase the power of the two located between the wing planes. This meant a major job that was decided not to undertake, especially considering that the GASN torpedo bomber was already being built, which seemed much more perspective. Thus ended the development.
Grigorovich/Schetinin MK-1 Sea Cruiser Power plant: 2 x 220-hp Renault & 1 x 140-hp Hispano-Suiza Upper plane span: 30 m Length: 16.50 m Height: 4.50 m Accommodation: 4
TB-5 the day of its first flight at Jodinka airfield. June 30, 1931
In the winter of 1929-1930 the OGPU leadership decided that it would be necessary to continue the chain of success of the TsKB -39 with a new bomber. In the spring of 1930 and again with great pressure on design and construction times, the requirements were delivered.
There is a version that alleges that the initiator of this idea was the then head of the TsKB-39 Ye. S. Paufler, who, seeing a high-wing aircraft with engines under the wings in a Farman promotion, decided that he should build something like that. All the builders refused except Grigorovich, who decided to take up the challenge.
Be it this way or not, the documents confirm that in the spring of 1930 and practically without the traditional approvals, the TsKB-39 was given the task of building a heavy bomber that was named Airplane-8 or TsKB-8. The VVS however refer to the model under the designation TB-5 (Russian: Григорович ТБ-5).
The deficit in aluminum production seems consistent that the air forces had opted for the creation of a model built from more affordable materials.
By the early 1930s, a new “Sháraga” or Special Technical Bureau (OTB) of the OGPU dedicated to the development of aircraft engines had appeared in the Soviet correctional system. Noted builders such as BS Stiechkin, NR Brilling, AA Bessonov were there.
This group was given the task of designing, testing and producing a 24-cylinder engine that was known as FED (an acronym for Félix Edmúndovich Dzerzhinski). This engine with 4-row distribution in X and central injection system, had to develop a power of 1,100 – 1,250 hp at an altitude of 3,000 meters and its construction was directed by AA Bessonov. These values were considerable for the time.
The FED was conceived as the power plant for the new TB-5 bomber and its installation was planned in two variants: on the wing leading edge or in gondolas fixed to the wing intrados. Different situations led to the FED not being available at the established time, so the TB-5 had to be equipped with 4 Gnôme-Rhône 9Aq engines , a licensed copy of the excellent British Bristol Jupiter VI engine later built under license in the Zaparozhie Factory No.29 as M-22. The engines were located in tandem under each wing console. Despite the fact that the total power was almost similar to that calculated, the new drive installation had much more frontal resistance and the efficiency of the propeller was reduced by the tandem configuration, which had a negative impact on performance.
Practically all the personnel of the TsKB and a large part of the personnel of the VR Menzhinski Factory No.39 in Khodinka were mobilized for the work on TB-5, where Paufler’s “Sháraga” would be transferred from the Butirka prison.
Airplane-8 was built in just one year, which was record time for such a large and complex aircraft. Grigorovich in the same period, in parallel, worked on the IZ fighter. The appearance of both models in May 1931 (and the resounding success of the I-5) practically caused Grigorovich to receive amnesty.
The TB-5 was designed as a high-wing bomber with a double tail unit. Its construction was mixed, with little use of aluminum, a metal short in the USSR of those years.
The spacious fuselage featured a skeletal structure constructed from fabric-covered welded steel tubes. For ground transportation, the fuselage could be divided into three sections: the forward section to the wing trailing edge, the intermediate section to the beginning of the stabilizer, and the tail section.
The TB-5 wing featured a three-spar structure and constant rib pitch. The stringers were built with special profiles made of duralumin and tubes. The ribs were formed by stamping. The construction of the wing was quite complex, especially when it came to covering the fabric.
The airfoil selected was the R-II with 18% in the midplane area and 12% in the extremes. The wing had some small bracing supports that also helped to give the necessary rigidity to the power plant.
The tail was built on the basis of a fabric-covered aluminum frame. The horizontal plane presented a second, thinner unit, located at a greater height and called “stabiliron”, creating a kind of biplane box. Its function was to decrease the force on the joystick during landing operations and trim changes.
In the TB-5, on each side of the fuselage, under the wing, two 480 hp Gnôme-Rhône 9Aq engines were installed in tandem, so that they moved a propeller with two wooden blades in a driving configuration and another in a driving configuration. This engine would later be built under license under the designation M-22. In order to improve cooling, the rear engine was fitted with a Townend ring around the cylinder head.
The projected bomb load (with the use of the FED engines reached 2,500 kg) was located in an interior hold in the fuselage. DER-18 supports were located on the sides of this hold, allowing the crew to move freely inside the aircraft.
Defensive armament consisted of three TUR-5 turrets with paired Degtyaryov light machine guns for aircraft. The first of these turrets was located above the forward navigator’s position, just in front of the cockpit; the second just behind the wing and the third in the tail section of the fuselage. Apart from these positions in the bow there was a mobile firing tower, developed in the armament section under the direction of AV Nadashkievich. This can be considered the first Soviet attempt to obtain a remotely operated turret using mechanical and electrical controls.
This tower was built in the form of a cylindrical tank that rotated around its vertical axis. In the front part it had a slot that allowed the vertical displacement of the two machine guns. The horizontal movement of the machine guns was ensured by the rotation of the tower. The gunner was located inside the tower and if necessary, could leave it using a rear door towards the nose of the aircraft. For the first time in the USSR two PV-1 machine guns were installed here, built on the basis of the infantry Maxim, but using air cooling instead of water. For the first time, uninterruptible belt feeding was also used.
The rotation of the tower was carried out by means of an electrical system and the vertical movement of the machine gun was carried out by the shooter, located in a small seat.
Pilot and co-pilot were located in a closed cabin, with seats side by side. The crew of the TB-5 had some facilities that could be considered a novelty for the time: a toilet and four hammocks for resting.
Grigorovich TB-5 shortly before starting his first flight.
In the early summer of 1931 the TB-5 was first brought out onto the airfield. After engine tests and a few runs, the decision was made to allow the flight. On June 30, 1931, test pilot B. Buxgolts made the first test flight over Jodinka airfield.
After landing, Buxgolts came down from the cabin smiling and said:
“Stability in the air is good. Ease of control excellent. Very little pressure on the rudders.”
By July 20, the plane had made four successful flights. With a weight of 11,200 kg and a fuel capacity of 1,850 kg, it had managed to cover a distance of 1,100 km during 6.7 hours of flight with an average speed of 162 km/h and a ceiling of 3,000 meters. Range with maximum fuel load of 2,410 kg and takeoff weight of 12,060 kg (including 500 kg of bombs) was 2,100 km. The maximum speed recorded was 180 km/h, the ceiling was 3,500 meters and the take-off run was about 400-420 meters.
The TB-5 during the development of the tests.
The performance obtained was not high, especially when compared to the Tupolev TB-3 bomber that had already been flying for a few months. The main cause of these results was the powertrain. The propellers used were more suitable for a fighter than for a bomber of that size. To make matters worse the rear propeller had to be shortened so that it could operate under the wing.
Despite these difficulties, the TB-5 presented a not insignificant set of advantages, among which stood out a better distribution of defensive weapons, better distribution of the bomb load on the plane, smaller dimensions and weights, much lower cost and simpler construction. The group of builders did not lose hope of being able to count on the promised FED engines, with which performance should be increased significantly. It should be noted that by the summer of 1931, Factory No.24 had 12 engines of this type in production and had aggregates and components for another 10 units.
Front view of the Grigorovich TB-5 bomber.
All these possibilities were evaluated and finally on July 25, 1931 the Labor and Defense Council (STO) asked the Pan-Soviet Aviation Union to prepare the conditions to produce six TB-5 bombers (one as a prototype of the series and the other 5 to perform military operation tests). Almost in parallel with this decision, these specimens were included in the plans for the formation of the new bomber squadrons for 1932.
The head of the VVS PI Baranov considered that, due to the delay presented by the FED engines, it was advisable to postpone the manufacture of the TB-5 copies for the year 1932 and he sent a request with these reasons to the United Council of the Economy of the USSR (VSNJ according to the initials of Vsiesoyuzni Soviet Narodnovo Jozyaistva). However, the chairman of the Council of People’s Commissars (SNK) VM Molotov had other ideas, so he ignored Baranov’s request and instead requested to take the necessary measures to speed up the construction of the series. According to M. Maslov the reasons for this decision could be of a political nature. The TB-5 bomber had been created within the OGPU and just a few days before, on July 6, 1931, this organization had given Stalin a demonstration of its achievements. There he was shown the I-5 fighter, the R-5 reconnaissance aircraft, the TSh-1 attack aircraft, the TB-5 bomber and the modern IZ gun-wielding fighter. Stalin was widely pleased and hinted that the OGPU leadership seemed to have succeeded in finding the most productive formula in aeronautical development. As a collateral consequence of this presentation, on August 27, 1931 the TsKB and the TsAGI would be unified under Czech control in the TsKB-TsAGI organization headed by Ye. S. Paufler.
During this time the TB-5 had received a significant group of improvements. In the month of June 1931, work was done on the structural reinforcement and the fixing system of the engines. The cockpits were fitted with upper access hatches, glazing was introduced in the midplane trailing edge area, the Townend ring was removed from the rear engines.
During the winter of 1931-1932 the bomber was prepared to operate with skis and several flights were made to analyze its behaviour. The design group was working on improving the conditions for installing the still awaited FED engines, but other variants of installing engines on the leading edge of the wing were analyzed. Works on this configuration were led by SA Kochierigin. Scale models with this configuration were tested in the TsAGI wind tunnel.
During this stage, other aeronautical constructors such as BI Cheranovski, VP Yatsenko and AN Refaeliants worked on the plane.
Unfortunately, the construction of the series could not be carried out, mainly because Factory No.39 was overloaded with the production of several experimental models.
The TB-5 flights continued and Soviet pilot MM Gromov would participate in them.
During one of the days of May 1932 and during a flight at a height of 800 meters a strong vibration began. The cause was that the left rear engine detached from the mounting bracket and the propeller broke the fuselage and embedded itself in a wooden bomb mock-up. The fuel caught fire.
Gromov ordered to shut off the fuel supply to the engines and began to glide with dives over the left wing to try to put out the fire. Eventually this was achieved and the pilot made a forced landing at Factory No.22 airfield in Fili. Only at this moment did they become aware that when the flames intensified the engineer AV Chesalov, who was in the wing area, had parachuted down to land without difficulty.
Condition of the left engine of the TB-5 after the accident of MM Gromov.
After this mishap, the TB-5 remained in Fili until December, without repairs being attempted. Grigorovich had switched to the development of fighters.
At the end of 1932, after verifying that the manufacture of the Túpolev TB-J bomber (military version of the ANT-14) was even more complicated than those of the TB-3, it was decided to return to the subject of the TB-5.
To assess the possibility of re-establishing the TB-5, a commission was created led by the representative of the TsAGI VN Chernishevich, who worked on December 1, 1932. As expected, the competing aircraft was harshly criticized: the aircraft was valued as overweight, with poor motor installation and design problems. On the other hand, the TB-5 had had its engines, part of the flight instruments, and weapons disassembled, and it was estimated that to give the bomber full flight capacity again, it would be necessary to invest 75 or 100 thousand rubles.
The commission considered that to improve the bomber it would be necessary to reinstall the engines on the wings, which would guarantee an increase in speed, which would reach 190-200 km and a ceiling of 4000 m, but the cost of the modifications would amount to 200 thousand rubles.
Incredibly, despite these assessments, it was decided to restore it with the proposed modifications, for which it would be returned to Factory No.39. A short time later, at a meeting of the VVS management, it was recognized that even with the modifications, the benefits of the TB-5 did not satisfy the requirements of the moment.
In the month of February 1933 the head of the GUAP Baranov instructed:
“The plane disarm it. Works on him stop them.”
With this it all ended. TB-5 was not restored and its remains were handed over to the TsAGI structural resistance department. The Tupolev TB-J also did not see the light of day, as by the end of 1933 the specifications for bombers had grown considerably.
On the basis of the TB-5 in 1931 Chertverikov developed the reconnaissance flying boat MDR-3 or TsKB-11, which kept the design of the wing, tail and structural elements of the bomber. Finally, this design would not be produced either.
TB-5 Powerplant: 2 × 480 hp M-22 ( Bristol Jupiter VI Wingspan: 31.00m Wing area: 150.00 m² Length: 22.10m Height: 5.02m Empty weight: 7483 kg Normal takeoff weight: 12535 kg Wing loading: 83.5 kg/ m² Power Load: 7.0kg/hp Fuel + lubricant capacity: 3300 kg Top speed: 200km/h Cruising speed: 182km/h Range: 2100 km Ceiling: 3500 m Accommodation: 5 – 7 Armament: 3 x TUR-5 type turrets with paired Degtyaryov light machine guns / 1 x pair of PV-1 machine guns Bombload: 1000 kg
By 1929, the TsAGI in Sevastopol researchers began to develop experiments with a view to defining the ideal characteristics of the hulls of ships and aircraft.
Between 1929 and 1930 the engineer NN Podsevalov began to experiment with the different pressures experienced by the hull of a flying boat in the different regimes of navigation; take-off and landing. For this, a series of membranes fixed to dynamometers were installed in different positions at the bottom of the hull of the Grigorovich MUR-1 prototype.
For the continuation of the tests, Grigorovich was asked to build a slightly different hull with a 14º increase in the angle of incidence in the keel area. Built by GAZ No.3 “Krasni Liotchik” from Leningrad, this new flying boat model received the name MUR-2 (Russian: Григорович МУР-2) and was tested in flight, showing characteristics similar to those of the MUR-1. Later it was delivered to the TsAGI for further testing, so this model, of which only one example was built, can be considered purely experimental.
The hydrodynamic tests continued until 1931 allowed the TsAGI to issue the Stiffness Norms for the design of flying boats.
Attempts to modernize the M-5 flying boat gave no improvement and the objective could only be achieved through a totally new construction. Grigorovich decided to take on the task. The new design would see the light as MU-2 (Russian: Григорович МУ-2) or Morskoi Uchebni – 2 (Naval Trainer).
For the MU-2 Grigorovich selected the 100 hp Soviet M-11 engine. The hull was built entirely of metal and featured a new deck design with straight contours and an angular groove, which should give it good seaworthy characteristics, apart from being easier for production. The structure of the MU-2 contained 27 frames, of which 5 constituted the supports for the watertight compartments of the hull.
The wooden wing had a double spar structure with an Eifel-367 profile. The interplane uprights were also made of wood. Ailerons were on both planes.
The structure of the tail was made of duralumin, covered with fabric.
The shrouded M-11 radial engine sat on a pyramidal structure of metal tubes and drove a pusher propeller. The main fuel tank, with a capacity of 105 liters, was located in the hull, behind the cockpit. An auxiliary tank for direct supply to the engine, with a capacity of 11 litres, was located in front of it, protected by the elongation of the cabin. The transfer of fuel from the main to the auxiliary tank was carried out by a compressor or a manual reserve pump.
The MU-2 flying boat featured an open cockpit with a windshield for its two crew members sitting side by side. The control was by lever and the instrumentation was duplicated. The pilots’ pedals were synchronized.
Construction of the MU-2 began in 1927 at GAZ No.3 “Krasni Liotchik” from Leningrad and was completed without the presence of Grigorovich, who was in prison at the time.
During the construction process it was found that the MU-2 would be 150-200 kg heavier than the calculated values. The empty weight reached 820 kg, of which 220 corresponded to the hull. This was because the dimensions of the hull remained generally similar to those of the M-5, when according to the regulations, taking into account its metallic construction, they allowed a 10% decrease in size. Although the construction was quite careful, it was impossible to maintain the 660 – 700 kg of the project.
The tests of the flying boat began on August 29, 1929 at the testing station of Factory No.31 in Taganrog with the naval pilot ST Rybalchuk as responsible.
On September 6, 1929 the future of the MU-2 was discussed during a meeting of the Technical Committee of the Aviatrust. The most renowned shipbuilders of the time were present at this activity: Richard, Artamonov, Zhuravchenko, Samsonov, Chetverikov and Polikarpov.
MU-2 was reported to be at Taganrog, where the pilot Rybalchuk had executed the first flight. Preliminary results showed that the cabin was narrow, but the access hole was very wide. The flying characteristics of the flying boat were assessed by the pilot as rather poor and he also stated that the plane would not be able to get out of a spin. The climb did not stand out either, since the MU-2 reached 3,500 meters after 85 minutes of flight. The take-off run was quite long.
It was further noted that the centering of the MU-2 was similar to that of the Italian model Savoia S-16, located at 38% of the length, so it was proposed to carry out tests in the wind tunnel of the TsAGI and then proceed to improve the apparatus.
In practice nobody did anything to improve the MU-2. Shortly after, using this design as a basis, the builder of Factory No.23, A. S. Moscaliov, would present his project for a wooden-hulled training flying boat that would receive the name MU-3. This model was built during 1931 and later successfully tested, but would not go into series production as it was displaced by the Shavrov Sh-2.
Powerplant: 1 × 100 hp М-11 Wingspan: 11.80m Wing area: 35.60 m² Length: 8.60m Empty weight: 820kg Normal takeoff weight: 1086 kg Fuel weight: 90kg Maximum load capacity: 266 kg Wing loading: 30.5 kg/m² Power Load: 10.9kg/hp Maximum speed at sea level: 136 km/h Cruising speed: 108km/h Landing speed: 70km/h Practical range: 380 km Endurance: 3 hours Practical ceiling: 3150 m Time to 1000m: 10.8min Time to 2000m: 26min Time to 3000m: 53min Turn time: 18 sec Take-off run time: 35 sec Landing run time: 12 sec Accommodation: 2
