The Twin Astir was a two-seat 1970s development of the Standard Class Astir CS, differing from it principally in having a fuselage lengthened by 9.75 in to accommodate the second seat, and also reduced in depth by 1.5 in; wing span has been increased to 17.5m (57 ft 5 in) and the wings are now swept forward 3° 18′. The gear retracts by folding up to the left and lying horizontally under the rear seat. The 3.3 degree forward wing sweep was replaced by a straight wing with leading edges at right angles to the fuselage centerline early in the production run. Dual controls are provided under the two individual canopies, and the Twin Astir is offered to customers both with and without the basic instruments in the front cockpit and with or without water ballast, of which up to 198 lb can be carried.
The Twin Astir has the same mid wing position and T-tail as its single-seat counterpart, and is of the same glassfibre construction. In contrast to later G 103 models, the Twin Astir has the main wheel ahead of the center of gravity, and does not have a nose wheel. It was offered with a tailskid or an optional tail wheel. The G 103T Twin Astir had a fixed main wheel.
Design of the Twin Astir began in September 1974 and construction of the prototype was commenced in March 1976; this made its first flight on 31 December 1976. By the end of 1978 over 225 Twin Astirs had been delivered; production has now ended. The type is also known as the Twin Astir Trainer when used for this task.
Twin Astir G 103
Formerly the G118, the Twin II is a new tandem two-seater for training and club use to succeed the Twin Astir, from which it differs in having a narrower and more streamlined fuselage, improved cockpit layout and larger canopies, lower-set wings, a fixed monowheel plus a small wheel (likewise semirecessed) under the forward cockpit and a tailwheel, downturned wing tips and reduced empty weight. The same type of elasticated flaps as featured on the Speed Astir are fitted, and the T-tail is similar to the Twin Astir’s. Unlike the latter, no water ballast is carried. The Twin II first flew late in 1979.
The G-103 A Twin II was the successor of the Twin Astir with a nose wheel and a fixed six-inch main gear fitted behind the center of gravity in a fairing. The main wheel is equipped with a hydraulic brake. Modified ailerons produce a substantially improved roll response. Approach control is by top surface Schemmpp-Hith type airbrakes.
The Twin II won the world Out & Return record for two-seat sailplanes (1000.88 km/ 621.92 miles) flown by Tom Knauff of the U.S. The Twin II Acro is similar to the earlier model, but with strengthened mainspar caps and steel control pushrods which permit greater aerobatic performance. The Royal Air Force acquired 100 Acros (known as the Viking T. MK.1) for its air cadet training program. The G 103 has a FAA approved modification kit for all-hand control for handicapped operation. Air Transport Certified.
G 103 C Twin III
The G 103 C Twin III is a development of the Twin II with a new Discus plan wing of slightly increased span and modified airfoil section. The cockpit has detailed improvements including better ventilation, relocated airbrake levers to give better purchase, and canopies restrained by gas-filled struts. The unpowered sailplane is cleared for aerobatics similar to the Twin II Acro. The self-launching version (Twin III SL), which is non-aerobatic, has an electrically actuated mast-mounted retracting engine and steerable nose wheel. Fuel is stored in a main tank in the fuselage close to the engine, and in an auxiliary tank in the left wing root from which fuel is moved by a transfer pump. The variable pitch propeller has climb and cruise setting.
Twin Astir G 103 Wing span: 17.5 m / 57 ft 3 in Wing area: 17.89 sq.m / 192.6 sq.ft Length: 8.1 m / 26 ft 8.75 in Height: 1.6 m / 5 ft 3 in Empty Weight: 390 kg / 859 lb Payload: 286 kg / 631 lb Gross Weight: 676 kg / 1490 lb Wing Load: 37.79 kg/sq.m / 7.73 lb/sq.ft Water Ballast: 90 kg / 198 lb Aspect ratio: 17.1 Airfoil: Eppler E 603 Max speed: 155 mph / 135 kt / 250 km/h (smooth air) Max aero-tow speed: 105 mph Stalling speed: 40 kt / 74 km/h MinSink: 0.68 m/s / 2.23 fps / 1.32 kt at 56 mph / 40 kt / 75 km/h L/DMax: 38 at 109 kph / 59 kt / 68 mph Seats: 2
Grob G-103 Twin II Span: 57 ft 5 in Length; 26 ft 10 in Height: 8 ft 1 in Wing area: 191.6 sqft Aspect ratio: 17.2 Empty weight: 794 lb Max take-off weight: 1,278 lb Max speed: 155 mph (smooth air) Max aero-tow speed: 105 mph Min sinking speed: 2.1 0 ft/sec at 50 mph Best glide ratio: 37:1 at 65 mph
Twin II and Twin II Acro G 103A Wing span: 17.5m / 57.4ft Wing area: 17.8sq.m / 191.6sq.ft Empty Weight: 368kg / 811lb Payload: 212kg / 468lb Gross Weight: 580kg / 1279lb Wing Load: 32.58kg/sq.m / 6.67lb/sq.ft Water Ballast: 0 L/DMax: 35 105 kph /56 kt / 65 mph MinSink: 0.75 m/s / 2.45 fps / 1.45 kt Aspect ratio: 17.2 Airfoil: Eppler E 603 Seats: 2 No. Built: 549
Twin III Acro and III SL G 103 C Wing span: 18m / 59ft Wing area: 17.5sq.m / 188.4sq.ft Empty Weight: 390kg / 860lb Payload: 210kg / 463lb Gross Weight: 600kg / 1323lb Wing Load: 34.29kg/sq.m / 7.03lb/sq.ft Water Ballast: 0 Aspect ratio: 18.5 Airfoil: Eppler E583 L/DMax: 36 107 kph / 58 kt / 67 mph MinSink: 0.70 m/s / 2.3 fps / 1.36 kt Engine: SL model only Seats: 2 No. Built: 167
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
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).
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
Model of the Grigorovich IP-2 during the construction process at the beginning of 1936
Grigorovich designed the IP-2 / DG-54 (Russian: Григорович ИП-2 (ДГ-54)) fighter in the winter of 1935-1936. The IP-2 appeared as a modification of the IP-1 gunship fighter and as main differences it had slightly increased dimensions and a 760 hp Hispano-Suiza 12Ybrs engine. The manufacturing name of the model was DG-54 and in some literature it has been called PI-2 by the acronym P uchechni I sterbitiel or Gunship fighter.
The IP-2 fighter was designed as a single-seater monoplane with a low cantilever wing. In plan view it was similar to the British Supermarine Spitfire.
The IP-2 kept the elliptical wing introduced in the IP-1 and built according to the “Grigorovich wing without stringers” formula. The main difference is that in the case of the IP-2, the builders were forced to install an inverted gull-type wing in order to raise the nose of the device from the ground in the presence of a larger diameter propeller.
The fuselage in this case maintained a construction similar to that of the IP-1, but it featured an elongated nose in order to accommodate the Klimov M-100A engine, a licensed version of the 860 hp Hispano-Suiza 12Ycrs. The tailplanes, elliptical in shape, presented in this version medium implantation and cantilever.
The landing gear maintained the retracting system with the wheels semi-inserted in specially designed fairings and installed at the wing angle change point.
Another new detail in the IP-2 was the closed cockpit for the pilot. This fighter incorporated a powerful armament consisting of a 20 mm ShVAK cannon located in the V of the engine and 4 ShKAS 7.62 mm machine guns located in the wings. This could be increased up to 10 machine guns in the ground attack version. Under the wing, supports were provided to carry up to 40 kg of bombs.
During the first half of 1936 a full-size mock-up was built at Factory No.1 “Aviajim” followed by approval to build an experimental prototype.
The project was completed and in the first half of 1936 a set of parts and components had already been produced, but once again Grigorovich was affected by the restructuring of the Soviet aircraft industry. On May 11, 1936, the Labor and Defense Council (STO) decreed the specialization of aeronautical factories and the linking of builders with the serial production of their models.
In the summer of 1936 Grigorovich’s OKB was closed and he transferred to GUAP as head of the naval department. His group, made up of 25-30 people, was sent to the TsAGI Experimental Construction Factory (ZOK). All the unfinished projects ended up there, including the IP-2 fighter. The ZOK had been intended to specialize in the development of scout aircraft, so all documentation and items produced were sent to Kharkiv Factory No.135, where the IP-1 was produced. A year and a half later, when the production program was redefined for 1936 –1937 the IP-2 was excluded.
Powerplant: 1 × 860 hp Klimov M-100A Wingspan: 11.00m Wing area: 20.60 m² Length: 8.06m Height: 3.27m Empty weight: 1430 kg Take off weight: 1952kg Wing loading: 94.75 kg/m² Power load: 2.27 kg/hp Accommodation: 1
first prototype of the IZ fighter in the workshop of Factory No.39.
At the end of the 1920s work related to the development of a new type of barrel known as a dynamoreactive barrel (DRP) and characterized by the absence of recoil.
Great attention was devoted to the development of the 76.2 mm aviation guns. The main reason for this decision was the need to increase the firepower of the fighters, whose machine guns proved ineffective against the new all-metal bombers.
The first gun of this type, called APK-1 after the acronym for Avtomaticheskaya Pushka Kurchevskovo or Kurchevski ‘s Automatic Cannon, began tests on July 26, 1929. It became clear that the use of APK guns required the design of new types of aircraft with great structural reinforcement.
The task of designing this new type of aircraft was assigned in parallel to the TsAGI led by AN Tupolev and the TsKB under the direction of the OGPU, headed (unofficially) by DP Grigorovich as technical director.
Grigorovich had been under arrest since September 1928 and was under the supervision of the OGPU. After the collective of prisoners under his leadership succeeded in developing the excellent I-5 fighter in the spring of 1930, Grigorovich, though still under arrest, was appointed chief consultant to the TsKB. Prison conditions for him were improved, even allowing him to travel with his family on vacation to Yalta (with the necessary company of OGPU staff). Returning from the south, Grigorovich was asked to develop a fighter aircraft with three-inch barrels.Kurchevsky.
The aeronautical development system applied in the TsKB-39 did not conceive the existence of a main constructor. The designs were developed by brigades directed by a specialist and from the initial conception, different departments were in charge of carrying out the work related to their specialty. For this reason, the models developed in the TsKB during this period are generally not referenced to a specific author (generally in the literature they are named TsKB and the particular name of the model). However, in the case of the IZ fighter, the same is not the case. Despite being built within the structure of the TsKB, the task was so secret and a priority that Grigorovich received the approval to form a small group under his direction, which was to be in charge of all the development of the model.
The new task force of the Grigorovich began work in one of the hangars of Factory No.39. Among its members were: AN Sidielnikov, VL Korvin-Kerber, AN Nadashkievich, Ye. I. Mayiranov, VD Yarovidski, G. Ye. Chupiloko and S. N. Shishkin. In general, this group had stood out during the development of the I-5 fighter , so many of the construction elements of the new fighter would be designed under this influence.
In relation to the origin of the name for the new fighter there are several versions. The first version establishes that due to the secrecy in relation to the project, it was decided to name it using the Latin letter Z (something unconventional since letters of the Cyrillic alphabet were generally used for these cases). In this way the name of the fighter combines the Cyrillic letter И (corresponding to the I and acronym for Istrebitiel or hunting) with the Latin letter Z.
Other sources state that since the fighter was developed in hangar No.7 of Factory No.39 its initial name was I-7, but due to the appearance of another model I-7 mass-produced in Factory No.1 from Moscow (licensed version of the Heinkel HD-37), Grigorovich suggested adding a line at the bottom of the number so as not to have to redo all the documentation and thus the 7 became Z (Russian: Григорович И-Z – ЦКБ-7).
Which of these versions is the real one is difficult to establish. In period documents the fighter is referenced as TsKB7, TsKB-7, Z(N-7). Only a couple of years later, when the model had already been approved, the term И-Z began to be used in the documentation, but due to the fact that most typewriters in the USSR lacked the possibility of writing Latin letters generally everything was written in Russian as И-ЗЕТ (I-ZET).
By the spring of 1931 Grigorovich’s work had attracted widespread attention. Members of the GPU leadership and later from the Kremlin would soon begin visiting the TsKB. The TsKB would be visited by Molotov, Ordzhonikidze, Andreyev, Voroshilov. As a result of this interest, most of the prisoners would soon be released.
In May 1931 the newspaper “Pravda” would publish “granting amnesty to the builders listed below, previously accused and sentenced by the OGPU college to different sentences of a social nature and at the same time rewarding them. To the chief builder of experimental models Grigorovich, Dmitri Pavlovich, retracting his previous positions and proving after a year’s work of his sincerity – the recognition of the TsIK USSR and a cash prize of 10,000 rubles.”
The IZ fighter was designed as a single-seat, low-wing braced monoplane. The fuselage featured metal construction. The entire front and center fuselage was made of a skeleton of welded chrome-molybdenum steel tubes. In general, this entire forward section presented little difference from that of the I-5 fighter. The tail section was all new, semi-monocoque construction and attached to the front at four points.
The structure of the tail section was made up of 11 elliptical frames, of which the last four were integrated into the keel. The fuselage featured a duralumin coating.
The wing had a double spar structure and its fixing was reinforced o by a pair of steel supports with a drop-shaped section. The wing construction in the prototype was developed using stainless steel (Enerzh-7) joined by welding, but the production examples used wooden wing structure. The stringers had a box-like structure to which 22 plywood ribs were attached. The wing covering was made of fabric, except for the area where the cannons were fixed, where it was reinforced with aluminium.
The wing profile was Gettingen 436, but its thickness decreased in the area where it joined the fuselage. The centroplane had a rectangular shape, but the wing consoles, in order to reduce the inductive resistance, received an elliptical shape.
The tail unit was duralumin and heavily reinforced. The entire empennage skin, excluding the leading edge of the keel, was corrugated. The stabilizer was raised on the empennage in order to avoid the harmful effects of exhaust gases from the guns and was braced to the empennage by two parallel metal studs. Initially, the rudder had a fabric covering, which was soon replaced by a duralumin one.
The landing gear featured steel N-legs with rubber cushioning and a central axle linking the 750 x 125mm main wheels. Tensioning straps started from the undercarriage to the wing. In the tail a steerable skate with rubber cushioning.
Instrument panel in the cockpit of the IZ fighter.
The power plant of the IZ consisted of the M-22 engine (version of the Gnôme-Rhône 9Aq, a licensed copy of the British Bristol Jupiter VI engine built in the USSR at Zaparozhie Factory No.29) and its installation it was virtually identical to that of the I-5 fighter, built by Polikarpov and Grigorovich some time before. The cylinder heads on the prototype featured individual fairings, which were replaced on production models by a Townend ring.
The pilot was located in an open cockpit, located behind the engine and lacking a windshield.
The armament consisted of a 7.62 mm PV-1 machine gun located in the fuselage, to the right and in front of the pilot, which was used as a sighting rifle for the cannons. This machine gun was fitted with a PUL-9 synchronization system to allow firing through the moving propeller. Under the wings were the two APK-4 or APK-4bis cannons.of 76.2mm. Its installation on the wing allowed firing without interference from the propeller. In the first IZ the guns were located in the inner area of insertion of the wing supports. Later the guns would be moved further out on the wing. Each barrel was equipped with a cylindrical magazine with 6 shells and a seventh already mounted on the gun and featured an automatic reloading system from the use of exhaust gases. 0.6 m cylinders designed as exhausts were located at the rear of the guns.
The IZ prototype was ready for the summer of 1931. The date of its first flight is not known with certainty, but it is known that it was made in this period by test pilot Benedict L. Buxgolts.
On July 6, 1931 Factory no.39 was visited by Stalin, who had previously been informed about the IZ fighter. Stalin not only checked the plane, but climbed into the cockpit and moved the flight controls. The main builder was not there at that time, so the presentation of the model was made by the head of the TsKB for the GPU Ye. S. Paufler.
YV Stalin in the cabin of the first IZ at Factory No.39 on July 6, 1939. On the wing (from left to right) engineer G. Ye. Chupilko, VM Molotov, K. Ye. Voroshilov, AN Rafaeliants and GPU Commissar Ye. S. Paufler.
During this visit Stalin was presented with other models developed at the TsKB such as the I-5 fighter in various variants, the TB-5 heavy bomber, the TSh-1 attack aircraft and TSh-2, modifications of the R-5. Stalin was favorably impressed. As a result, by the Aviation Union Order No.265 (VAO according to the acronym of B ciesoyuznoye A viatsionnoye O biedinienie) of August 27, 1931 the TsKB and the TsAGI would be united into a single organization (known generally as TsKB-TsAGI), under the direction of Paufler.
The IZ had been built in a hurry and this was reflected in its initial results. Grigorovich’s collective was forced to work on improving the model for a year. Despite successful tests, Kurchevski’s guns generated constant headaches. Building and testing the single-shot APK-1 cannons proved to be an extremely simple task compared with the development of autocannons capable of self-reloading and multiple shots.
The first modified IZ with new cowl and undercarriage
This situation began to worry some personalities. During a meeting at Factory No.39 held on March 2, 1932, the head of the VVS RKKA PI Baranov stated:
“The Z(N-7) aircraft has been built for almost a year, Factory No.39 presented it to the government in June-July 1931 and promised to improve it. where is the result?
Paufler replied that the plane had been ready for a long time, that 74 shots had been fired from the guns on the ground and 10-12 in the air, during which the exhaust of one of the APK guns had been damaged, but in general everything was fine. well and the factory was ready for series production. Kurchevski, who was present, complained that he was not allowed access to the plane to work.
It was established that the Z(N-7) would be used as an interceptor aircraft, designed to destroy enemy bombing forces in frontal encounters. Impact 3 kg shells with an initial velocity of 347 m/s were expected to make a formidable weapon. It was decided to submit the Z(N-7) for state testing on March 12.
After the first prototype, a second improved specimen would appear, which in some literature has been called I-Zbis. This model would fly for the first time in 1932.
Serial Grigorovich IZ – wooden wing and Townend ring
No evidence has been found to show that the acceptance tests were carried out by the military, but on April 27, 1932, the director of Factory no.39 S. Margolin signed an agreement with the VVS Directorate to build 20 “Z” fighters with special weapons worth 77594 rubles per unit. Taking into account unforeseen expenses until September 1, 1933 (fixed delivery date) Factory No.39 would receive 2,398,909 rubles, which brought the actual price of each aircraft to 119,945 rubles.
Series IZ with Townend cowl and APK-4 barrels.
This series were intended to carry out field tests and develop the tactics of use of the cannons and differed from the prototype by the use of a wooden wing and an M-22 engine faired with a Townend ring.
Front view of the series IZ fighter.
Between 1934 and 1935, another 50 aircraft were built at the Kharkov Factory No.135, but their flight characteristics and performance were not very good; moreover, the APK guns were also unconvincing. The maximum speed in these aircraft was about 40 km/h lower than that of the prototypes. Most of these ended up being used in different test programs.
One of the first serial specimens, the IZ with number 39009, was tested in February – March 1933 at the VVS polygon in Mónino. The tests were carried out by test pilot Yu Piontkovski.
Ground fire tests of the IZ number 39009 at the NII VVS (Shelkovo) in Feb – Mar 1933.
The aircraft carried a working cannon under the left wing and a mock-up of similar weight and dimensions under the right. For the development of ground tests in Shelkovo. This land had recently been handed over to the NII VVS and there were no buildings of any kind on it. There, a structure 5-6 meters high was prepared with an inclined ramp from which the shots were fired. During these tests, intended to check the resistance of the aircraft during the action of the gun, no problems were found.
From September 14 to October 1, 1933 in Shelkovo the tests of the IZ 39010 were carried out, armed with the APK-4 serial guns equipped with magazines for 6 projectiles (plus one directly located in the barrel).
The flights were carried out by M. Stselnikov and in total they lasted 16 hours and 20 minutes.
The results highlighted that 39010 was built quite similarly to the prototype and due to its dimensions and characteristics, no differences were observed.
The cockpit was comfortable and spacious. During takeoff the IZ lifted off the ground with ease and horizontal flight was performed with the stick fully free. Stability was good at all speeds and control was smooth and easy.
The data obtained for time of ascent to 5,000 m (14 minutes) and flight ceiling (7,000 m) were considered acceptable, but the maximum speed of 259 km/h and the range of 310 km were evaluated as poor. The main cause of these difficulties was defined as the inefficient landing gear and the great aerodynamic resistance of the APK guns.
The artillery armament passed the tests, but its shell capacity was considered too small. Kurchevski proposed to install a magazine with 10-14 shells in the wing, but this would not come to fruition.
As a conclusion, it was defined that the IZ fighter could be received into service with the RKKA VVS with the fulfillment of the following conditions: Raise top speed to 300 km/h Increase fuel capacity Raise the amount of shells to 20 units Install electrical equipment and radio Desire to increase the structural rigidity of the plane, because after 300 – 500 shots it was necessary to carry out a complex maintenance intervention on the aircraft. The VVS wanted to raise this number to 1,000 shots. The modified aircraft was to be ready by March 1, 1934.
The installation of the cannons added a significant number to the aircraft’s weight. The two APK-4 guns weighed about 150 kg, and the 14 ammunition – 55 kg. This meant 12% of the model’s takeoff weight. The APK-4 dynamoreactive cannons were installed in the wing of the aircraft with angles of 2 – 3º. All this part of the wing was coated with duralumin. This location contributed significantly to the poor performance due to the high aerodynamic resistance of the installation.
In April 1935, a special aviation group was created, consisting of a squadron of IZ fighters, one of R-5 reconnaissance aircraft for cone towing, and a TB-1 bomber. This unit was transferred to Yevpatoria in order to test the behavior of the gun in the air, its influence on the construction of the IZ fighter and the definition of its service time.
Test flights began on May 15, 1935. The tactics provided for firing in a dive, ascent or horizontal flight, both in individual salvos and in series.
It was found that after 100 to 150 shots the aircraft had to be inspected in depth as it generally suffered extensive damage to its structure and coating, making it necessary to replace the damaged elements and components. Fundamentally, the rivets, joints and coating suffered. It was also established that each cannon could withstand about 240 shots.
Cases are recorded of number 13534, which was capable of withstanding just over 340 shots without the need for repair. From the results of the tests it was considered that the period of active service of the IZ model should be defined by the scope of the figure of 400 shots.
In the development of multiple tests, most of the IZ specimens produced became unusable. At the beginning of 1936 the units received only a few copies. By that time the work on the DRP guns had practically been abandoned and the use of these fighters was out of date. For this reason the IZ did not get to operate in the designed roles.
The IZ was one of the aircraft used by VS Vaxmistrov in the development of his combined or ”Zvenó” aircraft. From the beginning of 1931 Vaxmistrov began work on the suspension of an IZ fighter under a Tupolev TB-3 bomber. In 1934 Vaxmistrov decided to develop a new version of the Zvenó by combining a TB-3 with two IZ fighters. this combination would be known as Zvenó-3 or 3-3.
IZ with the trapeze used for the suspension in Vaxmistrov’s Zvenó.
In this combination the fighters were fixed on the ground by special supports to the wing of the bomber. Before release, these supports separated from the wing by 0.5 meters in order to avoid impacts of the empennage against the wing at the time of detachment.
The first flight of this combination was made in July 1934. The TB-3 bomber crew was led by PM Stefanovski and the IZ fighters included AV Korotkov and Grodz. During the release Korotkov’s fighter rose, breaking the bomber’s wing skin and getting stuck in it. An emergency landing was necessary. Luckily, at the time of landing, the plane broke free as a result of the impact with the ground. The fighter pilot was killed but the rest of the crew managed to save themselves. As a result the Zvenó-3 combination was abandoned.
Zvenó No.5 – Grigorovich IZ fighter and Tupolev TB-1 bomber.
The next variant of use of the IZ fighter in combined aircraft was known as Zvenó-5 (3-5) and involved suspension of an IZ fighter under the TB-3 bomber once it was in the air. The mother plane released a kind of trapeze that was fixed to the DER-15 rear supports. The release of this structure was carried out by the on-board mechanic from its location and its subsequent retraction was carried out with the help of a crank.
The IZ fighter was also modified. In the upper part of the fuselage a fixing structure with a security system was installed. The wing consoles were also reinforced, since the section of the wing ribs 12 – 14 ended up resting on the bomber wheels once the trapeze was retracted. The other support point was at the top, behind the cockpit.
Testing of the Zvenó-5 began on March 15, 1935. In this case, the IZ was piloted by VA Stepanchonok, while PM Stefanovski was once again at the controls of the TB-3. Initially, training flights were carried out consisting of placing the fighter behind the bomber, equalizing their speeds at about 140 km/h and then making approaches and separations to a percale tape fixed to the bomber. Until March 21, 25 trainings of this type were carried out.
The world’s first capture of one aircraft in flight by another took place on March 23, 1935. After fixation the IZ was elevated. The Zvenó dropped to a height of 500 meters and flew over the aerodrome where a VVS commission sent to supervise the test was located. After recovering the 1200 meters of height, the separation took place, again without problem. Until March 29, 5 flights like this were carried out with capture and release of the IZ fighter in the air.
The Aviamatka PVO in flight with its 5 fighters. At the bottom hangs the Grigorovich IZ.
By the fall of 1935 Vaxmistrov prepared for tests a new combined system known as Zvenó TB-3 4M-17 + 2 I-5 + 2 I-16 + IZ. Vaxmistrov himself named this creation Zvenó Aviamatka PVO (AM). On the ground under the wing of the TB-3 two I-16 fighters were fixed and on the wing the two I-5 fighters. The last member, the IZ fighter, was fixed once the Zvenó was in the air.
During the tests the TB-3 was flown by PM Stefanovski, the I-5s by AI Nikashin and SL Suprún, the I-16s by TT Altynov and KK Budakov and the IZ VA Stepanchonok.
The experiments demonstrated the feasibility of using the chain consisting of one bomber and five fighters. Never before or since in the world has anything like it been tried. The tests were carried out jointly with the Moscow Factory No.22, in charge of carrying out the modifications to the fighters and the mother plane.
The conclusions of the tests determined that the Zvenó with TB-3 4M-17 + 2 I-5 + 2 I-16 + ZET can be effectively used in RKKA units. However, the final conclusions were different. It was considered that the presence of the I-5 fighters on the wings and the IZ under the fuselage limited the possibilities of the TB-3 bomber, so it was preferred to develop a variant with only two I-16 fighters in attack version under the name Zvenó SPB and would be used successfully during World War II.
IZ Powerplant: One 480-hp M-22 radial Wingspan: 11.50m Wing area: 19.5 m² Length: 7.65m Empty weight: 1180 kg Normal takeoff weight: 1648 kg Wing loading: 84.5 kg/ m² Power Load: 3.4kg/hp Fuel + oil capacity: 180 kg Maximum speed at sea level: 258 km/h Top speed at 5,000m: 239km/h Cruising speed: 212km/h Landing speed: 100km/h Practical range: 600 km Endurance: 2.5h Maximum rate of climb: 358/min Climb time to 5000 m: 14 min Practical ceiling: 7000 m Landing run: 180m Take-off run: 110m Armament: Two 76.2mm Kurchevski APK-4 cannon with 14 rounds / one 7.62mm V-1 machine gun Accommodation: 1
The IP-3 fighter, which received the manufacturing name DG-53 (Russian: Григорович ИП-3 (ДГ-53)), basically differed from the DG-52 (IP-1) due to its smaller dimensions, its reduced surfaces and its lower flight weight. It seems that with the IP-3 Grigorovich tried to obtain a fighter for close combat armed with machine guns, but for some reason he drifted towards a utility model equipped with Kurchevski ‘s dynamoreactive cannons. In this case, the cannons were simply smaller in terms of caliber, weight and dimensions.
The IP-3 fighter was designed to use the 37 mm APK-11 recoilless automatic cannon, proposed by Kurchevski in 1932. These cannons stood out for their magazine feeding, which allowed the number of projectiles per gun to be increased to 25. Up to 12 projectiles were placed in two magazines and the last one was placed directly in the gun when preparing it. The weight of the APK-11 with the magazines reached 39.1 kg. The explosive projectile weighed between 475 and 500 grams and was ejected from the barrel at a speed of 438-475 m/s. The reloading of the barrel after each shot was done automatically using compressed air located in a 5-liter tank.
In addition to its smaller dimensions, the IP-3 was easily differentiated by having individual exhaust pipes that came out of holes in the hood and the introduction of cantilever wing planes. A novelty in this model was the installation of landing flaps. The Shvetsov M-25 radial engine, developed on the North American Wright Cyclone, remained as the power plant.
This fighter was designed to carry two 37mm Kurchevski APK-11 cannons as well as two light machine guns. Unfortunately, at the time of finishing its construction, the APK-11 guns were not yet available. By the end of 1934 it was decided that the APK-11 guns were not ready and for their acceptance it would be necessary to modify them.
On July 2, 1935 the head of the OKB of Factory No.1 Aviajim DP Grigorovich informed the head of the GUAP GN Korolyov about the completion of work on the prototype. In his letter he wrote: “The IP-3 aircraft with Wright Cyclone is ready for factory tests and has been received by the LIS of Factory No.1 to carry out the tests. I request your approval to start them.”
Factory tests were started in July 1935. Apparently the hope of receiving the APK-11 guns remained latent and the definition of the future of the plane depended on these works.
With the decision to suspend work on the dynamoreactive guns, the interest in the IP-3 disappeared and the development of the model was not continued. In later documents appears the instruction to delete the IP-3 Shvetsov M-25 of Factory No.1 from the construction plan for 1937.
A second prototype known as the IP-4 or DG-53bis and designed to carry two ShVAK guns instead of the Kurchevski ones, remained in the project phase.
Kurchevsky continued to improve his 37mm guns and even managed to get it approved for mass production, but this weapon never found practical application.
IP-3 Engine: Shvetsov M-25, 700 hp Wingspan: 9.60m Length: 7.08m Wing area: 16.36 m² Normal takeoff weight: 1548 kg Maximum speed at sea level: 382 km/h Maximum speed at height: 435 km/h Cruising speed: 298km/h Practical range: 830 km Practical ceiling: 8800 m Armament: Two 37mm Kurchevski APK-11 cannons, 25 rds & two 7.62mm ShKAS machine guns. Accommodation: 1
Grigorovich IP-1 with ShVAK cannons and machine guns in the wings.
A proposal arose to use new-type cannons in airplanes, in which the recoil was compensated by the reactive force of the gases expelled during firing, for which they were known as dynamoreactive cannons (DRP). These guns were lighter than normal guns of a similar caliber.
The development theory of dynamoreactive guns was developed in the late 1920s by professor and later academician BS Stiechkin. The engineer LV Kurchevski was in charge of materializing these ideas. The guns designed by him were named APK after Avtomaticheskaya Puchka Kurchevskovo or Kurchevski Automated Guns and would be used for the first time in the IZ fighter developed by Grigorovich.
In 1934 D. P. Grigorovich prepared a new fighter armed with APK cannons, which received the factory name DG-52 and was known by the military as IP-1 (acronym for Istrebitiel Puchechni – Gunfighter) (Russian: Григорович ИП-1 (ДГ-52)).
Structurally, the IP-1 was designed as a low-wing cantilever monoplane with all-metal construction. The fuselage terminated in a large-area empennage with the planes set high and braced by struts. The fuselage skin was made with sheets of 1.0 – 1.5 mm. The central wing occupied 55% of the entire span to locate the cannons outside the propeller arc.
The elliptical-shaped wing was designed to achieve the lowest inductive resistance. The wing construction was made up of tubular chrome-molybdenum steel stringers with skeletal ribs made up of rolled profiles with stringers supporting the coating. This wing would later be known as the “Grigorovich Stringless Wing”. The wing covering, with sheets of 0.6 – 0.8 mm, was fixed to the edges of the stringers by means of additional profiles and to the edges of the ribs. The ailerons and landing flaps were designed as shutter type.
The tail was totally metal, but in the production copies the rudders were covered with fabric.
Originally a retractable type landing gear was selected with the ability to carry wheels in the summer and skis for the winter. The undercarriage retracted backwards, leaving the skis inserted in fairings in the wing. This solution, used for the first time in the USSR, reduced aerodynamic resistance to such an extent that the model could maintain performance throughout the year. The landing gear had oleo-pneumatic suspendion and the retraction system had a hydraulic drive. The prototype’s tail skid lacked retraction, but on production examples it would be replaced by a fixed wheel.
The power plant selected was the 640 hp Wright Cyclone SGR-1820 F-3 covered by a long NACA hood. The propeller had metal construction and ground adjustable pitch.
The pilot was accommodated in an open cockpit with a faired headrest in the fuselage.
The armament was similar to that of the IZ fighter, with two APK-4 dynamoreactive recoilless cannons under the wings capable of firing 5 rounds, but instead of the PV-1 machine gun a more effective ShKAS were installed. These machine guns were to serve as aiming rifles for the main recoilless guns.
Grigorovich IP-1 fighter with its APK-4 cannons under the wing midplane.
The state tests of the IP-1 fighter were developed between January and March 1935. The fighter was characterized by high speed and good manoeuvrability, with a turn time of 14-15 seconds. The climb was poor due to the great weight of the cannons.
The military gave an excellent evaluation of the model, highlighting the high speed, the good manoeuvrability and stability in flight, the simplicity of piloting, and the good visibility from the cabin. The great stability of the dive was also highlighted.
The tests showed that the fighter had reservations and problems appeared. Among them, the weakness of the engine hood, the overheating of the oil, difficulties with the control of the plane at the time of departure or retraction of the landing gear, the inconvenience of using the machine gun and the lack of rigidity in the fixing of the APK cannons, among others.
Grigorovich IP-1 prototype color scheme
After the tests carried out between August and September 1935, other defects appeared, such as weakness in the fuselage coating and low effectiveness of the ailerons. It is noteworthy that none of these problems was serious and all could be solved with a certain amount of work, so they did not overshadow the potential of the model. The design collective kept improving the IP-1 until 1936.
The head of the VVS Ya. I. Alksnis demanded that the RKKA VVS Directorate submit its requests to increase the request for IP-1 fighters at the cost of reducing the requests for other fighters.
The IP-1 went into production at Kharkiv Aviation Factory No. 135, where a metal aircraft was being built for the first time. In parallel, modifications and improvements began, which were introduced directly into the production process. Early examples were armed with two APK-4s and two ShKAS machine guns.
first production versions with a tapered fuselage
At that time the VVS’s perception of dynamoreactive guns had changed. The results of Kurchevski ‘s APK guns were not what was expected and, on the other hand, conventional guns had already appeared, of smaller caliber, but with greater speed. The Directorate of Special Works (USR), led by LV Kurchevski, was dissolved in February 1936 and this builder would soon be a victim of the repressive wave of those years.
Already in the summer of 1935 Grigorovich had received a request to develop a modification of the IP-1 with 20-mm cannon and machine guns. In January 1937 the first example with this configuration, with factory number 034, was ready and successfully passed the factory tests. Production examples were fitted with two 20mm ShVAK cannons installed in the midplane and the machine gun armament was increased to six 7.62mm ShKAS machine guns (two under each wing console and one in the midplane). The Shvetsov M-25, a license-produced version of the Wright Cyclone F-3, was selected as the powerplant.
Between 1936 and 1937, up to the time production closed at Factory No.135, some 90 IP-1s were built.
These changes brought about a backward movement of the centre of gravity. During the spin tests, carried out at the NII VVS by PM Stefanovski, it was found that the model had problems.
Already at the stage of state tests in 1935, on one of the flights, the plane entered a flat spin from which it was difficult to get out, losing about 800 meters in height in the attempt. At that time it was considered a casual situation, but now, with the changes, the defect was showing up again.
Flight tests were planned to study the phenomenon. During the flight the test pilot AI Nikashin tried all possible manoeuvres, but it was impossible for him to get the IP-1 out of the flat spin and at the last moment he abandoned it by parachuting.
It was decided to begin a research process to improve the aircraft’s behavior in a spin. TsAGI participated in this process. The specialists of this institution came to propose a special parachute located in the tail section to facilitate the exit of the spin, but this solution was finally discarded. Professor AN Zhuravchenko proposed to install a long fin from the headrest to the vertical keel, which should improve directional stability. With these changes the plane was able to get out of any type of spin without difficulty.
IP-1 with new keel installed
A large part of the 90 examples produced ended up being delivered to the 43rd Aviation Brigade. RKKA VVSs used the IP-1 until 1939, when it began to be replaced by the Polikarpov I-16. From there the traces of the IP-1 disappear. The final destination of the withdrawn examples is unknown.
In November 1939 at the NII VVS the flight tests of the IP-1Sh model with a Shvetsov M-25 engine and modified by the institute’s specialists as an armoured attack aircraft were carried out. The modifications were made on a serial IP-1 model produced by the Kharkiv Factory No.135 in 1935.
The model featured armament similar to that of later versions of the fighter, consisting of two 20mm ShVAK cannons located in the midplane and six 7.62mm ShKAS machine guns. The “P” type armor consisted of 6 – 6.5 mm cement plates capable of withstanding impacts from 7.62 mm bullets from distances of 125 m and at angles of up to 35 degrees. This armour covered the vital points of the construction. The fuel tanks were protected by two armour plates weighing 72.8 kg.
The pilot was defended from shots from behind by an 18.5 kg armour plate and on the sides by two 12.6 kg vertical side plates. Frontal impacts were to be covered by the engine. In total all the armour added a weight of 125 kg.
The takeoff weight of this version reached 1,940 kg, so the maximum speed decreased to only 320 km/h at sea level and 343 km/h at 2,000 meters.
In the report of the conclusions of the tests, it was reflected that due to the poor flight performance, the construction difficulties and the appearance of associated difficulties (vibrations in flight and new problems with spin entry), the model lacked prospects for growth.
In order to study the effectiveness of this armour, it was decided to transfer the model to the NII-48 to study the resistance to the impact of different types of weapons.
The tactical specialists of the VVS planned to use the IP-1Sh fighters in chains or brigades, attacking the enemy in dive encounter contacts from distances of 1000 – 1500 from the target.
It was considered that the fighter would be basically intended for attacking ground targets located in a radius of action of 200-350 km or as part of Vaxmistrov ‘s Zvenó combined structures, in order to increase the range of actions.
The IP-1 was Grigorovich ‘s last aircraft to be mass-produced. In 1927 he became seriously ill and the following year died.
IP-1 Powerplant: 1 × 710 hp Shvietsov М-25 Wingspan: 10.97m Wing area: 19.98 m² Length: 7.23m Empty weight: 1200kg Normal takeoff weight: 1880 kg Maximum speed at sea level: 343 km/h Maximum speed at 3000 m: 410 km/h Cruising speed: 298km/h Practical range: 1000 km Maximum ascent speed: 574 m/min Practical ceiling: 7700 m Climb to 1000 m: 1 min 19 s Armament: Two dynamoreactive 76.2 mm Kurchevski APK-4 cannon – 10-14 shells / one 7.62 mm ShKAS machine gun. Accommodation: 1
IP-1 fighter in its original version with APK-4 cannon
In September 1927, when the assembly of the first prototype of the open sea explorer ROM-1 was finished, it was decided to give the green light to the construction of a second prototype, which received the designation ROM-2 or MR-3bis (Russian: Григорович РОМ-2 (МР-3БИС)).
Already in mid-1927 the Aviatrust leadership was convinced that the work of the OMOS naval department in Leningrad was not bearing the expected results, so all experimental work had to be concentrated in the capital.
In September 1927 the decision was made to dissolve the OMOS TsKB and transfer all its specialists to Moscow, placing them in the facilities of Factory No.22 in Fili. About 200 workers were transferred from Leningrad to Moscow, including 44 builders. The organization in the new location was renamed OPO-3 (acronym for O pytni P roizvodsvenni O tdiel – 3 or Experimental Productive Department – 3). In practice, this transfer process lasted until the first quarter of 1928. In the documents of this period related to the start of the activity of the EPO-3 it can be seen that the financial situation was destabilized and losses of state assets were recorded.
On 27 June 1928 the president of the Aviotrust , MG Uryvayev, called a meeting in the building of the EPO-3 in which the director of the factory No.2 FS Malakhov participated PD Samsonov as a representative of the OPO-3 (Grigorovich was in Sevastopol in the process of continuing the ROM-1 tests), VI Nikitin as replacement for the head of the OPO. The meeting basically touched on the problems of the new situation. It was reported that in Moscow the acceptance of the Leningradense group had not taken place and that the interrelation with the factory was progressing with difficulty. The facilities provided for the work were small and insufficient for the staff, their repair extended over time. The phone connection had only been running for a month and a half.
The supply of materials was defined as lousy, the workers assigned by the factory were all of low qualification, the salary for the members of the OPO-3 was lower than that of the rest of the factory workers (this was explainable because despite that the OPO-3 was considered a section of Factory No.22 was not subordinate to its technical line). It was also said that for housing issues of the 13 employees received, half had already left the department (later, the abandonment of the OPO-3 by specialists and collaborators would increase in such a way that by the end of 1928 only 50% remained of transferred personnel).
Under these conditions, ROM-2 was built.
Originally the main difference between the ROM-1 and ROM-2 was the installation in the latter of two German BMW-VI 500/680 hp engines located separately on the wing, but during the construction process important modifications were made. In the work records of the OPO-3 it is stated that in Factory No.22 a new hull and elliptical wings were built for this hydrofoil.
The upper wing kept its wooden construction, but its plan view showed an almost elliptical shape with ailerons of increased area and a surface area greater than 5 m². The leading edge had less curvature than the trailing edge. On this occasion, the extrados of the centroplane featured a corrugated aluminum coating. The wing consoles featured a double stringer structure with plywood covering from the leading edge to the position of the second stringer. From then on, the covering was made of fabric. The ailerons and the tail section kept the fabric covering.
The lower metallic wing was little different from the original ROM-1, but the underwing floats lost their reef and were fixed with small piles to the wingtips.
The hull was lowered by 1.5 meter. The contours of the ROM-2 were quite different and were characterized by increased transverse sagging in the keel area with the sides concave on the bottom, which ensured a smoother landing, especially in swell. In the lower zone, near the recess, the coating reached 1.5 mm. In the rest of the helmet 1 – 1.2 mm.
The fuel system was modified. Three fuel tanks with a total capacity of 810 liters were installed in the center of the hull. A fourth tank with a capacity of 310 liters was installed in the center plane. During the tests, the engines used 3.25 and 3.5 metre propellers interchangeably.
The ROM-2 crew was maintained with 4 people and its defensive armament consisted of two points of fire operating paired Lewis or DA machine guns. A TUR-6 turret was mounted in the fore area and a TUR-5 in the rear position. Small bombs could be placed on the gunwales as on the Dornier Wal. Larger calibre pumps could be installed under the lower wing. The total capacity of ropes reached 600 kg. As special equipment highlights the installation of a Kodak camera in the rear cabin and a tank with drinking water for long flights.
An anchor was located in the bow, which during the flight was fixed to the upper front deck.
Another distinctive feature of the ROM-2 was the ability to be dismembered in such a way that the hydrofoil could be moved overland using four rail platforms.
ROM-2 in Taganrog
The ROM-2 was to be projected to fly for 5 hours covering a radius of 500 km. Its construction began in Leningrad at the then-renamed Factory No.23 (Formerly GAZ No.3 “Krasni Liotchik”), but was soon moved to Moscow, to the collective’s new location at Factory No.22 in Fili.
The ROM-2 left the OPO-3 workshops at the beginning of July 1929, but only a month and a half later it would be fully ready. At the end of September the prototype was shipped by rail to Sevastopol, where it was assembled and prepared for flights. There it was found that the hydrofoil showed an increase of 690 kg in relation to the projected data.
The date of the first flight of ROM-2 is not exactly known, but it must have occurred around October 1929. As a test pilot, S. Rybalchuk, who had previously flown the unsuccessful ROM-1, was selected.
There is evidence that the short testing period was characterized by minor problems and breakages. On November 6, during the launching process, the lower right wing and the stabilization float broke. On the 29th of that month another accident occurred in Sevastopol, near the Konstantinov battery. That day at 1:45 am Rybalchuk took off and landed with quite rough seas. During the third landing the plane entered facing a wave and as a result several construction elements were damaged.
ROM-2 during the tests in Sevastopol.
The report that was produced highlighted the successful hull design, the spaciousness of the cabin and the good performance in takeoff over the sea. The stabilization float scheme was considered unsuccessful and the lack of rigidity in certain elements of the construction was highlighted. The radius of action of 445 km, maximum speed and manoeuvrability in the air were also highlighted as negative.
In Rybalchuk’s report can be found: “The performance of the ROM-2 can be considered somewhat superior in relation to the ROM-1, especially in relation to maximum speed and control. The overall performance rating can be considered below average. The machine remains heavy and in this configuration it has no prospects. “
As a conclusion in December 1929 it was considered that the ROM-2 2BMW6 was not ready to enter service with the VVS. It was decided to return it to the factory to repair the defects and deliver it for retesting before August 15, 1930. It was recommended to lengthen the nose to improve the behaviour on the water, review the design of the floats, locate the engines towards the depth of the wing and advance the location of the pilots.
Once at the factory, they worked on repairing the prototype. The hull was shortened by 0.20 meters, the engines were raised on the wing, being located on some N-type structures. Baptized ROM-2bis, the new variant, according to the opinion of military specialists, had nothing to offer either.
Despite the fact that by the end of 1929 in the OPO-3 all the detailed plans for the series production of the ROM-2 had been completed and that Factory No.22 had prepared to take on a small series of 22 copies, for reasons not very clear this production would not be carried out. Work on ROM-2 was abandoned and the project for an improved model, known as ROM-3, was never completed.
Grigorovich ROM-2 Engines: 2 x 500/680 hp BMW VI Wingspan: 26.80 m Wing area: 108.20 m² Length: 17.40 m Empty weight: 4150 kg Normal takeoff weight: 6587 kg Oil weight: 90 kg Total load capacity: 2437 kg Wing loading: 61.0 kg / m² Power load: 4.9 kg / hp Maximum speed at sea level: 180 km / h Maximum speed at 3000 m: 163 km / h Landing speed: 95 km / h ROC: 143 m / min Turn time: 50s Range: 900 km Endurance: 5 h Service ceiling: 4500 m Time to 1000 m: 7.0 min Time 2000 m: 14 min Time 3000 m: 22 min Practical range: 900 km Landing run: 170 m Take-off run: 250 m Accommodation: 4 Armament: 3 x Lewis or DA machine guns in turrets TUR-6 (forward) and TUR-5 (in the rear fuselage). Bombload: 600 kg
The second work of D. Grigorovich was an airplane built according to the design of the French Bleriot XI aircraft, also with the Anzani engine, but with its own control system and chassis design. It was built by Grigorovich together with the Kiev motor sport amateur Ilnitsky. Financial assistance Ilnitsky was enough to complete work on a new airplane and demonstrate it at the Kiev exhibition of aeronautics. The aircraft attracted the general attention of aviation specialists and amateurs. The magazine “Automobile and aeronautics” called it the best design of the exhibition.
All Aero 