Aviation of World War II
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The twin low-wing G-20 Gribovsky with the M-11 engine was intended for training flights and aerobatics training. A feature of the aircraft was the wing, narrowed in the area of attachment to the fuselage. To obtain the necessary rigidity, the wing was reinforced with L-shaped struts connecting the center section with a rigid arc under the canopy of the pilot's cabin. According to the designer, such a scheme made it possible to significantly improve forward and downward visibility, and the fuselage strut, which fastened the struts, provided the necessary safety when the machine was cowling.
In the wing section, the profile "TsAGI R-I" of variable thickness was used with a maximum value in the area where the struts were attached. Wing sheathing up to the second spar made of plywood 1-2 mm thick - then a canvas was used. The ailerons are slotted, each is suspended on three curly brackets. The wing is equipped with Schrenk landing flaps, which are released using a handwheel connected to a worm gear. The use of shields made it possible to reduce the landing speed to 66 km / h. The fuselage is wooden, semi-monocoque, covered with 2 mm plywood. The cockpit of the pilots, sitting one behind the other, is covered with a common celluloid lantern. Paired management.
The rear cabin had a complete set of engine and navigation instruments and was considered the main one. The front cockpit was located near the center of gravity and therefore the absence of a pilot in it had practically no effect on the centering of the aircraft. The tail unit is wooden, reinforced with steel struts to provide the necessary rigidity. The stabilizer and keel of the aircraft are sheathed with plywood, the rudders are covered with linen. The main landing gear is non-retractable, made in the form of bent tubular axle shafts with cushioning inside the fuselage. Wheels 700x120 mm, covered with drop-shaped fairings. The crutch is guided, with lamellar rubber depreciation.
Engine M-11 with a power of 110 hp. closed by a cylindrical hood with protruding, teardrop-shaped punches around the cylinder heads. There were cooling windows in front of the hood. The main fuel tank for 47 kg of gasoline was located in the fuselage, two wing tanks, each for 35 kg, were placed in the space between the spars of the center section.
In August 1935, shortly before the flight of sports aircraft, the G-20 underwent accelerated tests at the Air Force Research Institute. It was pointed out that the flight data of the aircraft were satisfactory, that it was quite simple to fly, and that the mastering of the aircraft did not pose any difficulties for pilots. "The flight properties of the G-20 are somewhat close to those of fighter-type aircraft, but are simpler and more easily digestible, so the G-20 can be recommended as a transitional or training aircraft." In September 1935, the G-20 with the registration number "USSR-S 838" took part in the flight. The plane was piloted by pilot Altynov, who successfully coped with the route and the resulting minor problems.
The G-20 took second place in the class of two-seat machines (after the AIR-10 designed by Yakovlev), the MKB team received a cash prize of 4,000 rubles. For an apparatus made in artisanal conditions, such a result was considered quite good.
After two years of intensive operation in the Central Aeroclub, the G-20 underwent alterations. For more efficient performance of aerobatics, a forced M-11 with a power of 150 hp was installed on the aircraft. Due to the low quality of the celluloid, which quickly became cloudy, the canopy was abolished and replaced by open cabins with visors. The anti-hood arch on the fuselage was removed, and the struts were fixed on the power frame. The hood was also simplified, with the top of the engine cylinders open for more efficient cooling.
Under the designation G-20bis, the updated car took part in the 1937 sports aircraft race along the Moscow-Sevastopol-Moscow route, where it took third place. Subsequently, the G-20bis was used to train pilots of the Central Aeroclub in Moscow.
By 1936, Gribovsky had finally taken shape as a designer of light aircraft. Talking about his immediate plans on the pages of the magazine "Airplane" (No. 4, 1936), he says:
"This year I will only work on the light aircraft needed in the Osoaviahima system.
For the development of mass aviation, the material part must be cheap. A radical means to reduce the cost of the aircraft is the transition to a reduction in engine power. In this context, the work of the Moscow Design Bureau (MKB), which I manage, is going on.
Until now, the aircraft designed and built had engines with a capacity of at least 100 hp. with. We are working on aircraft designs that should give not the worst flight performance at significantly lower engine power (30-50 hp). Therefore, we are especially interested in a 30 hp motor, the design and working drawings of which were developed by engineer V. Dollezhal.
This year I have designed G-21 and G-22 light aircraft and, obviously, two more aircraft will be designed, but their type has not yet been determined."
It should be noted that, despite the transition to design activities, Gribovsky constantly improves his flying skills and performs the first sorties on his aircraft personally. He takes part in various aviation festivals and propaganda flights.
On this occasion, the famous glider pilot and test pilot I.I. Rustle in his book "From Wing to Wing" writes:
Combining the qualities of a designer and a pilot, Vladislav Konstantinovich preferred to test his cars himself. This reached the height of creative mutual understanding between the creator of technology and its tester. However, how do you know? Did he sometimes get on the threshold of a split personality? A heated fight could have broken out in it: the designer considered the original project infallible, and the pilot demanded to improve the quality of the aircraft or glider. How Gribovsky resolved the dispute in such cases is unknown. But his cars, as a rule, turned out to be successful.
In order to reduce the load on the wing in aircraft with automobile engines, the G-25 was designed and built according to the biplane scheme. It was intended for training pilots and, in case of obtaining positive flight characteristics, could compete with the famous U-2 in terms of manufacturing and maintenance costs.
The aircraft was built at the Osoaviakhim glider plant in Moscow until the end of 1937. Due to the delay in the delivery of the expected GAZ-11 85 hp engine. it was equipped with a Pobjoy "Niagara" radial engine of equivalent power. With this engine, which, however, weighed 70 kg less than a car engine, the G-25 had excellent performance. With one pilot, the run was only 40 m, landing run - 60 m. All pilots who piloted the G-25 highly appreciated its flight characteristics.
With the installation of the GAZ-11 engine in 1938, the empty weight of the aircraft increased from 430 to 500 kg, but flight performance deteriorated very slightly. The maximum speed has decreased from 170 to 165 km/h, and the landing speed has increased from 55 to 65 km/h.
"Aviation newspaper" December 3, 1938 wrote:
"The great and hard work of Comrade Gribovsky was crowned with success - the G-25 aircraft was created, which is not inferior in its flight qualities to the U-2, and in terms of cost it is almost half the price.
On Aviation Day, August 18, the new aircraft made its debut at the Tushino airfield. Later it was flown by the best athletes of the Central Aeroclub of the USSR. The results of these tests showed that the G-25 is an aircraft that deserves great attention."
Soon, the Central Council of Osoaviakhim discussed the possibility of further production of aircraft with automobile engines, and even such an entry appeared in the draft of further plans: "Build five prototypes of the G-25 for a more complete test of the new machine in operation." However, already at the beginning of 1939, the glider plant in Moscow was closed and, in the absence of a production base, the production of the G-25 was stopped.
The prototype G-25 suffered the fate of most designs created by enthusiasts. In 1939, the author of the conversion of an automobile engine into an aircraft engineer, Agitov, organized a propaganda flight around the Gorky region on it. In the city of Murom, the G-25 crashed and was no longer restored.
Technical description. G-25 is a two-seat biplane of wooden construction. Aircraft control is double.
The fuselage is wooden, rectangular in shape with a rounded top. It was assembled from four pine spars, frame frames and plywood sheathing 2 mm thick. The bow, including the rear cabin, was sheathed with plywood on both sides, which increased the safety of the crew in the event of an accident. The seats are height adjustable. The pedals were retractable. Behind the second seat in the fairing was a small trunk for forms, tools and other small items.
Black dashboards in both cockpits had only navigation and flight instruments. The control devices of the power plant were placed in the cutout of the upper wing, which made it possible to see them well from both cockpits and, accordingly, manage with one set.
Wing box of normal single-column design. Racks V-shaped from duralumin pipes of elliptical section. The consoles are braced with 4 mm steel bands. Each plane of the wing (profile R-11) has a two-spar design. Spars are box-shaped. The ribs are truss, installed in increments of 260 mm. The wings were sheathed with canvas, and the ailerons with thin plywood. Angle of installation of upper to lower wings +3°. The transverse V of the wing is also 3°.
Conventional chassis with lamellar rubber damping. Cable braces were installed between the rear struts. Wheels measuring 470 x 210 mm with dark green hubs. Chassis track 1600 mm. Spring non-orienting crutch.
The horizontal tail had a two-spar stabilizer sheathed in plywood and a single-spar elevator covered with fabric. For rigidity, the stabilizer is braced from below with one brace and one brace. The angle of the stabilizer could be changed on the ground.
The vertical tail consisted of a plywood keel, made integral with the fuselage, and a single-spar rudder with fabric covering.
The power plant is a six-cylinder water-cooled engine with a radiator located at the bottom of the power plant. The latter was closed by a fairing with adjustable blinds in the front.
The color of the aircraft is dark cherry, with the exception of the engine cowlings and spinner, painted "silver". The edges of the cutout in the fuselage above the cockpit were upholstered in brown leatherette. Cabins inside are beige. Standard green (olive) screw. The emblem of the Moscow Design Bureau Osoaviahima (MKB) was depicted on the keel of the aircraft on both sides, and the emblem of the Gorky Automobile Plant (the same as on the nose of the GAZ M-1 car) was depicted on the engine hoods.
January 05, 2023.
January 09, 2023.