Aviation of World War II
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In the second half of the thirties, new high-speed bombers SB, DB-3 and others began to enter service with the Soviet Air Force. Naturally, in order to train pilots and navigators in the technique of piloting new machines and the specifics of the combat use of their weapons, appropriate training machines were required, which were cheaper to manufacture and operate than combat aircraft. One of these training bombers was developed and built at the Glider Plant of Osoaviahima by a design team headed by V.K. Gribovsky. The new aircraft, designated G-27, was a twin-engine cantilever monoplane of wooden construction. Monocoque aircraft fuselage with plywood skin. The navigator's cabin is equipped in its glazed bow part. Behind it is a double closed cockpit. Her plexiglass lantern opened to the side. In accordance with the main purpose of the aircraft in its center section, between the spars, the designers placed a bomb bay.
A small two-spar wooden wing with an area of only 17 m² had an elongation of 6.62, and an average aerodynamic chord of 1.62 m. Up to the first spar, the wing toe was sheathed with plywood, and from the first spar to the trailing edge - with percale. The specific load on the wing of the G-27 was greater than that of other training aircraft - 84 kg / m². However, the shields located on the wing with an area of 1.53 m² made it possible to bring the landing speed of the aircraft to only 80 km / h. Trimmers mounted on the ailerons and rudders reduced the effort on the control stick and pedals. The two-column non-retractable landing gear had a tail wheel. To improve the overall aerodynamics, the designers closed the main wheels with fairings. When operating the aircraft on snow-covered airfields, the wheeled chassis could be replaced with a ski one.
On the first copy of the experimental G-27, the power plant consisted of two M-11 engines with a capacity of 100 hp. with fixed pitch propellers. The aircraft was also designed for the installation of two engines, also air-cooled M-11E with a power of 150 hp each. They provided a noticeable improvement in all flight characteristics. A characteristic feature of the new training bomber was very small, even smaller than that of the widespread U-2, dimensions and weight.
During the flight tests started by the pilot N. Fedoseev, the training bomber showed good results. With a takeoff weight of 1430 kg (empty weight 900 kg), the speed of the G-27 reached 250 km / h, the service ceiling was 5000 m. such a speed testified that the designers successfully solved many problems of the general aerodynamics of the aircraft. But the G-27, as noted by all the testers, turned out to be very strict in piloting. For a training machine, this is a serious drawback, and the designers were asked to eliminate it during the refinement of the aircraft.
Unfortunately, the designers could not follow the recommendations of the testers. The glider plant was closed, and the head of the team was assigned to another job. However, the experience of developing a light training bomber was not in vain. It was widely used in the design of another aircraft of the same purpose and, to a certain extent, in the development of a multi-seat glider, which was put into mass production during the Great Patriotic War under the designation G-11.
Initially, in December 1939, the Gribovsky design bureau was created as a branch of plant No. 301, with the building of the unfinished Mosvoitorg garage in the village of Pavshino near Moscow. During this period, several draft designs of training aircraft were being developed, one of which, the single-seat training fighter G-28 (TI-28, Gr - Krechet), was approved by the Air Force leadership and included in the plan for further work. On March 10, 1940, an order was issued to form an experimental design bureau No. 28 (OKB-28) of the NKAP, headed by Chief Designer V.K. Gribovsky.
The G-28 is a low-wing cantilever with a trapezoidal wing with an area of 11.6 m². RAF-34 wing profile. Semi-monocoque fuselage. The pilot's cockpit is closed with a canopy that can be moved back. The tail of the usual scheme with graceful, characteristic of Gribovsky's work, contours of the keel and rudder. To simplify the aircraft and reduce production costs, single-column landing gear attached to the wing spar, like the tail wheel, are designed non-retractable. In the design of the training fighter, wood was used to the maximum. Not only the fuselage, but also the wings of the G-28 are wooden. The stabilizer, shields, frames of the rudders and elevators are made of duralumin, lined with fabric. Handlebars with full weight balancing and aerodynamic compensation.
The power plant consisted of a six-cylinder inline air-cooled inverted MV-6 engine. Its takeoff power is 240 hp. The propeller is two-bladed, fixed pitch. In accordance with the main purpose, the cockpit had the equipment necessary to improve piloting techniques not only during the day, but also at night, at high altitudes. To practice shooting and bombing skills, the G-28 was equipped with one ShKAS synchronous machine gun with a supply of 400 rounds, a photo-movie machine gun and a PAK-1 collimator sight. Bombs with a caliber of 10, 25 or 40 kg could be hung on the beams under the wing.
The plane was built in the spring of 1940, and the first flight on it was made by the LII pilot V. Gavrilov on May 22. In less than a month, the G-28 passed all flight tests. In addition to the factory tester V. Gavrilov, the G-28 was tested in the air by leading test pilots M. Gromov, A. Yumashev and P. Stefanovsky. The testers noted its good aerobatic properties. To improve the acceleration characteristics, it was recommended to install the MV-6A engine and test the aircraft again. But in connection with the outbreak of war, all work on the G-28 was stopped. In 1941, a prototype flew to Sverdlovsk, but its further fate is unknown.
A second copy of the G-28 was also under construction, which Gribovsky took with him during the evacuation, hoping to bring it to a flying state. However, there was no such opportunity at the new location.
In March 1941. In OKB-28, the development of a twin-engine training aircraft "Berkut" began. In accordance with the preliminary design, a full-size layout was built, which was considered by the Air Force commission. But during the evacuation, it was not possible to save the "touch" on the car. The documentation and layout of the "Berkut" were destroyed, in the future, work on it was not resumed. The design team concentrated its efforts on the creation of landing gliders, in particular, the serial G-29 (G-11).
Summing up the work of V.K. Gribovsky in the People's Commissariat of the Aviation Industry, it should be noted that in a short time he managed to create a full-fledged design bureau capable of independently developing complex models of aircraft.
Shortly after the German attack in 1941, the Soviet headquarters recognized the need for transport gliders and ordered several designs to be developed. Vladislav Konstantinovich Gribovsky agreed to design a light glider within two months, and on September 1, 1941, testing of a prototype began. Given the designation Gribovsky G-29, it was put into production under the Air Force designation G-11 (according to Gribovsky, 11 people, including the pilot).
G-11s were produced from the end of 1941 to the middle of 1942 at two factories: 138 built in Shumerla (factory No. 471) and 170 in the village of Kozlovka (factory No. 494), 308 in total. Production resumed in 1944 in Ryazan and continued until 1948. Since October 1944, the dual-control training glider G-11U was also in production. There is no data on the total number of airframes produced, but according to some estimates, about 500-600 units were completed.
The motor version, designated VVS G-11M (designation Gribovsky G-30), had an M-11 radial engine mounted above the center section. Tests were carried out from the summer of 1942, but the G-11M was not produced.