UT-3 (AIR-17, S-17 or No. 17)
The starting point on the way to the first combat aircraft of the OKB-115 was the UT-3 training bomber (AIR-17 "Samolyot (Aircraft) 17 (S-17)" or "Ya-17") - the first machine with weapons, created specifically for the military. In April 1935, the SRT adopted Resolution No. C-41CC “Plan for the Development of the Air Forces of the Red Army for 1935–37”, according to which the flight strength was to be increased by 25,000 people. This meant that new training aircraft would be required for their training. This was especially true of bomber aviation, since it was expected that training bombers would significantly reduce the consumption of fuel and lubricants and the cost of training pilots and navigators.
To this end, relevant works have been developed in a number of design offices. This trend was not spared by the team of A. S. Yakovlev, where in 1937 they began to design a three-seat UT-3 aircraft (AIR-17, C-17 or No. 17) with two French 220-horsepower engines (rated power) Renault 6Q- 01 “Bengali” and metal double-bladed propellers with variable pitch “Ratier”. Production of these engines was mastered in the Soviet Union under a license under the designation MB-6.
The aircraft was designed in accordance with the requirements of the customer, positioning the crew, as on a high-speed bomber SB: navigator with ShKAS machine gun in the front cockpit, pilot behind him and ShKAS machine gun in the back cockpit. In the export version of the aircraft in the cockpit in the front cockpit, as on the instructional CSS, the pilot-instructor was located, for which a second control was provided: a steering wheel and folding pedals. But the designers didn’t stop there and used flap control units for greater similarity with the SS.
The aircraft was a mixed-bomber monoplane. In the cargo hold, were provided Der-21 cluster bomb racks for the suspension of both practical (P-40) and high-explosive (FAB-50 or FAB-100) bombs. In addition, they provided for, but did not install defensive armament from two ShKAS machine guns from the navigator (in the front cockpit) and the gun in the rear cockpit on the turret TUR-8.
The first copy of the car was presented to the factory tests with a ski chassis in the spring of 1938. The leading pilot was Yu. I. Piontkovsky, who performed 52 flights with a total duration of 11 hours. Then the machine was returned to the factory to eliminate the detected defects and install the planned equipment. The modifications were delayed, and the plane was presented to the Air Force Institute only on May 15. Pilots M. A. Lipkin and navigator A. M. Bryandinsky were leading at the first stage of state tests. Although the aircraft was close to the SAT in terms of piloting technique and behavior in all flight and landing modes, it revealed many flaws. In particular, in some modes vibrating plumage was noted. The military wanted to install brakes on the wheels.
The car passed the second stage of state tests and, as follows from a report on their results, could find application in the Air Force combat units as a transitional one for the training of high-speed bomber pilots and flight crew training. In addition, she allowed to prepare navigators and gunners-radio operators. But this did not mean that the aircraft in this form could be launched into the series on the move. There were still enough defects in it, and for training inexperienced students, it required additional refinement. However, this is a common practice in aircraft manufacturing, especially domestic.
By order of the Defense Committee it was ordered to release the first batch of ten UT-3 by September 1, 1939. Since all the documentation for the car had to be reworked for the technological processes of plant number 81, the first machine left the assembly shop three days late. In addition, it was necessary to replace imported engines with heavier Soviet MV-6, built under a license, and with variable-pitch propellers AV-3.
To solve the problem with the training machine, the Soviets even bought three samples of the aircraft of similar purpose FW 58 in Germany and borrowed some technical solutions from it. FW 58B, equipped with small arms and bomber weapons, was intended for training navigators and air gunners, and a double version of the FW 58C - for training pilots. This latest version of the Fockewulf was the reason for changing the concept of a training bomber.
In the new aircraft, designated S-17a, little remained of its predecessor. Thus, the crew was reduced from three to two people, placing the seat of the student (cadet) in front, and the instructor behind him in a common cabin. The aircraft had reduced volume of fuel tanks, dismantled all the armaments, made the chassis with wheels 600 × 180 mm in size non-retractable with an increased stroke of the main supports (to 300 mm instead of 110 mm) and extended the engine mount (by 150 mm).
In fairness, it should be noted that few of the training aircraft developed in the Soviet Union entered service with the Air Force. And among them were the training bomber and fighter V. Gribovsky and the aircraft designer V. V. Nikitin. But all of them for various reasons remained in the discharge of experimental.
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