Aviation of World War II
High Altitude Fighter
A new aircraft, the designing of which V.M. Petlyakov began in the summer of 1938 at the head of a team in the Special Technical Department of the NKVD (STO) of 50 designers, was supposed to become a high-altitude fighter with a long range and powerful offensive weapons, designed to accompany the ANT-42 (Pe-8) in long-distance raids. To ensure altitude, the cockpits in the aircraft were supposed to be sealed with pressurization from tube compressors.
According to the terms of reference, the practical ceiling of the aircraft was supposed to be 12,500 m, and at an altitude of 10,000 m the "weaving" was supposed to fly at a speed of 630 km / h. The deadline set for the creation of the machine was also tough - the plane was supposed to take off the next year, 1939. In May 1939, a full-size mock-up of the new aircraft was made, and by the end of the year, on December 22, the "weaving", built at plant No. 156, took off for the first time.
The fuselage design of the new machine, developed by A.I. Putilov, in type approached the monocoque. The fuselage consisted of three technological units, which were bodies of revolution with a light gargrot between the cockpit and the cockpit of the navigator and gunner. The fuselage skin was relatively thick, on average 1.5-2 mm, and the frames were sparse, 0.3-0.5 m apart. Stringers were not used to reinforce the skin. The wing of the aircraft was trapezoidal two-spar, with practically no sweep along the leading edge, and consisted of a center section and two consoles, with a dense set of stringers and ribs, covered with a skin 0.6-0.8 mm thick. The ailerons were split, the flaps were of the Schrenk type. The tricycle landing gear with a tail wheel was designed by T.P. Saprykin. The main supports were two-post, retracted by turning back into the engine nacelles; the tail wheel was also retracted.
The plane "100 with two M-105 engines, with two TK-2 turbochargers and two pressurized cabins" - this was its full official name - can be considered truly innovative, despite the traditional layout scheme. The car was equipped with two M-105 engines, the latest for that time, with TK-2 turbochargers and VISH-42 propellers. The compressor turbines were located on the sides of the nacelles under the leading edge of the wing. Comfortable conditions for the crew of three were created by two pressurized cabins (developed by M.N. Petrov), supplied with compressed air from turbochargers and maintaining constant pressure, starting from an altitude of 3700 m and up to a maximum ceiling of 10,000 m.A tenfold safety factor ensured the safe performance of any aerobatics ... The fly-by-wire control units developed by L.A. Yengibaryan and I.M. Sklyansky.
The aircraft had a powerful offensive armament, which included two 20-mm ShVAK cannons (ammunition - 300 rounds per barrel) and two 7.62-mm ShKAS machine guns (900 rounds per barrel). To protect the fighter from attacks from the rear hemisphere, it was envisaged to install a stationary ShKAS machine gun in the tail cock with 700 rounds of ammunition.
For use as a fighter-bomber on an aircraft, it was possible to suspend two 250 kg or 500 kg bombs on external holders. In addition, a new type of weapon was used on the "hundred" - a K-76 cassette with 40 three-inch artillery (non-fledged) shells dropped on enemy bombers. In another, later version, 96 bombs weighing 2.5 kg each were placed in the K-100 cassettes. At that time, such bomber weapons for hitting air targets were considered quite promising.
First flight on "100" PM Stefanovsky performed on December 22, 1939. During the tests of the new machine, many comments were revealed. It was necessary to refine the shock absorbers of the chassis struts, the oil cooling system had insufficient performance at altitudes above 5000 m and, starting from an altitude of 6000 m, exceeded the maximum allowable. Despite the two-fold replacement of motors, oil pumps and other equipment, the tests failed to achieve satisfactory altitude and speed characteristics of the "weave". The rate of climb dropped at high altitudes.
The highest speed obtained during the "run of the site" at an altitude of 6600 m was 538 km / h. A fighter with a normal flight weight of 7265 kg gained altitude of 1000 m in 6.8 minutes. During the period of factory tests from December 22, 1939 to April 10, 1940, the aircraft was in fine-tuning and repair (after a forced belly landing due to non-release of the ski landing gear) for 122 days, and flew only 11 days. A total of 23 flights were performed.
Since April 11, 1940, the "weaving" has undergone state tests at the Research Institute of the Red Army Air Force. The first copy of the plane was again piloted by Major Stefanovsky, the navigator was Major Nikitin. The second copy, the so-called "backup", was flown by the pilot captain A.M. Khripkov and navigator P.I. Passes. In addition to the cassettes, the "understudy" had an internal suspension of 25-100 kg bombs. However, the "understudy" turned out to be an unlucky car. During the 11th flight, a fire broke out in the cockpit due to leaks in the petrol system and sparking of the switch contacts. Blinded by the smoke, Khripkov was forced to quickly land the plane, as a result of which, due to the high vertical speed, the fighter skipped. The crew was injured, the car was almost destroyed.
Testing was continued on the only remaining first copy of "weaving". To increase the directional stability on the car, the keels were increased by about a third of the area (from 0.77 to 1 m & # 178;). The longitudinal stability of the machine was also found to be insufficient, and to improve it, it was proposed to increase the sweep angle of the consoles, which was later done on the Pe-2. With the landing flaps fully extended, the landing of the "weave" at the "three points" was impossible, since there were not enough rudders, so it was recommended not to release the flaps completely, but to change the angle of the stabilizer on serial machines. The most unpleasant discovery was the properties of the wing profiles at speeds close to landing. At high angles of attack, typical for landing, an asymmetric stall occurred.
In the course of state tests, 34 flights were performed with a total flight time of 13 hours 25 minutes and, in general, the aircraft met all the requirements of the technical specifications, with the exception of speed, since at different altitudes it did not reach 10-20 km / h. Despite the identified shortcomings, the general conclusion on the tests of the "100" aircraft was favorable. It noted:
"1. The aircraft" 100 "is the most successful solution to the problem of creating an armed vehicle with a pressurized cockpit. It is necessary to build an experimental series of aircraft" 100 "...
... 3. In order to use the high aerodynamics of the "100" aircraft, it is advisable to create on its basis a dive bomber without a pressurized cabin. It is necessary to build an experimental series.
The model of this aircraft shall be submitted for approval by June 1, 1940 ... "
The third point of conclusion has dramatically changed the fate of the "weave". The leadership of the Soviet aviation industry was faced with the problem of quickly replacing the main front-line bomber of the Soviet Air Force - SB, designed back in 1934 and obsolete by the beginning of the Second World War. A new mass machine was required for front-line aviation, and it was supposed to be a dive bomber. As a result, on the report on the tests of the "weaving" there was a resolution of the Chief of the Red Army Air Force, 2nd Rank Army Commander Ya.V. Smushkevich: "The act was approved with an amendment to the conclusion: the aircraft" 100 "in the diving version should be recognized as appropriate for serial construction.