For the first time, the question of creating in the USSR a dive bomber capable of bombing at angles up to 60 ° was considered by the Air Force in 1934. It was supposed to issue a task for a car with an M-34FRN engine to V. F. Rentel, but the plant at which he worked at that time refused the order. An attempt to involve in this work the staff of the N. Ye. Zhukovsky VVIA was also unsuccessful.
In 1936, the ship reconnaissance aircraft G. M. Beriev KOR-1 was created. Tactical and technical requirements provided for its use as a dive bomber. The experimental aircraft construction plan for 1936-1937 envisaged the construction of a single-engine dive bomber PB with an M-85 engine at plant No. 1 with a maximum speed of 400-450 km / h at a normal flight range of 800 km. But in view of the specialization of this plant in reconnaissance, in 1937 the entire reserve for the PB M-85 aircraft was transferred to plant No. 135. So far it has not been possible to find out how it all ended.
In the same year, NN Polikarpov, on his own initiative, began to develop a twin-engine high-speed high-altitude three-seat SVB bomber with M-100 engines. Since it did not provide for the use of pressurized cabins and turbochargers, then we could talk about creating a conventional front-line bomber in accordance with the existing concept. Soon Polikarpov was assigned a production base at plant No. 84 in Khimki. The plant, which was recently transferred to the aviation industry from the Civil Air Fleet, was distinguished by outdated equipment and did not have a sufficient number of qualified specialists.
By mid-February 1937, the drawings of the SVB aircraft were completely ready. But it did not get into production, and on its basis a two-seat twin-engine air tank destroyer VIT-1 was developed.
At the same time, Polikarpov proposed a twin-engine multi-seat cannon fighter (MPI).
It should be noted that, having invaded the "Tupolev" theme, Nikolai Nikolayevich not only did not find support in the SUAI, but also encountered direct opposition from the chief engineer of the aviation industry.
The Air Force did not accept the idea of an anti-tank aircraft and recommended Polikarpov to focus his efforts on a multi-seat cannon fighter for the earliest possible implementation of the project. The customer hoped that the MPI would demonstrate the declared flight data and become a kind of accelerator when creating promising machines that fit into the concept of the Air Force leadership.
On January 31, 1937, a mock-up commission for the MPI aircraft worked. On July 25, the government approved the Air Force plan in 1934. It was supposed to issue a task for a car with an M-34FRN engine to V. F. Rentel, but the plant at which he worked at that time refused the order. An attempt to involve in this work the staff of the N. Ye. Zhukovsky VVIA was also unsuccessful. experimental aircraft construction for the current year, which provided for the construction of two prototypes of a fighter with two M-100 engines and a maximum speed of 500-550 km / h.
Alternative designs of Soviet dive bombers
On October 13, Polikarpov presented a draft design of a VIT-2 aircraft with M-103 engines (there were no completed M-105 engines yet). In total, seven variants of this machine were worked out, including a dive bomber. Officially, the VIT-2 in the draft design was presented in three versions: a short-range high-speed bomber (BSB), VIT and MPI. The first option aroused the greatest interest among the military.
The next day, we completed the assembly of the first flight copy of the VIT-1 (MPI). Its factory tests, which lasted until February 1938, were not completely completed due to the inconsistency of the flight characteristics with the specified ones. And yet, the plane was mostly successful, but due to the lack of support from the SUAI, the car was not brought to the test and was not transferred for state tests. Since the VIT-1 had a strong armament at that time - two wing cannons ShFK-37 of 37 mm caliber, the Air Force accepted the car for joint field tests. At the same time, the guns were highly appreciated, and the pilots noted the aircraft's good dive behavior.
On the second copy of the machine (VIT-2) Polikarpov installed a two-fin tail and introduced the third crew member - the navigator. Now there was no need to worry about the defense of the rear hemisphere, and to improve flight data, the designer opted for more powerful M-105 engines. But the engines did not appear on time, and on May 10, 1938, an experienced VIT-2 with old M-103 engines was rolled out of the assembly shop.
The next day, V. P. Chkalov made the first flight on it. All subsequent flights at the stage of factory tests, which ended on July 11, were performed by test pilot of plant No. 84 BN Kudrin. With a takeoff weight of 6166 kg, VIT-2 at an altitude of 4500 m developed a maximum speed of 498 km / h, and with a weight of 5310 kg - 508 km / h. Not bad for a start.
After the end of the factory tests, the M-103 motors were replaced by the M-105. Polikarpov was the first to take on the entire burden of mastering the engines that were completely undeveloped by that time. It all started with a scandal. The plant sent samples that were absolutely unusable, which subsequently played a fatal role in the fate of the VIT-2 modification - the SBP aircraft.
VIT-2 without weapons at the stage of factory tests
The second stage of factory tests of VIT-2 took place from August 2 to September 10, 1938. Considerable time was spent on testing and fine-tuning not so much the aircraft as the engines. Despite the fact that their power increased, the maximum speed reached only 513 km / h. By that time, this was a good result, but the NKAP still did not provide support to Polikarpov in the work on VIT-2.
As the leading engineer of the Air Force Research Institute for the VIT-2 aircraft PM Nersisyan wrote, the director of plant No. 84 Osipenko was prohibited from showing the aircraft to the Air Force leadership. It was only after Nersisyan's letter to KE Voroshilov that the plane was shown to Ya. V. Smushkevich. After inspecting the car, Smushkevich interrupted the factory tests and ordered to overtake it to the Chkalovskaya airfield to show it to the government. After the show, VIT-2 was left at the Air Force Research Institute for joint tests. The test brigade, in addition to Nersisyan, included pilot P. M. Stefanovsky, shooter P. Nikitin and P. Perevalov.
From September 13 to October 4, 1938, 35 flights were performed with a total duration of 13 hours 40 minutes. With a flight weight of 6300 kg at an altitude of 4500 m, they reached a speed of 483 km / h. The speed obtained in the factory tests was overestimated by 15 km / h. At the same time, the detected tail vibrations in various modes and the impossibility of a long flight on one engine did not allow determining the ceiling, range, maneuverability and other characteristics. Before the aircraft was put into production, it had to be finished, and on October 5, VIT-2 was returned to the plant.
From 9 to 26 February 1939, secondary state tests of the modified VIT-2 were successfully passed. After installing new VISH-2E propellers, changing the contours of the canopy of the gunner's cabin and water radiators, the maximum speed at the ground was 446 km / h and at an altitude of 4600 m - 500 km / h.
As a result, the aircraft had indisputable advantages in speed over all existing serial and prototype aircraft of its class. The military insisted on using the VIT-2 as a dive bomber, which is why the name SPB (high-speed dive bomber) appeared. Polikarpov did not agree, believing that he had created an SBP, a high-speed bomber that could be used as a dive bomber if necessary. Such caution is understandable - the SVB aircraft, on the basis of which the VIT-2 arose, was developed as a high-speed bomber, and when it is turned into a dive bomber that meets more stringent strength standards, flight characteristics will inevitably have to be sacrificed. It so happened that in the documents of the Air Force, the plane was originally called SPB, and in the documents of the NKAP - SBP, and only later also SPB.
In a letter to the People's Commissar of the Aviation Industry M. Kaganovich, the head of the Red Army Air Force Loktionov noted:
“The aircraft has reserves of up to 50 km / h to increase the speed, which consists in: a) installing a more powerful and high-altitude M-105 engine; b) radical improvement of the outer surface of the aircraft; c) the best selection of the screw.
It was noted that the control of the aircraft became normal (it was unacceptably heavy). Tail vibrations in all modes, including the supra-maximum speed of 650 km / h, disappeared. Flight on one engine became possible. Despite the high load on the wing (up to 157 kg / m2), VIT-2 in terms of piloting technique was accessible to an average pilot, and in terms of take-off and landing properties, it was even easier than SB-2 and DB-3, requiring a smaller landing area.
On March 9, 1939, the chief of the Red Army Air Force A. D. Loktionov wrote to M. Kaganovich:
“The Military Council of the Red Army Air Force considers it expedient:
Make a decision on the provision of the SPB (VIT-2) aircraft for launch into serial construction.
Simultaneously with the development of drawings and preparation for the production of serial aircraft, to speed up the construction of 2 test samples of aircraft (…) with the expectation of delivery for state testing at the Air Force Research Institute no later than IX. 1939 and the head series of aircraft for military trials no later than IV. 1940 g.
Continue testing of the existing VIT-2 aircraft under the program of full state tests and eliminating detected defects during serial construction."
On March 28, K. E. Voroshilov and M. Kaganovich prepared and sent V. M. Molotov and I. V. Stalin a memorandum on the organization of serial production of SBP at plant No. 124. The next day, Molotov signed the corresponding decree, but soon it had to be canceled …
On April 27, 1939, M. Kaganovich, after a trip with Polikarpov and Deputy Head of the Air Force Research Institute I. F. Petrov to the 124th plant, wrote to Stalin and Molotov:
Comrade. Polikarpov categorically objects to the production of the SBP aircraft at this plant, in view of the fact that the drawings of the aircraft that have passed state tests are currently being completely redesigned by Comrade Polikarpov structurally and technologically, which will require the manufacture of two prototype prototypes for static and flight tests, so how these cars will be completely different from the state-tested car.
I, in agreement with the head of the UVVS comrade. Loktionov appointed a commission to determine the technical condition and the possibility of introducing the SBP into the series."
In the decree of the KO under the Council of People's Commissars of the USSR dated May 5, 1939 "On the introduction into serial production of modified aircraft and the creation of new aircraft in 1939-1940. type of bombers, attack aircraft and reconnaissance aircraft ", prepared under the leadership of Smushkevich, it was noted that the organization of production of SPB (VIT-2) at plant number 124 is impossible
"Due to the unavailability of the plant's technological base for a new aircraft"
and setting up serial production of the TB-7 bomber.
In the same year, a meeting of representatives of the Air Force and Industry Research Institute was held on the issue of establishing the tactical and technical characteristics of the SPB aircraft launched for construction at Plant No. 22. The meeting participants, after hearing Polikarpov's report, approved the changes made to the SBP aircraft, in comparison with the VIT- 2c (the letter "c" means serial - author's note), as contributing to higher speed, simplification of assembly technology and a quick transition to another motor.
Airplane VIT-2 with ShVAK cannons
The reaction to this decision was immediate. Two days later, KO SNK decrees # 221 and 249 appeared on the organization of serial production of SPB at plant # 22. The first two aircraft for flight tests and one in units - for statistical tests had to be handed over before January 1, 1940. The document ordered to release the plant No. 22 from the introduction of the MMN aircraft into the series (the last modification of the SB).
This decision created the preconditions for the aggravation of relations between Polikarpov and the chief designer of the 22nd plant A. A. Arkhangelsky and director Okulov, which subsequently influenced the construction of the SPB.
The Resolution stated:
“Works on the introduction of SPB aircraft at plant number 22 (…) comrade Polikarpov should be considered a priority …"
By the decree of the KO SNK, Polikarpov was assigned the task of designing and building on the basis of SBP-1 two PB-1 (dive bomber) aircraft with two M-120 or M-71 engines with the presentation of the first prototype on July 1, 1940.
On October 25, 1939, a preliminary design of an SBP dive bomber with M-71 and M-81 engines was sent to M. Kaganovich. In the memo, Polikarpov noted: "The SBP is a promising aircraft and has large speed and strength reserves." It was proposed to provide a quick transition to other engines without radical alteration of the aircraft design. In order to further develop the SBP and increase its flight and combat data, install on it the M-106, M-81 or M-71 engines (including those with turbochargers).
To reduce the dive speed to 500 km / h and improve maneuverability when taxiing, it was supposed to install reversible propellers. In the future, the SBP could be built with the M-82A and M-82FN motors, which made it possible to reach speeds of 600-620 km / h. The Air Force Research Institute gave a positive opinion on the preliminary design of the SBP (PB-1) with M-71 and M-81. But the leading engineer for VIT-2, Nersisyan, believed that Polikarpov should not be given an assignment for PB-1, so as not to be distracted from completing work on the SPB 2M-105, the layout of which was approved on October 26.
It seemed that there were no obstacles for the work of Polikarpov's team. In reality, everything was different. In November 1939, having sent the chief designer to Germany, M. Kaganovich ordered the creation of a design bureau for maneuverable fighters headed by A. I. Mikoyan at plant No. 1. How it ended is well known. At the same time, an experimental design department (OKO) was created at the same plant, where about 80 designers were transferred from the Polikarpov design bureau, including those who worked on the "D" machine (factory designation SBP).
In fact, the defeat of the Polikarpov Design Bureau began. It is surprising that one of the most talented aircraft designers constantly moved from plant to plant and by the beginning of the 1940s had not received his production base. This, of course, affected his morale at such a crucial moment as the completion of experimental work and testing of the SPB.
Shortly before the New Year, Polikarpov sent a letter to the NKAP with a message about the financial difficulties of the OKB in connection with the incompletely paid work of 1939 and the lack of programs and loans for 1940.
In the same place, he recalled that a response to the preliminary design of the PB-1 has not yet been received from either the NKAP or the GUAS (Main Directorate of Air Supply). But the last day of 1939 was a little pleased: the plant in 2, 5 months built the first copy of the SPB aircraft No. 1/0.
At the same time, Polikarpov's competitors were actively working. On April 14, S. A. Kochergin sent the customer a draft design of the original single-engine single-seat high-speed dive bomber OPB with the M-90 engine, and on May 20 he presented its layout.
From April 11 to May 10, the state tests of the "100" aircraft (the predecessor of the famous Pe-2 - editor's note) in the version of a high-altitude fighter took place. In the conclusion of the report, the Air Force Research Institute noted:
“In order to use the high aerodynamics of the aircraft“100”and create on its basis a mass dive bomber without a pressurized cabin, with a maximum speed at an altitude of 5000 m of at least 550 km / h with a bomb load inside 600 kg and outside 1000 kg, the design bureau must develop the aircraft“100 "In the version of a dive bomber. The model should be presented by June 1, 1940. According to the approved model, build a military series."
On May 28, a report on state tests of the SB-RK aircraft was approved with a recommendation, after fine-tuning, to launch it into series in the version of a dive bomber.
On June 1, Resolution KO No. 239 was issued on the construction at plant No. 156 of three prototypes of the aircraft "103" by A. N. Tupolev with AM-35A or M-120 engines, and on August 30, its draft design was approved.
On June 15, the model of the aircraft "100" in the version of the PB-100 dive bomber was approved. Eight days later, the Resolution of the KO under the Council of People's Commissars No. 275 was issued on the introduction into serial production of the "100" aircraft in the version of a dive bomber based on a high-altitude fighter.
On August 7, KO decree No. 342 was issued on the construction of two prototypes of the OPB M-90 aircraft.
On September 21, the NKAP commission considered the draft design of the modernization of the A. S. Yakovlev BB-22 airplane into the BPB-22 near dive bomber, developed at plant number 81 by L. P. Kurbala. Despite the fact that the Air Force did not approve the project, the BPB-22 began to be built. A month later, he took off in the version of the BB-22bis close-range bomber.
On October 15, the Air Force reviewed the layout of the cockpit of the B-2 dive bomber designed by A. A. Arkhangelsky.
On November 18, a commission consisting of S. N. Shishkin, I. F. mass series. For some unknown reason, the existing SPB aircraft was excluded from the competition. Of these machines, only SB-RK and B-2 were built.
The conclusions of the commission said that according to flight, tactical and combat data, the best aircraft from those considered is the PB-100 aircraft, as it has the highest bomb load, the greatest range, the best fire protection and speed, with the possibility of its further increase by modifying the aircraft, as well as - highest strength.
The main disadvantages of PB-100 were its relative high cost and the use of duralumin. Therefore, when introducing the PB-100 aircraft into a mass production, it is necessary to preserve the BB-22 in production as a cheap aircraft made of non-scarce materials, suitable for training and training crews, as well as for use in some sectors of the front. As for the SB-RK, it was inferior to the PB-100 and did not have the prospect of a significant improvement in flight data. The decision on aircraft "B" was postponed pending testing.
On December 2, the lead production aircraft PB-100 (Pe-2) was built. On December 14, the conclusions on draft designs of twin-engine escort fighters Polikarpov - TIS and Mikoyan and Gurevich DIS-200 with AM-37 engines were approved. Both aircraft were designed with the possibility of using them as dive bombers.
TIS, being a direct development of the SPB aircraft, had the ability to drop four FAB-100 bombs from the internal suspension using a special exhaust cassette. Up to two bombs of a caliber not exceeding 500 kg could be suspended on an external sling.
DIS-200, to some extent, was also a development of the SPB, since Gurevich participated in its development, taking into account the accumulated experience. For the DIS-200, only the version of the external suspension of one FAB-1000 bomb was provided.
During 1940, the customer presented a number of dive bombers that had not yet been implemented.
On January 3, 1940, in the conclusion on the preliminary design of the PB-1 (SPB) with M-71 engines, it was noted that it meets the requirements for a dive bomber. In particular, to provide dive bombing at an angle of 90 °, a twelve-fold safety factor is required. The bombing was to be carried out from internal suspensions. Note that the Pe-2, which was later adopted for service, the German Ju-88 and Do-217 allowed dive bombing only from external hangers. In addition, bombing with angles of more than 70 ° had no practical meaning and, therefore, the strength declared by Polikarpov turned out to be quite sufficient.
By January 10, the second prototype of the SPB No. 2/0 was built. After 8 days, pilot B. N. Kudrin and flight mechanic I. S. Popov made the first flight in car # 1/0. On March 26, flight tests of SPB No. 2/0 began. On April 17, the first serial aircraft No. 1/1 made its maiden flight.
On April 26, flight tests of the first serial aircraft No. 2/1 began, and the next day, piloted by test pilot P. G. Golovin, it crashed. The flight task was to determine the controllability and stability of the aircraft at an altitude of 2000-3000 m in the area of the Central Aerodrome. The flight was watched by Polikarpov and his deputy Zhemchuzhin, as well as the head of the technical bureau of the Usachenko plant.
Half an hour after takeoff, the plane fell into a tailspin and fell on the airfield of the Research Institute of the Civil Air Fleet, burying the crew.
Having examined the remains of the aircraft and the crew, the commission chaired by the head of the 8th department of TsAGI A. V. Lyapidevsky came to the conclusion that at the time of the disaster the ailerons and tail assembly were in good working order, the landing gear was in the retracted position. The absence of metal shavings in the oil filters seemed to indicate the normal operation of the motors. The commission noted that the cause of the crash was the plane going into a flat spin. The cause of the breakdown could be the hit of the aircraft, which had insufficient longitudinal stability, into the clouds. A stall could also occur from a bend due to rough piloting.
The first experimental aircraft SPB No. 1/0
All these versions have practically not been proven by objective facts and are largely subjective in nature. Let's pay attention to some circumstances missed by the commission. On April 26, Golovin overtaken the SPB aircraft No. 2/1 from the factory to the Central airfield. When asked how the car behaves and what his impressions are, Golovin replied that the car is in order, only the right engine has a water and oil temperature 15 ° higher than the left one. And Shishmarev, in his testimony, noted that earlier there were jamming of the M-105 engines.
We have already mentioned the absence of metal shavings in the oil filters, on the basis of which it was concluded that the motors were working normally. But from the text of the act it follows that only the left engine oil filter was investigated, since the right one was burnt. This means that the conclusion about the correct operation of both motors was not confirmed. And the most interesting thing is that the emergency report contains a photograph of the remains of the destroyed right engine, on which the whole propeller blade is very clearly visible! This could have happened if the right engine had jammed before the plane crashed. Why the commission did not pay attention to this circumstance is not clear.
Most likely, the accident occurred due to engine failure with the subsequent loss of spatial orientation by the pilot. Undoubtedly, a certain role was played by Golovin's insufficient experience in flights to SPB and a small margin of longitudinal stability of the aircraft in critical modes.
As a result, the commission recommended:
“1) Continue the factory flight tests of SPB 2/0, 1/1 and 3/1 aircraft, preventing flights in the clouds and beyond the clouds.
2) Approve the decision of the director of the plant number 22 com. Okulov on the prohibition of test flights of machine No. 1/0 in view of the tendency revealed on the machine to dive at high speeds until significant deviations in leveling are eliminated.
3) To oblige the chief designer Polikarpov to immediately blow out the SPB aircraft in nature in a wind tunnel for longitudinal stability, to obtain the conclusion of TsAGI and to make all the necessary design changes.
4) To oblige the chief designer Polikarpov to calculate the SPB plane for a spin and obtain a conclusion from TsAGI."
During the tests of the first two experimental SPB aircraft Nos. 1/0 and 2/0 and the serial aircraft No. 1/1, the engines continuously failed. Oil was thrown out from prompters, its pressure dropped sharply, there were cases of engine wedge. Let us recall that Polikarpov was the first to master the M-105, which was still "raw" at that time. There were forced landings and breakdowns associated with the low quality of the aircraft manufacturing at plant number 22.
At the same time, the commission did not give any recommendations to the engine builders and TsIAM, as well as to plant No. 22.
At the beginning of May 1940, Smushkevich informed Stalin that the question of choosing the aircraft "100" or SPB would be decided in the coming days.
schemes SPB
On May 15, the head of the GUAS KA Alekseev, in a letter to the People's Commissar of Defense Tymoshenko, noted that
"Switch to SB-RK, but not reduce the program for SPB …"
After 10 days, Alekseev abruptly changed his attitude towards Polikarpov's car and, in a letter from Timoshenko, suggested that the PB-100 be put into production and that the SPB be discontinued. He fought for PB-100 and Smushkevich, informing in his letter to the People's Commissar Shakhurin:
"1. "Sotka" to be introduced at Plant No. 22 only in the version of a dive bomber, it is hardly possible to squeeze out of the SB.
2. To remove the SPB, to stop work. It can be seen that nothing will come of it (like a dive bomber). Instead of "weaving".
From the correspondence, the conclusion suggests itself that Alekseev, the first to go to the People's Commissar of Defense, initiated the "funeral" of the SPB. After that Smushkevich raised the issue at the “home” level.
On June 2, due to a drop in oil pressure in the right engine, an accident occurred in the SPB aircraft No. 3/1. Turning off the engine, M. A. Lipkin decided to land at a factory airfield of very limited dimensions.
Incorrectly controlling the landing flaps, he did not reach the runway and hit the propeller with the stabilizer, which was on the ground. During the fall, the right landing gear broke down, after which the plane soared 60 m and, having hooked the ground with its right plane, lay down on its "belly". The car required a major overhaul.
On June 14, the head of the NKAP flight group M. M. Gromov, having familiarized himself with the test results, purging materials and interviews with Kudrin, Lipkin and Zhemchuzhin, in a letter to A. S. Yakovlev gave the following assessment to the aircraft:
"The engine unit is not finished, as a result of which there are forced landings (…)".
This assessment was not paid attention to when investigating flight accidents, having made a not entirely justified emphasis on excessive rear (31%) alignment.
In June 1940, after the reorganization at the plant No. 1 of the Mikoyan Design Bureau, OKO "D" lost many of its leaders, and with the arrival of the new leadership in the NKAP, about 135 more designers left this department.
Surprisingly, in the conditions of the destruction of the Polikarpov design bureau and a prejudiced attitude towards the machine, a resolution of the Defense Committee of June 1 ordered the release of 15 SPB military series.
Emergency landing of SPB aircraft No. 3/12 June 1940
Another disaster struck on 30 July. Pilot M. A. Lipkin and engineer G. A. Bulychev were killed in St. Petersburg # 1/1. On that day, in particular, it was necessary to conduct flutter tests at a speed of 600 km / h on the device. According to the testimony of witnesses, the car, flying at high speed (as evidenced by the too harsh sound of the engines) at an altitude of 2000-2500 m, began to crumble. The emergency commission, having worked only for two days, decided that the bending-aileron flutter of the wing was the most likely cause of the disaster. There is nothing to be surprised at. The commission consisted of administrators and the only professional was TsAGI professor V. I. Polikovsky, a specialist in the field of engine building.
All the blame for what happened was blamed on the deputy chief designer N. A. Zhemchuzhin, who did not follow TsAGI's instructions to install weight compensation on the ailerons. According to TsAGI's calculations, the critical flutter speed could occur when the indicated speed of 500 km / h was reached. But there was no confirmation of the achievement of this speed, and no one in the commission was involved in checking the calculations of TsAGI.
Even after the disaster of St. Petersburg No. 2/1, the emergency commission demanded that the plane be blown in the T-101 wind tunnel of TsAGI. The next commission again put forward this requirement, but made conclusions without waiting for the test results. They did not take into account the fact that no external signs of flexural-aileron flutter were found on the surviving left wing console and aileron. In the conclusion of TsAGI, signed on July 23 by Grosman, it was confirmed that the bending-aileron flutter of the wing at speeds up to 800 km / h could not take place.
From the wreckage of the left wing, it can be established that the destruction of the wing occurred from bending. At the same time, the loss of compression stability by the aileron thrust and its rupture are not explained by the occurrence of a flutter. In the cases of the aileron flutter known so far, the wing did not collapse instantly, which is the only argument against this, which has not yet been proven.
At the same time, the commission did not consider a possible spinning of the propeller, which very often occurred both during a dive and with a rapid increase in speed due to the "gas supply". For this reason, there have been many accidents, in particular, on the experienced "103U" and serial Pe-2.
The fact of the separation of the left engine nacelle in the air remained unclear, although eyewitnesses noted a strong roar of engines and the presence of traces of light smoke, indicating the spin of the propeller and the destruction of the VMG.
The likelihood of this version is very high. The conclusion suggests itself that the SPB plane was completely unreasonably compromised by the emergency commission.
On July 29, 1940, People's Commissar Shakhurin signed an order, which, in addition to the distribution of punishments, said:
“To stop further factory tests of SPB aircraft. Director of Plant No. 22 Okulov and chief designer Polikarpov within three days to submit to me a report on the costs incurred for the construction of prototypes and the zero series of SPB, the state of the groundwork and considerations about its use."
The slow funeral of the "dive bomber" began. At the same time, the People's Commissariat took a wait-and-see attitude, not taking any measures to implement the proposals of the emergency commission. The last pre-war year was coming to an end. At the request of Polikarpov to send reports of investigations into the disasters of Golovin and Lipkin, the director of plant No. 22 refused.
On the letter from Polikarpov and the management of plant No. 22 about the future fate of St. Petersburg, People's Commissar Shakhurin put a resolution:
1. Transfer one SPB aircraft to TsAGI for purging.
2. The issue of the possibility of further flight tests should be decided based on the results of blowdowns and the conclusion of specialists in strength and other issues."
However, five days later, the People's Commissariat demanded that the costs of the plane be written off at a loss. The rest of the tooling was partially used in the serial production of the Pe-2. In the same year, with the permission of Shakhurin, one SPB was transferred to the MAI. So the story of the creation of the Polikarpov dive bomber ended, and Soviet pilots began to master dive bombing only in 1943, and then not all.
List of sources:
Wings of the Motherland. Vladimir Perov, Nikolay Vasiliev. Mystery of St. Petersburg
Aviation and Cosmonautics. Mikhail Maslov. SPB
Mikhail Maslov. Bomb carriers Polikarpov
Shavrov V. B. The history of aircraft designs in the USSR 1938-1950
Simakov B. L. Aircraft of the country of the Soviets. 1917-1970
