La-7 fighter was truly the pinnacle of the development of Lavochkin aircraft of the Great Patriotic War. He was superior to his main opponent, the German FW-190А, in speed, climb rate and maneuverability, he had quite powerful weapons. Of course, there were cars and weak points, caused primarily by the peculiarities of production in the war years. In the initial period of operation, the unreliable operation of the power plant delivered problems. The mixed design of the airframe with the predominant use of wooden materials led to the fact that the life of the La-7 was determined at three years, which was critically small for operation in peacetime. However, in the war, La-7 was perhaps the best Soviet fighter.
Despite the fact that “La Seventh” appeared in 1944, the story about it should start from the pre-war years. It should be noted that Soviet fighters during the Second World War were a unique phenomenon. In those days, not a single country in the world, except the USSR, created its own fighter, and indeed military Aviation based on wood as the main structural material. In the West, combat aircraft with a wooden frame ceased to be built in the early thirties, and soon sheathing was finally gone. In our country, almost all the fighters created immediately before the war (in any case, serial ones) had either a mixed or solid wood construction.
It is known that with equal strength, duralumin construction on 40% is lighter than wood, not to mention such advantages as durability, incombustibility and resistance to weathering. Nevertheless, in the run-up to the war in the USSR, other tendencies prevailed. The availability and cheapness of raw materials, simplicity and manufacturability of the design were put in first place; in short, the possibility of large-scale construction of aircraft at minimum cost and minimum need for skilled workers.
On the basis of this, many claim that our aviation developed according to the principle of “more as much as possible, cheaper”, and this could not but affect its combat capabilities and, ultimately, at the level of casualties.
Meanwhile, the war confirmed the correctness of the chosen concept. When the production of duralumin in the USSR fell by 80% in a few months of the German "blitzkrieg", the orientation to wooden aircraft construction turned out to be most welcome. Of course, the country's leadership could hardly have foreseen such a scenario, but история gives many examples when more than a dubious decision suddenly turns out to be the only true one.
Of the pre-war "triad" of new machines - the MiG-1, Yak-1 and LaGG-3 - the latter is the most unusual for its time. Its all-wood construction is unprecedented in the world fighter aircraft. Comparison with the famous English "wooden miracle" ("Mosquito") is hardly appropriate. Firstly, in Mosquito everything is subordinated to one single idea - speed. On the possibility of air combat, its creators did not even think. And although the plane later turned into a heavy night fighter, he had to solve completely different tasks than the Lavochkin on the Eastern Front. Secondly, exotic ultralight balsa and phenol-formaldehyde resins were widely used in the Mosquito design. The creators of "LaGG" also dealt with heavier, but common pine and birch trees in our forests.
The popular belief that LaGG was built from delta wood is not true. This material (wood impregnated with VI-B-3 plasticizer, which increased strength) was present only in the flanks of the side members, ribs and some nodes in the forward fuselage. And on La-5 they refused to do it at all, so as not to depend on foreign supplies of chemical components that were not produced in the USSR.
Working with deliberately unprofitable materials, the designers of Lavochkin Design Bureau were able to create the LaGG-3 fighter, which is generally at the level of modern requirements. Its maximum speed, armament and combat survivability did not cause any special complaints; But the incurable diseases of the heavy-duty machine — inertia, poor maneuverability, and poor rate of climb — left our fighter's pilot with little chance of winning the battle with the Messers. No wonder front-line pilots called LaGG-3 "iron".
“Heart transplant” - replacement of the VC-105 water cooling engine with a star-shaped M-82 breathed new life into the aircraft. The new engine was heavier than its predecessor on the 250 kg, however, due to the abandonment of the fluid cooling systems (radiator, pipelines, pumps, etc.), the take-off weight of the vehicle remained unchanged. But the power of the power plant increased from 1050 to 1330 hp The flight characteristics also improved accordingly. In March, the aircraft 1942, designated LaGG-3 M-82, successfully passed factory tests at the airfield of the Gorky plant No. 21 - the head enterprise for the production of LaGGov.
The data of the car was so promising, and the need for it was so strong that, in parallel with the treatment of its “childhood diseases” and even before the state tests, preparations for serial production began. In October, the 1942 th fighter, named La 5, went to the troops.
Meanwhile, although the new fighter surpassed its predecessor in almost all parameters (except horizontal maneuverability), it could not reach the Me-109G and FW-190 indicators that appeared at about the same time on the Eastern Front. In addition, the aircraft was characterized by suffocating heat in the cockpit, caused by poor thermal insulation of the engine and lack of ventilation, not very reliable operation of the engine and weapons. And although as the serial production was deployed, these flaws were gradually disposed of, the La-5 did not bring our aircraft a qualitative superiority over the enemy. Therefore, in the autumn of 1942, the work on the further modernization of the fighter began in the Lavochkin Design Bureau.
Engineers engaged in reducing the weight of the machine while increasing engine power. In December, state tests were carried out and put in the La-5F series with the M-82F engine (forced). The mass of the car decreased due to the rejection of cantilever fuel tanks (such aircraft were called “three-packs,” unlike earlier “five-packs”) and, a number of other, smaller tricks. On 1,5 mm, the thickness of the armspink is reduced, the landing light is removed, etc. Fuel capacity dropped by 60 l. Accordingly, the flight range was reduced, but it was considered unimportant, the main thing was to catch up with the Messerschmitt. But it was not possible to catch up yet.
On the prototype, which was tested in April 1943, in order to facilitate, they even replaced one of the two ShVAK cannons with a UB machine gun. However, the fighter with weakened weapons did not dare to “put on stream”.
The next step was La-5F, lightened, with improved visibility. It was lowered behind the cabin gargrot and increased the glass area of the back of the lamp. Instead of an armored headpiece appeared 66-mm bulletproof glass.
Finally, in May 1943 of the year, state tests of the La-5 with the M-82FN engine took place (in the spring of the 1944 of the year it was renamed ASH-82FN - forced with direct injection). Takeoff power of the engine increased to 1850 hp, maximum - to 1630 hp on the first and 1500 - on the second altitude limit. In addition, on the La-5FN improved cabin thermal insulation, reduced efforts on the controls and eased landing gear. The external distinguishing feature of the new modification is the long intake pipe of the engine on top of the hood.
La-5FN first appeared on the front in the summer of 1943, during the fighting on the Kursk Bulge. In Soviet times, it was pointed out that on this variant of the La-5 a complete qualitative superiority over the German fighters of that period was achieved. As evidence, data were given of comparative flight tests with captured aircraft. But at first glance, quite convincing figures require a serious critical analysis.
First of all, a brand-new, carefully regulated La-5FN was compared with battered in battles, and even survivors of forced landings, with airplanes. Our mechanics did not possess the features of setting parameters for German power plants. Serial La-5FN, due to a lower production culture than on experimental machines, had correspondingly less flight-technical characteristics. By the way, when the Germans experienced the trophy La-5, they obtained data that differed for the worse from the test results of this fighter at the Air Force Research Institute. If we compare the results of the tests of German machines, obtained under comparable conditions, with the tactical and technical characteristics of the La-5FN, it turns out that, in a number of parameters, we again had to play the role of a follower.
The situation was complicated by the fact that the ASH-82FN engine had exhausted the boost reserves. Attempts to further increase the power did not succeed, and no other power plant for the La-5 was taken from anywhere. There were two ways: the next weight reduction and the scrupulous "licking" of aerodynamics.
Back in April 1943, a full-scale copy of the La-5 was tested in the TsAGI wind tunnel T-104 in order to determine the factors affecting the drag reduction. As a result, recommendations emerged for the introduction of a series of improvements in the series, providing a total increase in speed on 30-35 km / h. The greatest effect was given by the internal sealing of the aircraft - 24 km / h - and the complete closure of the chassis - 6 km / h. In addition, it was noted that transferring the oil radiator from under the bonnet under the fuselage, where the cross-sectional area is much smaller, reduces its drag in half and increases air flow through the radiator by 35%.
Later, a positive effect was established on the aerodynamics of the machine for transferring the air intake of the power plant, from the roof of the bonnet to the root of the center section. So, literally drop by drop, additional kilometers of speed were gained.
As for weight loss, this task was also not an easy one. Nothing superfluous that could be removed without serious consequences, practically did not remain on the plane. And to facilitate the design by reducing the strength and endurance (as it was done by AS Yakovlev) S.А. Lavochkin did not. But there was another huge reserve - the replacement of wooden structural elements with metal.
In 1943, for La-5, all-metal wing spars were developed, consisting of steel T-flanges connected by duralumin walls. Weight gain was 100 kg. This alone shows how much wood is inferior in weight efficiency to “winged metal”.
At the end of 1943, the La-5 No. 206 appeared, with partially improved aerodynamics. And at the very beginning of 1944, the construction of a new modification, originally designated as “La-5 - the 1944 standard of the year”, was completed. In addition to the installation of metal spars, it took into account all the recommendations of TsAGI on aerodynamic refinement of the machine. First of all, external and internal sealing of the propeller group and airframe was implemented, additional guards were installed, completely covering the chassis. The oil radiator was transferred under the fuselage, and the suction inlets of the supercharger were placed in the toe of the center section. Changed the shape of the wing wings, reduced the number of caps on the hood and reduced the size of the movable side flaps.
In addition, to reduce the efforts on the handle increased aerodynamic compensation of the elevator. Instead of the previous control knob with a grip for both hands, they placed a shortened P-1 knob of a “Messerschmitt” type, like under the right hand. The engine was equipped with individual exhaust pipes of cylinders and installed a new screw variable pitch VISH 105В-4. The landing gear was extended by 80 mm, and an anti-bonding frame was mounted in the back cover of the lantern.
Significantly more powerful weapons. Instead of a pair of SP-20 cannons (a synchronous version of the ShVAK cannon), three new Berezina UB-20 air cannons were installed. 2 February 1944, this machine, which was destined to become the best Soviet fighter of the Second World War, rose into the air. The results of the factory tests were very encouraging. The maximum ground speed was 597 km / h, versus 546 km / h in La-5FN and 560 km / h in FW-190-5.
February 16 car passed pas state tests, which was not without trouble. February 20 due to an engine crash in flight (connecting rod break), test pilot Kubyshkin hardly landed the plane. The trials continued on March 8. And on March 22, when most of the program had already been worked out, due to a gross assembly defect on the taxiing, one of the fuselage frames collapsed. And this time the skill of the pilot helped to avoid a serious accident.
But despite all the difficulties, the 27 March test cycle was successfully completed. By this time, the KB received the task of the State Defense Committee to bring the maximum speed of La-5FN to 685 km / h. The new fighter was supposed to be the answer Lavochkin designers to this task.
In the test report, Major Kubyshkin pointed out that the “standard” increased significantly, compared with the standard La-5FN, speed characteristics. At the height of 6000, the fighter accelerated to 680 km / h - the best result of all Soviet fighters of that period.
But aerodynamic perfection was bought at a high price. When the engine was running at high speeds, the temperature in the cabin reached 40 degrees (in February) and there was a strong smell of exhaust gases and burning rubber. Thus, the “generic defect” of the early La-5 has re-declared itself - poor thermal insulation.
The situation was aggravated by the fact that with the installation of the oil cooler under the fuselage, the hot oil pipelines began to pass right under the pilot's legs, and the external sealing of the bonnet forced the exhaust gases through the slightest slots to seep into the cabin. It is clear that in such conditions ordinary flight, not to mention air combat, turns into torture. In addition, the tester noted that moisture condensate accumulates in the cab (another result of the lack of ventilation), the loads on the pedals are excessive, and there is no quick emergency escape from the car.
But despite this, the conclusion of the report read: “The plane according to its flight data is one of the best fighters. It is necessary to force the serial construction with the simultaneous elimination of the above defects. " Specific recommendations followed: to improve thermal insulation and cabin ventilation, to facilitate emergency escape of the aircraft, to reduce efforts on the pedals, to improve cooling of the cylinder heads and to facilitate the control of the motor group, for which to make joint control of the propeller pitch and gas, to install an automatic gearshift for the supercharger and automatic valve control the hood.
Such automation was installed on the Focke Wool 190 fighter, thanks to which a comprehensive change in the operating parameters of the power plant was carried out by a single throttle movement. The pilots of the Lavochkin had to do up to eight consecutive movements for this, which is almost impossible in the fleeting conditions of air combat.
Unfortunately, when launching a new fighter into a series of all of these recommendations, only one was fully implemented: the mechanism for automatically changing the pitch of the propeller was installed (it is not clear why they didn’t do this before, because “HANG-automata” were known in the thirties). Attempts to normalize the temperature inside the cabin by hanging heat-insulating covers on the oil tank and oil lines almost did not work, and the heavy heat, reaching 55 degrees in the summer months, continued to complicate the already difficult work of the pilots.
Only later on some of the serial machines appeared vent cap over the frontal bulletproof glass. Then the air intakes of ventilation were placed in the leading edge of the center section. The charge of outboard air prevented the penetration of hot gases from the engine into the cabin, and the microclimate improved markedly. As for the automatic adjustment of motor modes, devices of this kind for the ASH-82FN appeared after the war.
Meanwhile, with all its flaws, the aircraft at altitudes up to 6000 m exceeded in flight characteristics almost all types of both domestic and German piston fighters.
In the first days of May, the “1944 standard of the year” under the new name La-7 was put into serial production. It is noteworthy that in July the last LaGG-31 came off the assembly line of the Tbilisi plant number 3. Production of the La-5FN (already with metal spars) continued, gradually decreasing until November 1944.
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