How interceptor planes gained weight to fight high-altitude bombers
According to the results of air battles during a special military operation, the Su-35S and MiG-31, belonging to the heavy class, are the most effective fighters. Their maximum take–off weight exceeds 30 tons, the power plant is represented by a pair of two-circuit turbojet engines with an afterburner, the main armament is air-to-air missiles with a range of up to 300 km.
The fighters produced today are quite heavy machines, the take–off weight of which, depending on the model, varies from 10 to 50 tons. Among the fighters in service, the MiG-31 is considered the heaviest. Its maximum take–off weight is 46.75 tons, and individual modifications - about 50 tons.
The SSJ-100–95LR airliner (another designation RRJ-100–95LR), also known as the Superjet, weighs almost the same (49.45 tons). However, in the first case, the winged car "carries" only the pilot and the navigator-operator, and in the second – about a hundred more passengers.
Modern fighters are so weighty because to achieve high speeds and altitudes of flight, as well as the range values set by the customer with the specified combat load, a powerful power plant and capacious tanks with aviation kerosene are required.
The internal tanks of the MiG-31 hold 21,900 liters of fuel. The main supply of kerosene is stored in seven tanks inside the fuselage, occupying about 70% of its useful volume. However, even such a huge supply of kerosene as that of the MiG-31 is not enough to fulfill the assigned combat mission.
It is necessary to increase the litre by fixing suspended fuel tanks (PTB) on external suspension units (pylons). The wing pylons of the MiG-31 can carry 2500-liter PTB instead of missiles.
On the experimental E-266M aircraft, created in the interests of the development of the MiG-25 program, a variant with a 5,300-liter additional tank on the central pylon has been worked out. If the need arises, the MiG can additionally take about 10 tons of aviation kerosene in the discharged fuel tanks.
Carrying much more fuel, the interceptor has a range comparable to the flight range of an airliner of regional lines. The practical range of the MiG-31 without PTB is: without weapons – 2480 km, with four R-33 missiles – 2240 km, and if a pair of PTB is under the wing – 3000 km.
These indicators can be increased with the help of air refueling equipment. In 2013, the MiG-31BM crews flew over a distance of over 8 thousand km, replenishing the tanks three times due to docking with Il-78 air tankers. Note that these figures are given for optimal modes and are significantly reduced in the case of afterburner operation of the power plant.
The formula of air combat, derived three times by the Hero of the Soviet Union, the famous ace pilot Alexander Ivanovich Pokryshkin, sounds like this: "Altitude - speed – maneuver – fire." Let's consider the final term related to armament. In relation to the MiG-31, the main type of combat load is a combination of air-to-air missiles. When flying to intercept, the aircraft, as a rule, carries 4 P-33s under the fuselage, as well as 4 P-74M on wing pylons. Each P-33 weighs 490 kg, P-74M – 110 kg, in total eight missiles give 2400 kg. To this should be added a built-in six-barrel gun (76 kg) and 260 shots to it (0.2 kg each), and this is another 128 kg. In a word, the burden of the fighter is heavy! To carry it with honor, the car must be strong and hardy.
And the fighter must also have the ability to perform maneuvers with high overloads. To do this, the design is additionally reinforced. Anyway, you have to "pay a lot" for all this.
It is possible to reduce the weight of the aircraft structure by applying appropriate materials. The designers involved in the design of the MiG-31 cared primarily about achieving high flight speeds. Therefore, they chose welded grades of steel (they account for half of the weight of the aircraft structure) and titanium (17%). The welded airframe allows the MiG-31 to accelerate to a speed three times the speed of sound. A long flight is allowed on the flight Mach number M = 2.83.
These are record figures for fighters, due to the choice of structural materials. If you use aluminum or composite materials, the gain in weight will be significant. However, at higher speeds, there will be difficulties with thermodynamic heating from aerodynamic friction. Hence the forced restriction on the maximum speed and duration of the flight on it. Therefore, military aircraft with a large proportion of aluminum alloys in the design rely on maximum speeds of M = 2 with a short–term output of 2.3-2.5.
AIRCRAFT FOR AIR COMBAT
The popular image of a fighter: a relatively compact military aircraft, the element of which is a maneuverable dogfight. It is believed that such a machine is capable of maneuvering any other enemy aircraft due to its low mass in order to reach an advantageous position for opening fire from a built-in cannon or launching missiles.
Fighters as a special type of military aircraft appeared during the First World War. The first aircraft specially designed for air combat was the French Nieuport II Bebe. At the front, "Bibi" has been used since the fall of 2015. By the end of the war, there were more than 10 thousand aircraft in the active armies, and the share of fighters exceeded 40%.
Without exception, all serial machines of this class were equipped with a power plant from a single piston motor with a pulling (less often – pushing) screw. The armament consisted of machine guns of rifle caliber (7-8 mm) with a rate of fire of 400-500 bullets per minute. In the line of weapons, exceptions were rare. The competition between the powers and the design schools was mainly along the line of aerodynamics. The layout schemes "monoplane", "biplane" and "triplane" were used. The designers tried to achieve high weight perfection of their winged machines, trying to give them the best possible maneuverability.
The outstanding Russian aviator Pyotr Nesterov wrote: "A military pilot cannot do without the ability to do aerobatics. Vertical turns, coups and loops should be a mandatory program for the pilot who does not want to play the role of a chicken or a peaceful pigeon in the war… The inevitable dogfights will be similar to the attack of hawks on crows… And who of us wants to be a crow?!"
As if developing the idea of Peter Nikolaevich, the French aviator Jean Duval instructed the young pilots as follows. "Perform flips through the wing, corkscrew, dive and other numbers in relation to the opponent doing the same. Accurately calculate the distance from where you came out, the amplitude of the volt and where the volt will end. Take a firing position so that the machine gun is already aimed at the target, and all this in a quarter of a second, only then will you be successful ... At this moment, intelligence, dexterity, eye, reflective ability, in a word, the whole person, manifest themselves. A fighter pilot is a swordsman in the air, and his plane is a rapier. A fight between two dexterous rivals explains all the flying art. This is a dazzling jig, a dizzying carousel in a deadly duel."
All fighters of the First World War were made light, weighing less than a ton. Otherwise, it was impossible to provide acceptable maneuverability with limited engine power, and the power units of that time did not issue more than 250 hp. So, on the German Albatros variant D.Va built in 1917, a 180 hp engine was installed.
Armed with two rifle-caliber machine guns, the Albatross had a take-off weight of 915 kg, developed a maximum speed of 190 km/h, climbed to a maximum height of 5500 m. Although the Albatros D.Va turned out to be faster, in terms of the number of aerial victories (1294), it lost the championship to the English Sopwith Camel. According to the results of the battles in the sky, the latter turned out to be the most effective fighter of the First World War. The British camel had not the most powerful engines, motors (125-170 hp), but the take-off weight was only 660 kg. Due to this, the car differed from competitors with a low wing load of less than 30 kg/sq. m.
BETWEEN THE TWO WORLD WARS
Maneuverable biplanes and high-speed monoplanes fought for the right to further life between the world Wars. Finally, the battle between them ended only by the end of the 30s. Monoplanes won, because they better corresponded to the prevailing trend at that time to increase speed – up to 500 km/ h or more. In order to achieve the desired indicator, the designers had to sacrifice horizontal maneuverability, go for a significant increase in the load on the wing. Thus, the I-16 fighter developed by Nikolai Polikarpov in the "type 29" version (entered production in 1939) had a corresponding indicator equal to 122 kg / sq. m (against 30 for Sopwith Camel).
Differing in external outlines, all serial fighters of that time retained a certain similarity in the composition of the power plant (one piston engine equipped with a pulling propeller) and weapons (small-caliber machine guns). As a result, the aircraft of different countries and designers differed little in take-off weight, which ranged from 1.5 to 4 tons.
The overall weight increase was also due to the power units. The power of the aircraft engine in the 30s exceeded 1000 hp. The aforementioned I-16 (in the original version of the TSKB-12 sample of 1934) had a design weighing 445 kg, while the weight of the power plant was almost the same - 440 kg (the M–22 engine with a capacity of 435 hp weighed 330 kg, the rest they "added" a screw, engine oil, etc.). The plane taxied on takeoff, having a mass of 1311 kg.
The serial I-16 type 29 produced in 1940 was equipped with an M-63 engine with its own weight of 515 kg and developed a power of 1100 hp. Accordingly, the take-off weight of the aircraft increased to 1.8 tons.
Prerequisites for the split of a single class of fighters arose due to a sharp increase in the mass of aviation weapons. The weight of a salvo (bullets fired by an onboard weapon per unit of time) increased from 25 kg per minute in 1917 to 200 or more. On the Italian fighter CR.During the Spanish Civil War, 7.7 mm machine guns, Breda-SAFAT machine guns were replaced with 12.7 mm of the same company, exceeding 2.3 times in weight. The rate of fire decreased by 20%, but due to heavier bullets, the weight of the volley increased fourfold.
On the basis of captured samples, large-caliber machine guns began to be made in the Soviet Union. The Berezin machine gun, known by the abbreviation "UB" or "UBS", became a popular domestic model. At first, it was installed on Polikarpov fighters. The aforementioned I-16 Type 29 had a pair of 7.62mm wing ShKAS (like the I-16 Type 5), and in addition to them – one UBS. The I-200 high-altitude fighter (MiG-1) also received a similar composition of weapons. The firstborn of the Mikoyan and Gurevich design bureau entered production in 1940.
The very first air battles with the aircraft of fascist Germany showed the insufficient force of the fire of our "hawks". Therefore, several hundred improved MiG-3 fighters assembled in 1941 were additionally armed with a pair of large-caliber BS machine guns in gondolas under the wing.
Shortly after the large-caliber machine guns, automatic aircraft guns entered service with the aircraft. Note that some of their models were created as large-scale (enlarged) copies, others – by replacing the trunk. The most massive Soviet air cannon of the late 30s - early 40s of the last century was a 20 mm ShVAK. For the first time such a weapon was tested by the pilots of the I-16 type 17 in the battles on Khalkhin-Gol. The variant installed in the collapse of the cylinders of V-shaped piston engines (such as the M-105P designed by V.Y. Klimov on the Yak-1 and LaGG-3) was called a "motor gun".
Many gunsmiths preferred to work with a 20 mm caliber. The Americans went further: They created a 100-kilogram 37 mm T-9 cannon. For comparison, the weight of the Breda-SAFAT 12.7-mm machine gun was 29 kg. After spending almost a decade in development, the American "super-gun" in 1941 went into production under the designation "M-4". The rate of fire reached 150 rounds per minute. This gun was installed on the Bell P-39 Aeracobra fighter, which was supplied in large quantities under lend-lease to the USSR. "Aerocobra" gained great popularity among Soviet pilots, became the favorite aircraft of Pokryshkin and his students. Note that the mass of the M-4 cannon, together with a magazine of 30 rounds, was 137 kg.
SHOOT DOWN THE "AIR FORTRESS"
The development of guns like the M-4 was a response to the emergence of heavy long-range bombers. According to the Douai doctrine, popular in the 1930s, these giants were intended to achieve victory by destroying the enemy's military-industrial centers. Scientific and technological progress led to the creation of turbocharged engines and pressurized cabins, thanks to which bomber aircraft moved from low and medium altitudes to high (8 km or more). Thus, the range of action has increased and the vulnerability to air defense fire has decreased.
Soviet test pilots, who expressed their opinion on this issue in the conclusion of the Air Force Research Institute on the four-engine TB-7 (Pe-8), stated the following. The high-altitude and high-speed characteristics of the Petlyakov machine made it little vulnerable to attacks by interceptor fighters. High survivability was achieved thanks to an all-metal airframe with a large wing area and elongation. In addition, the TB-7 climbed to a great height due to a combination of a turbocharger based on the M-100A and four AM-34FRNB engines.
To get a high-flying bomber, the MiG–1 fighter (at that time, the best high–altitude interceptor in the world) needed 40 minutes of time, after which the pilot had only enough fuel for one, in the best case, two approaches to the target. It was necessary to attack "in pursuit", as a result of which the fighter was a convenient target for the bomber's shooters.
Chief Designer Alexander Mikulin understood that the AM-34 engine he developed was too heavy for an interceptor. Therefore, he suggested using his "half" as the basis for a new engine for a light fighter. This idea was opposed by Nikolai Polikarpov. Arguing his position, the "King of Fighters" pointed to the trend of increasing the weight of aviation weapons that had manifested by that time. Together with the increase in the customer's requirements for speed and altitude, this required an increase in the absolute and specific characteristics of the power plant. Accordingly, with the long-range development of his engine line, Mikulin focused on creating a more powerful and high-altitude AM-35A, which was put not only on bombers, but also MiG-3 fighters.
As noted above, the MiG's standard armament consisted of three machine guns, including a pair of rifle caliber. When setting up one 12.7 mm machine gun and a pair of 7.62 mm. It turned out to be too weak to fight the German He-111 and Ju-88 bombers. It was also important that the strike aircraft operated in groups, built so that the onboard shooters were able to concentrate fire on the approaching interceptor, which poses the greatest danger.
According to calculations carried out by British specialists in the late 30s, to destroy the He-111 or Ju-88, a battery of 12 rifle-caliber machine guns should have been installed on the fighter (at that time the British did not have aviation guns yet). So much was put on "Hurricanes" (for example, modifications of Hurricane Mk.IIB).
Studying various ways to get a high-altitude bomber, aircraft designers began to put pressurized cabins and aircraft engines on interceptor aircraft with maintaining power at altitude due to turbocharging units and drive centrifugal superchargers with two or more operating modes.
The increase in the mass of aircraft armament and power plant, as well as the fuel reserve required to climb 11-12 km (which sometimes took an hour!), led aircraft designers to the idea of a twin-engine interceptor. A little later, they came up with the idea of a long-range fighter designed to escort bombers.
Aviation Major General Mikhail Stroev published a number of articles on the eve of the Great Patriotic War on the further construction of the Red Army Air Force. One of his publications in the magazine "Air Fleet Technology" stated the following: "At this stage, it is necessary to have three types of fighters: a single-seat high-speed and maneuverable monoplane and a two-seat twin-engine wide-range aircraft." Mikhail Pavlovich's foresight allows him to be attributed to the number of prominent organizers and theorists of the air force of that time.
In the late 30s - early 40s, Polikarpov, Mikoyan and Yakovlev were engaged in designing a heavy fighter. Nothing worthwhile happened to the triumvirate of outstanding Russian aircraft designers. Perhaps the best solution was proposed by Petlyakov, who, in the company with his comrades in the development of TB-7, got into a "sharashka" for disrupting the timing of such an important topic. In other words, the design of the VI-100 interceptor was carried out by the same specialists who had previously worked on the high-altitude bomber. Therefore, they were well aware of the complexity of the fight against him.
The need for a twin-engine scheme for the future interceptor became obvious to those of the designers who in the 30s faced difficulties in bringing promising high-altitude aircraft engines with a capacity of more than 1,350 horsepower (engines with a capacity of 2 thousand hp or more were put on racing aircraft, but withstood only a few hours of work). Great hopes were pinned on the AM-37 and AM-39 with "inter-coolers" of Mikulin's design. However, they could not be brought to an acceptable level of reliability.
It is interesting to note that the MiG-1 with a single AM-35A engine (instead of the planned AM-37), although it turned out to be the fastest (640 km/h) and high-altitude (12 km) fighter of 1940, could not effectively fight the Ju-86P scouts that occasionally appeared over Moscow. Due to the superchargers, their altitude has increased to 14 km .
As for the VI-100 (a power plant of two M-105s with TK-3 turbochargers and a drive centrifugal supercharger), the aircraft turned out to be interesting and promising. However, the customer ordered it to be modified into a dive bomber and put into production in this form under the designation "Pe-2". Shortly after the attack of Nazi Germany, a Pe-3 heavy fighter was launched in a small series based on the Pe-2, and then a Pe–3bis with an onboard Gneiss-2 radar.
DEMOCRATIC COUNTRIES
The idea of a twin-engine fighter was gaining popularity among European military and aircraft designers. However, only some developments have been embodied in metal. Before the outbreak of World War II, several dozen French Potez 631, Dutch Fokker G.I, Italian Meridionalli Ro.57 and English Westland Whirlwind were produced. Due to their small numbers, they did not have any impact on the course of hostilities.
The British also failed with their twin-engine Bristol Beaufighter fighters (almost 6 thousand copies were built) and de Havilland Mosquito (about 8 thousand copies were collected, mainly scouts and bombers). Due to the low efficiency in the role of interceptors, these aircraft also had to look for other applications (anti-submarine aircraft, reconnaissance, etc.). Whatever it was, the British fighters mentioned above helped to launch a new interesting direction. Having accumulated experience on similar projects, aircraft designers moved on to the next topic – night interceptors equipped with an onboard radar station (radar).
Towards the end of the war, a special night fighter was developed by the American company Northrop. She created a two-girder aircraft with a P-61 Black Widow front landing gear. Since 1944, the machine has been used in both the European and Pacific theaters of military operations.
Quite heavy (take–off weight of 17 tons), the "black widow" for its time flew low (the practical ceiling is 10 km) and slow (600 km/ h). At the same time, she carried very powerful weapons. Four 20 mm cannons built into the bow were designed to fire forward along the course. Four more of the same guns were placed in a rotary rifle turret mounted on top of the fuselage.
The forward part of the fuselage was allocated for the location of the radar in it. Thus, the P-61 became the first screw fighter specially designed as a radar carrier in the nose of the fuselage. Subsequently, this decision became a classic of the genre.
A total of 742 aircraft of the P-61 family of all modifications were produced. And the most massive twin-engine fighter of the Second World War was the Lockheed P-38 Lightning ("Lightning"). It was released in an amount of about 9400 copies.
The Lightning was equipped with an Allison V1710 engine. Engines of this brand also went to the single-engine fighters P-39 Aerocobra and P-40 Kittyhawk, produced in parallel in a large series in the early period of World War II. However, there was one important difference. The variant of the Alizon engine for the lightning was equipped with a turbocharger to maintain power at high altitudes. Thanks to this, the P-39 turned out to be the only US Army fighter capable of effectively fighting more maneuverable Japanese fighters.
Although the car came out heavy (under 10 tons), in terms of speed (670 km / h), altitude (practical ceiling 11.5–13.5 thousand depending on the modification) and firepower (a 37 or 20 mm cannon, four 12.7 mm machine guns), it surpassed all Japanese aircraft produced in 1941-1943.
The introduction of the P-38 into battle turned the tide of the air battle over the Pacific Ocean. Having switched from single-engine fighters to "lightning", American pilots switched from the previous tactics of combat on turns (more advantageous to the Japanese) to those on verticals. Diving from a great height, they shot down a Japanese plane that had hit the sight and, having completed a steep slide, easily broke away from the enemy fighters chasing them at speed. Richard Bong, the best US ace who shot down 40 enemy planes, flew on the P-38.
ACCORDING TO THE GERMAN MODEL
The German Bf.110 became the first twin-engined fighter in the world to enter mass production. Since 1938, about 6 thousand copies have been produced in total. In addition, German aircraft factories assembled 550 Me.210 and 1160 Me.410, representing the further development of the basic model. The Luftwaffe tried to use the Bf.110 as a fighter to isolate the combat area. However, in this capacity, the aircraft did not justify the hopes placed on it. Therefore, subsequently, the Bf.110 was used mainly as a shock (carrying bombs and missiles), as well as in the air defense system of the Third Reich, but even here the results were lower than expected.
The first successful interception of aerial targets using airborne radar information was performed by the Dornier Do-215 bomber converted into a night fighter. Junkers Ju-88G turned out to be a more successful conversion of the bomber into an interceptor with radar. It was released in a fairly large series – 2,800 copies. In addition to the Germans, the British were also engaged in the same alterations, although not so massively. Such "misuse" of bombers stopped only when specially designed interceptor aircraft with radar appeared.
The first such interceptor was the Heinkel He 219 Uhu. The take-off weight of the machine was 13.5 tons. The power plant consisted of two DB603E engines with a total capacity of 3600 hp. In total, about 300 such machines were assembled in a variant with a FuG 212 Lichtenstein radar and an armament of four to eight aircraft guns.
The experience of the Second World War showed that heavy fighters have the right to life. The main task they solved was the fight against strategic bombers. Ironically, the best example of a new type of interceptor was formed not by the winning countries, but by the loser Germany. It became the Me-262. This is the world's first production jet aircraft with two engines. Various variants of the Me-262 were equipped with Jumo or BMW engines. The aircraft was mass-produced at the end of World War II. In total, more than 1 thousand copies were built. The take - off weight of the machine was about 7 tons . The aircraft had a maximum speed of 900 km/h and climbed to an altitude of 11.5 km.
Wilhelm (Willy) Messerschmitt conceived the Me-262 as a high-speed fighter. However, Hitler believed that it was better to produce more Bf.109 and FW.190 propeller fighters, and use the Messer jet for bombing attacks. As a fighter-bomber, the machine began to be used in the summer of 1944. However, massive Allied air raids on German cities forced Me-262 to be repurposed again. It was used as a Berlin air defense interceptor starting in February 1945. The main armament is four 30 mm cannons in the forward fuselage. On the external suspension, the aircraft could carry unguided missiles and additional cannon containers.
Individual copies of the Me-262 were equipped with the FuG 218 Neptun or FuG 350 Naxos radar. In this form, the aircraft had all the distinctive features of a new class of aircraft – a jet interceptor: a swept wing, powerful rocket and cannon armament, an onboard radar, a tricycle landing gear with a nose rack.
This is how a certain look of a heavy twin-engine interceptor was formed, which in the post-war years found development in the USA, Great Britain, France and the Soviet Union.
The strongest influence of the Me-262 can be traced in the layout solutions of Alexander Sergeevich Yakovlev. The Yak-25P twin-engine interceptor turned out to be quite heavy due to the twin-engine scheme, the presence of a powerful radar and air-to-air missiles guided by its beam. Based on it, a more advanced Yak-28P was created. The Yak-25P and Yak-28P aircraft were not exported, but for a long time they were in service with the air defense forces of the Soviet Union.
Vyacheslav Ivanov
Vyacheslav Viktorovich Ivanov is a military expert and historian.
