The Soviet military leadership was greatly impressed by the effective use of the Israeli Air Force of American AWACS E-2C Hawkeye aircraft during the Lebanon War of 1982. At that time, the Soviet Union had a limited number of heavy Tu-126s, which had already become quite obsolete. To replace obsolete machines built in the mid-60s, the development of the A-50 aircraft was carried out with the Shmel radio complex, which was innovative for the USSR. However, already at the design stage of the AWACS aircraft based on the Il-76, it was clear that it would not be able to become inexpensive and massive. In addition to the "strategic" heavy aircraft of the radar patrol and control, the Soviet Air Force needed a tactical aircraft with a flight duration of 4, 5-5 hours and the ability to detect low-flying and stealth targets at long ranges.
In 1983, the command of the Air Force and Air Defense, with the participation of research organizations and industrial enterprises, agreed on the requirements for a new middle class AWACS aircraft. The on-board radar system was supposed to ensure the detection of low-altitude targets at a distance of at least 200 km and the simultaneous tracking of 120 targets. In the passive mode, with the help of an electronic reconnaissance station, it was envisaged to detect working ground (sea) radars and air defense missile guidance stations at a distance of up to 400 km. The data transmission equipment was supposed to provide multi-channel control and guidance of both in service and promising fighter-interceptors, as well as broadcasting radar information to ground command posts in real time.
For a promising front-line AWACS aircraft, two versions of radio systems were envisaged: decimeter (with the traditional location of the radar antenna in the fairing above the aircraft fuselage) and centimeter (with antenna spacing in the nose and tail of the fuselage). An-12, An-32, An-72 and Il-18 were considered as an aviation platform. By that time, the An-12 and Il-18 aircraft had already been discontinued, but there were many fairly new and in good condition machines that could be easily converted into AWACS aircraft. The promising medium transport An-32 with the new AI-20D-5M turboprop engines was just being tested. The project on the basis of the light transport An-72 with two bypass turbojet engines D-36 seemed very promising. A significant advantage of the An-72 was the high location of the engines, which made it possible to operate it from poorly prepared field airfields. The use of the so-called Coanda aerodynamic effect significantly increased the lift and reduced the takeoff run. Specialists of OKB named after OK Antonov managed to work out the project very carefully, and the military unambiguously spoke in favor of the version based on the An-72. Thanks to deep preliminary research, it was possible to go directly to the detailed design, bypassing the stages of sketch design and the construction of a full-size wooden model.
An-71
The need to place the disk-shaped antenna of the radio engineering complex predetermined the aerodynamic layout. The large dimensions of the rotating antenna did not allow for optimal placement on a relatively small aircraft according to the traditional scheme. In this case, the antenna had a great influence on the tail, and there were zones of radar shading by the airframe elements. In addition, when installed with the help of pylons "on the back", the antenna inevitably fell under the influence of jet jets of high-mounted engines. In this regard, after analyzing all possible schemes, the developers settled on the option of installing the antenna at the tip of the vertical tail, which gave the aircraft a very exotic appearance. The rotating antenna of the surveillance radar was located inside the fairing, structurally consisting of a metal caisson part and fiberglass shells.
To do this, it was necessary to redo the tail section of the fuselage and a new vertical tail, which had a reverse sweep, as well as a large chord and thickness. To reduce vibration loads, the tail section of the fuselage was raised up, which made it possible to increase the height of the stabilizer by half a meter. But even so, despite all the efforts, the An-71's controllability was markedly different from the An-72 for the worse. The unusual layout led to the need to solve a number of problems, among which were insufficient stability and controllability in the lateral and longitudinal channels, and the forced installation of a large area rudder, which complicated control and significantly reduced the effectiveness of the rudder trim.
To improve the takeoff characteristics of the An-71, more powerful D-436K engines with a thrust of 7500 kg were used. However, at the request of the military, in order to realize the possibility of taking off from shortened runways or with one inoperative main engine, an RD-36A accelerating engine with a thrust of 2900 kg was additionally installed under the tail of the fuselage. Since the power consumption of the onboard equipment increased significantly instead of the two GP-21 generators used on the An-72, four GP-23 generators with a total power of 240 kW were used.
Tail section of An-71
In comparison with the transport An-72, the internal volume of the An-71 has undergone a rearrangement. The designers had to go to a number of tweaks to accommodate all the necessary equipment and the fuselage was now divided into three compartments. Immediately behind the cockpit were operator workstations with equipment racks and information display screens. In the middle compartment, isolated from the habitable space, there was the computer equipment of the radio engineering complex and aircraft equipment. The third compartment housed the radar equipment, the booster engine, cooling systems and elements of the control system. A metal screened partition with a door was installed between the first and second compartments.
In order to increase the reliability of the radar complex and reduce the harmful vibration effect, the equipment installed in the third compartment was located on a single depreciation platform, which simultaneously served as an air duct for the cooling system. Part of the equipment was placed in the underfloor space of the fuselage, landing gear fairings and wing fairings. Thus, the density of equipment installation on the An-71 was significantly higher than on the much larger A-50 aircraft. To get to a failed electronic unit, it was often required to dismantle several neighboring ones. And yet it was necessary to provide acceptable working conditions for three operators.
Based on the experience of operating the first Tu-126s, great attention was paid to measures to ensure biosecurity and normal crew living conditions. To prevent the penetration of harmful high-frequency radiation, glazing of the cockpit canopy with a protective metallized coating was used, the passages of pipelines, electrical cables and rods through the partitions and elements of the airframe of the aircraft were carried out with the obligatory observance of radio-tightness requirements.
After the final approval of the project, the construction of three experimental machines began. Two aircraft were supposed to be used for flight tests, and one for static tests. The first An-71 was attached from the fourth experimental An-72. This machine, which had a lot of flying time and one emergency landing, was not in flight condition before the conversion. The second and third copies were also not built anew, but were altered from the used An-72. On July 12, 1985, an experienced An-71 took off for the first time.
The first copy of the An-71 while jogging
If the re-equipment of the aircraft themselves went strictly according to the schedule, then problems arose with the radio engineering complex. The first version of the radar and the computer complex created at NPO Vega showed unsatisfactory results in terms of detecting air targets against the background of the earth. This led to a radical alteration of the radar and computing equipment. However, by that time, the customer's requirements had changed in terms of interaction with fighter and strike aircraft. It was necessary to increase the number of guidance channels, ensure interaction with long-range air defense systems, increase the degree of automation of the operators' work and effectively work on ground and surface targets, which led to the creation of a third set of equipment.
The An-71 tests were carried out not only in Ukraine, but also in other regions of the USSR, including the Caucasus, the Volga region and Central Asia, in various meteorological conditions and over various landscapes. During the tests, the hardware part of the radar complex was brought to a high level of reliability. At the same time, the An-71 could operate in isolation from the main base for a month, dispensing with minimal maintenance. According to the assessment of the military and specialists of the Ministry of Aviation Industry, who participated in the tests, the use of the An-71 could increase the effectiveness of fighter aviation by 2.5-3 times.
On tests, an aircraft with a maximum take-off weight of 32100 kg developed a maximum speed of 650 km / h. Cruising speed - 530 km / h. The service ceiling is 10,800 meters. The time spent on patrol is 5 hours. That is, according to flight data, the An-71 was at least not inferior to the American E-2C Hawkeye. According to information published by Global Security, the radar installed on the An-71 could detect targets against the background of the earth at a distance of more than 200 km, with a patrol altitude of 8500 meters.
You can often hear the opinion that the An-71 was originally developed as a carrier-based AWACS aircraft, but this is not the case. In 1982, after the laying of the heavy aircraft-carrying cruiser pr 1143.5 on the slipway of the Black Sea shipyard in Nikolaev, the question arose about the formation of its air wing. If everything was more or less clear with fighters and anti-submarine and rescue helicopters, then there were no ready candidates for the role of carrier-based AWACS aircraft in the USSR at that time.
In 1983, after the start of work on the front-line AWACS aircraft, the An-71 deck modification was being worked out. However, it soon became clear that, due to the high altitude of the An-71, basing it on an aircraft-carrying cruiser is extremely difficult. If the wings could still be folded to save space, then what to do with the high tail unit, crowned with a bulky radar antenna, was not clear. However, the main obstacle was the lack of a catapult on the ship. This made it impossible for the An-71 to take off from the deck due to insufficient thrust-to-weight ratio. For a short take-off from a runway with a springboard, at least three accelerating engines were required, for which it was necessary to redesign the entire aircraft. Taking into account these circumstances, the customer, represented by the Ministry of Defense, decided to abandon the order for the development of a carrier-based AWACS aircraft based on the An-71 and concentrate efforts on another model.
For the first time, they started talking about the new Soviet AWACS aircraft in the West in 1986, after visiting M. S. Gorbachev of the Kiev Mechanical Plant, where at the Gostomel airfield the General Secretary of the CPSU Central Committee was shown promising models of aircraft. In this case, the tail section of the aircraft, bearing the symbols of Aeroflot with a radar fairing, fell into the lenses of photo and video cameras.
The fate of the An-71 was negatively affected by the economic difficulties that the economy faced in the late Soviet period. In 1990, work on the An-71, which had reached a high degree of readiness, was frozen, and after the collapse of the USSR, in the conditions of the loss of financial and economic ties, they did not return to them. Although, from the point of view of common sense, relatively inexpensive AWACS aircraft of the operational-tactical link are even more needed for our country than the heavy A-50, for the most part idle at the airfield. Possessing good takeoff and landing characteristics and acceptable operating costs, the An-71 could be used as an operational means of enhancing air control during a "special period" or during local conflicts. During the two Chechen campaigns and the armed conflict with Georgia in 2008, the extremely expensive AWACS A-50 aircraft had to be used to direct the actions of military aviation.
According to American sources, in the early 2000s, Ukraine was negotiating with India on the possible supply of modernized An-71s at a price of $ 200 million per aircraft. At the same time, the Kiev enterprise "Kvant-Radiolokatsiya" undertook to develop a new radar "Kvant-M" with a detection range of low-altitude targets up to 370 km. At the same time, the number of tracked targets was supposed to reach 400 units. However, the deal was never concluded. Most likely, the Indian representatives were unable to obtain guarantees that Ukraine is really capable of fulfilling its obligations.
Since 1979, A. S. Yakovlev, where they traditionally dealt with sea-based vertical takeoff and landing aircraft, research was carried out on the deck aircraft AWACS. The main difficulty in creating such a machine, based on the characteristics of Soviet aircraft-carrying ships, was the rise of the aircraft into the air in the absence of a catapult on the deck. For this, the thrust-to-weight ratio of the aircraft, which could spend 4-5 hours on patrol, had to be very high. Initially, the aircraft, which received the designation Yak-44E, provided for the installation of four additional takeoff turbojet engines and two marching theaters. According to the terms of reference agreed with the Navy, the radio-technical complex was supposed to detect air targets at a distance of 150-200 km and direct naval fighters at them. The detection range of surface targets is more than 300 km. When stored on a ship, the wing consoles were folded. The number of the Yak-44E crew in the original version is 4 people.
However, the placement of four lifting motors and additional fuel did not leave room for a bulky radio-technical complex and normal working conditions for operators. And the onboard radar and communication equipment itself was created with great difficulties. It soon became clear that this version of the AWACS deck aircraft was a dead end, and the project was revised.
On the aircraft of the updated project, it was decided to abandon the additional lifting engines, which were "dead" cargo in flight. The thrust-to-weight ratio of the aircraft was increased by the installation of two new D-27 turbofan engines with a capacity of 14,000 hp. The choice of an engine of this type was due to the fact that at a sufficiently high subsonic cruising speed, it had significantly better fuel efficiency than the available turbojet engines. In addition, in comparison with turboprop engines in takeoff mode, it provided better traction characteristics, thrust-to-weight ratio and increased lift due to wing blowing.
Comparative sizes of E-2 Hawkeye, Yak-44 and An-71 AWACS aircraft
It was decided to use the advanced E-700 radar with an antenna in a disc-shaped rotating fairing with a diameter of 7, 3 meters on a pylon above the aircraft fuselage as an onboard radar for all-round visibility. At the same time, the Soviet carrier-based AWACS aircraft began to very much resemble the American Hawkeye, but at the same time it was somewhat larger.
Full-size model of the Yak-44E aircraft
In the summer of 1989, the work entered the phase of practical implementation of the project. The first step was the production of a full-size structural and technological model of the aircraft and a reduced model for radio engineering research and preparation for the construction of prototypes.
Yak-42LL
For flight tests of the D-27 aircraft engine, the Yak-42LL flying laboratory was prepared. The construction of prototypes of the Yak-44E and its serial production was to be carried out at the Tashkent Aviation Plant. In the future, it was planned that this machine will also be supplied to the Air Force.
Photo for memory. After the completion of the tests of the Yak-44E model on the aircraft-carrying cruiser "Tbilisi"
To assess the possibility of placing the Yak-44E on the flight deck and in the hangar of the aircraft-carrying cruiser "Tbilisi", a full-size model of the aircraft in August 1990 was delivered by a barge on board a ship that was being tested in the Sevastopol region. During the tests, the possibilities of placing the aircraft in the internal hangars, rolling out onto the platform from the lift and lifting from the internal hangars, towing and mooring the aircraft on the flight deck and in the hangar, interfacing the aircraft with technical support posts were tested. After completing the evaluation program, the model returned to the assembly shop of the Yakovlev Design Bureau. After testing the layout, the laying of the first prototype took place.
According to the design data, an aircraft with a maximum take-off weight of 40,000 kg could reach a maximum speed of 740 km / h. Cruising speed - 700 km / h. Landing speed - 185 km / h. The service ceiling is 12,000 meters. The duration of patrolling at a distance of 300 km from the aircraft carrier in the speed range of 500-650 km / h is 5-6 hours. Crew: 2 pilots, 2 RTK operators and a guidance officer. Compared to the An-71, the deck-based Yak-44 was distinguished by a very dense layout.
The layout of the Yak-44
In the future, to increase the duration of stay in the air, the aircraft had to receive a refueling system. On the basis of the Yak-44E airframe, a carrier-based anti-submarine aircraft and a tanker were also designed.
The E-700 radio complex provided stable detection of air targets against the background of the underlying surface at a distance of 220-250 km, depending on the RCS. Surface targets could be detected at a distance of up to 400 km. The Yak-44E equipment could simultaneously track 150 targets and aim 40 fighters at them.
Although the full-scale layout of the Yak-44E was successfully tested on board the aircraft carrier 1143.5, it was clear that on this ship, which, moreover, did not have a catapult, the AWACS would be too cramped for carrier-based aircraft. In total, the aircraft carrier's wing was supposed to include up to 4 AWACS aircraft and 2 refueling aircraft. Therefore, the design of the deck "radar picket" before the closure of the program was mainly carried out in relation to its placement on the nuclear aircraft carrier pr.1143.7 "Ulyanovsk". This modification, intended for launch from a catapult, received the designation Yak-44RLD. Unlike the ship now bearing the name "Admiral of the Fleet of the Soviet Union Kuznetsov", "Ulyanovsk" was supposed to become a full-fledged aircraft carrier with roomy internal hangars and a steam catapult. Its planned commissioning was scheduled for 1995.
The Ulyanovsk-class nuclear-powered aircraft carrier could become the first Soviet aircraft-carrying ship, not inferior in size and capabilities of the air group to the American nuclear-powered multipurpose aircraft carriers of the Enterprise and Nimitz class. The installation of steam catapults and the ability to lift AWACS aircraft significantly expanded the ship's functions in comparison with previous Soviet aircraft-carrying cruisers. In the option of providing the air defense of the squadron on board the Ulyanovsk, it was envisaged to place 36 Su-33s and 8 Yak-44s.
It could look like the nuclear aircraft carrier "Ulyanovsk"
However, after the collapse of the USSR, the construction of the aircraft carrier "Ulyanovsk" at the shipyard in Nikolaev stopped, and when about 20% of the ship's hull was ready, the ship's hull was dismantled in 1992. At the same time, the government of the "new" Russia stopped funding the Yak-44 program, and this very promising AWACS aircraft was never built. Since the enterprise that was engaged in the creation of the "front-line" An-71 turned out to be in "independent" Ukraine, and with the refusal to finance the machine that had become foreign, one can still somehow agree, the Yakovlev Design Bureau remained in Russia, and in our country there were all the possibilities for the construction of prototypes and refinement to serial production of the Yak-44. Without a doubt, this versatile aircraft would be in demand not only in the Navy, but also in the Air Force.
If the An-71 reached the stage of building prototypes, and the Yak-44 was built in the form of a full-size mock-up, then the P-42 aircraft, developed at the Design Bureau named after G. M. Beriev in Taganrog, never left the stage of the project. This versatile aircraft platform outwardly resembled the American S-3 Viking anti-submarine carrier-based aircraft. On the basis of the P-42, it was supposed to create an PLO aircraft, a tanker, search and rescue, transport and AWACS. This approach could save production costs and speed up the development of flight and technical personnel. Like the Viking, it was a moderately swept over-wing monoplane. Two turbofan engines D-36 were located under the wing, the consoles of which could be folded. The keel was also foldable according to the project. The plane was supposed to be launched using a ship's catapult and land using an air arrestor. It was a fairly compact aircraft with a maximum take-off weight of 29,000 kg and a crew of three. Its top speed was supposed to exceed 800 km / h. Patrol time at a distance of 300 km from the ship - 2.5-3 hours.
Project appearance of the aircraft AWACS P-42
The construction of a prototype was scheduled for 1976. It was assumed that the P-42 will become part of the aircraft carrier's air wing with a nuclear power plant pr. 1160 "Oryol". The development of this project has been carried out since the late 60s at the Nevsky Design Bureau. By the mid-80s, the USSR Navy was to receive three of these ships. However, the construction of aircraft carriers with a nuclear reactor was considered too costly, and in 1973 all work was curtailed in favor of the further construction of ships of Project 1143. Work on aircraft of the P-42 family did not advance beyond the paper stage.
