Yun-20 will be derived from early warning aircraft, and how will air marshal develop in the future

 Yun-20 will be derived from early warning aircraft, and how will air marshal develop in the future

In fact, this is not an unexpected news. It is a routine operation to develop an early warning aircraft on the basis of a large transport aircraft. Russian Air Force has developed A-50 and A-100 early warning aircraft based on Il-76. Early warning aircraft is the multiplier of war power in the information war, which is known as the commander in the air. So, from the development trend of early warning aircraft in the world, what will it look like in the future, or the new generation of early warning aircraft?

Yun-20 delivers medical personnel and supplies to the front line of anti epidemic. Chinese military network

The contradiction between anti stealth and precision

Operational requirements determine the technical approach. The tactical requirements of the early warning aircraft in the future determine the technology and layout form it adopts.

A reasonable requirement is that the detection distance of the new generation of early warning aircraft to the high stealth target should reach or exceed the detection distance of the active early warning aircraft to the third generation of aircraft. At present, the distance is generally more than 300 kilometers, and the early warning aircraft with good performance can reach more than 500 kilometers.

Of course, the detection range of radar cross-sectional area (RCS) is rogue. Just as how far a human eye can see an object depends largely on how big it is. How far the radar can see depends largely on the RCS of the target. What is the RCS of the typical stealth target for the new generation of early warning aircraft? Generally speaking, the forward RCS of heavy aircraft in the third generation is about 15 u33a1, and that of medium and light aircraft is about 3-5 u33a1. The third-generation semi fighter with limited stealth technology is less than 1 u33a1. The real stealth plane is still secret. Americans have said that the forward RCS of the F-35 is equivalent to a golf ball, while the F-22 is equivalent to a steel ball. The RCS of a golf ball is about 0.0025 u33a1 at 3.3 GHz. According to the testimony of the chief of staff of the U.S. Air Force in the Senate in 1990, the RCS of the B-2 stealth bomber is equivalent to the size of some insects, while the RCS of three kinds of insects given by the B-2 stealth bomber are 0.001 m2, 0.0001 m2 and 0.000063 M2 respectively. Therefore, analysts estimate that the positive RCS of B-2 is between 0.001 and 0.0001 u33a1. As technology advances, this RCS will be reduced. From this point of view, the typical forward RCS of the early warning aircraft in the future is mainly located between 0.001-0.0001 u33a1, and the omnidirectional average RCS will be slightly larger.

It is a routine operation to develop early warning aircraft on the basis of large transport aircraft. CCTV military screenshot

At present, the detection ability of radar for such targets is extremely limited. Taking the spy-1d (V) used by the Aegis system of the United States as an example, the radar can track a golf sized target 165 kilometers away, according to the report beyond the horizon shield of the union of concerned scientists. Then the detection distance of 0.0001 u33a1 target is about 70 km. This performance is difficult to meet the operational requirements. If we want to extend this distance to 300 or even 500 kilometers or more, the requirements for radar technology are very high.

Of course, detecting air targets is never the only function of an AWACS. Early warning aircraft must also have command and guidance, data fusion and other functions. The network operation also requires the early warning aircraft to have the ability of relay guidance to air defense and even air-to-air missiles. According to the Americans, its latest shipboard E-2D early warning aircraft can guide standard-6 anti-aircraft missiles launched by aegis to attack targets below the horizon (relative to the ship). At present, this ability mainly depends on the fusion of all kinds of sensor information, not on the radar of the early warning aircraft itself. So in the future, if the cost of early warning aircraft is acceptable in other aspects, it may also be a new demand to rely on its own radar for guidance.

Russian A-100 early warning aircraft adopts the layout of the back loaded disc

With or without dual band radar?

There are two technical paths to complete the anti stealth task. One is to select radar with longer wavelength, such as UHF band between decimeter wave and meter wave. The E-2D radar is in this band. The other way is to improve the power and sensitivity of the radar, which is used by the us to replace the spy-6 of the Aegis spy-1 radar. Whether using long wavelength band or increasing the radar power, it is inevitable to require the early warning radar antenna to have a large size. The size of radar antenna is usually related to its working wavelength. The longer the wavelength is, the larger the size is. But the main problem of LWR is its poor accuracy, especially for the radar antenna with limited size used by early warning aircraft.

In order to carry out the midcourse guidance task of missile, it is necessary for radar to have high data repetition rate (update speed of target data) and high accuracy, which in turn usually requires radar to have high working frequency, that is to say, radar wave length is short. At present, the active phased array radar is very sensitive to the generation and control of the beam. Whether it adopts the combination of machine scanning or full electronic scanning, it can meet the requirements of data repetition rate. The key problem is the accuracy.

The Israeli G550 early warning aircraft uses the conformal array structure, which is more suitable for the aircraft with single wing layout.

At present, the longest wavelength of fire control radar is in S band (decimeter wave), most of which are concentrated in C band (central wavelength 5cm). The main reason is that because the wavelength is too long, the beam width is relatively wide and it is difficult to ensure the accuracy. As an early warning radar, the frequency should not be too high, otherwise the beam is too narrow, which is not conducive to the search speed; secondly, the atmospheric loss is large, which is not conducive to long-distance detection. The midpoint between early warning detection and fire control guidance is in S-band. Even in the S-band, a large radar aperture area is needed to achieve the basic fire control requirements. The antenna area of the early warning aircraft may not meet such requirements. At the same time, using S-band is not conducive to anti stealth.

How to solve the contradiction between detection accuracy and anti stealth requirements? A feasible way is to develop dual band radar. It is reported that Russias A-100 early warning command aircraft is equipped with a new generation of premier active phased array radar developed by vegaconcern company, which is installed in the rotating radome above the fuselage. Of course, dual band radar is not a new concept. Israels series of conformal array early warning aircraft uses the dual band technology. For example, Sea Eagle warning aircraft actually uses a dual band radar. The fuselage conformal array is L-band, and the nose uses S-band radar. This layout is mainly to meet the balance requirements of omnidirectional detection. Due to the small space of the nose, if the L-band wavelength is longer, then the receiving and transmitting components are less, so the S-band radar with shorter wavelength is used, so as to insert more receiving and transmitting components, improve the power and increase the forward detection distance. Even so, the forward detection distance is still significantly smaller than the conformal array detection distance on both sides.

From this point of view, the benefits of dual band are also obvious. However, only when the dual band is used in the early warning aircraft with the knapsack disk layout, can the omni-directional equalization detection be realized. Therefore, this will further lead to the comprehensive evaluation of antenna layout.

On the basis of the balance beam, the e-737 early warning aircraft added a top hat structure for forward and backward detection, which is located above the balance beam, forming a T-shaped array.

Tangle of antenna layout

When choosing the antenna layout, we should not only consider the available antenna area (usually the larger the area is, the farther the detection distance is), but also consider the detection balance and the aerodynamic impact on the aircraft. The radar layout of the active early warning aircraft can be roughly divided into four types.

The first and earlier form of layout is the knapsack disc. In other words, a mushroom shaped disk is added to the fuselage, which is equipped with radar antenna. This kind of antenna can be a single-sided array, a double-sided array or a three-sided array, while India has introduced a more amazing four-sided array antenna a while ago. The biggest advantage of the knapsack disk is its balanced detection ability, that is to say, there is no dead angle coverage in all directions, and the detection distance in all directions is equal. Another advantage is the ease of use of dual band antennas. For example, a P-band antenna and an S-band antenna are installed in the form of back-to-back respectively, and the combination of machine scanning and scanning can solve the omni-directional detection problem of the two bands. The problem is that the size of antenna is limited.

The second is conformal array. The conformal array places the radar antenna and radome on both sides of the front and rear fuselages, and some of them have a radar antenna at the front and rear of the aircraft. Its main advantage is that it has little adverse effect on the aerodynamic performance of the aircraft, and because it can make full use of the surface space of the fuselage to increase the antenna area, it is convenient to obtain a large detection distance on a small aircraft. On the gulfstream-550 with a maximum take-off weight of 46 tons, the antenna area on both sides of the sea sculpture radar is close to 20 square meters, which is larger than the antenna area of the early warning radar carried on the E-3 with a maximum take-off weight of 150 tons, and the operating distance is equivalent to that, realizing the goal of small platform and long distance. Its disadvantage is that the antenna installed at the head and tail of the aircraft is small, the detection distance is short, and the coverage of radar detection distance in all directions is not balanced. In addition, generally speaking, conformal array is more suitable for airliners with lower monoplane. Because the engine of wing crane will affect its horizon.

Swedish aliyan early warning aircraft with balanced beam antenna

The third is balance beam layout. The antenna is just like the balance beam in gymnastics, which is arranged on the upper part of the fuselage. It can make full use of the length of the head and tail of the aircraft. The length of the array is far larger than the size of the disk, or even larger than the conformal array (the conformal array is located on both sides of the fuselage, sheltered by the engine and wings, so it cannot span the front and rear areas of the fuselage longitudinally). For example, the radome on both sides of the front fuselage of the Boeing 707 conformal array with a maximum takeoff weight of 150 tons has a lateral dimension of no more than 10 meters, while the balance beam used in the saab-2000 in Sweden has a radome length of nearly 12 meters, which is impossible to achieve in any large-scale aircraft using a disk at present. A small platform can be used to achieve a longer antenna and detection distance, but There are 60 degree blind areas before and after the detection. Due to the narrow antenna, the balance beam carried by the current minicomputer does not have the function of precise height measurement. Therefore, the balance beam is largely a synonym for cheap low-end.

On the basis of the balance beam, the e-737 early warning aircraft developed in the United States has expanded its area, increased its radiation power, increased its height measuring ability, and formed a T-shaped array with a top hat structure above the balance beam for forward and backward detection. It can greatly expand the size of the antenna, has a good detection balance, and can also achieve three-dimensional measurement, which should be an important development direction of high-end early warning aircraft. If the dual band arrangement is not considered, it will be an ideal way.

In fact, the answer to this question is not the only one. Each country will develop programs suitable for its own national conditions according to its own needs and technical expertise.

Early warning aircraft also have radar on the belly

(function() {(window. Slotbydup = window. Slotbydup| []). Push ({ID: u5811557, container: ssp_, async: true});}) ()); source of this article: responsibility editor of surging News Network: Yao Wenguang