J-11D Flanker-L
The purpose of the J-11D project was to replace the existing J-11B flat slot antenna radar with AESA active phased array radar, and to improve the structural strength of the aircraft, reduce weight to improve flight performance. Because of some unsolvable problems encountered in the project, the Su-35SK was purchased as a reference.
With the same aerodynamic shape, only through the redesign of the structure and the use of new materials, the center of gravity is moved back by nearly 2 meters. As a result, the static stability of the Su-35S is -15%, and that of the Su-27S is -5 %, coupled with technologies such as vector nozzles and 117S engines, the flight performance of the Su-35S has been directly improved by a step compared to the Su-27S. It is not difficult to understand why the Chinese Air Force bought the Su-35S and used it so comfortably to fly with the J-20 to the South China Sea and even filmed a program to put it on TV. It is no exaggeration to say that if the performance indicators of the J-11D are similar to those of the Su-35S, then the cost of changing from the J-11B to the J-11D will be very high, because the difference is too great.
Although the shape is the same, the internal structure has been reborn. Some structural defects of the airframe have been optimized and adjusted, the flight performance has been improved in all directions, and the maneuvering performance has been greatly enhanced. The fourth-generation aircraft stealth technology is used for partial stealth processing of the body, and the flight control system also uses a large number of fourth-generation aircraft technology, which is very different from the old model.
The upgraded D variant of China’s J-11 fighter jet, a copy of the Russian Sukhoi Su-27, made its maiden flight 29 April 2015. The jet reportedly had new radar and an air refueling system. The J-11D model incorporates technologies developed for the J-16 fighter jet. It was reported to have better active phased array radar, use more composite materials in its wings and tail, and be capable of firing more advanced air-to-air missiles like PL-10 and PL-15. Photos of the J-11D prototype tested at a Shenyang Aircraft Corporation airfield also showed an in-flight refueling probe installed on the port side similar to the arrangement used on J-15.
The J-11B is actually the domestically produced Su-27SK (T-10S), while the J-11D refers to the Su-30MKK, which uses a large number of Su-35 (T-10M) components. The main difference between the two is that the T-10M adds a heavy-duty pylon with a load of about 2000 kg at the root of the wing, thereby strengthening the wing and fuselage, so that the heavy-duty weapon pylon of the T-10M reaches 8 However, there are only 6 T-10S. Because the Su-27 adopts the layout of the belly air intake, the mounting space is limited. The fuselage pylon is limited to mount large air-to-ground weapons, and the wings increase these two Heavy-duty weapon racks are precious.
The jet reportedly has new radar and an air refueling system. The J-11D model, which was tested in the air for the first time, incorporates technologies developed for the J-16 fighter jet. It is reported to have better active phased array radar, use more composite materials in its wings and tail, and be capable of firing more advanced air-to-air missiles like PL-10 and PL-12 (SD-10).
The J-11D is called the "Chinese version of the Su-35". In fact, it is China's way of trying to fundamentally improve the performance of the Su-27 heavy fighter family that has nothing to do with the Su-35. The J-11D has different airborne electronic equipment, and the fuselage design and pneumatic aspects of the two are also very different.
Despite impressive technical characteristics and capabilities, the Chinese J-11D jet is not a true analog of the super-maneuverable Russian Su-35 multirole fighter. It is a separate and independent attempt to radically increase capabilities of heavy fighters belonging to the Su-27 series. The radio electronic equipment installed aboard the J-11D differs from that of the Su-35, and the two aircraft also differ from one another in terms of frame construction and aerodynamics.
The first J-20s were apparently being delivered to PLA training units in 2017, but it’s hard to predict when these aircraft will be ready for combat deployment. And, due to their rather high cost, China will have to produce these warplanes alongside the less sophisticated fourth-generation fighters. This, in turn, means that upgrading and improving the J-11 series aircraft will continue to be very important for China. This is why Beijing is so keen to study the Su-35 design and, possibly, to continue purchasing Russian engines.
China signed a contract to purchase a shipment of D-30KP2 engines for Y-20 transport aircraft, along with a contract for new AL-31F engines for Chinese fighter jets; each contract is worth $658 million. It is unclear exactly which type of fighters they want to outfit with these engines: it could be both J-20 and J-16 aircraft. In any case, while China’s industrial sector has made considerable strides in providing an adequate supply of engines to the nation’s air forces, Beijing is still far from being completely self-sufficient in that area, especially when it comes to the new types of aircraft.
In late 2020 a photo on the Internet attracted the attention of many people, because the fighter in the picture is suspected to be the rumored J-11D, which is the latest model in the J-11 series of fighters. In fact, as early as a few years eargo, the rumors about the J-11D on the Internet were widely known, but with the mass equipment of new fighters such as the J-20 and the J-16, the popularity of the J-11D gradually decreased.
The latest improved model of the J-11, the J-11D, may have air combat capabilities. It is on a par with the J-16, but the multi-purpose capability of the J-16 is undoubtedly more attractive to the Air Force, which is transforming into both offense and defense. However, the failure of the J-11D does not mean that the J-11 series has taken a back seat. The J-11 has produced hundreds of aircraft, and this number alone can form a clear quantitative advantage over the fourth-generation aircraft of any surrounding party.
Perhaps from the beginning, the J-11D was not ready to be installed in batches, but to verify whether some fifth-generation aircraft technologies could be applied to the fourth-generation aircraft. On the aircraft platform, in order to prepare for the future J-11A/B upgrade. For those who fully understand this platform, the capital and time costs required to upgrade the J-11 fleet are significantly lower than the new production of medium-sized fourth-generation and a half fighters such as the J-10C. the J-11B can apply some of the technologies of the J-11D, but it is too difficult to completely change the J-11B to the level of the J-11D.
The J-11B's radar is relatively backward, it is a 1474 radar, which is a traditional PD radar, while the J-11D is an active phased array radar. If the J-11B is replaced with a radar, its detection and search distance and accuracy are expected to be close. J-11D, but the gap in other photoelectric sights cannot be made up.
The J-11B uses the Taihang WS10A engine, and the J-11D uses the Taihang WS10B engine. One thrust is 13.2 tons, and the other is 14 tons. The difference between the two thrusts is large, and the proportion of composite materials used in the body is also different, so the J-11B uses a Taihang WS10B engine. Even if the engine is replaced, the J-11B needs to be re-tested to re-determine the flight envelope after the replacement, including the maximum speed, ceiling, turning angle, rate of climb and other performances that need to be re-tested, which consumes time and energy.
The most difficult part is the replacement part of the flight control. The flight control of the J-11B is not as advanced as the J-11D. The J-11D is a multi-axis four-degree telex flight control system, while the J-11B is still mechanically controlled in some places. Residual, such a comparison is too obvious. Although the replacement of the flight controller can improve the sensitivity of the aircraft and enhance the response ability and agility of the aircraft, replacing the flight controller is equivalent to rewriting the operating procedures of an aircraft. The scale of such an update is already too large.
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