Nanchang Q-6 [first instance] - Design
The Q-6 was a variable-geometry wing aircraft, based on the MiG-23 design, though with a different air intakes and cockpit. It copied most of the MiG-23 aft structure, but substituted a ventral air intake in the fuselage under the the cockpit. The Q-6 planned to use the 122.4 kN thrust WS-6 engine. The aircraft weighed 14,500 kilograms, with a maximum load of 4500 kilograms bombs. A combat radius of 900 km was expected, with a flight performance in excess of that of the MiG-23.
The original design was based on the MiG-23BN, but the PLA Air Force and Navy needed a radar, which was not provided for in the pure attack version. And then decided to create a project based on the MiG-23MS. It was decided to use the F-111 aircraft avionics (there possibly is a question of technological espionage) suited to the Q-6. The radar was to be similar to the American AN/APQ-110 system used on the F-111 and giving the aircraft a terrain following ability. But this resulted in a long-term development. The original size of the aircraft were to be similar to MiG-23MS, but the Chinese electronics industry of that time could not reduce the size of the equipment and the aircraft's fuselage was sized close to Su-24.
Compared with the Q-5, the Q-6 was to have improved avionics system, and it was intended to use the certain components within the equipment MiG-23BN as a reference. The Q-6 was to use an avionics systems that included laser target indicators, tail warning radar, radio altimeter and radio gyro plate, but also intended to introduce a terrain contour matching and tracking system and modern flat-panel displays. However, most of the avionics system from the Soviet Union compared with Western avionics system was clumsy and old. China's aviation industry started to pay attention telex control system and spend a lot of time to learn foreign technology, as well as editing software. The final Q-6 design used a highly automated telex control system. The JH-7 also used a telex control system, which meant that it was China's most advanced fighter before the introduction of the Su-27 to the Chinese Air Force.
The variable swept wing configuration of the cantilever upper single-wing structure had small resistance and good stability and is suitable for aircraft. High-speed penetration and an ideal launch platform for ground attack weapons. Although from the end of the 1960s, China has begun research on variable swept-wing technology and obtained direct learning opportunities from the F-111 and MiG23, but before the development of the Q-6 China's variable swept wing technology has not yet reached the level of practical installation.
In order to overcome this obstacle in 1980, under the auspices of Lu Xiaopeng, China carried out a large-scale ministerial research project--the pre-research task of the variable swept-wing technology. After more than eight years of hard work, this research topic has made a major breakthrough in design technology. This achievement successfully solved the aerodynamic layout of the variable swept-wing technology (rotary shaft position, airfoil, dynamic response, etc.), wing structure optimization (spinning on the street, three-dimensional stress calculation, multi-constraint optimization technology, etc.), drive mechanism and a series of problems in the aircraft control system laid the foundation for the development of the Q-6 and filled the domestic gap.
A common disadvantage of aircraft employing variable swept wing technology is poor maneuverability. Because the Air Force proposed a new type of aircraft to have a certain air combat capability, the aircraft was replaced with a belly air intake to accommodate the problem of air intake when the aircraft was flying at a large elevation angle.
From the appearance point of view, the Q-6 seemed to be a "hybrid" combined with the characteristics of the F-16 and MiG-23. Its main wing with a single-wing rear wing layout, as well as a vertical tail and a flat tail similar to the MiG-23, the intake method uses a belly-like intake similar to the F-16. In terms of specific performance indicators, the aircraft had a maximum weapon load of 4,500 kg and a combat radius of 900 km. In addition to its powerful ground attack capability, its air combat performance is superior to that of the MiG-23.
The development of the Q-6 fully reflected the desire of the Chinese aviation industry to catch up with the world's advanced level - in addition to the variable swept wing technology, another new one that emerged after the 1980s. Technology of the the electromechanical transmission control system was also the target of researchers in China's aviation industry. Chinese researchers first launched an impact on the analog three-degree fly-by-wire control system. Based on the relevant technologies obtained from abroad, Chinese researchers use the method of reverse compilation , and with the amazing perseverance, interpret the design language of foreign technology, and based on this, develop the first generation of China's warfare Transmission control system.
The first set of aircraft simulation telex control system designed in China had the characteristics of good reliability and high automation level. The fly-by-wire system was mainly composed of a signal conversion device, a flight control computer, a cable, and an action device. This kind of control system can convert the pilot's control signal into an electrical signal through the converter, and then directly transmit it to the autonomous steering gear through the cable. The system had the advantages of simple structure, small size, light weight, easy installation, improved aircraft handling quality, improved reliability of the control system and reduced workload of the pilot.
The engine is the heart of all aircraft, and whether the engine is selected properly or not directly determines the success or failure of the aircraft development plan. The Q-6 chose China's first practical and practical large thrust turbofan engine - turbofan 6 (WS-6). The engine was developed in 1964. After 17 years of hard work, it reached a practical level in 1981. The maximum military thrust of the aircraft is 71 kN, the maximum afterburning thrust is 122 kN, and the thrust-to-weight ratio is 5.93. In order to meet the needs of the third generation J-13 fighter developed at that time in China, in 1983 China developed the WS-6G engine. The afterburning thrust reached 138 kN and the thrust-to-weight ratio reached 7. These indicators and the US and Russian Air Force's current main engines F100 (for F-15) and AF-31 (for Su-27 series fighters) basically reached the same level.
As a multi-role fighter with both ground attack and air combat capability, the Q-6 had a revolutionary advancement in its avionics than its predecessors. The Q-6 airborne electronic equipment was basically selected from China's imitation and improved related equipment from the MiG-23BN, including: improved radar from the "high-altitude skylark", with a variety of ground attack modes , Laser range finder , sight-type 6 sights, radar warning systems and communication stations, radio altimeters, radio compasses, close-range navigation and landing systems.
Among them, the new radar and advanced sights with the function of the ground enable the Q-6 to fully exert its powerful firepower against the ground. The simulation results show that after the fire control system is equipped, the effective hit accuracy of the Q-6 launch air-to-ground rocket is three times higher than that of the Q-one, and the new air-to-ground missile can be guided to achieve the target's precision strike outside the target.
However, the system, like other Soviet electronic devices that were copied, mostly used tubes and transistor hybrid components, resulting in a large size and weight of the device, which is lagging behind Western products in the same period. However, if the installation is successful, the expected goals of the functional design can be achieved. In the design process, Chinese researchers have exercised the comprehensive capabilities of the system by copying and improving Soviet-made avionics equipment.
In general, the technical level of the Q-6 surpassed the international second-generation jet fighters such as the MiG-21, MiG-23, F-4, etc., but there was still a certain gap compared with the F-15 and other three-generation fighters. Positioning the Q-6 as a second-generation jet fighter-bomber with some 3rd-generation fighter features is more appropriate.
In China, a common problem that troubled a number of other projects was the power plant, indeed one of the biggest problems facing many combat aircraft programs. In 1981, it became clear that the WS-6 engine, with a thrust of 71 kN (122 kN with Afterburner) would be insufficient. After further improvement, the WS6 engine, after the completion of the WS6G in 1983, was rated at 138.2 kN thrust. This engine, with the J-9 and J-13, experienced several delays due to technical problems. It was finally decided to adopt the MiG-23's R-29-300 engine, developed through reverse engineering by 410 Plant, named the WP15. This was a double rotor turbojet engine, with a maximum afterburning thrust of 125.2 kN, and 85.1 kN maximum thrust without afterburner. However, WP-15 ultimately did not equip any of the Chinese air force planes.
In addition to the power plant, the biggest obstacle the Q-6 had to overcome was the reverse development of variable-geometry wing structure. In the 1960s and 1970s, the variable-geometry wing was widely favored by military aviation around the world, with several having variable-geometry wing aircraft in service. China had noticed this trend and began its own research, and actively carried out variable-geometry wing development work. The Q-6 was developed early, some people advocated that China should build its next generation of strike Fighter along the lines of the F-111 or MiG-23. China had at least four conceptual proposals for the use of variable-geometry wing, including the Shenyang Aircraft Company's J-10 heavy fighters (unrelated to the current J-10), the Q-6, similar to the F-111 / SU-24 attack aircraft.
During its development the Nanchang design team of the Q-6 encountered insurmountable problems with its variable-geometry (VG) wing mechanism. For the Chinese engineers it was impossible to "copy" the original Soviet design. Chinese industry struggled with the requirement, but the weight and dimensions were 12% larger and heavier than the MiG-23 system, thereby reducing payload capacity of fuel tanks and combat radius of the machine.
During the development of the Q- 6, the various sub-equipments equipped with the MiG-23 fighters were copied, including the radar warning system, the high-altitude new radar, the close-range navigation system, the sights, the laser range finder, etc., The new airborne radar with attack capability made the Q-6 have a greater ground attack capability. But the subsystems and sub-equipment did not represent the international leading level at the time. The main reason was that the Soviet Union was not too advanced in its own technology. Therefore, even if the imitation of the MiG-23 equipment was completely used, it was still behind the same period. Western products.
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