Why is the Su -27 engine so far away?

The design of Su -27 is not a "trade-off", but a standard plagiarism. It is a tragic case of stealing the original F- 15 development (F-X plan) from the United States and adding some technologies owned by the Soviet Union.

Lengthy warnings, because the events are interrelated, must be written very long to be easy to understand.

Let's start with the story background. Because the Soviet Union, like the United States, entered a dead end of high-altitude and high-speed missile vehicles in the development of the third generation aircraft, the United States suppressed 30 tons of air-to-air bomber F-11,while the Soviet Union suppressed 2.2G manned rocket MIG -25, which was more and more inclined to the direction that it could not fight air combat. But the United States produced a legendary eyesore, which was the later fighter plane. He formulated the performance parameters of the fighter plane by pure mathematical method, and formed the theory of energy maneuver. From this, he found that the factors that affect the performance of fighters are nothing more than the ratio of lift, resistance and weight. By substituting lift-drag ratio, lift coefficient and residual power into the past fuselage design, he found that the existing idea was completely wrong. Therefore, the development direction of American fighters turned 180 degrees, and a generation of famous aircraft F-6550 was introduced.

On the other hand, the Soviet Union, because it is different from the United States where chickens fly and dogs jump everywhere, and because the Air Force is extremely lacking in actual combat experience, it is extremely biased towards applied disciplines and ignores theoretical disciplines. In the case that the third-generation aircraft has shown serious technological backwardness, it still continues to take the high-altitude and high-speed route. So unlike the United States, the next-generation fighter launched by the Soviet Union is a more extreme interceptor than the MIG -25.

By 1970, the Soviet MIG -25 was in service, confident that it could completely explode the high-altitude advantage of the United States. The new interceptor jointly developed by the Central Institute of Fluid Mechanics, Su Huoyi and mikoyan has also completed the initial research, that is, the drawing design, and moved to the trial production stage.

However, only two years later, the U.S. F- 15 made its first flight, and a small amount of information obtained by the Soviet Union through the intelligence department showed that F- 15 not only had high altitude and high speed, but also had amazing maneuverability. Now we know that the actual flight performance of F- 15 is far more amazing than that of the Soviet Union.

The relevant departments of the Soviet Union were as anxious as ants on hot bricks. Because the whole country of the Soviet Union didn't know the theory of energy maneuver, and didn't carry out relevant research, it didn't know what high maneuver was numerically (although MIG -2 1 mistakenly conformed to the correct design of high maneuver), and there was no theoretical basis and pre-research to improve the lift-drag ratio. If you start research and development from scratch, the time period will still be ignored, and even the probability of success is almost zero.

Therefore, the Soviet Union completely abandoned all the research results since the third generation of aircraft and decided to completely copy F- 15 through the intelligence system in a short time. However, American imperialists are not vegetarian. All the top secret design data of F- 15 were completely confidential, and it was not made public until 1992 after the disintegration of the Soviet Union. The Soviet Union only obtained several drawings of the elimination scheme through spy network, but during the research and development of F- 15, the United States put a lot of smoke bombs in finance and logistics, ostensibly F- 15. But in fact, the bidding schemes of American manufacturers are all fake. The real F- 15 is completely designed by NASA and has nothing to do with the bidding company. It also caused the Soviet Union to go to the wrong door when searching for information. The final result was that although Su -27 was chasing the shadow of F- 15, except for the result of F- 15, the detailed design was very similar to that of other US military aircraft.

In the process of imitation, the Soviet Union also fell into the pit where copying homework was difficult (besides, at least half of this homework was hand-painted). Due to the extension of Soviet electronic technology, all the equipment, including the radar expected to be deployed, is too large, resulting in the overall size of the aircraft (a lot), so the nose length+side strip takes up space, exceeding the upper limit of 2 meters, and the decompression area behind the shock wave will cover the intake area at high speed. All the fitted inlets originally designed by F-X will cause serious engine intake and flameout problems at supersonic speed (you can refer to the design of large interceptors in the early United States, and the inlet is very forward because of this problem). When imitating the inlet part of Grumman's original gearbox (later F- 14), it was forced to design it far away from the fuselage and change it into a double vertical tail (interestingly, Grumman thinks that the overall lift efficiency of F- 14 is much higher than that of Su -27, which saves some performance). The vertical tail adopts the classic MIG tail, and the horizontal tail remains unchanged. The problem of excessive rolling inertia caused by this layout also makes Su -27 one of the third-generation machines with the worst rolling speed. The air inlet is a classic Northrop sloping plate, and the side strip was reserved in the later design of F- 16. Other parts of the design are still the same as those of North American companies. After many twists and turns, the prototype T- 10- 1 was finally made. Results In the experiment, it was found that the original curved wing is actually a very complicated new thing, which involves the design of variable camber, angle and thickness that the Soviet Union has not tried, and needs a lot of basic research. The performance of the Soviet Union's current horizontal design is very poor, so the wing has to be changed to the tail of a new generation of interceptor that has been eliminated. However, because the volume has been enlarged to an unacceptable level, even at the expense of huge rolling inertia, the defect of poor air intake has always existed on the Su -27. This series of defects has caused the current Su -35 to fail to meet the performance index when the Su -27 was established.

In addition, Su -27 has an oversize strake, which leads to the nonlinear transformation of lift center in flight. However, Su -27 itself is not an aircraft with CCV follow-up layout. It has a static design (originally planned), but in a certain flight state, it will suddenly become a static state, leading to stall spin or the so-called cobra that passes through the spin after the angle of attack increases uncontrollably. Therefore, it is necessary to lock the number of rods in the flight control assistance (yes, among all Su-27s in Russia at present, only the air show advertising machine belonging to Sukhoi Company can pull the cobra, and other fuselage is strictly avoided by the flight control, which leads to the wonderful phenomenon that the Su-27s cannot effectively maneuver in these envelopes that should have reached the maximum turning rate.

As for the legendary "podded engine layout designed by Central lifting body", it is a completely far-fetched rumor, not to mention that the entire F-X plan is lifting body layout, and the Soviet Union has no idea why the F-X should adopt these designs. It can only infer its own design ideas through imitation test, and naturally it can only know the function of a single design, and can't imagine the guiding ideology behind it. So the whole Su -27 is a mosaic monster. There is almost no matching between the parts (for example, the small side strip has little effect on the airfoil of Su -27 except for increasing the resistance, on the contrary, the central part that needs to make up the vortex can't eat any compensation, and the fuselage stalls after a high angle of attack, which will lead to a series of problems). Moreover, the Soviet Union knew that the distance between engine compartments was too far, and the distance between T- 10- 1 was as close as possible. However, because the performance requirements of N- 1 radar were improved in the process of design and manufacture, and its volume was larger than expected, the subsequent nose was continuously enlarged, even blocking the pilot's field of vision, so it had to be changed to a drooping design, which blocked the inlet again, causing the inlet to move further outward and backward, and also affecting the total pressure recovery coefficient of the inlet itself. These changes show that the Soviet Union did not have a clear design direction when designing the Su -27. It is simply imitating the speculative performance index of F- 15. Sadly, the Soviet Union did not simulate the overall lifting body of F- 199 1 until two months before the disintegration, resulting in the lift index of Su -27 being only 60% of that of F- 15, and its weight exceeding.