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Chapter 715 Is it difficult?

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    Of course, it is still far away to talk about C-17 now that we have just entered the 1990s. In addition, McDonnell Douglas's YC-15 has been discontinued as early as the early 1980s. Therefore, in today's world, Y-15plus has become the only  A mass-produced light tactical transport aircraft using external blown wing flap technology.

    Its biggest feature is that the blown wing flap accounts for 75% of the entire wing trailing edge. In other words, except for a small area at the wing tip, most of the other wing trailing edges can unfold downward until  Completely cover the engine tail nozzle.

    So much so that when people look forward from the tail of the aircraft, they will only see the large-angle deflection and drooping flaps that protect the front engine, just like a large bird converging its wing feathers to protect its young.

    In this way, the airflow generated by the engine tail nozzle will be deflected downward by the drooping wing like a deflector. As for the analysis of the overflowing airflow from the middle of the two flaps, there is no waste, because the arc is drooping.  The flaps just produce a "Coanda effect" on the spilled airflow, which guides the airflow to deflect downward again and continue to generate upward lift.

    Coupled with the supercritical airfoil that Ascendas Group has been researching for many years, it is possible to convert the powerful airflow ejected into full lift when the Y-15plus engine is started, thereby shortening the take-off distance and completing the purpose of short-distance take-off.

    When landing, the blown wing flaps that are lowered can become a great drag reduction mechanism, cooperating with the drag reduction plate above the wing, the engine's thrust reverser and the landing gear braking system to complete the short-distance flight of the Y-15plus.  landing.

    In short, a set of blown wing flap technology gives the Y-15plus unparalleled short take-off and landing capabilities.

    But with such good technology, why didn¡¯t Antonov of the Soviet Union and Boeing of the United States use it, but instead came up with the rather alternative An-72 and YC-14?

    It¡¯s not that I don¡¯t want to use it, but this technology seems simple and the principle is not difficult, but it is not easy to create it.

    First of all, it is a good idea to use the wake of the jet engine as the lift for the aircraft to take off. However, you must know that the temperature of the wake ejected by the jet engine is not low. Ordinary aluminum alloy materials simply cannot withstand such high temperature burning. Three  Two hits and the engine will spray it and it will be scrapped.

    Only high-temperature-resistant titanium alloys can do the job, but the problem is that the flap area, which occupies more than half of the trailing edge of the wing, is so large, and there are so many small connecting rods and other precision parts. If all titanium alloys are used, the cost will definitely be higher.  Soaring up.

    In contrast, the An-72 and YC-14, which use shoulder-mounted engine layouts, only need to use a small part of the titanium alloy skin to wrap the area burned by the wing near the engine tail nozzle, and the cost is relatively low.  Similar aircraft using blown wing flaps are more than one level lower.

    Secondly, in terms of control, the blown wing flap is generally divided into two layers, each layer is a movable movable part. This brings up a problem, that is, how to integrate such an important and complex wing movable part.  into the entire aircraft operating system.

    Whether it is mechanical hydraulic or fly-by-wire control, it is not a job that can drive aviation engineers crazy. After all, the moving parts of the wing have a great impact on the control of the aircraft. If it is not done correctly, it may be fatal.

    In contrast, the An-72 and YC-14 with shoulder-mounted layouts do not have this concern. Except for the weird shape and the impact on air resistance, the wings are not very complicated and can be operated according to mature aircraft.  The system can be built as is, with at most some minor adjustments based on aerodynamic factors.

    The last and most critical thing is production and manufacturing. Aircraft like the An-72 and YC-14 may seem strange, but in fact the production and manufacturing process is no more complicated than traditional transport aircraft, except that the position of the engine is different.

    Aircraft that can use blown wing flaps are different. When it is displayed in a static display, the wings look just like that, just two wings pressed against the fuselage, but in fact they contain extremely cutting-edge aerodynamic technology.

    If you want to realize these technologies and meet the design requirements, the requirements for processing and production must be extremely high. Not to mention the processing of other supercritical wings, few countries in the world can do it.  Come out, because the arc, curvature and final shape cannot be described in words.

    With everything listed in this way, the pragmatic Soviet Union will naturally not make it so complicated. The essence of the bear is simple and direct, so the An-72 was born.

    Boeing in the United States does have technology, but what capitalists pay attention to is cost-saving. Blowing air wing flaps is too expensive, and no one will buy it even if it is so expensive, so the yc-14 was born.

    McDonnell Douglas resisted fiercely, but the result was that the cost remained high. When bidding for the follow-up model of the C-130, the unit price made the wealthy U.S. Air Force burst into tears. In the end, after thinking about it, it was better to forget it. The C-130 is pretty good.  , if I change it, it can still be used for another thirty or forty years, so I put McDonnell Douglas's yc.?15 was cut off.

    Although McDonnell Douglas used the later C-17 to prove that blown wing flaps were the mainstream and the kingly way, by that time McDonnell Douglas had been swallowed up by Boeing, and the C-17 had also gone from McDonnell Douglas's Oiran to Boeing's number one.

    ???? Can the small Ascendas Group afford technology that even aviation giants like the Soviet Union and the United States cannot afford?

    The answer is of course yes, otherwise Zhuang Jianye would have had a headache to do such a money-burning thing.

    As for why, it¡¯s very simple. The aviation giants of the United States and the Soviet Union were rushing to develop short take-off and landing transport aircraft in the 1960s and 1970s. At that time, composite materials had not yet come out of the laboratory. The cost of smelting titanium alloys was terrifyingly expensive. Even the drawings  It had to be drawn stroke by stroke manually, and the popularity of high-precision CNC machine tools was not high. This resulted in the cost of using blown wing flaps at that time being really not too high.

    It was the late 1980s when Ke Tengfei Group made up its mind to develop the 15plus. At this time, aviation technology, especially aviation material technology, had made a qualitative leap, and aviation processing technology had also made rapid progress.

    Not only can the production and manufacturing of blown wing flaps be realized, but the cost is also greatly reduced.

    Of course, this is not important. The most important thing is that Ascendas Group¡¯s accumulation in materials, aviation design, aerodynamic layout, production and processing over the years has reached a certain level, and it can fully control this complex airfoil with blown flaps.  design, processing and manufacturing.

    If nothing else, let¡¯s take the supercritical wing as an example. As early as the mid-1980s, Tseng Airport cooperated with the military to develop a supercritical wing undetected-8plus high-altitude weather detection drone.  .

    After that, a lot of experiments and research were done in this area. When it came time to develop and produce Yun-15plus, Ascendas Group already had rich experience in this area, so it was not a problem at all.

    As for high-temperature resistant lightweight materials, Tengfei Group has more choices, such as aramid fiber honeycomb structure combined with titanium alloy; carbon fiber reinforced titanium-based composite materials; t700 or t800 carbon fiber composite materials; and even in-process  The developed m-series carbon fiber material can withstand higher temperatures, offset greater tensile forces, and has higher indicators than the t-series.

    With the help of modern processing equipment such as CNC shot peening machines, CNC high-pressure water cutting machines, CNC laser welding equipment, laser additives, flexible fixtures, automated riveting, and the cost advantages of Tengfei Group, we can produce a cost-effective short-distance starting machine.  Is it difficult to land a tactical transport aircraft?

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