Chapter 715

Of course, it is still a long way to talk about the C-17 in the early 1990s. In addition, McDonnell Douglas's yc-15 was launched as early as the early 1980s. Therefore, in today's world, the yun-15plus has become the only light combat transport aircraft that has been mass-produced with external blowing flap technology.

In other words, except for a small part of the wing tip, most of the other wing trailing edges can be expanded downward until the engine tail nozzle is completely covered.

So that when people look forward at the tail of the aircraft, they can only see the flaps that protect the engine in front of them, just like the convergent wing feathers of large birds protecting the cubs.

In this way, the airflow generated by the engine's tail nozzle will deflect downward like a deflector under the action of the drooping wing. As for the analysis of the spilled airflow from the middle of the two flaps, there is no waste, because the arc drooping flap just produces a "CONDA effect" on the spilled airflow, which leads the airflow to deflect downward again and continue to generate upward lift.

Combined with the supercritical airfoil which has been studied by Tengfei group for many years, the strong air jet can be transformed into full lift when the yun-15plus engine is started, so as to shorten the takeoff distance and complete the purpose of short takeoff.

When landing, the downed flap can become a good drag reduction mechanism, which can cooperate with the drag reduction plate above the wing, the engine thrust reverser and the landing gear brake system to complete the short landing of yun-15plus.

All in all, a set of blowing flap technology gives yun-15plus unparalleled short takeoff and landing capability.

But with such good technology, why did Antonov of the Soviet Union and Boeing of the United States not use it? Instead, they produced quite different ann-72 and yc-14?

It's not that I don't want to use it, but the technology seems simple and the principle is not difficult, but it's not easy to make it.

First of all, it's really a good idea to use the wake of a jet engine as the lift of an aircraft taking off. But you should know that the temperature of the wake emitted by a jet engine is not low. Ordinary aluminum alloy materials can't withstand such high temperature burning at all, and they will have to be rejected by the engine in three or two times.

Only high temperature resistant titanium alloy can be competent, 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 tiny connecting rods and other precision parts. If all titanium alloys are used, the cost will soar.

In contrast, an-72 and yc-14 with shoulder mounted engines only need to cover the burned part of the wing with a small part of titanium alloy skin near the tail nozzle of the engine. The cost is lower than that of similar aircraft with blowing flap.

Secondly, in terms of control, the flap is generally divided into two layers, each of which is a movable part. There is a problem, that is, how to integrate such important and complex wing moving parts into the whole aircraft operating system.

No matter it's mechanical, hydraulic or fly by wire control, it's not a job that can drive aviation engineers crazy. After all, the influence of the moving parts of the wing on aircraft control is not very big. If one can't do it well, it may be fatal.

In contrast, the shoulder mounted an-72 and yc-14 have no worries in this respect. Apart from the weird shape and the influence of air resistance, the wing is not very complicated. It can be built according to the mature aircraft operating system, or at most slightly adjusted according to the aerodynamic factors.

The last and most important thing is the production. The an-72 and yc-14 aircraft seem strange. In fact, the production process is not more complicated than the traditional transport aircraft, just because the engine position is different.

The aircraft with blowing flap is not the same. It's the same when you look at the wing in static display. The two wings are pressed on the fuselage, but actually there are extremely cutting-edge aerodynamics technologies in it.

In order to realize these technologies and meet the design requirements, the requirements for processing and production are almost as high as changing state. Not to mention the processing of other supercritical wings, few countries in the world can do it, because the radian, curvature and final molding can't be described in words.

After all these things are listed, the pragmatism of the Soviet Union will not be so complicated. The essence of bear is simple and direct, so there is an-72.

Boeing in the United States has technology, but what capitalists pay attention to is cost saving. The flap is too expensive. Even if it costs so much money, no one will buy it. So we have yc-14.

McDonnell Douglas is the head iron's hard resistance. As a result, the cost is still high. When bidding for the C-130 follow-up model, the unit price makes the U.S. Air Force full of tears Forget it, the C-130 is still very good. It will take another 30 or 40 years to make a change, so we cut down McDonnell's yc-15.

Although McDonnell Douglas used the later C-17 to prove that the flap was the mainstream and the king, McDonnell Douglas had been swallowed by Boeing at that time, and the C-17 also became the number one of Boeing from McDonnell Douglas.

Can the small Tengfei group afford the technology that even the aviation giants like the Soviet Union and the United States can't afford?Naturally, the answer is yes. Otherwise, Zhuang Jianye would be so busy with money.

As for why, it's very simple. The US and Soviet aviation giants launched short takeoff and landing transport planes in the 1960s and 1970s. At that time, composite materials had not yet come out of the laboratory, and the smelting cost of titanium alloy was frightening. Even the drawings had to be drawn by hand, and the popularity of high-precision CNC machine tools was not high, which led to the use of blow flap Don't be too high.

But when Tengfei group made up its mind to make yun-15plus, it was in the late 1980s. At this time, aviation technology, especially aviation material technology, had a qualitative leap, and aviation processing technology also had a rapid progress.

It can not only realize the production of the flap, but also reduce the cost greatly.

Of course, this is not important. The most important thing is that Tengfei group has accumulated a certain degree in materials, aviation design, aerodynamic layout, production and processing over the years. It can fully control the design, processing and manufacturing of this kind of complex airfoil with blowing flap.

Let's take supercritical wing as an example. As early as the mid-1980s, Tengfei airport cooperated with the military to develop a super critical wing uav-8plus for high altitude weather detection.

After that, a lot of experiments and researches have been done in this area. When it comes to the development and production of yun-15plus, Tengfei group already has rich experience in this area, so it is 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 matrix composites, T700 or T800 carbon fiber composites, and even M-series carbon fiber materials which are under development and can resist higher temperature and offset greater tensile force and are higher than T-series indexes.

With the modern processing equipment such as CNC shot peening machine, CNC high pressure water cutting machine, CNC laser welding equipment, laser additive, flexible fixture, automatic riveting, and the cost advantage of Tengfei group itself, is it difficult to produce a cost-effective short takeoff and landing tactical transport plane?