Chapter 380 High Angle of Attack and High Maneuverability (HARV) Technology Verification

In addition to the changes in the shape of the outer edges of the wings and vertical fins that were seen in Ding Gaoheng's office, as well as a set of extra fuel tanks on the back of the aircraft, the design plan before Chang Haonan also modified the shape of the wing strips. , extending directly from the root of the wing's leading edge to the side of the canopy.

Because the length is too exaggerated, it may even cause the pilot's crotch to get stuck when getting on and off the plane. Therefore, in your plan, a small folding boarding ladder is inserted under the side strips...

"It's quite thoughtful..."

It doesn't really matter if you have your own boarding ladder for land-based aircraft, but if you want to board a ship in the future, it is still necessary.

After all, the land on the aircraft carrier deck is precious and the number of ground crews is limited. It would be the same if there were fewer bits and pieces around the aircraft.

Of course, Chinese aircraft designers in 1997 would definitely not design according to the standards of carrier-based aircraft. This was probably just to make use of the ineffective space under the side wings.

Chang Haonan didn't even need to do the calculations to know that this kind of improvement must be specifically to enhance the aircraft's maneuverability within a specific angle of attack range.

After such modifications, the entire aircraft looked a bit like an F18 with a single vertical tail and a single engine.

"After returning from Chengdu last time, we followed your ideas and made a complete overhaul of the JJ-7. At present, the aerodynamic design of the first version has been basically completed."

Seeing that Chang Haonan had opened the project file, Sun Huizhong quickly came to the side and took out a stack of photos from his pocket while introducing the results of his recent work:

“One of the current problems is that I really don’t know how to design the DSI air inlet, so I first used an ordinary D-shaped baffle air inlet instead. The other is that there is no way to do structural calculations due to conditional factors, so For the time being, I just made a wooden model and filled in the internal equipment to have a look."

Chang Haonan took the photo and looked at it briefly.

It's really a bit fresh.

In his last life, when he entered the aviation industry and finally came into contact with aircraft design after many hardships, even the Beijing Olympics was about to start, so naturally he had never been exposed to this traditional craft.

"I'm not telling you, Mr. Sun, your model is quite good. It feels like it could be used as a handicraft."

"Sigh... I'm ashamed to say that in recent years, our best business in Guizhou Airlines has been wooden furniture, which has even been exported to several Middle Eastern countries."

When it comes to this matter, Sun Huizhong, as an aircraft designer, always feels a little embarrassed——

The aircraft manufacturing company has not even exported aircraft, but it exports furniture.

But this is nothing to Chang Haonan, who came back from more than 20 years later.

As for side jobs, of course you can do some if you have the conditions.

Chang Haonan did not dwell on the internal structure for too long.

As far as a simple light trainer aircraft is concerned, it does not require particularly exaggerated structural strength. The focus of optimization is to reduce weight as much as possible. It can be left to Guizhou Airlines for practice.

"I see that you have made some changes in the design of the side wing. Is it to improve the linearity of the lift curve at small and medium angles of attack?"

Hearing this question, Lin Tongxin, who had been staying behind Sun Huizhong just now, his eyes lit up:

"Director Chang, you...see it?"

In fact, in terms of age, Lin Tongxin, who graduated with a Ph.D., is several years older than Chang Haonan, but after this period of experience, the latter can no longer see many traces of being an undergraduate graduate in his early twenties. In addition, If you don't know the position between his eyes, most people would think that although he looks young, he must be in his late thirties.

"This design was proposed by Xiaolin after he joined the company. After modifying it, we did some simple calculations ourselves and found that it is indeed good for improving maneuverability."

Sun Huizhong explained next to him.

"Of course, small-sized slat wings, or structures similar to slat wings, are the main reason why the slope of the lift curve of the aircraft decreases at small and medium angles of attack. For early mechanical or analog fly-by-wire flight controls, this strong and inexhaustible The non-linearity of the rules is very difficult to control.”

Chang Haonan put the photo aside, picked up the mouse again, and enlarged the upper part of the screen:

"Both the early designs of the Su-27 and F15 suffered in this regard, and I think you should have found some inspiration from the F18."

"You... got it all right."

Lin Tongxin became excited instantly:

"This is the conclusion that my supervisor told us when I was working on a project for my master's degree. I didn't pay much attention to it at the time, but I encountered a similar situation as soon as I joined the job this year..."

The other party's reaction made Chang Haonan couldn't help but smile. He recalled that when he had just graduated and entered the aviation industry in his previous life, he seemed to be in a similar state to him...

Then I was quickly taught a lesson by reality.

There is still some difference between actual work and what you learn in school.

In fact, many early third-generation aircraft with slatted wing designs face the problem just mentioned, that is, the aircraft can maintain a certain degree of maneuverability at large angles of attack, but is prone to losing control at medium angles of attack.

That is to say, the torque characteristics are very poor.

Many seemingly strange designs were born to solve this problem.

It’s just that the development of aerodynamics far exceeded initial expectations. By the mid-to-late 90s, there were already many ingenious designs to improve the linearity of torque. Combined with the huge progress in flight control technology, this problem actually Basically no longer exists.

Thinking of this, he decided to say a few more words:

"The knowledge learned is indeed very solid, but I still need to work harder to learn and apply it."

Lin Tongxin, who just now thought that his train of thought was completely guessed and recognized, suddenly turned pale:

"Ah this..."

"It must have been the early 90s when I was studying for my master's degree, and the situation was still somewhat different from now. In fact, with the response speed and control capabilities of today's fly-by-wire flight control, as long as the design level is appropriate, there will be no problems in this regard. "

Having said this, Chang Haonan pointed to the vertical tail of the aircraft on the computer screen and said:

"On the contrary, the side strips you design like this may induce a divergent oscillation in the tail part, which is a test for the strength of the vertical tail root. If you observe carefully, you will find that the F18's vertical tail root is designed with three sets of reinforcement ribs. Just to deal with this problem.”

"This one……"

Lin Tongxin had been feeling relatively good about himself just now, but when he was told this, he suddenly felt a little embarrassed and had to scratch his head in embarrassment.

Of course, Chang Haonan also knows that at this time, he cannot blindly undermine other people's self-confidence, so he changed the subject:

"But, if you can have this idea, instead of just mechanically following the leader's instructions, you are already ahead of many people."

The reason for saying this is definitely not that Chang Haonan was in Versailles.

After all, there are very few geniuses who can single-handedly change the world.

Take him for example. Without the help of the system, he could certainly achieve some impressive results relying on his experience and skills in his previous life, but it would never be possible for him to reach this point.

The career development route of most people is gradual.

The key is to have the opportunity, resources and courage to try.

Therefore, although this Lin Tongxin may not be very strong spiritually, he is definitely a malleable talent.

Apart from anything else, how many people, after graduating with a Ph.D., can still recall a casual remark made by their supervisor while working on a project at the master's level?

But he remembered it.

"If you are interested, I happen to have a simpler solution here that can further improve the available angle of attack based on the original design."

Chang Haonan said as he pulled a piece of graph paper from the side and drew a picture on it:

"Designing a retractable small-sized side strip on the side of the nose can reduce the unsteady lateral force and yaw moment generated by the asymmetric vortex of the nose of a large attack angle, and at the same time, it can also make use of the side strip vortex. The lateral force generates a moment that hinders yaw. In addition, since the size of the nose strip is almost negligible compared with the wings and tail, it will not affect the longitudinal aerodynamic balance you have prepared."

"However, the telescopic structure takes up a considerable part of the nose space, so it is really useless for fighter jets that pursue the size of radar antennas, so I did not apply this design to a specific model."

He handed the schematic diagram he drew to Lin Tongxin next to him:

"If you are willing, you can take advantage of this period of time in Beijing to try out this new trainer aircraft to see if you can develop a specialized high-angle-of-attack high-mobility technology verification aircraft."

"On the one hand, training aircraft have certain requirements for the controllability of extremely large angles of attack. Compared with other methods, this solution is very low-cost and can be used. On the other hand, it can also be used as a way for your airline to show its face. An opportunity. Selling airplanes is sometimes the same as selling other things. You have to come up with some gimmicks to get people to pay attention..."

Now that the words have come to this, how could the latter have any reason to refuse? He immediately took the graph paper with both hands:

"Of course I am willing. Thank you Director Chang for the ideas and opportunities!"

Writer's Assistant has a new green content plan. When I posted the last chapter, I clicked on it and tried it. As a result, it directly deleted the next paragraph of my content... which made the last chapter almost less than 2000 words...