Chapter 1321
Wind Tunnel Success, Sky Pioneers, J-6 Defects, Collaborative Improvement
"So, are we about to make history in domestic aviation?" the superior asked half-jokingly.
"Not only has it created a new chapter in domestic aviation history, but it has also made history in global aviation. The high-speed wind tunnel that Comrade Li Aiguo built is even more advanced than the one Xiaomei built," Chief Engineer Qi said from the side.
"Great, great." The superior was also a little excited.
Back then, we couldn't even build a decent airplane.
Today, we have unknowingly reached the forefront of the world in wind tunnel technology.
The superior took a deep breath and pressed the switch.
A buzzing sound, almost inaudible, emanated from the air.
The airflow inside the wind tunnel suddenly accelerated, and the inner wall of the steel test section trembled slightly.
A 1:8 scale model of the J-6 fighter jet was firmly fixed in the center of the support, and the schlieren camera instantly captured a clear trail of airflow passing over the wing.
“Mach 0.8, uniform flow field.” Li Aiguo stared at the monitoring and control screen.
"Mach 1.2, no shock wave separation in the transonic region."
The professional wind tunnel operators' hands flew across the control panel, rapidly adjusting various complex parameters, their reports rising and falling in a continuous stream:
"The main compressor speed is up to standard, and the pressure regulating valve is open at 15%."
"Mach 1.2, transonic load normal! Synchronization error of the six components of the balance: 0.06%!"
The superiors leaned close to the observation window and could faintly hear the whistling sound of airflow tearing through the air.
"This...this is already the start of testing?" the leader asked, somewhat surprised.
"Reporting to the leader, you may not see much movement from the outside, but the wind speed inside has already reached 544 meters per second, which is the design limit for the J-6!" General Xu loudly reported from the side.
Worried that his superiors might not understand, he added, "You know what a Category 17 super typhoon is, right? That's only about 62 meters per second. The speed inside this wind tunnel is equivalent to nine super typhoons stacked together!"
"Well, man can conquer nature. This wind tunnel that Comrade Li Aiguo built is an amazing thing." The superior nodded in admiration.
Three minutes later, the wind tunnel test run was successfully completed, and the violent airflow gradually subsided.
The control room fell into dead silence, with everyone's eyes fixed on the paper tape recorder next to the analog oscilloscope.
Li Aiguo walked over and pressed the keys on the keyboard.
The paper tape recorder began to hiss and scratch, leaving marks on the graph paper.
"Mach 0.5, flow field uniformity 0.03%".
"Mach 0.8, Schlieren system activated."
"Mach 0.9, model attitude angle deviation less than 0.01 degrees!"
Upon seeing the record on the paper tape, General Manager Xu's expression instantly turned serious.
It should be noted that in the wind tunnel room of Santaizi, they had conducted countless wind experiments day and night, but due to the limitations of the equipment's precision, they were unable to detect any fatal problems with the model's attitude angles.
"Found it! Found it!"
Just as Chief Engineer Xu was getting excited,
"Mr. Xu, don't get excited yet. This is just the first question. There's more to come." Li Aiguo pointed to the paper strip that was still being spat out.
General Xu looked down.
The record clearly states: At Mach number 1.1, the left tilt angle of the wing showed an abnormal deviation.
At Mach 1.2, the downwash airflow under the fuselage severely interfered with the tail section...
Just one test uncovered three extremely serious hidden dangers!
Three serious problems were discovered in just one test.
If this is not detected, once the J-6 engages the enemy at high speed, it will lose control before the enemy can even fire.
The more General Xu thought about it, the more apprehensive he became.
"Comrade Patriot, on behalf of all the designers at Shenyang Aircraft Corporation, thank you."
"Mr. Xu, you're too kind. It's just my duty. However, this is only one test, and the data is not comprehensive enough. I suggest you conduct several more experiments under different operating conditions, and we can take this opportunity to collect more operational data from the wind tunnel."
"Of course you can."
Even though the higher-ups didn't understand those professional aviation terms, they could tell at this point.
He burst into hearty laughter: "Congratulations, Comrade Patriot! You've built this super wind tunnel, allowing us to completely overtake others in the field of aviation testing!"
"It's exceeded!"
"That's really over!"
A thunderous round of applause erupted in the control room. Zong Xianfeng and Chief Engineer Chen were so excited that their faces turned red, and their hands went numb from clapping.
Several chief engineers from the aircraft factory who came to visit were so excited that they jumped up and down on the spot like children.
After the applause subsided slightly, the superior leader waved his hand and set the tone: "The success of this wind tunnel is of great significance! I think its capabilities go far beyond testing fighter jets."
In the future, other types of aircraft, new rockets, and even missiles can all come here for a demonstration!
"That's right, our Fifth Academy is planning to research a new type of missile, and Professor Qian will definitely be very happy to hear this news," said the leader of the aviation department.
At this point, someone raised a practical question: "Sir, which department will be specifically assigned to manage this wind tunnel room in the future?"
After a moment's thought, the higher-ups made the final decision: "Since it was developed by Comrade Aiguo himself, then let's not waste any more time on it. Just hand it over to the Qianmen Locomotive Depot's workshop for overall management!"
Upon hearing this, Section Chief Xing was naturally overjoyed.
Although the aviation leaders were somewhat disappointed, they were relieved to think that all the technology was now in the workshop.
"Also, confidentiality must be maintained."
"Rest assured, this wind tunnel was designed personally by Comrade Li Aiguo, and only Comrade Li Aiguo has the blueprints for the core components," Chief Engineer Qi said.
The higher-ups still have a lot of confidence in Li Aiguo.
Who wouldn't like a comrade who doesn't seek credit and only wants to help his own family with development?
The way the superiors looked at Li Aiguo was like how they looked at their own junior.
The personal assistant next to him noticed this as well and said with a smile, "Boss, how about we have Comrade Aiguo show you around the wind tunnel again and give you a proper introduction?"
"Good idea! Then I'll have to trouble you, young comrade."
Afterwards, Li Aiguo acted as a guide, leading the superiors on a tour of the safe area of the wind tunnel.
The core compartment, which had just undergone high Mach number testing, was extremely hot, so it was naturally off-limits to enter.
The higher-ups were quite impressed; this was their own large-scale wind tunnel.
Thinking back to those difficult years, when we couldn't even get enough to eat and couldn't even manufacture pistols.
Now we can create this gem of the aviation industry, and it's at a world-leading level.
Touching the warm metal, there was nothing that could be done; the motor inside was too powerful, and even with heat insulation, the outside temperature was still quite high.
The superior looked at the control panel and saw a dazzling array of instruments and meters, all labeled with Chinese characters.
The superiors watched for more than an hour before returning to the preparation room.
"Come on, young comrade, let's take a group photo in front of this wind tunnel as a souvenir!"
The higher-ups were clearly in high spirits. They not only took a photo with Li Aiguo, but also a group photo with the researchers in the wind tunnel and the technicians in the workshop of the Qianmen Locomotive Depot.
After a few casual words, Section Chief Xing invited the higher-ups to stay for the celebration banquet. However, the higher-ups had to receive visitors from the John Bull family, so they planned to leave first.
After the superiors left, a celebration banquet was held in the wind tunnel at noon.
As before, there were enamel basins filled with large pieces of braised pork, and each person had a bottle of beer.
Because they had to continue testing in the afternoon, everyone restrained themselves and only drank a little to satisfy their cravings.
The subsequent testing was handed over to Chief Engineer Liu, and the plan was jointly customized by Chief Engineer Liu and General Manager Xu, which also facilitated more detailed testing of the J-6.
Such high-intensity, comprehensive testing often takes several days.
Seeing that there was nothing more for him to do, Li Aiguo returned to his studio, where he wrote the wind tunnel operation manual while thinking about the J-6 fighter jet.
How were those shortcomings of the J-6 eliminated in later generations?
With his wife's soft, warm body in his arms, Li Aiguo finally put aside the industrial blueprints that had been swirling in his mind. He shook his head with a smile, then wrapped his arms around her and closed his eyes in peace.
Early the next morning.
Li Aiguo saw photos of the wind tunnel and a group photo of leaders published in the newspaper.
As for the group photo of Li Aiguo and the technicians with the leaders, it was not published.
The interior of the wind tunnel was not published.
This is also due to absolute safety considerations.
You have to understand that these days, all the major intelligence agencies are very powerful. They can deduce technical specifications and processing precision just by looking at a few photos of the wind tunnel's inner wall.
Why do I say that? Because the Russians and the Americans are also planning to build new types of wind tunnels, and they are conducting research on them.
Although there was only one photo and the newspaper's description of the wind tunnel was very brief, only stating that it was a high-speed continuous wind tunnel, it still attracted a lot of attention.
Western countries don't seem to care, after all, the large wind tunnel in the US is also under construction, and it's even bigger and has a faster wind speed than the one in the east.
However, the big brother in the north is getting restless.
In the past, they made a lot of money by selling fighter jets and transport planes here.
Now look what's happened! The little brother who used to only follow behind and buy complete machines has quietly risen up and actually built a large-scale high-speed wind tunnel that even they don't have yet!
What does this mean?
This means they're going to go it alone and build advanced fighter jets from now on!
Unfortunately, the Korean emperor's position is already clearly unstable, so he can't care about anything else and just pretends not to know.
The former president, Ken, who used to glare at him, has now come up with a wild idea; he doesn't want his chair to be pulled away.
Despite the turmoil in the outside world, Li Aiguo paid no attention to it.
That morning, as soon as he arrived at work, he was called to the office by Section Chief Xing.
"These are for you."
"Thank you, Section Chief."
Li Aiguo curiously untied the binding of the file folder, pulled out the contents, and found a stack of developed black and white photographs, along with a roll of negatives.
These are the very internal photos that weren't published yesterday!
The first picture shows Li Aiguo standing next to his superior when the leader pressed the start switch.
You can see Li Aiguo's profile and the frontal view of his superiors. Li Aiguo doesn't remember how many people were taking pictures at the time.
"Tsk tsk tsk..." Section Chief Xing leaned over and watched, clicking his tongue in envy.
The second photo is a snapshot of Li Aiguo explaining something while a higher-level leader reaches out and touches the exterior wall of the wind tunnel; the scene is extremely vivid.
The third picture shows a superior leader smiling and having a friendly conversation with Li Aiguo.
There are words on the back.
Li Aiguo turned the photo over and, sure enough, saw the words "Road Builders in the Sky" written in pen on the back of the photo!
In fact, when the higher-ups visited the wind tunnel, they were thinking of fighter jets soaring in the air. After all, fighter jets can only fly if they are tested in a wind tunnel.
Although Li Aiguo was a worker and a technician, the work he did was essentially the work of those who built roads across the sky.
Section Chief Xing slapped his forehead: "That's right, Patriotism, the higher-ups asked you what other reward you want?"
In Section Chief Xing's view, the fact that the leader gave Li Aiguo these photos and even wrote a note on them already showed that... well, you know.
The higher-ups had met other people before, but at most one or two photos were selected for publication, and the rest were all sealed away.
When it came to Li Aiguo's side, not only were the photos delivered, but the negatives were also provided.
"Section Chief, please pass on a message to the higher-ups for me. Just say... I want this kind of reward again next year!" Li Aiguo knew he needed to make a statement; saying anything else at this point would seem too vague, so he spoke up.
Section Chief Xing was taken aback at first; what kind of request was this?
He immediately understood: "That's a good request. I'll report it to them in a bit."
When the other leaders of the locomotive depot heard about this, they all felt sorry for Li Aiguo. He got no benefits at all. It would have been better if he had been selected as an advanced worker instead.
What they didn't know was that when Section Chief Xing reported this sentence verbatim through Leader Teng, the higher-ups listened and happily said "good" several times in their office.
After taking the photos, Li Aiguo didn't delay and went home to have Xiao Chen put them in the box.
It was two days later when they returned to the wind tunnel.
The first all-round wind tunnel test of the J-6 has been completed.
The data above was extensive and disorganized. After some sorting, a conclusion was reached.
The reason why the J-6 experiences fatal wing vibration at high speeds is fundamentally due to its signature 55° large sweep thin wing.
While this design can achieve extremely high speeds, its stiffness is relatively weak, making it prone to aerodynamic coupling and severe flutter under high-speed airflow.
It should be noted that in the original historical trajectory, Shenyang Aircraft Corporation's three-stage wind tunnel chamber had a relatively low Mach number, which made it impossible to blow out extreme working conditions at high speeds and reproduce such extreme states.
So the experts at the time could only guess that it was a problem with the workshop's processing technology, that the stress during assembly was not properly released, or that it was caused by the vibration transmission of the engine itself.
Because of this misjudgment, the aviation professionals of the previous life spent several years groping and investigating in the dark, taking countless detours.
"General Xu, we've found the problem with the J-6, but there are quite a few problems, and they're a bit difficult to fix," Li Aiguo said directly.
General Manager Xu's expression was also rather unpleasant.
It's important to understand that the large sweepback and thin wing is a design flaw, just like the MiG-19, and it's practically impossible to change it now.
Now that we have doctors, the patients have congenital diseases, and not just one type.
How can we treat this? We can't just bury the patient, can we?
The faces of Shenfei's chief engineers also darkened.
Li Aiguo sat down, looking at the specifications of the entire wing structure, wanting to see if it could meet his expectations.
As he looked at it, his brows furrowed slightly.
"General Xu, I've done the calculations, and the specific strength of this wing... how come it's only a little over 150 MPa/t?" Li Aiguo asked, looking up.
He originally wanted to say "It's only 150," but he felt it would be too hurtful, so he politely omitted the word "only."
General Manager Xu looked a little embarrassed: "Well, the specific strength of aerospace aluminum alloys is inherently limited. With our current smelting and processing technology, this is the best we can achieve."
General Xu smacked his lips, intending to add, "The MiG-19 from Big Brother's country also uses this material."
But after thinking about it, he swallowed those words back.
Other families have the same problem, but that doesn't cover up the fact that we are lagging behind.
Although Li Aiguo was a genius, he knew that the current industrial base was barely enough, so he asked again, "What are the specific parameters of the materials we can currently produce?"
A chief engineer standing nearby immediately reported fluently: "Static tensile strength 420MPa, yield strength 275MPa, density 2.78g/cm³, the calculated specific strength is 151MPam/t."
Chief Engineer Li, this is absolutely the best batch we could produce even with all our efforts!
Wow, this is really hitting the ceiling. No wonder we can't change it now that we know the problem.
Li Aiguo nodded and continued to offer his thoughts: "General Xu, if we take a step back and try to increase the flutter critical speed of this wing to Mach 1.15, or even better, is that possible?"
After hearing his words, General Xu shook his head.
"It's incredibly difficult! With M=1.02, we're already approaching the material's limit. Putting aside everything else, this material simply can't withstand any greater stress."
General Xu took a piece of scrap paper and drew and calculated for Li Aiguo: "If you want to further increase the flutter critical speed, our only clumsy method is to reinforce it."
We need to thicken the wing spars by 30% and the skin by 20%! Can you guess what the consequences will be?
"As a result, the wing weight of a single wing increases by 120 kilograms, the weight of the whole aircraft increases by 240 kilograms, the range is reduced by 200 kilometers, and the climb rate decreases by 15%, making it completely unusable in combat."
Li Aiguo was not intimidated: "Can we increase rigidity without thickening the wings?"
"The aluminum alloy we are currently using is LY12 hard aluminum, whose parameters such as specific strength, elastic modulus, and fatigue strength have reached their limits."
Either insufficient stiffness causes flutter, or excessive weight affects performance; both are subject to strict flight load limits.
We're back to the old problem: materials.
LY2 hard aluminum is not a brand, but a model number of aluminum alloy.
It is an aluminum-copper-magnesium alloy, and it is the most widely used aerospace aluminum alloy in the world since World War II.
It is no exaggeration to say that almost all propeller-driven aircraft in the world, as well as early jet fighters, used it as a structural component.
Later, to make it easier to distinguish, the industry has come to generally refer to aluminum, copper, and magnesium alloys as "2-series aluminum alloys".
The more advanced aluminum-zinc-magnesium-copper series of super-hard aluminum is called "7-series aluminum alloy".
In this day and age, LY2 hard aluminum is, to put it bluntly, the highest-grade aerospace aluminum alloy that we in China can obtain by any means possible.
Although Western countries have developed the even more powerful 7012 super-hard aluminum, such strategic-level materials are unattainable no matter how much money is spent.
General Xu gave Li Aiguo a general explanation.
LY2? 7012?
Li Aiguo really didn't understand these outdated models.
However, he knew something that General Xu and the others did not.
"Mr. Xu, if we had an aluminum alloy with a specific strength of 220 MPa·m/t, an elastic modulus of 72 GPa, and a density of 2.83 g/cm³, would it be useful to you?"
Li Aiguo was excited.
Other things aside, he probably can't do anything about it.
Large aircraft are now being manufactured, using the 7085 high-toughness aluminum alloy from later generations.
Although the 7085 would certainly not be up to par with a fifth-generation fighter jet in later generations, since it lacks stealth capabilities.
If it were applied to the character of Sixth Master, who specializes in aerial combat, it would be perfect.
"How much? How much?" General Manager Xu could hardly believe his ears.
If I had this thing, why would I complain to you? I could make ten sets of wings for you by hand.
Li Aiguo repeated himself, adding, "I've tested some of the other mechanical properties: static tensile strength 620MPa, yield strength 570MPa, fracture toughness 43MPa√m, fatigue strength more than 60% higher than LY12, and thermal expansion coefficient about 10% lower."
General Manager Xu was delighted, as this mechanical property system is completely compatible with duralumin.
You don't even need to make major changes to the wing design; you can get pretty close to the original.
"Chief Engineer Li, if you can really give me this aluminum alloy, I can at least give you a flutter critical velocity of M=1.22!"
He was unequivocal in his decision; he had to get his hands on this aluminum alloy, not only for the J-6, but also for the future J-7 and J-8.
As for invisibility, we're not considering that right now.
With a specific strength of 220 MPa/t, this means that for the same weight, the stiffness can be increased by 45%! Or, for the same stiffness, the weight can be reduced by nearly one-third!
Li Aiguo laughed heartily: "Alright! It's a deal!"
The other comrades nearby were completely dumbfounded when they saw the two of them.
Is communication between tech gurus really this direct and smooth?
You want this? Okay, here you go.
"Chief Engineer Li, what kind of material is it?"
Li Aiguo smiled and said, "Type 7085 high-strength, high-toughness aluminum alloy!"
High-purity aluminum and trace elements such as zinc, magnesium, copper, and zirconium are smelted in precise proportions.
The zinc content is controlled at around 7.5%, copper 1.6%, magnesium 1.5%, zirconium 0.12%, and it is an ultra-hard aluminum alloy obtained through solution treatment and graded over-aging.
Unlike regular duralumin, this material has a finer grain structure formed by adding trace amounts of zirconium.
At the same time, the ratio of zinc, magnesium and copper was optimized, which significantly improved the strength while maintaining extremely high fracture toughness and resistance to stress corrosion.
It is the preferred material for the wing spars and integral panels of large transport aircraft and wide-body passenger aircraft such as the C-17, Boeing 787, and Airbus A350.
The Y-20's main wing spars also use its improved version.
For General Xu, this thing was completely unheard of. What was it?
However, he was excited when he heard that Li Aiguo had made this thing and had even conducted limited mechanical performance tests.
Although they are not professional metallurgical experts, at least the basic items they have tested are unlikely to have major problems.
"It seems Chief Engineer Li is also involved in materials science, and he's quite an expert. He's been so modest all along," General Manager Xu thought to himself.
Actually, no. Li Aiguo only knew the composition and process of the material; he knew almost nothing else.
After the material formula was finalized, the remaining work was handed over to Chief Engineer Chen. This old gentleman also had another identity: the chief engineer of the metallurgical institute. Don't forget that.
General Xu now understands Li Aiguo's plan.
Since the J-6's problems are inherent, let's just replace its core components, just like Nezha, who replaced his flesh and blood with lotus roots.
"Yes, just like Nezha." Li Aiguo thought to himself, what would Nezha think if he knew that he would be turned into milk tea in the future?
General Xu knew that Li Aiguo was researching airplanes, but he didn't know which kind of airplane. He only knew that the Aviation Industry Bureau was also paying close attention to it, so it was normal for them to produce some materials.
"Chief Engineer Li, when would you like to send the materials to Shenyang Aircraft Corporation? If they are usable, we can modify the wings."
However, Li Aiguo's next words shocked him.
“Why send it over there? It’s too much trouble. We have professional equipment here. I’ll teach you how to do it. If there are any defects, we can use your expertise to improve it.”
Li Aiguo spoke very generously, and Shenyang Aircraft Corporation's research on fighter jets is indeed profound.
However, in terms of materials, there is no doubt that the studio and the metallurgical institute are far superior to them.
However, in Mr. Xu's opinion, this was far too generous.
They provide materials and even offer to use the equipment to manufacture wings; who could resist that?
"No, Chief Engineer Li, please don't misunderstand. We just want to use this material for trial production. We didn't mean to take up your time."
General Xu thought that something he said had caused Li Aiguo to misunderstand, and in his haste, he even used honorifics.
Li Aiguo laughed heartily: "General Xu, please don't misunderstand. I really want to give you this material to continue your research so that it can be used in the next generation of fighter jets. I also have other work to do here."
General Xu was starting to understand, but he didn't know what kind of aircraft this guy was researching that led him to discover this material.
However, the application of this material is a new topic, and it's not something that can be decided by one person alone.
Just as General Xu was about to speak, Li Aiguo suddenly slapped his forehead and continued, "When you submit your J-6 improvement project, just include our Qianmen Maintenance Depot workshop. It will also demonstrate the superiority of our family system."
Mr. Xu was both amused and exasperated. Was this some kind of alliance between the two companies?!
However, General Manager Xu was more than happy to accept it.
For no other reason than that the studio has top-notch equipment, ample funding, and even its supplies are sourced through special channels.
Just look at how much meat they've been eating these past few days, and you'll know.
envy!
What he didn't know was that Li Aiguo wasn't really interested in just having a title; his real intention was to become a familiar face in the fighter jet community.
Let's not talk about the design of the J-6 now, as it has already been finalized and can only be improved in some aspects.
When the J-7 and J-8 are being developed, we can take the opportunity to develop the fighter jet of our dreams.
(End of this chapter)