Back in 1978, I was admitted to Northwestern Polytechnical University.

Chapter 382 IDF Fighter Jet, Designed by Northwestern Polytechnical University?

Chang'an, Flight Test Institute.

Amidst the roar of engines, J-9 fighter jet number 1006 is approaching and landing.

On the ground, Qin Liang looked up at the sky, deeply moved.

"To speed up the test flight progress, we have already built six prototypes to participate in the test flights. It is expected that the prototype will be officially finalized this year and then enter the mass production stage." Old Song looked at the fighter jet with bright eyes: "At present, apart from the engine being somewhat outdated, there are no other shortcomings."

"Yes, once our cooperation with Rolls-Royce proceeds smoothly, the problem of high-thrust engines for third-generation engines will also be solved," Qin Liang said. "At that time, we will choose an American or Soviet engine to reverse engineer..."

With Rolls-Royce's manufacturing process, it wouldn't be too difficult to copy the F100 or F110. However, Qin Liang still preferred the Russian engine, the third-generation high-thrust engine, which was robust and durable, making it more suitable for use in the East.

However, we can't rush this; it will take three to five years. During this period, the WP-15 turbojet will still be the mainstay.

"Oh damn it, PIO, jump now!" someone suddenly shouted.

Everyone looked at the J-9 fighter jet as it entered the landing path. At this moment, the aircraft was swinging back and forth horizontally like a seesaw, and the amplitude was getting larger and larger!
Everyone stared intently at the fighter jet, holding their breath.

Just now, because of a crosswind, the pilot instinctively pushed the control stick to correct, but... because the fly-by-wire system was too flexible, the correction was too large. So, he reversed the operation, and... the swing became even greater!

This is a defect in the aircraft's fly-by-wire control. If it is not sensitive enough, the maneuverability will be poor. If it is too sensitive, it is easy to over-adjust. The pilot has to make repeated adjustments, which leads to pilot-induced oscillation, or PIO for short.

Historically, every fly-by-wire fighter jet has crashed due to PIO (Push-In-the-Air) issues, even the famous F-22 is no exception!

At this point, the plane was only twelve meters above the ground and was about to lose control and crash. Parachuting was the only option!

However, the pilot clearly wasn't going to abandon the aircraft! He stopped lateral maneuvers and instead pulled the throttle lever to its maximum, deflecting the canards and raising the nose of the plane. The J-9 climbed rapidly, standing upright like a duck!
Everyone wiped the sweat from their brows. At this critical moment, the pilot's actions were textbook perfect!
Continuing to adjust horizontally is pointless and will only make things more dangerous. The pilot will induce increasingly severe turbulence until the aircraft crashes. The only solution is to pull up and go around!
With a roar, the J-93 made a turn and aligned itself with the runway again.

Crosswinds continued to blow intermittently, and this time, the pilot was even more careful with the controls. Finally, the plane landed smoothly!

The canopy opened, and the test pilot stepped out. As he removed his helmet, sweat dripped from his forehead.

"Comrade Qian, you've done a great job!" Old Song stepped forward: "You've successfully brought the aircraft back this time, providing us with invaluable data. Next, we'll further modify the flight control system to reduce PIO occurrences!"

“Of course, we test pilots have to give it our all as long as there’s even a sliver of hope. Besides, we received PIO training six months ago,” the test pilot said. “We have to thank Mike for that.”

As exchanges between the East and the West increased, test pilots from the East also went to the West for training. This old Mike was one of their instructors during their Western training.

"Yes, our domestic aviation industry has developed rapidly. Besides our own efforts, cooperation with the West is also indispensable." Old Song said with emotion, "Liangzi, we still have to thank you for this."

"How did this get involved with me?"

"Your wife was the matchmaker."

"Oh."

Just then, someone ran over: "Comrade Qin Liang, Comrade Qin Liang, Datang Company called and asked you to come back!"

"it is good."

Qin Liang knew his uncle was coming today, but... they were still not quite sure what his uncle was here for. He himself had a lot of work to do, so the reception work was left to his father. Now it seemed that there were things his father couldn't handle.

Could it be related to the Anxiang Project?

Speaking of which, life over there is really tough.

In the 1970s, with the help of the Americans, they introduced the F-5 production line and were finally able to assemble the F-5E fighter jet. The first fighter jet rolled off the production line just in time for someone's 88th birthday, and was named Chung Cheng.

More than 300 fighter jets were produced, which made them feel confident in dealing with the J-7. They were very pleased with themselves. At the same time, they decided to develop their own AT-3. However, their former big brother no longer wanted to take them under his wing. The sweetheart turned out to be a shrew.

They were furious, so the AT-3 was named "Self-Reliance," representing their determination to be self-reliant. They even upgraded the aircraft, creating the "Thunder" attack aircraft.

Just as it was developed, my older brother came to my door, repeatedly saying that he was in the wrong and that to show his sincerity, I would sell him another two hundred F-5s.

Thus, the Thunder-class attack aircraft project was completely scrapped.

In the late 1970s, they wanted to buy F-16s again, but the leader still refused to sell. I had just signed that proclamation, and you're putting me in a difficult position!

So, filled with resentment, they mobilized the entire island to develop their own fighter jet! The name was Indigenous Defense Fighter, or IDF for short.

After nearly a decade of development, the IDF was finally released. Then, the big brother came knocking again: "Brother, I was wrong before. You want an F-16? I'll give it to you!"

As a result, the originally planned 250 IDF aircraft fleet was eventually reduced to 130.

Currently, the IDF fighter jet is in the early stages of development. The following four programs—Eagle Soaring Program for airframe design, Cloud Han Program for engine design, Thunderclap Program for avionics design, and Sky Sword Program for weapon design—are integrated into a complete Anxiang Program.

As Qin Liang recalled these things, he took a car back to Northwestern Polytechnical University.

Datang Corporation, Headquarters.

"Liangzi, you're back? Your time is precious, so let's skip the pleasantries and get straight to the point. This time, your uncle and the others came to ask Northwestern Polytechnical University for help in designing a trainer aircraft."

Qin Liang had mixed feelings.

Does this mean my uncle came to deceive us? Could it be that my uncle has already...?

"Uncle, what kind of company do you run over there?"

"I run a company that makes soy sauce and daily necessities. This collaboration is mainly due to Huizi's father, who works for Mitsubishi Heavy Industries Aviation Corporation. He wants to commission Northwestern Polytechnical University to design a trainer aircraft..." Qin Baoguo quickly explained.

Qin Liang suddenly felt relieved.

It seems that Uncle was unaware of the situation, and I, Da Ming, was probably kept in the dark as well. The whole mess was caused by Waseda Keiko!

If the people over there contacted me, it must be because they wanted Northwestern Polytechnical University's advanced technology, especially aviation technology, which is exactly what they need. So... they used Mitsubishi Heavy Industries' name?
"Uncle, if Mitsubishi Heavy Industries wants us to design something, why don't they come to us in person?"

Qin Baoguo was taken aback, then looked at Waseda Keiko: "Keiko, why didn't your father and the others come in person?"

"Because it would be very embarrassing. Mitsubishi Heavy Industries has a long history, and during World War II, it developed the famous Zero fighter. However, during the Cold War, it made almost no achievements. If the news that they commissioned Northwestern Polytechnical University to design it gets out, they will be ridiculed by the whole world." Keiko Waseda had obviously thought of this problem long ago and had already prepared her answer.

"At the same time, our island nation and Northwestern Polytechnical University don't have much of a relationship. It was only when Daming and I came to the East last time that I learned that Daming's younger brother is Qin Liang, who is very famous in the industry. After returning, I told my father about it, and he was very impressed. I also thought that Daming needs a graduate thesis project..."

Okay, so developing an advanced trainer aircraft is just a graduation project? You're making this up...

"Due to various factors, my father decided to develop this project, with an estimated investment of 100 million yen. Uncle Qin will also invest several million NT dollars. As long as we use this money to complete the basic design, I can ask my father for more funds to proceed with the detailed design."

Qin Baoguo nodded: "That's right. Our Weiwang Soy Sauce's involvement in this project can be seen as expanding into a new industry. Of course, the most important thing is to help Daming and Huizi complete a project during their student years, which will greatly benefit their future development..."

He hoped his son would become a dragon among men, but he ended up falling into someone else's trap! Qin Liang was filled with mixed emotions.

"Liangzi, do you think this project is feasible?" Qin Baomin asked.

"That depends on the specifications of this trainer aircraft. If they're not too high, we can just hand the project over to the second-year students from the Fifth Department."

"What, a sophomore?"

"I'm a third-year graduate student!" Qin Ming's eyes widened in disbelief. He had only just begun learning basic aerodynamics in his second year of university; he couldn't possibly have mastered the fundamentals, let alone pursue research and development.

Just how incredible is Northwestern Polytechnical University?

"Well, don't underestimate them just because they're sophomores. Many of them have already learned the material of juniors and even seniors," Qin Liang said with a smile. "Although their level is not yet comparable to that of graduate students, Northwestern Polytechnical University has first-class research and development equipment, which can still support them in completing these basic research and development tasks."

"Okay. Keiko, tell me your needs."

"This trainer aircraft is positioned as an advanced trainer, with the goal of enabling trainers to directly adapt to the operation of third-generation fighters after learning from this aircraft. Therefore, its flight characteristics must be exactly the same as those of third-generation fighters. For example, the maximum overload must reach 9G, the maximum angle of attack must be 40 degrees, and the maximum lift coefficient must be above 2.0..."

Keiko Waseda kept saying that Qin Liang's brows were furrowing deeper and deeper.

Are you kidding me? Is this still a trainer aircraft? This is clearly a two-seat fighter jet! Moreover, the requirements are even higher than those for the IDF. So, they can't develop advanced fighter jets over there, so they handed the design work over to Northwestern Polytechnical University?
How much do you think of Northwestern Polytechnical University?

Seeing Qin Liang's expression, Waseda Keiko's voice grew softer and softer: "Liangzi, actually, when my father mentioned these specifications, I also felt they were excessive. However, my father said that in his heart, Northwestern Polytechnical University's aviation technology is the best in the world! The advanced trainer aircraft we're developing must reach world-class levels to ensure it won't be outdated for the next thirty or even fifty years..."

Is this a compliment?

Qin Liang took a deep breath: "Alright, after all this talk, what kind of engine are you planning to equip this trainer aircraft with?"

As long as the engine is powerful enough, even a brick can fly. In the end, it all comes down to the quality of the engine!

"Currently, we have contacted Garrett Aircraft Company. Their TFE-1042 engine is very suitable for our trainer aircraft. It has an afterburner and a maximum thrust of 3 tons..."

“3 tons is not enough. This engine needs major modifications. The thrust needs to be increased to at least 4.5 tons, preferably five tons, in order to meet these requirements.”

Since you're offering to help, let's lend a hand! Currently, China is lacking small-thrust turbofan engines!
The Mountain Eagle trainer jet modified at Base 011 was good, but it was still a second-generation platform. In later generations, Hongdu Aviation developed the Falcon trainer jet, which was a true modern twin-engine supersonic advanced trainer jet.

Leading wing, blended wing-body, fly-by-wire... it can easily simulate any characteristic of a third-generation fighter jet and can fly supersonic. Unfortunately... it has always been troubled by engines in later generations. Originally, it used the AI222 engine from Russia, but with the changes in the international situation, the crisis faced by imported engines has become increasingly greater.

Fortunately, China has the WS-17 Minshan turbofan engine, which solved the problem.

This type of small-thrust engine has many uses. In addition to trainer aircraft, it is also needed for stealth unmanned combat aerial vehicles, high-altitude long-endurance drones, small regional airliners, and so on.

Previously, Qin Liang had no time to get involved in this field, but now that someone is offering him money, he might as well develop this industry!

Keiko Waseda's eyes widened.

At the aero-engine center, the people there at most dare to think about modifying the engine to four tons of thrust. Qin Liang came up with four and a half tons, and even said he wanted five tons. Is that... possible?
However... if we had a five-ton engine, the IDF fighter jet's heart problem would be completely solved!
"Liangzi, how do you plan to change it?"

Qin Liang smiled and said, "A complete overhaul!"

The TFE731 is a very unusual engine. From the front, the fan is not directly driven by the low-pressure turbine, but rather by an added gear reducer!

The reason is simple: this thing was originally a turboprop engine, which already had transmission gears, so simply turning the propeller blades into a fan was enough.

Following that is a four-stage low-pressure compressor, and then a single-stage high-pressure compressor with centrifugal blades instead of axial-flow blades! This design is to achieve higher efficiency at low speeds. In addition, to complement it, the combustion chamber is also a recirculation type, which means that the high-temperature and high-pressure gas is injected forward and needs to be rotated 180 degrees to be injected backward!
It can be said that the design of this engine did not take into account the needs of supersonic flight at all; it was originally intended for subsonic trainer aircraft and business jets.

In an attempt to compete in the fighter jet market, Garrett went even further by adding an afterburner to the rear of the aircraft and then marketing it. Anyone with eyes could see that this was a complete rip-off!
Therefore, in history, when those guys on the other side of the river were carrying out their plans, they had to completely overhaul their engines!
The fan gear drive system is adopted, the number of stages is increased to three, and it is directly driven by the low-pressure turbine. All the low-pressure compressors at the front are replaced with high-pressure compressors, while the centrifugal high-pressure compressor at the rear is retained. The combustion chamber is significantly redesigned...

By this time, Garrett had been acquired by Honeywell, and the engine was eventually renamed the F125 engine.

The improvements were satisfactory, with the maximum military thrust increasing to 2.7 tons and the maximum afterburner thrust increasing to 4.2 tons. After further tapping into its potential, the power was increased to 4.5 tons.

This was still not the highest. In 1988, the engine was redesigned, and a few years later, the TFE1088 was developed, which increased the maximum thrust at sea level to 5.4 tons. With this level of power, the problem of insufficient power in the IDF was completely solved.

but……

Since there were already many options available at the time, including the F-16 and Mirage 2000, Honeywell required that at least 162 aircraft be produced before they would begin production of the engine. As a result, the IDF ultimately missed out on this engine.

Now, Qin Liang, spittle flying everywhere, explained the modification method clearly and concisely, making Waseda Keiko and Qin Ming nod repeatedly.

“Yes, that’s good. This improved engine certainly has top-notch performance, and it will allow our trainer aircraft to achieve its planned performance…” Waseda Keiko said, “When I get back this time, I’ll discuss this with my father. For now, let’s talk about the overall design of the aircraft, shall we?”

"Yes, the estimated design cost is five hundred million US dollars." Qin Liang did not hesitate to start rigging. Research and development is definitely necessary. This is to prepare the power for a large number of our future aircraft. As for the people on the other side of the river... they definitely can't get it. Even if they did, it would definitely have serious defects!

Including airplanes!

Aircraft design? Sure, we can just tweak the aerodynamic layout. Subsonic speeds are no problem, but once we enter supersonic speeds, the drag will increase dramatically, just like the David's Lion fighter. If we want more detailed design, we'll have to modify the structural frame, making it the kind that will disintegrate in mid-air at 7G overload...

What does IDF mean? It means "I don't fly," meaning it definitely can't be allowed to fly.

"As for the overall design of the aircraft, it's not a big problem. We'll run a model on the supercomputer as required, and then test it in the wind tunnel... Hey, what's with all those surprised expressions?"

"Liangzi, you're saying these changes will cost five hundred million US dollars? This... isn't that too high?" Qin Baoguo was stunned when he first heard such a figure.

“Uncle, that’s not a high price. Aero engines are the crown jewel of industry; there’s never a cheap one. Five hundred million dollars is just a rough estimate. If that’s not enough, we’ll need to increase funding later. Of course, we can test-fly with the existing engines first, and then come to us for R&D when the customer has the money. Uncle, your investment of a few million is just a token gesture; it’s better to stay out of it. This kind of project isn’t something your company can handle…”

　PS: The early TF731 design featured gear drive at the front, a centrifugal compressor at the rear, and a unique recirculation combustion chamber. Below are later modifications, which became the standard design. Finally, there's the Type 054 F-5.
　　
　
(End of this chapter)