The military-industrial scientific research system of the academic master.

While the two were circling the plane and chatting, the ground staff from the 611 station who followed them had also begun to perform maintenance on the plane.

Although the J-7F has undergone a complete overhaul in appearance, it is still a MiG-21 in essence, and its performance in terms of maintainability is still relatively average.

The biggest improvement was the use of a side-opening radome at Chang Haonan's insistence, so that there was no need to take the trouble to remove the entire nose cone and place it on the ground when maintaining the radar equipment.

He reached out and touched the air intake lip and radome that he had optimized and designed by himself.

Although the aircraft in front of me is different in details from the one shown in Professor Liu Hongbo's class nearly a year ago, the overall structure is still very similar.

Most of the projects Chang Haonan has handled so far are key technology research and development or modification of old models. After all, it is different from the J-7F, where the feeling of "the aircraft I drew landed on the ground" is still different.

From a relatively close position, he could already see that the aircraft's radome actually contained an old radar.

"Is this 208A?"

At present, China's radar models are still on the eve of a technological explosion. There are only a few models that can be installed. Among them, there are models that can be truly called "radar" rather than range finders, and can also guide semi-active radar bombs. Except for the 8/1471 on the J-1472C, basically there are only 208A left.

It was the radar that was equipped with the J-8B in the past. This model was used by the Air Force when it successfully completed the Aspad target shooting test for the first time.

"Yes, the 14 small-diameter radar originally planned to be developed by the 1452th Institute is still undergoing ground testing and cannot be installed for the time being. However, we have to demonstrate the beyond-visual-range interception capability this time, so we can only use this first."

Speaking of this, Lu Yuying seemed to suddenly remember something:

"Do you want to take a photo? This time we specially brought a camera."

Chang Haonan hesitated for a moment, and finally nodded:

"Alright."

"Just in time, I called the pilot comrade over. I'm going to take a group photo with the outsiders later."

After hearing what Lu Yuying said, Chang Haonan noticed that in addition to the ground staff, there were also some staff who were not wearing work clothes, but were still busy.

He has already seen banners and traditional arts of the aviation industry such as big red flowers in the hands of these people.

Finally, Chang Haonan and Lu Yuying took a single photo standing on the side of the opened radome.

At this time, a pilot wearing a blue cotton jacket trotted over from a distance, carrying a white flight helmet with a red star in his hand.

The pilot is not fine after getting off the plane. He still needs to hand over to the ground and fill in the flight record. Judging from his appearance, he must have just come from there.

Originally, Chang Haonan felt that he had already asked about everything he wanted to know before, and he did not want to participate in the group photo with foreign parties, so he was planning to go back and rest.

But as the pilot got closer, he found that the other person turned out to be a familiar face.

"Comrade Zhang Jiujiang?"

The person who came here was the flight instructor who took Chang Haonan to the sky in a J-7 when he first participated in the 03rd Project to observe the air flow separation on the surface of the No. prototype.

In this day and age, there is no contradiction between the two identities of senior flight instructor and test pilot.

But this meeting was quite surprising.

Zhang Jiujiang, who was directly called out by name, also stared at Chang Haonan for a few seconds. It wasn't until he walked closer that he remembered the latter's identity:

"Are you that... Engineer Chang from the 601 Institute? Have you flown on my plane?"

"Uh... yes, we worked well together that time."

Just as Chang Haonan nodded, he heard Lu Yuying interrupt next to him:

"Old Zhang, Xiao Chang cannot be considered a member of 601..."

This topic is already considered a daily topic for the former, but Lu Yuying feels that she should emphasize it to prevent the other party from forgetting her promise to 611 years ago.

Although this promise has nothing to do with his project.

"Don't worry, Mr. Lu. During this time, when I was helping them modify the JH-172 at Factory 7, I specially requested a lot of data from the test flight of the prototype that year, which can be used later when studying active stability control technology. of."

Chang Haonan looked at Lu Yuying who looked nervous, and naturally understood the meaning of the other person's words, so he quickly spoke to comfort him.

"Active stability control..."

The generalization of this term is indeed a bit high, and it is not even possible to directly determine which subsystem of the aircraft the technology is used in.

"This is something I have been thinking about since I completed the flutter analysis of the MA603 wing for the 60 last year."

Chang Haonan, who knew this was a brand new concept, explained:

"Since the flutter of the wing can be controlled through active means, can a similar idea be used to control, or at least predict the engine surge in advance?"

"Later, when I was responsible for improving the turbojet 14, I discovered that before the engine entered the surge state, there were actually some observable characteristics inside the compressor. If we could intervene in time at this time, we could improve the performance to a large extent. Avoid entering abnormal operating conditions, or at least maintain a spinning stall, so as not to cause damage to the engine and the aircraft itself."

Lu Yuying and Zhang Jiujiang next to them both brightened up after hearing this explanation.

For both aircraft designers and pilots, engine surge is one of the most undesirable failures.

Since it is a self-excited oscillation of the air, once it actually enters the surge state, it is too late to save it.

Especially when flying at low altitude, high speed or with heavy g-load, if power is lost and the aircraft becomes unstable, there is a high probability that the aircraft will be destroyed without enough time to deal with it, and both people will be killed.

It just so happens that surge is prone to occur under these circumstances.

Many first-class accidents are caused in this way.

For pilots, even if they discover the problem just one or two seconds in advance, they can avoid accidents to a large extent.

"If that's the case, would it be possible to install a sensor inside the compressor..."

Zhang Jiujiang was naturally the most excited.

"It's not that simple."

Chang Haonan smiled and shook his head:

"On the ground or on the test bench, the external airflow is relatively stable, and the accuracy of capturing abnormal conditions is relatively high. However, under real flight conditions, especially for fighter jets that require frequent large overload flights, even if no occurrence occurs Surge and the flow conditions of the compressor are also relatively chaotic. If you just put a sensor, the false alarm rate may be very high."

For automatic control systems, the severity of false alarms and missed alarms is at least the same.

"So you are going to verify this system on the J-10?"

Although Lu Yuying is not responsible for Project No. 10, he is naturally concerned about the projects of the same institute.

"Yes, in order to achieve active stability control, the premise is to integrate flight and propulsion. The most promising one at the moment is the J-10 that uses a three-axis four-redundant digital fly-by-wire flight control system. And on the other hand, Single-engine aircraft also have higher safety requirements."

In fact, the J-10 itself has achieved full-envelope first-class flight quality and "no scruples" control at the aerodynamic level.

What Chang Haonan has to do is to achieve this at the aviation power level.

But he had another reason that he didn't say -

The air inlet of the Su-27 is a bit too simple, and it is possible that data under certain circumstances cannot be collected...