Chapter 276 Taming the Airflow
While the two were circling the plane and chatting, the ground staff from the 611 station 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 is that at Chang Haonan's insistence, a side-opening radome is used, so that there is 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 still feels different from the J-7F, where "the aircraft I drew landed on the ground." Same.
From a relatively close position, he could already see that the aircraft's radome actually contained an old radar.
"Is this 208A?"
Currently, China's radar models are still on the eve of a technological explosion. There are only a few models that can be installed, and among them can truly be called " "Radar" instead of a range finder can also guide semi-active radar bombs. Apart from the 1471/1472 on the J-8C, there are basically only 208A left.
This is the radar that was equipped with the J-8B in the past. This model was used by the Air Force to successfully complete the Aspad target shooting test for the first time.
“Yes, the 1452 small-diameter radar originally planned to be developed by the 14th 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. Top it up."
At this point, Lu Yuying seemed to suddenly remember something:
"Do you want to take a photo? This time we brought a camera."
< br>Chang Haonan hesitated for a moment, and finally nodded:
"That's fine."
"I just happened to call the pilot comrades over, and I will take a group photo with the foreigners later."
Hearing what Lu Yuying said, Chang Hao Nancai noticed that in addition to the ground staff, there were 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 this posture, he must have just rushed over 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 83rd Project to observe the air flow separation on the surface of the No. 03 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 by his name, also stared at Chang Haonan for a few seconds. It was not until he walked closer that he remembered the latter's identity:
"You are from the 601 Institute That...Engineer Chang? The one who flew on my plane?”
"Uh... yes, we cooperated well that time."
Chang Haonan just nodded when he heard Lu Yuying next to him interrupting:
"Old Zhang, Xiao Chang Can’t be considered a person from 601..."
This topic is already a daily topic for the former, but Lu Yuying feels that she should emphasize it, lest the other party forget 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-7 at Factory 172, 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. ”
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..."
This term is indeed a bit general, 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 MA60 wing for 603 last year.”
Chang Haonan, who knew that this was a brand new concept, explained:
“Since the flutter of the wing can be controlled through active means, can it be controlled using a similar idea, or at least predict the engine gasp in advance? Vibration? ”
“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 it could be carried out in time at this time Intervening can avoid entering abnormal operating conditions to a large extent, or at least maintain a spinning stall state, so as not to cause damage to the engine and the aircraft itself."
Lu Yuying and Zhang Jiujiang heard next to them. After this explanation, everyone's eyes lit up.
For both aircraft designers and pilots, engine surge is one of the most unwilling failures to face.
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 overload, if the power is lost and the aircraft becomes unstable, there is a high probability that the aircraft will be destroyed without any time to deal with it, and there will be fatalities.
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, capturing The accuracy of abnormal conditions is relatively high, but under real flight conditions, especially for fighter jets that require frequent large overload flights, even if surge does not occur, the flow conditions of the compressor will be relatively chaotic. If there is 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 the No. 10 project, he is naturally also concerned about the projects of the same research institute.
“Yes, in order to achieve active stability control, the premise is to integrate flight and thrust. The most promising one at the moment is the J-10 which uses a three-axis four-redundant digital fly-by-wire flight control system. . 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 at the aerodynamic level. scruples” manipulation and other characteristics.
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...
(End of this chapter)