The Military-industrial Scientific Research System of the Academic Master Chapter 61

Chapter 61 Let's take a test flight [Please follow up! 】

At the front row of the conference table, Yang Fenghao and several other project team leaders gathered together to communicate quietly.

Before the August 3rd Project, the J-8B had conducted flight tests with four PL8 short-range air-to-air missiles.

Based on the results at that time, the adverse impact of the missile on the steering surface efficiency was within an acceptable range.

However, Aspad is a beyond-visual-range air-to-air missile with a large volume and weight. This is the first time for China Aviation Industry to come into contact with related design issues.

As Chang Haonan said just now, aerodynamic analysis at high speed and high angle of attack is still based on experience.

Since I have never seen it before, I can't say that I have any experience, let alone analyze it.

Similar to the situation at the time of the MA60, problems involving the rudder surface are difficult to restore using the wind tunnel alone.

And if you directly follow Chang Haonan's calculation results to conduct a flight test in one step, the risk will be relatively high.

The safest way is of course to conduct a large number of test flights, starting from relatively mild flight conditions, and gradually approaching the theoretical position where the aileron reaction occurs, so as to maximize safety.

But in this case, the progress may be delayed by weeks or even months.

So several people discussed it for a while, but could not come up with a solution that everyone thought was feasible.

In the area behind the conference room, the discussion became even more lively.

Even Chang Haonan had a lot of people gathered around him, looking at the report he brought over.

In fact, what was just taken to the front and projected onto the screen through the projector was only the final conclusion he reached after highly condensing and summarizing it.

In order to reach this final conclusion, he analyzed many problems in the past day and a half, some to verify the accuracy of the algorithm, and others to provide data for the calculation of aileron efficiency.

These analyzes cannot be said to have any guiding significance for the already highly completed August 3rd Project, but for the designers around Chang Haonan, compared to the somewhat shocking conclusion just now, it is the content they are more familiar with that attracts them. More powerful.

“This part of the calculation is...the pressure difference between the upper and lower wings when the aileron deflects?”

An engineer with thick glasses and gray hair picked up a few pages of the report, looked over them several times, and then asked in a somewhat surprised tone.

"That's right, this is the upper and lower wing surfaces at the three positions of 15%, 65% and 95% of the wingspan when the ailerons are deflected up and down 3° and 5° respectively under the flight condition of Mach 0.6 speed and 10° angle of attack. Pressure difference distribution map."

Chang Haonan raised his head and glanced at the contents in the opponent's hand, and showed a smile that seemed to succeed.

What the opponent held in his hand happened to be a wing pressure difference cloud map he made to show off his skills.

Originally, the computer output was just an ordinary line graph composed of discrete data points, but he spent about three hours plotting the data on the line graph on the cross-section of the wing.

For people who are used to seeing scatter data, seeing this kind of three-dimensional cloud image for the first time is no less shocking than seeing a movie for the first time.

"This data is quite similar to the results we obtained during previous test flights. Upward and downward deflection of the ailerons has the opposite effect. Downward deflection increases the lift and drag on the wing, while upward deflection reduces the lift and drag on the wing. "

A middle-aged female engineer next to him leaned over to take a look and commented: "And Dr. Chang's expression is very intuitive, especially the trend is easy to see."

“Yes, this is also one of the advantages of our digital design and simulation.” Chang Haonan nodded and replied:

"We can clearly see that the difference in lift on both sides of the wings causes the aircraft to roll, and the difference in the resistance of the wings on both sides will cause the aircraft to deflect and cause sideslip. After sideslip, an aileron roll will be offset. The effect of torque is reduced, thereby reducing the control efficiency of the aileron.”

“When the speed and angle of attack are relatively low, mainly in the subsonic range, this drag is the main reason for weakening the aileron efficiency, but in general the impact is very small, and it can be reduced through differential ailerons. alleviate this problem.”

Having said this, Chang Haonan took out another page from the report in his hand and handed it over, and then continued:

“Once it enters the supersonic range or flies at a high angle of attack, the moment generated by the elastic deformation of the wing will rapidly increase, becoming the main factor affecting the aileron efficiency, which is what I said before.”

"Looking at this table, after considering the wing elasticity, the aileron should have provided a clockwise rolling moment, but it is obvious from the calculation results that the bending moment of the left wing root is smaller than that of the right wing root. , which shows that the aircraft in this state generates a counterclockwise rolling moment around the roll axis, that is, aileron reaction occurs. "

As Chang Haonan's explanation continued to deepen, he could even feel that the attitudes of people around him towards the digital design team, and even towards digital design itself, were changing at a speed visible to the naked eye.

The main reason is that the several simulation results that Chang Haonan produced in succession are consistent with the test flight results they obtained before, and the gap is not big.

This is real persuasive power.

Many people still had a dismissive or disdainful expression when they first came over, but after listening to his explanation carefully, their expressions or eyes changed dramatically.

At this time, Yang Fenghao and others also ended the discussion and motioned everyone to return to their positions.

“Dr. Chang, now I really obey you.”

After the crowd around Chang Haonan gradually dispersed, Lin Shikuan, who had just been squeezed out, sat back down next to him with admiration on his face:

"The gray-haired old man just now is named Xu Jin. He has always felt that our digital design team is a complete waste of project resources. Every time we have such a meeting, he will target us intentionally or unintentionally. As a result, he only asked one question this time. , and then didn't say a word.”

“Old comrade, it's understandable that you have concerns about new things, but as long as you can present strong enough facts, I believe anyone who pays attention to science can be convinced.”

Chang Haonan did not look up, but replied while sorting out the report that had just been disrupted.

At this time, Yang Fenghata in front of the conference room also spoke again:

"I think after the exchange and discussion just now, everyone should be able to see that the issues raised by Comrade Chang Haonan are worthy of our serious consideration, so our next focus is to verify the aileron reaction effect when bombs are loaded. When will it appear?"

If Yang Fenghao had made such a decision twenty minutes ago, he might have encountered some objections, but after circulating the report just now, everyone has some trust in Chang Haonan's simulation calculation results.

Just like this, the finalization of the design of the 83rd Project will inevitably be delayed.

However, just when everyone was worried about the progress of the project, Chang Haonan spoke up again.

“I think the test flight verification work on aileron anti-effect can be divided into two stages. If it goes well, it should not delay too much progress.”

(End of this chapter)

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