Chapter 66 Solution [Please order first! ! ! 】(15)
After confirming that there is no problem with the accuracy of Chang Haonan's simulation method, the remaining work is to conduct several more test flights to obtain detailed data on the aircraft when aileron reversal occurs.
With the efforts of the test flight team, the two prototypes 03 and 04 took off in turns, and it took only five days to complete all the test flights.
In the end, it was proved that Chang Haonan's calculation was completely correct. When the airspeed and elevation angle of an aircraft with bombs reach a certain value, aileron reversal will occur.
In fact, even if the mount is adjusted to two Aspades plus two Thunderbolt 8s that are closer to the actual combat status, this situation is still unavoidable, but it will appear later.
With the end of the test flight, Chang Haonan's system status also changed.
[Scientific research points: 85
Theoretical level: LV2 (0/10000)
Engineering experience: LV1 (70/1000)
Management ability: LV0(65/100)
Comprehensive ability: LV1
Projects in progress: 0
Projects that can be carried out: 1]
Compared with before, 10 scientific research points have been added, and up to 50 points Management experience.
It can be considered a good harvest.
...
The afternoon of the day when I got the complete test flight data.
It’s still the same conference room, with the same people as last time.
Just because of Chang Haonan's unusually outspoken performance, today he, Yao Mengna and Lin Shikuan were directly invited to the seat near Yang Fenghao in front of the conference table.
This time, the atmosphere in the venue became much more solemn——
Aileron reversal occurs at less than twice the speed of sound, and the corresponding deflection angle when aileron reversal occurs is only 10°.
The corresponding roll rate is less than 30° per second, and it takes 3 seconds to make an ordinary 90° roll away action.
This is completely unacceptable for an interceptor aircraft that focuses on high-altitude and high-speed capabilities.
So everyone ruled out the answer of limiting flight performance through flight control from the beginning.
The wings must be modified.
In 1996, people were not so shy about smoking in public places, so not long after everyone entered the conference room, the whole room became filled with smoke.
Chang Haonan hated the smell of smoke very much, so he moved slightly closer to the window.
The first person to speak was of course Yang Fenghata:
“Don’t feel discouraged. Since the problem exists, it is better to find it as early as possible. The earlier, the more progress we will delay. Less, so from this point of view, this is a great gift given to us by Comrade Xiao Chang and Comrade Xiao Yao after joining the August 3rd Project Team.”
After a moment of silence, I don’t know who it is. The first one took the lead in applauding.
What followed was thunderous applause.
This sentence not only praised Chang Haonan and Yao Mengna, but also boosted the morale of the entire project team.
After the applause gradually died down, Yang Fenghata continued:
“In order not to delay the test flight progress of Project 83 as much as possible, I decided to let the No. 03 prototype go according to the previous plan. It will be transferred to Yanliang at the beginning of next month to conduct test flights that do not involve bombing items first, while the No. 04 verification aircraft will remain in the 112th factory for modification. "
"Considering this, the No. 03 aircraft will be carried out. It can no longer be regarded as a full-state verification aircraft, so after the wing problem is solved, a No. 05 verification machine will be built using spare parts and will be carried out with the No. 04 for a full-state verification flight. "
"In this way, we can have relatively ample time to improve the wing."
A few minutes later, Liu Ming, the deputy chief designer sitting first on Yang Fenghata's left hand side, finally opened the door mouth.
“Comrades, according to the data obtained from the test flights in the past few days, the cause of aileron reversal is not complicated, but is the common problem of boundary layer accumulation.” “The simplest solution is still A pair of wing knives were added to the most intense lateral flow on the wing."
Chang Haonan nodded slightly.
As expected, the engineers of Institute 601 chose the same solution as later generations.
In fact, from the current perspective, it is indeed the best way.
During the flight of an airplane, the airflow on the upper surface of the wing will automatically flow toward the wingtip, and accordingly, the boundary layer will gradually accumulate toward the wingtip.
The accumulated airflow will eventually separate at the wing tip, and this separation process will bring a large shear force, causing obvious elastic deformation of the wing, thus causing the aileron efficiency to decrease or even become counterproductive.
To avoid this situation, the simplest way is to add a pair of baffles on the upper surface of the wing to block the lateral moving airflow.
That is, the Wing Knife.
However, some people still put forward different opinions
“But Mr. Liu, there are already two pairs of wing blades on the J-8-3 wing. If we add another pair, Is it a bit..."
Although the wing blade is simple and effective, it is not without cost. The essence of its working principle is to cause the leading edge vortex to break early, thus reducing the lift coefficient and stall angle of attack, which is very important for flight performance. There is still a certain impact.
Moreover, designing too many wing-wing knives will not look good in terms of appearance.
"Is it possible to consider merging three sets of small wing blades into one large set of wing blades, like the J-6?" another person asked.
However, it was quickly rejected:
"That can only reduce a little weight, but the impact on lift and over-stall capabilities will be greater. For a aircraft as big as the J-8-3 The gain outweighs the loss for the aircraft.”
The heated discussion lasted for about half an hour, but there was still no solution that everyone agreed on.
Finally, someone turned their attention to Chang Haonan, who had been looking down at the report in his hand without speaking.
"Dr. Chang, since you discovered this problem, I wonder if there is a better solution?"
The conference room gradually became quiet.
Chang Haonan stood up and walked to the blackboard with test flight results and design drawings.
“First of all, I want to tell you some good news.” Chang Haonan turned around, looked at the engineers in front of him and said:
“After the efforts of the entire digital design team in the past few days, we have The parametric modeling of the aerodynamic and structural design of the J-8-3 prototype has been basically completed, so the time spent on modifying the design should be lower than expected.”
Another unusual result.
The optimization design of the aircraft aerodynamic shape requires the evaluation of various aerodynamic shapes, so the aircraft aerodynamic shape needs to be modified repeatedly in order to improve its aerodynamic performance.
Once you have a parametric model, you can drive changes in the geometric model by changing the design parameters, thus greatly shortening the geometric model modeling cycle.
Lin Shi Broadband's people had been working on a task for a year and a half without making much substantial progress, but Chang Haonan solved it in less than ten days after coming over.
Although the latter did not mention his name, almost everyone agreed that this was a manifestation of his hidden merit and fame.
Then there was another burst of applause.
Chang Haonan stretched out his hand and pressed it down to signal to keep a low profile:
"As for the improvement plan for the wing, I do have an immature idea." Chang Haonan picked up a He drew on the design drawing with an unsharpened pencil and continued:
“The idea of adding a pair of wing blades is no problem, but according to my simulation results, the cross-airflow on the wing surface is the densest. The area is near the trailing edge of the wing. "
"So I think the existing upper and lower aileron hinge fairings can be expanded into trailing edge wing blades, so that the added dead weight is almost negligible, and the The look and feel is also closer to the original double-wing knife.”
"At the same time, leading edge devices can be introduced into the wing design, such as leading edge flaps or leading edge slats. This can not only compensate for the impact of wing blades on the lift coefficient and stall angle of attack in the middle and low speed range, but can even greatly Improve the low-altitude and low-speed performance of the aircraft!”
(End of this chapter)