"The engine is running at high speed, so if there is a problem with the engine, such as the resonance between the engine and the body, this phenomenon may occur, and it has also happened in Shenyang before, because one of the hydraulic pumps of the engine resonates, which eventually causes the entire aircraft to burn out."

It is necessary to be rigorous in conducting scientific research, and it is even more so when studying aircraft, because a small mistake may lead to major consequences and huge losses.

"However, the probability of problems with the engines of our aircraft is not very large." Qin Feng analyzed: "Our engine is the original Spey engine, this engine is quite mature and reliable, if it has a problem, for example, resonates with the body, then when it is on the ground, we should be able to find it, after all, on the ground, we have also driven afterburner to work, but it turns out that this scene did not appear." ”

Qin Feng began to analyze it seriously, and when he said this, everyone nodded.

This time, everyone was confused, because no one had encountered this situation, and no one knew how to deal with it, but now, Qin Feng's analysis was reasonable.

"If it's not the engine, then the fuselage is left, our fuselage is blown through the wind tunnel, the overall shape is streamlined, in the air, it is said that there should be no problems, so now our fuselage is trembling, and the biggest problem may appear on our wings."

The wing is one of the main components of the aircraft, it is precisely because of the wing that the aircraft can have lift, with lift, the aircraft can fly, and now, the wing of the aircraft, if there is a problem, it will bring terrible consequences.

Flutter, caused by the wings?

"When flying, it can be found that this flutter starts after the speed increases, the greater the speed, the more obvious the flutter, in the airplane, the wing is used to provide lift, the faster the speed, the greater the lift, which should be related."

"Could it be that our wings are machining the problem?" Someone asked.

If there is a problem with the processing, resulting in an unbalanced wing, a swirl in the surface airflow, etc., this situation may eventually occur, but this is our first aircraft, and we are quite careful when processing, how can this problem occur?

If it's not a problem with processing, it's a problem with design?

"Our aircraft adopts a large aspect ratio fixed swept design, this form of wing, we are more familiar with, can be well mastered, at the same time, we also know that this swept wing design has a more serious wingtip stall problem, because the wing of the control of the airflow is insufficient, so we added wing knives to the wing of this aircraft to control the stall of the wingtip."

As a test pilot, being able to say these technical problems has impressed many engineers present, and now, some people have questions, Qin Feng said this, is he saying that there is a problem with the design of the wing? That is difficult for this part of the designers to accept, but they didn't ask any questions, because Qin Feng had already said that the wing knife was added to control the wingtip stall.

"Are you saying it's a wingtip stall?" Elder Chen asked.

Qin Feng shook his head: "No, I don't know about this, but since we have blown through the wind tunnel, I believe that we have solved this problem, I mean, although we are very familiar with the design of this wing shape, but this is the first time we have designed a wing of this length, and when we blow the wind tunnel, we use a model of equal scale, so some problems cannot be exposed, for example, the aeroelasticity of the wing with a large aspect ratio." ”

Qin Feng's words immediately made everyone stunned.

Many of the wings with large aspect ratio are used in high-altitude aircraft, such as U2, and for China, J-7 is the first large aircraft designed by itself, and the length of the wing is also the longest, so the wing of this kind of aircraft may have aeroelastic problems in the air, which is accompanied by structural tremors.

In a few years, this will not be a problem, because China has begun to conduct special research on this topic, and there are a large number of talents in this area, but now no one can correctly understand the risks contained in it, Qin Feng also went to the hospital to check his body, and suddenly thought of a foreign paper he had read.

"But we can't take this guy to the wind tunnel." Someone said.

This problem must be solved in the wind tunnel, but it is impossible to send this real plane to the wind tunnel, and its wings are found to be shaking in the wind tunnel.

Even if you know about it, what can you do? You can't go to the wind tunnel, you can't verify it.

"Yes, so, we can only solve it in practice, I suggest, you can give the leading edge of the wing, reduce the counterweight."

The problem of wing tremor has long been thought of by smart people, and in the design of aircraft, this can be regarded as a bionic knowledge.

This imitation is the dragonfly.

The dragonfly's wings are membranous, light and thin, and can be flapped dozens of times in a second, but this wings of the dragonfly are particularly stable, and there will be no problems with being so thin, what is going on?

Scientists caught dragonflies and studied their wings, and it was easy to find that there was a square "mole" on the front edge of the end of each wing, which was thicker than the rest of the wing, and other membranous winged insects also had similar "wing moles" or "wing eyes".

In order to study this thing, the scientists removed this thing, and as a result, the dragonfly, which was originally flying fast and steady, suddenly became wobbly, as if drunk.

This example proves that wing moles can help dragonflies maintain balance, so in the design of the aircraft, engineers imitated dragonflies' wing moles and added extra weight to the leading edge of the wing, so as to keep the wing stable.

Of course, this has the knowledge of engineering mechanics in it, in short, almost all aircraft wings are designed like this, and there is no need to add additional special devices, as long as the frame inside is thick, this is fine.

The wing of the J-7 is naturally like this, but everyone has not thought of another problem, that is, the aeroelasticity of the wing!

If you want to solve this problem, you need to reduce the weight of the wing, and even use composite materials to make the wing, in later generations, many aircraft wings have begun to use composite materials, in terms of solving the aeroelasticity, has outstanding advantages, and now, there is no other way, but to try to reduce the weight here!