Finally found it!

The fixed skin is not easy to be damaged, and this kind of place that can be rotated may appear, and now, everyone is gathered around, yes, there is indeed a problem, but what is the cause of the problem?

There shouldn't be a problem here.

"There are three possible scenarios for such sabotage." Song Lao kept looking at this place and began to analyze calmly: "First of all, it may be that the mechanical structures interfere with each other, causing the hatch to be displaced, or it may be that the retraction mechanism is working abnormally, which caused this accident, and of course, it may also be caused by aerodynamic damage. ”

There was a problem with the mechanical structure, and as a result, the hatch was bent, but if this had happened, there should have been a similar situation before, and it was impossible to have this flight.

As for the destruction of the aerodynamic torque, it seems impossible, right? What aerodynamic moment can push it to a deformation of five centimeters?

So, the most likely thing is that the receiver and release agency is working abnormally? This is a special case, or rather, an occasional failure.

"For us, this is just a small problem, it should be an occasional failure, fix it, let's continue the test flight." Finally, Song Lao made a decision.

In test flights, there will be some temporarily unexplained phenomena, which do not occur every time, but occur by chance under special circumstances, which is called accidental accidents.

"No, I don't think it was an accident." Qin Feng said: "The first time we flew at supersonic speed, the hatch was broken, and it was very likely that it was caused by the aerodynamic torque. ”

"Impossible, let's do a simple calculation, we can know that there is not so much pressure there, besides, this design, we have been using, J-7 J-8 can fly to twice the speed of sound, and there is no hatch that is damaged by air pressure, we still repair it first, and then test flight, it can't affect our progress."

Progress! Now the test flight progress has been put forward again, because the time for the No. 1 chief to come to inspect has been determined, and they must find out the performance of the aircraft before the No. 1 chief inspects, and then arrange a set of qualified actions to win the affirmation of the No. 1 chief!

The pneumatic torque that Qin Feng said was first ruled out, and he had done it before, and there was nothing wrong, so it shouldn't be such a problem, Song Lao was right, occasional failure, it should be very possible, the biggest possibility is that the landing gear is not flexible this time, and it was touched.

"Fix the hatch and move on to the test flight." Song Lao said.

Now that Song Lao has made a decision, Qin Feng can only retract his thoughts, and in the next few test flights, this failure did not reappear.

Could it really be an accidental failure?

Qin Feng still didn't relax.

The maneuverability of the J-10 still makes Qin Feng very satisfied, in the past few days of test flights, he has become more and more bold, and his movements are becoming more and more flexible.

On this day, Qin Feng began to fly and dive, and when he swooped down from a height of two thousand meters, he heard the sound of the malfunction again!

"The landing gear hatch is deformed again!" When landed, looking at the deformation of the landing gear hatch, all the technicians were deflated, the first encounter, can be explained by occasional failure, the second encounter, then it is not an occasional failure, there must be a problem!

So, what's the problem?

"This time, I found it when I dived down, and I dived into a low altitude, although it has not yet reached supersonic speed, but the air is dense, so I think the problem must be in the aerodynamic destruction." Qin Feng said: "Although we didn't encounter it on the Jian-7 Jian-8, those planes have different air intake methods from ours, so they can't be compared." ”

J-7 is the nose air intake, J-8 is the nose or both sides of the air intake, which has no effect on the belly, but it's different, J-10 is the belly air intake, and the front of the air intake is the position of the landing gear, that is, the air flow of the air intake may also affect the hatch here!

You know, a fighter like the F-16 has already taken advantage of the position under the nose of the front to pre-compress the air intake!

"Comrade Qin Feng's analysis is reasonable, we cannot act according to the previous empiricism, and when we encounter problems, we must seriously think and analyze them to solve them." Song Lao said: "However, how do we determine that it is the effect of the aerodynamic moment? ”

If you want to know that it is a problem of pneumatic torque, then add a barometric pressure sensor at this position? But in that position, the barometric pressure sensor is not easy to fix, because the hatch is to be rotated.

"I propose to add a displacement sensor to the hatch to detect the displacement of the hatch at different speeds." Qin Feng said.

The displacement sensor, which can be fixed at the door of the cabin without having to rotate with it, is much easier than a barometric pressure sensor.

"Okay, let's try." Song Lao said: "Repair the hatch and increase the sensors. ”

"However, we are running out of time, and there are still some subjects that have not been tested!"

"Now this problem was discovered in a test flight, and since it was discovered, it must be solved." Song Lao's attitude was very firm: "If this kind of problem arises when performing for the chief, should we continue to perform, or will we return and land?" ”

If you find a problem, you have to solve it, now, let's do it!

By the next day, everything was in place, and when it was linked to the flight control system, the data could be sent back directly during the test flight.

On the ground, the technicians were stunned as they looked at the data transmitted back in real time.

Sure enough, the hatch was moving!

When the speed is small, the movement is not obvious, as the speed increases, the movement is faster and faster, and when the speed reaches 800 km/h, the deformation has reached 3.8 cm!

This is how the hatch was destroyed, the last time when Qin Feng flew at supersonic speed, the hatch finally couldn't bear it anymore and began to deform!

The problem was found, and sure enough, it was the aerodynamic moment that they thought was the most unlikely, because this number was increasing with the increase of speed, and as the speed increased, the relative velocity of the air increased, which meant that the air pressure on the surface increased, who would have thought that it would increase to the extent that the hatch door would be deformed!

"We had to increase the strength of the hatch and improve our design immediately!" Song Lao said.

Now what happened to the hatch is caused by the insufficient strength of the hatch, so it is necessary to increase the strength of the hatch, so that the problem can be solved, where is not enough to make up for it, and the Su-27 also did this.