Chapter 1303 Flight Quality

"Supersonic maneuverability is better than F22?"

There was a hint of surprise in Lin Jihong's tone:

"But I don't think there's any specific mention of this in the project requirements..."

Although he holds the title of deputy chief engineer of the project, he is actually a graduate of electromagnetics and is not even an employee of Rongfei Group. Instead, he is from the Aviation Industry Integrated Technology (301) Institute. He had been assisting Yang Wei in program planning in the form of external aid. He was officially integrated into the R&D team only after the results of the fourth-generation aircraft selection were confirmed. Therefore, he did not know much about the bidding process.

"Well... at the time, I considered this requirement to be difficult, and more importantly, there was a lack of a comprehensive reference..."

Yang Wei explained:

"You should understand that for the sake of rigor, the written requirements given by Party A are generally compared with our own previous generation equipment... In short, in order to avoid obstruction in the subsequent finalization process, the content of benchmarking with F22 was not written as a formal content."

"However, I have communicated with the Air Force Equipment Department and the pilots who fought head-on with the US Air Force last year. They all said that the most profound impression the F22 left on them, apart from its stealth performance, was its high-speed flight performance. If the F22's maneuverability in the subsonic range is still just "good" in the normal sense, then once it enters supersonic speed, it can be said to be in another field completely..."

Most of the F22's parameters are still secrets of the US Air Force, so this kind of comparison can only be done through analysis and judgment of public information and oral accounts of some pilots who have encountered it.

Lin Jihong showed a look of enlightenment:

"So, an extra set of arched strakes were added behind the canard that existed in the concept design stage?"

He started preliminary research on stealth technology in the early 90s and participated in the development of the No. 137 J-7IIS stealth technology verification aircraft. Although he cannot be said to be an expert in aviation technology, he certainly understands some basic concepts and principles.

“This is the result of aerodynamic calculations combined with wind tunnel verification.”

The development of the fourth-generation fighter has just gotten on track, and Yang Wei is also willing to take some time to integrate the newly joined electromagnetics department with the traditional aerodynamic/structural design department:

"In order to ensure the stealth performance of the front hemisphere, the canard has made some compromises in shape and layout, and its efficiency is insufficient in a specific attitude and speed range. The newly added winglets combined with the canard controlled by the flight control system can not only strengthen the vortex generation, but also control the flow direction of the vortex, thereby effectively improving the aerodynamic characteristics and lift characteristics of the main wing at high angles of attack."

"Of course, the problems you and Lao Kong mentioned just now, that is, the stealth level in the lateral and rear directions, and the relatively small all-moving vertical tail is too sensitive to vortices, and it is difficult to ensure the lateral stability of the aircraft under extreme conditions. Since these two points exist objectively, they are the problems we need to solve next, or make a choice..."

Lin Jihong opened his mouth and wanted to say that the existence of this pair of arched edge strips would enhance the radar reflection from the side and below (above) to a certain extent, which would be especially unfavorable when facing dual-band early warning aircraft like the KJ-2000.

But this time, he kept the words in his throat.

He has realized that unlike the J-7IIS which was designed solely to verify stealth technology, the new generation of fighter jets is a comprehensive project that requires comprehensive consideration of overall performance. In many cases, for the sake of overall benefits, some decisions that may seem imperfect in some areas have to be made.

Therefore, Lin Jihong decided to make a decision after listening to the second half of the meeting.

At this time, Kong Chengan also took over the topic very appropriately, and switched the content projected on the screen to the wind tunnel test part he was responsible for:

"I've already talked a lot with Mr. Yang and Lao Lin, so I'll skip the previous part and continue directly from the second part..."

"We also verified the idea of ​​adding a stabilizer in Fucheng. We mainly considered setting one or a group of ventral fins below the root of the main wing. This is of course a very conventional solution, but we still found some unexpected conclusions during the test..."

The scheme selection a year ago has determined the basic layout of canard + large delta wing. Now that we have entered the actual design stage, what needs to be focused on are some minor details on the aircraft.

Especially for the new generation of fighter jets, these seemingly insignificant places may even become the key to determining the success or failure of a model.

Kong Chengan stood up and took out a few photos from the bag beside him, and placed them one by one on another scanning projector in the middle of the conference table.

Because the meeting was prepared in a hurry, the pictures in the materials were all printed in black and white. Some simple charts were fine, but things that were too complicated were really hard to see clearly.

"Please see, everyone. We have initially selected six characteristic schemes, namely, trapezoidal fins, curved fins and slender curved fins with single and double configurations, and then set different installation positions and internal anhedral angles. Of course, for the sake of stealth performance, the fin design does not have wing blades, but adopts a clean configuration..."

Having said that, he glanced at Lin Jihong opposite him out of the corner of his eye.

It can be seen that after hearing the last sentence, the latter's expression finally eased a little.

"The improvement of these solutions in terms of lateral stability and anti-spin performance under extreme conditions are basically consistent with our qualitative experience in the past. The best solution is a double trapezoidal fin with an external anhedral angle of about 30°. The specific data is between pages 95 and 110 of the document, so I will not elaborate on it."

"The really interesting thing is that when we combined the tail fin of this scheme with the slightly upward and inward-retracted tail section of the fuselage, we found that it had a very obvious drag reduction effect within a certain range of angles of attack, especially in the high subsonic to transonic range..."

"The initial speculation is that when the airflow flows through the tail section of the fuselage, due to the presence of a certain upward angle, the airflow is prone to separation. A properly designed double ventral fin can form an airflow acceleration channel at the tail section of the fuselage, slowing down and reducing the airflow separation at the tail section of the fuselage, thereby achieving the effect of reducing drag."

"Of course, this inference is not the final conclusion. The nature of this phenomenon still needs more in-depth research... Perhaps some theoretical help is needed, but if it can be properly utilized, it can effectively reduce the difficulty of achieving supersonic cruise. Moreover, considering that this drag reduction effect occurs near the trailing edge flaperon, it can also significantly improve the aircraft's maneuverability..."

For an aircraft operating within the normal performance range, the process of "breaking the speed of sound" is often more difficult than "maintaining supersonic speed".

Therefore, some third-generation and a half fighters such as EF2000 and Su-35 sometimes advertise themselves as having "partial" supersonic cruise capability, that is, breaking the sound barrier in afterburner state, and then turning off the afterburner to maintain supersonic flight.

Although the fourth-generation Chinese aircraft certainly does not need to play such word games when the WS-10G is expected to catch up with the construction schedule, reducing resistance and stability at the same time will undoubtedly greatly help improve the flight quality of the aircraft.

After the J-10 was put into service, Rongfei Group received a lot of feedback from the aviation forces. In addition to the routine praise and affirmation, there was also a lot of first-hand information provided by pilots.

These contents are not technical materials, and therefore lack rigorous data analysis. They are often just qualitative feelings described in simple language, but they have given the design team many new insights into flight work.

Therefore, during the development of the fourth-generation aircraft, they specifically proposed that they should not only build an advanced aircraft, but also an aircraft that is easy to fly.

The flight quality of an aircraft is the key factor that most directly corresponds to whether it is easy to fly.

After Kong Chengan finished his introduction, Yang Wei cleared his throat and began to summarize the period:

"Comrades, you should have felt that the comprehensive requirements for various aspects of performance of the new generation of aircraft are unprecedented, and our main task in the next stage is to optimize the relationship between flight performance and stealth performance, and strive to find an optimal balance between the two. I hope that you can unite and cooperate under the guidance of this great goal..."

It is impossible to resolve all the complicated tasks in one meeting.

So he just said a few nice words, then changed the subject and began to arrange the specific work that would follow.

After the meeting, Yang Wei specifically called the two deputy chief engineers to his office to give them some additional instructions.

However, before the meeting of the three people began, the intercom on the table rang.

It's the number of the administrative office.

After the call was connected, Gao Wenguang's voice soon rang out:

"Mr. Yang, the 606th Institute sent us a letter, saying that they hope to use the microwave darkroom in Yudu right away..."

Yang Wei frowned slightly, revealing a slightly confused expression:

"Why don't they just go to the Electromagnetic Testing Center directly? Why do they have to contact us specifically?"

"The other party said that they would not verify the radar reflection of the engine tail nozzle alone, but would combine it with our aircraft model for an overall test!"