The military-industrial scientific research system of the academic master

"Supersonic maneuverability is better than F22?"

Lin Jihong's tone was a little surprised:

"But I see that this item is not specifically mentioned in the project requirements statement..."

Although he holds the title of deputy chief engineer of the project, he actually has a background in electromagnetics. He is not even an employee of Rongfei Group, but from the Aviation Industry Comprehensive Technology (301) Research Institute. He has been assisting Yang Wei in the form of foreign aid. The project planning was carried out, and it was not officially integrated into the R\u0026D team until the fourth-generation machine selection results were confirmed, so I didn’t know much about the bidding process.

"Well...it was quite difficult to consider this requirement at the time, 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 usually compared with our own previous generation equipment... In short, in order to avoid hindrance in the subsequent finalization process, the content of the comparison with the F22 has not been officially Write the content in.”

"However, I have communicated with the Air Force Equipment Department and pilot comrades who had head-to-head combat with the US Air Force last year. They all agreed that the most profound impression left on them by the F22, apart from its stealth performance, was its flight under high-speed conditions. Performance, if in the subsonic range, the F22's maneuverability is only in the 'good' category in the normal sense, then once it enters supersonic speed, it can be said to be a completely different realm..."

Most of the parameters of the F22 are still classified by the U.S. Air Force. Therefore, this benchmark can only be completed through the analysis and judgment of public information and the oral statements of some pilots who have encountered it.

Lin Jihong showed a clear look on his face:

"That's why an additional set of arched edges were added behind the canards that existed in the concept stage?"

He has been engaged in pre-research on stealth technology since the early 1990s, and has also participated in the development of the No. 137 J-7IIS stealth technology demonstrator. Under the influence, although he is not good at aviation technology, he is certain about some basic concepts and principles. Still understand.

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

The development of the fourth-generation fighter has just got on track, and Yang Wei is also willing to spend some time to bridge the connection between the newly added electromagnetics department and the traditional aerodynamic/structural design department:

"In order to ensure the stealth performance of the front hemisphere, some compromises were made in the shape and layout of the canard wing. The efficiency is insufficient in specific attitude and speed ranges. The newly added side wing combined with the canard wing controlled by the flight control system, It can not only enhance the generation of vortices, but also control the flow direction of the vortices, 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 are the stealth level in the side and rear directions, and the relatively small full-motion vertical tail is too sensitive to vortices, making it difficult to ensure the lateral and azimuth stability of the aircraft under extreme conditions. , since these two points exist objectively, that is what we need to solve in the next step, or make a choice..."

Lin Jihong opened his mouth. He originally wanted to say that the existence of this pair of arched side strips would enhance the radar reflection from the lower (upper) side to a certain extent, which is especially unfavorable for dual-band early warning aircraft like the Air Police 2000.

But this time, the words were held in his throat.

He has realized that unlike the J-7IIS, which was simply designed to verify stealth technology, the new generation fighter jet is a comprehensive project that requires comprehensive consideration of overall performance. In many cases, out of consideration of overall benefits, some measures have to be made that are not locally sufficient. The perfect choice.

Therefore, Lin Jihong decided to make a decision after listening to the content of 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 have already said a lot in the exchange with Mr. Yang and Lao Lin just now, so I will skip the previous introduction and continue directly from the second section..."

"As for the idea of ​​adding a stabilizer, we have also verified it in Fucheng. The main consideration is to install one or a group of ventral fins under the root of the end of the main wing. This is of course a fairly conventional solution, but we still tested it during the test. Found some unexpected conclusions..."

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

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

As he spoke, Kong Chengan stood up, took out a few photos from the bag next to him, and opened them one by one to another scanning projector in the center 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 too complex things were really hard to see clearly.

"Please see, we have initially selected six characteristic solutions, namely trapezoidal fins, arc fins and slender arc fins in single and double configurations, and then set different installation positions and dihedral angles. Of course, for the sake of stealth For performance reasons, the fins are not designed with wing blades, but adopt a clean configuration..."

Having said this, he looked at Lin Jihong opposite from the corner of his eye.

It can be seen that after hearing the last paragraph, the latter's expression finally softened.

"The ability of these solutions to improve lateral stability and anti-spin performance under extreme conditions are basically in line with our past qualitative experience. Double trapezoidal fins with an external dihedral angle of about 30° are the best. The specific data is between pages 95-110 of the information, so I won’t go into details.”

“What’s really interesting is that when we combined the tail fin of this solution with the slightly upward retracted fuselage tail section, we found that there is a very obvious drag reduction effect within a certain range of angles of attack, especially at high subsonic speeds. In the transonic range..."

"The principle of preliminary speculation is that when the airflow flows through the tail section of the fuselage, due to a certain upturned angle, the airflow is prone to separation. Properly designed double ventral fins can form an airflow acceleration channel in the tail section of the fuselage to slow down the air flow. Reduce the airflow separation at the tail section of the fuselage to achieve the effect of drag reduction.”

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

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

Therefore, some third-generation fighter aircraft such as the EF2000 and Su-35 will sometimes advertise that they have "partial" supersonic cruise capabilities, that is, they can break the sound barrier under afterburner, and then turn off the afterburner to maintain supersonic flight.

Although the turbofan 10G is expected to meet the construction deadline, the fourth-generation Huaxia aircraft certainly does not need to play such word games, but reducing resistance and stability at the same time will undoubtedly greatly help improve the flight quality of the aircraft -

After the J-10 was commissioned into the army, Rongfei Group received a large amount of feedback from the aviation units. In addition to routine appreciation and affirmation, there was also a lot of first-hand information provided by pilots.

These contents are not technical information, so they lack rigorous data research and judgment. They are often just qualitative feelings described in simple language, but they have given the design team a lot of new understanding of flight work.

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

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

After Kong Chengan's introduction ended, Yang Wei cleared his throat and began to make a staged summary:

"Comrades should have felt that the new generation of aircraft has unprecedented comprehensive requirements for all aspects of performance, and our main task in the next stage is to optimize the relationship between flight performance and stealth performance, and strive to find a balance between the two. An optimal balance point. I hope everyone can unite and cooperate under the guidance of this big goal..."

Naturally, it is impossible for such a myriad of tasks to be solved in just one meeting.

So he just said a few beautiful words, then changed the subject and began to arrange the specific work behind.

After the meeting, Yang Wei specially called the two deputy chief engineers to his office, ready to give a few additional instructions.

However, before the small meeting between the three of them could begin, the intercom phone on the table rang.

It's the administrative office number.

After the connection, Gao Wenguang's voice quickly sounded over there:

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

Yang Wei frowned slightly, showing a slightly confused expression:

"Then they can just go to the electromagnetic testing center directly... Why do they need to contact us specifically?"

"The other party said that instead of verifying the radar reflection of the engine tail nozzle alone, it should be combined with our aircraft model for an overall test!"