Chapter 975 It's so ugly
In fact, Gao Zhendong only knows the MiG-21. In his previous life, Lao Zhan-7 has improved so much, and the wing fuel tank happens to be what he has memory.
Mr. Huang made a rough calculation in his mind: "Well, we can add some fuel here, but not too much."
Gao Zhendong suddenly laughed. Mr. Huang didn't know what he was laughing at. Just as he was about to ask, Gao Zhendong drew a silhouette of a MiG 21 on the paper, then waved his pen and pulled a line flat from the rear edge of the canopy to the vertical tail.
Then he drew a top view and drew outlines on the side.
"Here, add another spine fuel tank! I just estimated that it can increase at least 600 liters of fuel. And at the same time, the canopy cover is raised by several centimeters. First, it is matched with the spine fuel tank, and second, the cabin of this aircraft is too short."
The height of the aircraft cockpit is a very counterintuitive thing. In fact, whether it is tanks, infantry battles or aircraft, the pilot is not very big, and it is not as big as imagined. Our pilots feel uncomfortable when they enter.
And adding fuel tanks is something the old men have been doing from F-PF-S-MF to Bis, and they have been adding!
At the beginning, I was a little shy, only a part of it was increased, and I had to leave a little bee waist to maintain my appearance. Later, I was completely released. How to use it, the fuel tank on the back became bigger and uglier.
Mr. Huang almost spurted out an old blood. No wonder he wanted to laugh. When he saw this, the plane became even uglier!
Originally, the MiG-21 did have a ridge bulge, but it was not obvious and very coordinated. After Gao Zhendong's one-plus, the plane suddenly changed from a little waist to a flying can, with both sides!
And... with a big mouth, that's really ugly!
Mr. Huang complained wildly in his heart, but calmed down and had to admit that this reform was the most economical and direct.
The maximum forward cross-sectional area of the aircraft will not be changed, and the increased wet area and cross-sectional area are not much, which is easy to deal with according to the area ratio, and the added weight is relatively evenly distributed over the central fuselage, which does not have much impact on the changes in the center of gravity of the aircraft.
In other words, without major surgery on the entire aircraft, more internal fuel volume was obtained, which greatly improved the range. The fuel carrying efficiency of internal fuel was much higher than that of the secondary fuel tank.
Although this further increases the weight of the fuselage and may affect the flight performance of the clean configuration, Gao Zhendong did not care much. The engine thrust of the R-11F2-300 used in the Russian interceptor model MiG-21PF was increased by less than 10%. It was also used well and continued to use the M-type. Subsequently, the R13-300 engine used in SM/MF was only increased by about 15% compared to the MiG-21F.
In any case, installing more fuel into the body when allowed is actually more beneficial for the actual mounting configuration.
After weighing the pros and cons, Mr. Huang pinched his nose and accepted it. This thing is ugly, but it is so ugly.
"Okay, let's go back and calculate carefully to see how big it is." The schematic diagram given by Gao Zhendong was basically in one step, directly following the diagram given by the MF's spine fuel tank, like a huge pig worm crawling on the back of the MiG-21.
For later comrades, this was one of the few things that became uglier in Comrade Gao Zhendong's career, and it also added an interesting story.
"By the way, I think this place can be changed, move the speed reduction parachute upwards and put it at the base of the vertical tail wing." Gao Zhendong pointed to the tail of the machine on the line chart before Mr. Huang asked the next question.
The MiG-21F's reduction parachute compartment is below the engine nozzle and behind the ventral fins, but later both the Russians and us were placed in the position mentioned by Gao Zhendong.
"If you put this on? It doesn't seem to be a big difference, is it meaningful?" This thing is too detailed, and Mr. Huang didn't know what it was for a moment.
"No, this can improve landing performance..." Gao Zhendong explained: "In the original position, the connection between the deceleration parachute and the fuselage was lower than the center of gravity of the aircraft. In this way, once the deceleration parachute was opened, the aircraft tended to be buried, which is not good for landing. If it was put on it, there would be no problem." Gao Zhendong simply drew a force analysis on the side view just now.
"Hey, from the perspective of mechanics, it's really! The details are too detailed. The landing performance has improved, so is it possible to take off performance..." Mr. Huang was very happy. When he went back this time, several model bosses didn't know how happy they were.
Gao Zhendong thought about it and seemed that he was not kind to do halfway through his work: "It's not that bad, but it's a bit complicated."
"It doesn't matter if it's complicated. It's good to improve it. It's too complicated, so just change it back." Mr. Huang was very calm.
"Then like this..." Gao Zhendong pointed to a certain position of the engine on the line chart. The next words made Mr. Huang and the others almost jumped up: "Draw a hole here to draw out the high-pressure air in the engine and blow it out from this position and above the flap. Pay attention, in this case, the gap between the flap and the main wing should be small."
A hole in the engine? It's indeed a bit troublesome, and why not blow the top of the flap? Wouldn't blowing below on the curved flap more to create upward lifting force?
After hearing their questions, Gao Zhendong smiled and said, "The main purpose of using the airflow to eliminate the separation turbulence above when the flap is opened, forming a stable airflow on the back of the flap, further improving the efficiency of the flap and providing greater lift." Looking at the airflow diagram drawn by Gao Zhendong on the flap section, the two understood what it means for the comrades of the porcelain flight factory to say that Chief Engineer Gao has a deep aerodynamics in terms of expertise.
What else to say? Remember it quickly. This matter is troublesome and troublesome. It is actually quite simple to say that it is simple. It is easier to pump air in the compressor section than to pump gas in the back section of the combustion chamber?
Moreover, this does seem to be able to further improve the take-off performance of the aircraft based on the flap system, which is very important for aircraft that may increase weight due to radar, fuel and other weight after modification. Moreover, the take-off performance of the MiG-21F is quite average, and it still needs to be changed if it can be changed.
Speaking of wings, he remembered another important thing that came here this time, which was also the first initiative of Chief Engineer Gao. It is always right to ask him.
"Mr. Gao, you also proposed the edge wings. We also want to ask you about this." After all, after using the edge wings in the new war-7, the benefits can be seen from the naked eye. Whether the MiG-21 imitation can be used and how to use this edge wings
Wings, Gao Zhendong is even more exciting than Mr. Huang. In addition to the nose, the biggest change in the content he wants to change is the wings!
Looking at Gao Zhendong's excited eyes, Mr. Huang felt a little panicked inexplicably. Could he not make any big moves, right?
Sure enough, Gao Zhendong rejected his thoughts in the first sentence.
"This plane does not require wings!"
There is no reason. If you want to give a reason, it is that no matter we or the Russians have changed so much, they have no use of side wings, so Gao Zhendong will naturally not think about this.
"No wings?"
"The edge wing is not omnipotent. This is a high-speed aircraft. Let's think of other ways." After saying that, Gao Zhendong drew a wing on the paper, which looked a bit strange.
"We use double triangular wings! I have calculated that the sweep angle of the inner wing remains unchanged by 57 degrees, the sweep angle of the outer wing is changed to 42 degrees, and the trailing edge of the wing is swept forward. In this way, the high-speed performance is ensured as much as possible using the inner wing, and the outer wing takes into account the performance of medium and low altitude and medium and low speed, so that both ends can be better taken into account. Moreover, the space inside the wing is larger, and the fuel, lift characteristics, wing load, and range can also be improved."
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The previous life 7th Master's double-triangle wing model still has a maximum flight speed of Mach 2. Gao Zhendong is not too worried that this wing will significantly reduce the aircraft's high-speed performance.
Can this still be done? genius!
Although I only saw this idea and did not have specific design, calculation, and experimental data, most of the benefits are visible at a glance. Even the most overwhelming considerations of high and low speeds, it doesn't seem outrageous.
For example, after the large sweep section splits the air, the small sweep section can be followed up more easily.
The most important thing is that this design does not actually have much changes to the aircraft, and there is no manufacturing difficulty. Instead, it is more troublesome to determine the sweep angle and sweep angle change point in the two sections.
Even Chief Engineer Gao calculated the swept angle. As for the change point of the swept angle, it is probably because the plane still has unclear areas and needs to be adjusted according to the specific situation.
However, Mr. Huang is very confident about the double-decker wings. There is not much left in unknown numbers. The rest is easy to deal with. The wind tunnel will blow it up for me! Even if you don’t need to modify the MiG-21, this airfoil is also a very useful airfoil.
"57 degrees...42 degrees...hey, Lao Huang, is this number?" Another comrade confirmed to Mr. Huang while recording, for fear that he would remember it wrong.
"Yes, yes, that's the number."
While answering him, Mr. Huang was also recording himself, and muttering: "In this way, the original hanging points seem too few. Well, add two full-function wet hanging points on the outside of the wing to hang the auxiliary fuel tank and missile... Yes! There is also a rocket nest!"
There is a situation that ordinary people can't imagine. MiG-21F and our basic old 7th Master have only two wing hangers, and they are not wet hangers, so the secondary fuel tank cannot be hung. They only have one belly hanger point that can hang the secondary fuel tank, and the combat radius is even more pitiful.
As for why you can't see photos of the old 7th master with only two hangs, it's because the 7th master with two hangs gave birth less and retired earlier.
Premier Huang found that although the suggestions he had received from Gao Zhendong, he found that although it seemed to be very changed, there were actually very few places to move to the structure, mainly concentrated in the nose and outer wings.
(This chapter ends)