J-20 5th Gen Fighter Thread IV (Closed to posting)

[MiG-29]

Your deduction doesn't necessarily conclude that those planes can't supercruise without a F119 class engine, but simply that Russia didn't think those engines fit their performance requirements. It's not like all supercruising is equal. I think the primary contention over this point has been whether the J-20 can supercruise with the AL-31, not whether that supercruising performance is adequate.

The statement it does supercruise with Al-31s is a very very unlikely one.


Why? Su-27 weighs around 16 tonnes and Su-35 is said a bit heavier


Aircraft performance
Takeoff weight:
- normal (including rockets 2xR-27R1 + 2xR-73E, 5270 kg fuel), kg
23,430*

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The J-20 is heavier than both jets.

Модификация Су-27
Длина крыла, м 14,70
Длина самолета, м 21,935
Высота самолета, м 5,932
Площадь крыла, м2 62.037
Угол стреловидности крыла, град 42
Масса, кг
пустого самолета 16300 нормальная взлетная 22500

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In terms of airframe the J-20 is more draggy than a Su-27 without weapons, its designs has a huge frontal cross section area.

Let us suppose the Su-35BM will supercruise without a lot of weapons and fuel to reduce drag and weight.

The J-20 might be able to "supercruise" but is unlikely.


S-37 aka Su-47 Berkut used the engines of MiG-31, the D-30-F6, the Su-47 flew clean and had internal weapons bays and had a cross section more in line with J-20, so i really doubt Al-31 is the best choice to supercruise since Su-47 used more powerful D-30-F-6 to simulate supercruise

Su-47 performance
The Su-47 fighter aircraft can climb at a rate of 233m/s. The cruise speed is 1,800km/h. The range and service ceiling of the aircraft are 1,782nm (3,300km) and 18,000m respectively.

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[Engineer]

The statement it does supercruise with Al-31s is a very very unlikely one.


Why? Su-27 weighs around 16 tonnes and Su-35 is said a bit heavier


Aircraft performance
Takeoff weight:
- normal (including rockets 2xR-27R1 + 2xR-73E, 5270 kg fuel), kg
23,430*

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The J-20 is heavier than both jets.

Модификация Су-27
Длина крыла, м 14,70
Длина самолета, м 21,935
Высота самолета, м 5,932
Площадь крыла, м2 62.037
Угол стреловидности крыла, град 42
Масса, кг
пустого самолета 16300 нормальная взлетная 22500

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Weight has nothing to do with supercruise ability.

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, almost 8 times of that of Su-27. Yet, Concorde can supercruise at Mach 2.0 while Su-27 cannot supercruise all.

In terms of airframe the J-20 is more draggy than a Su-27 without weapons, its designs has a huge frontal cross section area.

When you take scaled frontal drawings of the two aircraft then count the non-white pixels, both aircraft has almost the same cross section area. So, you are just trying to conjure up an issue that doesn't exist in the first place.

But let's talk about airframe. The Su-27's airframe is optimized for performance at transonic and low supersonic speed. This is evident with the use of higher aspect-ratio wing. For the J-20's airframe, it is optimized with performance from transonic to high supersonic speed. Design for high supersonic speed is evident in the use of low aspect-ratio wing. A higher aspect-ratio wing has more drag at supersonic speed than a low aspect-ratio wing. So, the Su-27 is actually more draggy than J-20.

Let us suppose the Su-35BM will supercruise without a lot of weapons and fuel to reduce drag and weight.

The J-20 might be able to "supercruise" but is unlikely.

Supercrusing without external weapons highlights the supercruise ability on Su-35 is a marketing scheme and tactically useless.

S-37 aka Su-47 Berkut used the engines of MiG-31, the D-30-F6, the Su-47 flew clean and had internal weapons bays and had a cross section more in line with J-20, so i really doubt Al-31 is the best choice to supercruise since Su-47 used more powerful D-30-F-6 to simulate supercruise

Su-47 performance
The Su-47 fighter aircraft can climb at a rate of 233m/s. The cruise speed is 1,800km/h. The range and service ceiling of the aircraft are 1,782nm (3,300km) and 18,000m respectively.

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Of course AL-31 is not the best choice. However, not having the best choice does not exclude an aircraft's ability to supercruise.

 

[Engineer]

Well , most of the mass is devoted to bulkheads and supporting elements and they have relatively simple shape . The reason for using titanium in the first place was to provide strength to airframe . If they didn't want that they would use aluminum alloys which are both cheaper and lighter .

Smallest titanium parts are hinge fittings weighing 80lbs , according to the text I posted

No. Use of Titanium alloy actually results in lighter airframe than what's possible with Aluminum alloy. As you said, Titanium alloy has more strength, so less material can be used resulting in weight saving.

With 3D printing, it is the same idea. Manufacturing a complex component as a single piece reduces the number of joints, increasing strength. The increase of strength allows for the use of less material, contributing to weight reduction.

First of all , sintered titanium has less structural strength then cast titanium because of the gaps in crystal structure (sintering process is not perfect ) . So , you cannot afford to have larger gapes and holes .

Overcoming those difficulties was obviously extremely challenging, which is why only a few countries can 3D print aerospace parts.

Second , bulkhead shape is bulkhead shape These are mostly right and straight angles , you cannot construct stronger bulkhead by curving it .

Bulkhead shape is simple because milling process does not allow for complex shape. With 3D printing, more complex shapes are made possible.

Well , I know what could clean Su-27 do with Al-31 and what could clean Su-35 do with 117S . Given the J-20 or PAK FA shape and weight , and given the fact that Russians said that even 117S is not good enough for PAK FA , I could conclude certain things

An aircraft can either supercruise or it cannot. When the aircraft is capable of maintaining supersonic flight without afterburner, that's supercruise. Whether Russians or Chinese engineers feel satisfactory is an unrelated matter.

 

[MiG-29]

Weight has nothing to do with supercruise ability.

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, almost 8 times of that of Su-27. Yet, Concorde can supercruise at Mach 2.0 while Su-27 cannot supercruise all.


When you take scaled frontal drawings of the two aircraft then count the non-white pixels, both aircraft has almost the same cross section area. So, you are just trying to conjure up an issue that doesn't exist in the first place.

But let's talk about airframe. The Su-27's airframe is optimized for performance at transonic and low supersonic speed. This is evident with the use of higher aspect-ratio wing. For the J-20's airframe, it is optimized with performance from transonic to high supersonic speed. Design for high supersonic speed is evident in the use of low aspect-ratio wing. A higher aspect-ratio wing has more drag at supersonic speed than a low aspect-ratio wing. So, the Su-27 is actually more draggy than J-20.


.

Von Kármán Ogive and the fineness ratio show the Su-27 has lower drag than the J-20.

Since F-35 has basicly the same shape, we know the F-35 has lowered its performance requirements.

In Aerodynamics pixelation is not used, but equations, some using exponentials, therefore the drag of podded engines versus buried engines has an impact, you want the proof? P-42 helds several time to altitude records and it beated the streak Eagle.

Why the Su-27 beat the F-15 in performance records?

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answer Von Kármán Ogive and the fineness ratio.

Now i have no data about J-20, but for J-20 to beat P-42 it will need very powerful engines, and its is unlikely it supercruises at this moment.

If you want to think it does you are welcome, go ahead, i do not need to reply more regards

 

[latenlazy]

Von Kármán Ogive and the fineness ratio show the Su-27 has lower drag than the J-20.

Since F-35 has basicly the same shape, we know the F-35 has lowered its performance requirements.

In Aerodynamics pixelation is not used, but equations, some using exponentials, therefore the drag of podded engines versus buried engines has an impact, you want the proof? P-42 helds several time to altitude records and it beated the streak Eagle.

Why the Su-27 beat the F-15 in performance records?

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answer Von Kármán Ogive and the fineness ratio.

Now i have no data about J-20, but for J-20 to beat P-42 it will need very powerful engines, and its is unlikely it supercruises at this moment.

If you want to think it does you are welcome, go ahead, i do not need to reply more regards

The F-35 has the same shape as the F-22 and the F-22 can supercruise *rollseyes*. Fineness ratio comaprisons are things that can be proven with hard numbers. Where are yours?

 

[Engineer]

Von Kármán Ogive and the fineness ratio show the Su-27 has lower drag than the J-20.

Actually, the J-20 has a higher fineness ratio than the Su-27. This can be seen in the planform of the two aircraft. A general rule of thumb is that for two aircraft of equivalent size, the one with the higher fineness ratio will have the lower drag. So, I would correct your statement to say a Flanker has higher drag than the J-20.

Since F-35 has basicly the same shape, we know the F-35 has lowered its performance requirements.

So? F-22 has similar shape too. The F-22 can clearly supercruise and has yet been beaten on supercruise speed by another fighter.

In Aerodynamics pixelation is not used, but equations, some using exponentials, therefore the drag of podded engines versus buried engines has an impact, you want the proof?

So, you brought up frontal cross section, yet you now claim the measurement of frontal cross section is not used in aerodynamics. Thank you for contradicting your own statement, thereby verifying my statement about you conjuring up issues where none existed.

P-42 helds several time to altitude records and it beated the streak Eagle.

Why the Su-27 beat the F-15 in performance records?

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answer Von Kármán Ogive and the fineness ratio.

Now i have no data about J-20, but for J-20 to beat P-42 it will need very powerful engines, and its is unlikely it supercruises at this moment.

If you want to think it does you are welcome, go ahead, i do not need to reply more regards

Why? The answer is simple, and it is neither Von Kármán Ogive nor fineness ratio. The answer is that P-42 is not a standard Flanker, but one that has every non-essential components stripped -- from weapons to avionics to paint. In short, the P-42 is a stunt aircraft, not a fighter aircraft. Even with two tonnes of weight removed, there was still no supercruise ability, showing how little weight matters.

The simple fact is that the Flanker airframe is not designed with supercruise ability in mind, whereas the J-20 is. The J-20 is going to be less draggy as a result, and be able to go faster given the same amount of thrust. Therefore, what the Flanker can or cannot do is an irrelevant metric as far as J-20's supercruise ability is concerned.

 

[airsuperiority]

another stormy day over here at this thread

 

[AssassinsMace]

Probably waited until Deino was off on holiday.

 

[airsuperiority]

Probably waited until Deino was off on holiday.

There's still one escape pod left. Someone hurry and head to the Death Star to fetch the Sith Lord. The rest of us will try to hold off the swarm.

 

[MiG-29]

The F-35 has the same shape as the F-22 and the F-22 can supercruise *rollseyes*. Fineness ratio comaprisons are things that can be proven with hard numbers. Where are yours?

The sears-haack body is basicly the aerodynamic body with least drag, the Von Karman ogive is also the least drag body of revolution you can get.

J-20 has not such type of cross section in fact is not even a body of revolution, in the other hand corcorde and Su-27 do have sears-hack bodies and von Karman ogives, plus concorde and SU-27 have ventral podded engines.

If you want data go to the Yefim Gordon`s book Su-27, which was made with extensive help by the Sukhoi Bureau, go to page 515 and look at tables 2 and 3 and will see the Flanker has the lowest fuselage relative cross section even lower than F-16 and F-15.

F-35 like any stealth fighter has a large cross section due to weapons bays.

The F-22 supercruise thanks to its engines that have 4 tonnes more thrust than Al-31.

The likelihood the J-20 supercruises with Al-31 are so low, that is hard to believe a machine with the same engines and heavier weight with a no sears-haack body of revolution will supercruise while the Su-27 does not supercruise.

Su-35BM supercruises but has 117s engines and PAKFA will fly with type 30 engine that is supposed to replace 117 because the 117 is not as powerful to be economical for the T-50 to compete with F-22.

You are welcome to believe it supercruises, i differ.