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

[Engineer]

Some of you have suggested that the J-20 will not be equipped with TVC, is it this generally thought to be true?

There are two reasons why the J-20 will not be equipped with thrust vectoring. Firstly, it is the fact that there is no known demonstrator fitted with thrust vectoring in China. This is unlike America or Russia that have fitted thrust vectoring to legacy fighters before designing the F-22 and T-50. So, China is unfamiliar with such technology, and the chance of fitting unfamiliar technology to their next front-line fighters is pretty much non-existent given the risk involved.

The other reason is that the prototype is supposed to be a close approximation of the final production version. The J-20 prototypes would have been fitted with thrust vectoring engines if there were actual plans of using thrust vectoring on the production aircraft. Flight tests right now would be meaningless if the final product were to have a different flight characteristics. So, the fact that flight tests are being performed right now with two prototypes means what you see is going to be what the production version will look like.

Some argue that canards make tvc redundant. If that is the case. Anyone have an idea why the J-20 chose canards and the F-22/T-50 chose TVC?

Any useful tactical maneuver a thrust vectoring equipped fighter can do can be done by a fighter with all moving canard. The reason J-20 chose canard is that canard allows the aircraft to be controlled at very high angle-of-attack. This is the actual reason given by the designer. An aircraft with tailplane cannot do this, which is one of the reasons why F-22 and T-50 resort to thrust vectoring.

 

[Inst]

There have been photographs leaked of the Chinese testing out thrust vectoring designs outside of airframes.

I think another issue with regards to thrust vectoring is the position of the engine nozzles on the J-20; you could claim it's an accommodation to design technology, but if you notice the placement of the engine nozzles, these are relatively out of the main body and wing. This is suboptimal for thermal and radar stealth, by recessing the engine into the main wing, you allow the wing body to help shield the IR emissions. The engine placement then suggests that TVC is a designed / intended feature on the J-20.

===

With regards to the utility of TVC; if you look at the case of the Su-35, the Su-30 and Su-33 both use canards to improve maneuverability and reduce take-off/landing distances, but the Su-35 in its default configuration ditches the canards. Why is that?

According to the Russians, on the case of the Su-35, they found that with the Su-35 configuration, the maneuverability gains from canarding the Su-35 were mostly eclipsed by the maneuverability gains from the TVC and dropping the canards would reduce drag without giving a significant penalty to the Su-35.

Aside from that, TVC is very difficult to design and engineer, and can also result in maintenance nightmares due to the difficulty of having a moving part on your aircraft that is constantly exposed to high-heat and pressure. Why go for TVC when it comes with so many difficult development, production, and operation problems if it doesn't provide any advantages over canard-delta layout?

Another factor is that the J-20 basically has the same aerodynamic layout as the Rafale (Canard - Lerx - Wing), when you ignore the anhedral / dihedral canard / wing airframe. The Rafale has a similar thrust-to-weight, but is not supermaneuverable.

There are also significant costs placed with canards; for example, partial compromise of side and frontal stealth, increased drag, and so on.

 

[Inst]

Also, with regards to claims that canard deltas are every bit as good as TVC-equipped fighters, I'd like to remind you about the Herbst maneuver, where an aircraft can quickly reach zero speed by stalling, then maneuver out of the stall into the back of its opponent. This is something achievable only by TVC-equipped fighters.

 

[latenlazy]

Another factor is that the J-20 basically has the same aerodynamic layout as the Rafale (Canard - Lerx - Wing), when you ignore the anhedral / dihedral canard / wing airframe. The Rafale has a similar thrust-to-weight, but is not supermaneuverable.

There are also significant costs placed with canards; for example, partial compromise of side and frontal stealth, increased drag, and so on.

The Rafale and the J-20 do not in fact have the same configuration. Planar arrangement of each aerodynamic surface also matters.

 

[MiG-29]

Some of you have suggested that the J-20 will not be equipped with TVC, is it this generally thought to be true? Some argue that canards make tvc redundant. If that is the case. Anyone have an idea why the J-20 chose canards and the F-22/T-50 chose TVC?

If the J-20 is not fitted with TVC nozzles is not because of canards, canards do not give superior maneuvrability, back in the 1990s, the X-31 was usually beaten by F-18s until they fitted X-31 with TVC paddles, after that it was able to beat F-18s in an overwhelming way.

J-20 has canards because it has a delta, and delta wings while give higher AoA than other types of wings they generate less lift.

So if you add canards you add better AoA with higher lift than just a plain Delta, basicly canards are the band aids of deltas in the same way LERX are band aid of less swept wings.

However a canard and a delta are not superior.

The real reason why it might not have a TVC nozzles and it uses that type of weapon bays for short range missiles has to do with HHOBS, HHOBS stands for helmetless high off bored capability, new missiles need a cue from sensors like data links, like SPECTRA on Rafale and a head seeker with half sphere engagement capability, so if the J-20 has its missiles out of the weapons on a rack with the weapons bay door closed is to allow the seeker to get a cue while other sensors are working and tracking the target.


If HHOBS works well, the J-20 will beat any target without even needing to turn, allowing to do what F-35 does with EOTS Das, and that is the ability to fire over the shoulder and lock after launch capability.

 

[Engineer]

If the J-20 is not fitted with TVC nozzles is not because of canards, canards do not give superior maneuvrability, back in the 1990s, the X-31 was usually beaten by F-18s until they fitted X-31 with TVC paddles, after that it was able to beat F-18s in an overwhelming way.

J-20 has canards because it has a delta, and delta wings while give higher AoA than other types of wings they generate less lift.

So if you add canards you add better AoA with higher lift than just a plain Delta, basicly canards are the band aids of deltas in the same way LERX are band aid of less swept wings.

However a canard and a delta are not superior.

Fighters with canard don't have to be superior. They only have to be able to perform the same tactical maneuver as fighters with thrust-vectoring, which is the point. Rafale and Eurofighter have no thrust-vectoring, but they have no difficulties maneuvering against thrust-vectoring equipped F-22. This shows fighters with canard do what a fighter with thrust-vectoring can do, and thrust-vectoring does not automatically mean superiority.

An engine with thrust-vectoring by itself isn't going to fly. Aerodynamic is what's important at the end of the day.

The real reason why it might not have a TVC nozzles and it uses that type of weapon bays for short range missiles has to do with HHOBS, HHOBS stands for helmetless high off bored capability, new missiles need a cue from sensors like data links, like SPECTRA on Rafale and a head seeker with half sphere engagement capability, so if the J-20 has its missiles out of the weapons on a rack with the weapons bay door closed is to allow the seeker to get a cue while other sensors are working and tracking the target.


If HHOBS works well, the J-20 will beat any target without even needing to turn, allowing to do what F-35 does with EOTS Das, and that is the ability to fire over the shoulder and lock after launch capability.

The fact that the side weapon bay is specifically designed to allow the weapon to be extended out of the aircraft for long periods of time shows one important design criteria. That criteria is to allow the missile to use its own seeker to lock on to enemy aircraft, which can't be done if the missile is within the weapon bay. The aircraft itself must be highly maneuverable to enable this to happen.

 

[Engineer]

Also, with regards to claims that canard deltas are every bit as good as TVC-equipped fighters, I'd like to remind you about the Herbst maneuver, where an aircraft can quickly reach zero speed by stalling, then maneuver out of the stall into the back of its opponent. This is something achievable only by TVC-equipped fighters.

While it is true that post-stall maneuvers can only be performed through thrust vectoring, post-stall maneuvers are also shown to be tactically useless and using them is no different than suicide. Post-stall maneuvers cause the aircraft to lose speed very quickly, and in an air-to-air engagement, speed is life.

A fighter with thrust-vectoring pointing vertical up and hovering in the sky may look impressive. However, a fighter aircraft's ultimate mission is to out maneuver and shoot down the enemy, not doing crowd-pleasing ballets in an airshow.

 

[Quickie]

The J-20, Eurofighter Typhoon and the Rafale are very different aerodynamically although they all have the canard delta configuration. The placement of canards for these aircraft are different from each other with that of the Rafale's the closest. The Rafale does not use its canards as the main pitch control surface - it uses the elevons for this purpose unlike the J-20 which uses the canards.

 

[Engineer]

The canards ARE bad for stealth, however. It's a small reflective / absorptive surface in front of the main wings; which complicates emissions control compared to having a small reflective / absorptive surface behind the main wing. It is not an utter disaster and not something that cannot be partially negated, it probably contributes something around +5 dBsm, but if you were really focused on RCS reduction, you'd opt for a conventional wing-tail configuration.

There is no concrete proof showing canards are bad for stealth. None whatsoever. Canard and stealth being mutually exclusive is merely a misconception based upon a single statement from an American engineer, which goes something like "canard is only good on an enemy aircraft". In reality, the canard having edge alignment will reflect radar signal away from the source, just like edge alignment on a wing will do.

Please, Log in or Register to view URLs content!

doesn't show canard to have detrimental effects on stealth as some are claiming.

What IS different here with the Boeing sixth-gen, however, is the avoidance of tailfins. By removing the tailfin, you remove the RCS contribution from the tailfin, which seems to add quite a lot to emissions compared to a tailfinless aircraft. It probably more than compensates for the RCS emissions created by the canard, and a tailfinless canard configuration is probably superior in RCS to a conventional wing-tail-tailfin setup.

You must be unaware that there are many stealth fighter concepts featuring canard from the US. The

Please, Log in or Register to view URLs content!

. The

Please, Log in or Register to view URLs content!

. There is also this from McDonnell Douglas:

Tags: China; J-20 copy; McDonnell Douglas; canard; stealth fighter concept;

If canard is so bad for stealth, such configuration would have been the first to be eliminated and wouldn't have the opportunity to proceed into wind tunnel testing. And while we are at it, let's not forget

Please, Log in or Register to view URLs content!

.

I think that the J-20 also has the goal of being a tailfinless aircraft. The problem with the J-20, however, is that the TVC engines are not yet mature and reliable so tailfins are then completely necessary for stability. However, I would not be surprised to see a J-20C in the 2025 time-frame with TVC controls, no tailfin, and less RCS than the F-22.

This theory fails when one considers how F-22 and PAKFA have vertical stabilizers even with matured thrust-vectoring.

 

[kroko]

That you don't give a damn will be as true as the WS-15 flounders.

Prove it if you can. You cant, dont you?

Time for you to leave sinodefence forum altogether then? Since you don't care or give any interest to Chinese military projects, why stay in a community dedicated to keeping up with said projects? Or perhaps you're just here to troll, which seems more and more likely by the minute.

I have interest in knowing about china´s military development and how it will shape things in the future, but I wont be upset in the least if china´s military programs flounder. Why should I? I live half a world away from china.
And I since when doubting the validy of an information who doesn’t have any verifiable source constitutes trolling? Or are you saying that I (or anyone else) should believe in something just because someone says so?

i think his health is damaged already

See my response to t2contra post. Is this the best that you can do?