Aerodynamics thread

[Engineer]

That is not true, LCA is tailless and uses LEVCONs, what he really wants to say i want to win the argument.

Delta wings need long elevons due to the wing swept which reduces their effectiveness, thus they generate lot of drag.

Of course what I have said is true. You are just upset that I am right in pointing out how LCA and PAKFA do not rely on LEVCON alone for pitch authority.

 

[F-15]

LEVCON can be used to enhance lift and reduce drag, no one disputes that. What you do not understand is that canard not only do the same, but do so better. With longer moment arm, a long-coupled canard provides better pitch authority, which is simple law of physics. This pitch authority is a necessity especially for an unstable aircraft at high angle-of-attack. LEVCON cannot provide such pitch authority alone, and must rely on tailplane as well as thrust-vectoring-control. In other words, LEVCON offers some advantages as canard, but cannot serve as a replacement for canard. Furthermore, to design a canard layout properly is challenging, risky, costly and not everyone can do it. So, the next best alternative after canard is to control vortex through LEVCON.

Who says that? what study? ah Mister Engineer, a no one, i see, first bring me a study that compares the LEVCON and Canard, argue with you is senseless, the Indian and Russian researches have them, you do not have any by they way, Russia as well as India operate aircraft with canards, Su-30MKI, Su-30MS, Su-33 and SU-34 hellduck plus Russia designed S-47 and MiG-1.44.

So your whole rant is a lie, since even 1990s studies showed Vortex flaps can control lateral as well pitch on aircraft, the Americans in fact designed LEVCONS, but their studies centered on delta wings, the Russians and Indians did it on LEX.

LCA study with canards

 

[F-15]

Of course what I have said is true. You are just upset that I am right in pointing out how LCA and PAKFA do not rely on LEVCON alone for pitch authority.

oh i see, you do not even what you are saying, the vortex shift generates pitch forces, controlling the vortex means controlling the center of pressure shift as the wing goes into high ALPHA, LCA is tailless, it uses its elevons for control, but the LEVCON are also used too, the LEVCONs are to increase the effectiveness of elevon control by doing it, they are affecting pitch, by controlling the center of pressure they are controlling where the vortex burst.

 

[Engineer]

Who says that? what study? ah Mister Engineer, a no one, i see, first bring me a study that compares the LEVCON and Canard, argue with you is senseless, the Indian and Russian researches have them, you do not have any by they way, Russia as well as India operate aircraft with canards, Su-30MKI, Su-30MS, Su-33 and SU-34 hellduck plus Russia designed S-47 and MiG-1.44.

So your whole rant is a lie, since even 1990s studies showed Vortex flaps can control lateral as well pitch on aircraft, the Americans in fact designed LEVCONS, but their studies centered on delta wings, the Russians and Indians did it on LEX.

LCA study with canards

I point at physical planes, and that is better than studies. LCA and PAKFA do not rely just on LEVCON, and that is a fact. The PAKFA even needs thrust-vectoring-control in addition to tailplane, showing LEVCON does not provide good enough pitch authority to be used alone. Not only does your continuous talk about vortex lift affecting pitch not going to change how reality work, it shows you are in denial about simple law of physics regarding moment arm. What is better? Better is doing more, not less. LEVCON does less by not providing enough pitch authority. By doing less, LEVCON is not better than canard.

 

[Engineer]

oh i see, you do not even what you are saying, the vortex shift generates pitch forces, controlling the vortex means controlling the center of pressure shift as the wing goes into high ALPHA, LCA is tailless, it uses its elevons for control, but the LEVCON are also used too, the LEVCONs are to increase the effectiveness of elevon control by doing it, they are affecting pitch, by controlling the center of pressure they are controlling where the vortex burst.

You use LCA as an example, but the existence of PAKFA invalidates your generalization. The fact that PAKFA needs a tailplane and thrust-vectoring-control is a proof that LEVCON cannot affect pitch as easily as a long-coupled canard can. It is that simple.

Movement in center-of-pressure can certainly cause change in pitch, nobody is denying that. Yet, causing change in pitch is not the same as causing the change easily. So your premise does not support your argument. By being much closer to the center-of-gravity, the center-of-pressure has a shorter moment arm and cannot affect pitch as good as a canard, or a tailplane for that matter.

 

[F-15]

I point at physical planes, and that is better than studies. LCA and PAKFA do not rely just on LEVCON, and that is a fact. The PAKFA even needs thrust-vectoring-control in addition to tailplane, showing LEVCON does not provide good enough pitch authority to be used alone. Not only does your continuous talk about vortex lift affecting pitch not going to change how reality work, it shows you are in denial about simple law of physics regarding moment arm. What is better? Better is doing more, not less. LEVCON does less by not providing enough pitch authority. By doing less, LEVCON is not better than canard.

To end this debate which is just your insecurity that J-20 can not flat spin in controlled flight like PAKFA does, show me the J-20 doing the flat spin on pure canard control alone, you won`t find it, since fighters like Eurofighter or Rafale do not do it, all these jets rely on thrust vectoring control; and the canards or Levcons are used only to augment vortex generation.
Canards and LEVCONS by them selves do not make a fighter better, it is the combination of drag and thrust what makes the better fighter, in fact the fact J-20 needs to rely on LEX and canards show the whole configuration work as a system, none is decisive by its self but they are a combination to get a max total coefficient of lift.

Your whole hypothesis is false since the J-20 uses LEX and canards at the same time, the LEX is used to improve the lift the canard can not achieve, since the canard on J-20 is far forward and is less than ideal, however if the jet can achieve the lift needed to overcome the drag and is light enough could achieve excellent turn rates.

But that combination does not mean it is better to the a LEVCON tailess or aft tailed.

Because all delta canard jets use in their flight control a combination of elevons, leading edge and canards to achieve pitch control.

Your whole point is false, since F-22 and PAKFA use horizontal aft tails, you are just bragging on Chinese nationalism, the fact J-20 uses canards and not aft tail is not because the jet is better, it is because the parameters needed on the J-20 demand canards as a solution, otherwise F-22 would have needed canards and PAKFA would have added canards, they did not add canards to F-22 and PAKFA, and still PAKFA can fall like a leaf and has no problem to do it and the same is for F-22.

 

[Engineer]

To end this debate which is just your insecurity that J-20 can not flat spin in controlled flight like PAKFA does, show me the J-20 doing the flat spin on pure canard power alone, you won`t find it, since fighters like Eurofighter or Rafale do not do it, all these jets rely on thrust vectoring power and the canards or Levcons are used only to augment vortex generation.

F-22 can do controlled flat-spin as well, with no need of LEVCON. LCA with LEVCON has not shown the ability to do controlled flat-spin. These show that a controlled flat-spin, or more generally post-stall maneuvers, come from thrust-vectoring and not a benefit of LEVCON.

Canards and LEVCONS by them selves do not make a fighter better, it is the combination of drag and thrust what makes the better fighter, in fact the fact J-20 needs to rely on LEX, canards show the whole configuration work as a system, none is decisive by its self but they are a combination to get a max total coefficient of lift.

Your whole hypothesis is false since the J-20 uses LEX and canards at the same time, the LEX is used to improve the lift the canard can not achieve, if the jet can achieve the lift needed to overcome the drag and is light enough could achieve excellent turn rates.

But that combination does not mean it is better to the a LEVCON tailess or aft tailed.

Because all delta canard jets use in their flight control a combination of elevons, leading edge and canards to achieve pitch control.

Your whole point is a stupidity, since F-22 and PAKFA use horizontal aft tails, you are just bragging on Chinese nationalism, the fact J-20 uses canards and not at tail is not because the jet is better, it is because the parameters needed on the J-20 demand canards as a solution, otherwise F-22 would have needed canards and PAKFA woul;d have added canard, they did not, and still PAKFA can fall like a leaf and has no problem to do it.

We already have a graph showing canard is better than tailplane in pitch-authority, from the engineer of J-20. As to comparison to LEVCON, the issue of moment-arm length means LEVCON is not as good as canard in providing pitch authority. The rest of your post is just you being upset that I am able to provide factual information.

J-20 does demand a canard layout as a solution, because only a canard layout is good enough to satisify the requirements. PAKFA uses LEVCON, but requires tailplane as well as thrust-vectoring-control because LEVCON does less than canard. LCA is just too small for tailplane or canard, and does not prove LEVCON being better.

 

[F-15]

We a
lready have a graph showing canard is better than tailplane in pitch-authority, from the engineer of J-20.
J-20 does demand a canard layout as a solution, because only a canard layout is good enough to satisify the requirements.

You just repeat your self like a parrot, and post 1000 times the same graph due to your lack of proof LEVCONS are worse than canards, due to your insecurities.

China to this moment has not shown any fighter doing super maneuverability none, nil, nada.

The USA and Russia have show super maneuverability with aft tailed aircraft, ranging from F-16s to Su-35s.

In fact one of the big worries you have in J-20 is it does not have thrust vectoring, so big is your insecurity, that i can post you a PAKFA doing flat spins but you can not show me a J-20 doing the same, and you will sustain canards are better, i am bored of this conversation so get your J-20 and show me a J-20 doing a flat spin like PAKFA does in the video otehrwise i will ignore you and consider your rants as fanboy dreams

 

[Engineer]

You just repeat your self like a parrot, and post 1000 times the same graph due to your lack of proof LEVCONS are worse than canards, due to your insecurities.

PAKFA is already a proof that LEVCON is not as good as a canard, as the aircraft requires tailplane as well as thrust-vectoring-control for pitch authority. J-20 has the required pitch authority from canard alone. So, LEVCON is not better than canard. I understand why you don't want me to parrot facts to you, because you are upset that your arguments are being discredited.

China to this moment has not shown any fighter doing super maneuverability none, nil, nada.

The USA and Russia have show super maneuverability with aft tailed aircraft, ranging from F-16s to Su-35s.

In fact one of the big worries you have in J-20 is it does not have thrust vectoring, so big is your insecurity, that i can post you a PAKFA doing flat spins but you can not show me a J-20 doing the same, and you will sustain canards are better, i am bored of this conversation so get your J-20 and show me a J-20 doing a flat spin like PAKFA does in the video otehrwise i will ignore you and consider your rants as fanboy dreams

Post-stall maneuverability is not an advantage of LEVCON, so it doesn't help your argument. Moreover, post-stall maneuvers cause aircraft to lose lift, speed and altitude quickly. The aerodynamic control surfaces all lose effectiveness in situations such as a flat-spin.

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. This only serves to discredit your position further. So, contrary to your belief, I am not worry at all about J-20 having no thrust-vectoring. It actually makes me quite happy.

 

[Scyth]

Super-maneuverability/ Post-stall maneuverability is overrated. I guess the marketing boys of LM and Sukhoi really succeeded in selling TVC equipped aircrafts.

With the introduction of HOBS-missiles, instantaneous turn rates/ pitch rates may become more important than sustained turn rates in order to maximize the Pk of such a missile, the usefullness of going post-stall is very limited at best. ACM excersises have time and time again proven that it's still important to not go into a low energy, post-stall situation. Eurofighters and older F-15's managed to score kills against F-22s and SU-30 MKIs. Here's a link where an Eurofighter pilot explains why TVC isn't essential:

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