Aerodynamics thread

[latenlazy]

Re: J-20 The New Generation Fighter Thread IV

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The study doesn't detail the placement of the canards. As explored in a previous discussion, non-planar canards don't have the same drag penalties that co-planar canards do.

Also, you might want to read this paper, by the same person.

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Particularly this section on page 9

"In the case of a coplanar wing and tail, the vertical gap is 0 and the σ in
Prandtl’s equation approaches σ = b2/b1, where b1 is the span of the larger surface. This
approach was initially applied to canard configurations as well, often showing large
induced drag penalties since stability and trim considerations produced more than optimal
lift on the smaller span forward surface. Researchers were surprised to find that in
experimental tests canard designs performed much better than predicted (Butler 1982).
This was due to the fact that the actual load distribution on the wing of a canard
configuration was not elliptical, but rather closer to the optimal load distribution in this
case. Modifications to the biplane equation, based on optimal, rather than elliptical loads
provided much better comparison with experiments and yielded the correct result that for
two coplanar surfaces, the minimum total induced drag depends only on the maximum
span and total lift"

 

[MiG-29]

Re: J-20 The New Generation Fighter Thread IV

Yanliang is the city. CFTE (China Flight Test Establishment) is the facility.



Perhaps it is not I who doesn't understand that jets have different configurations, but you who do not understand that different configuration do not always mean net parity of results (I need to emphasize the word net here). The point I'm trying to make isn't that trade offs don't exist in flight design, but that despite those trade offs sometimes one design will still come out the aerodynamic superior on the net whole.

I understand perfectly, what happens is you want to win at what ever cost the argument, each configurations has strong points and weak points


this is a real report about the Swiss adquisition of a fighter, as you can see all the jets, the differences in configuration even having a delta wing-canard are obvious

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Eurofighter came on top on Supercruise over Rafale, nothing special since the canard position was set for that, however consider the Rafale is the best dogfighter and the canard was set for that

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The point is simple even a J-20 and F-22 configurations the F-22 has strong and weak points but J-20 is the same.

The configuration of Rafale chose agility over drag, and the oppposite was for Eurofighter.

F-35 shows that if you want stealth tailess is best, however for lowest supersonic trim drag triplane is best, F-35 sacrificed and traded off.
If you want less friction and wave drag, tailess again is best.

Sixth generation fighters for a reason are tailess and the most advanced have TVC nozzles


J-20 is the same, it has performance and stealth areas where it lost to F-22, see that based upon aerodynamic control an unstable wing tail was considered equal to a unstable canard configuration, no advantage there for any of the F-35 configuration.

F-22 is unstable see that point

However TVC nozzles is an advantage F-22 enjoys over J-20 at supersonic speeds in stealth.

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If you want aerodynamic high alpha without TVC nozzles then canard is best, the F-35 figure shows that, but add TVC nozzles no difference and TVC nozzles give you post-stall handling when the wing is stalled or semi-stalled an advantage of F-22.


The difference is always the fighter with the lowest wing loading and highest lift will be the most agile, but this has a set of contradictions in stealth, price size and weight.

 

[Munir]

Re: J-20 The New Generation Fighter Thread IV

TVC introduces high energy loss... You do not need your surface to change direction but o boy what will the drag increase if you force your plane into other direction. I only see advantages during landing, TO or high altitude maneuvering.

 

[Engineer]

Re: J-20 The New Generation Fighter Thread IV

TVC introduces high energy loss... You do not need your surface to change direction but o boy what will the drag increase if you force your plane into other direction. I only see advantages during landing, TO or high altitude maneuvering.

Exactly. It is all about lift, and TVC doesn't create extra lift for turning. Forcing the aircraft to fly in a direction that the plane doesn't want to will literally makes the aircraft fall out of the sky.

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. Simple flight dynamics.

 

[Air Force Brat]

Re: J-20 The New Generation Fighter Thread IV

Exactly. It is all about lift, and TVC doesn't create extra lift for turning. Forcing the aircraft to fly in a direction that the plane doesn't want to will literally makes the aircraft fall out of the sky.

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. Simple flight dynamics.

Actually it is all about energy management, if you do not allow your speed to decay you're not going to fall out of the sky, the situation that you are describing is a very low energy, low thrust situation, it is a circumstance that anyone who operates a TVC equipped aircraft well understands and the old heads do not allow their aircraft energy to decay, also the F-22 has a massive amount of thrust, which will allow the F-22 to accelerate pointing straight up. The F-15 pilot is describing a situation where a novice was suckered into "coffin corner" attempting to out maneuver the opponent by going into the post stall, and driving the nose into a firing solution with brute horsepower, this is an iffy situation at best. This is not the SOP of the F-22 pilot, it is rather a circumstance that was allowed to develop in order to illustrate how not to do it!

TVC is an obvious advantage in the close in, up close and personal world of ACM, to deny that is to deny the whole design philosophy of "dogfighting. AFB.

 

[Engineer]

Re: J-20 The New Generation Fighter Thread IV

Actually it is all about energy management, if you do not allow your speed to decay you're not going to fall out of the sky, the situation that you are describing is a very low energy, low thrust situation, it is a circumstance that anyone who operates a TVC equipped aircraft well understands and the old heads do not allow their aircraft energy to decay, also the F-22 has a massive amount of thrust, which will allow the F-22 to accelerate pointing straight up. The F-15 pilot is describing a situation where a novice was suckered into "coffin corner" attempting to out maneuver the opponent by going into the post stall, and driving the nose into a firing solution with brute horsepower, this is an iffy situation at best. This is not the SOP of the F-22 pilot, it is rather a circumstance that was allowed to develop in order to illustrate how not to do it!

TVC is an obvious advantage in the close in, up close and personal world of ACM, to deny that is to deny the whole design philosophy of "dogfighting. AFB.

Real world experience contradicts to your assertion. TVC is what goes against the very philosophy of energy management, since an aircraft flying in a non-optimal angle at post-stall bleeds off energy very quickly. The main advantage of TVC is cited to be super maneuverability. However, it is suicidal to pull that sort of maneuver in a situation where speed is everything. That's the reality. You even admitted that to be the case in your own argument.

The F-22 has a massive amount of thrust, which is good for dog fighting. However, that thrust has nothing to do with a TVN.

 

[Air Force Brat]

Re: J-20 The New Generation Fighter Thread IV

Real world experience contradicts to your assertion. TVC is what goes against the very philosophy of energy management, since an aircraft flying in a non-optimal angle at post-stall bleeds off energy very quickly. The main advantage of TVC is cited to be super maneuverability. However, it is suicidal to pull that sort of maneuver in a situation where speed is everything. That's the reality. You even admitted that to be the case in your own argument.

The F-22 has a massive amount of thrust, which is good for dog fighting. However, that thrust has nothing to do with a TVN.

Actually real world experience says that the combination of OVT/Massive Thrust/Mass Centralization/Superior Aerodynamics will win the day everytime, OVT will enhance the pitch transition of any fighter aircraft, the F-22 has it, the advanced Russian Flankers have it, and PAKFA has it, and Dr. Song obviously hoped to incorporate it into the J-20. To dismiss it out of hand, and say it will make your airplane fall out of the sky is belying simple fighter aircraft dynamics, and that my friend is the issue.

To dismiss it because China has not incorporated it on the J-20, whether because of lack of desire or inability to field that technology is moot. To bring up the specious argument that the US has not retrofit it to last years models is also moot, as is the argument that it is not on the F-35, which has been designed to be the joint STRIKE fighter. The Raptor is the Raptor because of OVT, not in spite of it, without OVT the Raptor would just be another awesome fighter, the design team built the Raptor around a powerfull OVT enhanced engine, and the OVT is the secret sauce of that aircrafts supermanueverability, and its overall excellence. BRAT

 

[Engineer]

Re: J-20 The New Generation Fighter Thread IV

Actually real world experience says that the combination of OVT/Massive Thrust/Mass Centralization/Superior Aerodynamics will win the day everytime, OVT will enhance the pitch transition of any fighter aircraft, the F-22 has it, the advanced Russian Flankers have it, and PAKFA has it, and Dr. Song obviously hoped to incorporate it into the J-20. To dismiss it out of hand, and say it will make your airplane fall out of the sky is belying simple fighter aircraft dynamics, and that my friend is the issue.

Lumping advantages of other features together with TVC doesn't mean TVC provides those advantages. While aerodynamics and massive thrust are what make aircraft like F-22 so superior, neither of which is contributed by TVC. So, what you have said is just an attempt to make TVC sounds better than it actually is. An aircraft's performance is limited by aerodynamics, which is one area that Dr. Song spent so much effort in. Real world exercises have shown multiple times that attempts to exceed those limitation through TVC get the aircraft killed faster. That is the fact, and will remain so regardless of how you or anyone spin it as some pilot error.

To dismiss it because China has not incorporated it on the J-20, whether because of lack of desire or inability to field that technology is moot. To bring up the specious argument that the US has not retrofit it to last years models is also moot, as is the argument that it is not on the F-35, which has been designed to be the joint STRIKE fighter. The Raptor is the Raptor because of OVT, not in spite of it, without OVT the Raptor would just be another awesome fighter, the design team built the Raptor around a powerfull OVT enhanced engine, and the OVT is the secret sauce of that aircrafts supermanueverability, and its overall excellence. BRAT

The fact that US doesn't retrofit its older fighters with TVC is very relevant. After all, if TVC provides so much advantages, the USAF wouldn't hesitate to retrofit all their aircraft with one. Money isn't an issue here, given how USAF plans on procuring large number of F-35s despite the high price tag. Dismissing this obvious indicator is nothing more than an attempt at cherry picking.

Lastly, super maneuverability is synonymous with post-stall maneuverability. It is something that gets the aircraft (even an F-22) killed faster. This has already been confirmed in the video as something you don't want to do in a dogfight. I don't need to go further.

 

[Air Force Brat]

Re: J-20 The New Generation Fighter Thread IV

Lumping advantages of other features together with TVC doesn't mean TVC provides those advantages. While aerodynamics and massive thrust are what make aircraft like F-22 so superior, neither of which is contributed by TVC. So, what you have said is just an attempt to make TVC sounds better than it actually is. An aircraft's performance is limited by aerodynamics, which is one area that Dr. Song spent so much effort in. Real world exercises have shown multiple times that attempts to exceed those limitation through TVC get the aircraft killed faster. That is the fact, and will remain so regardless of how you or anyone spin it as some pilot error.

1.OVT most certainly contributes to the F-22s ability to make rapid pitch transitions, to deny its foundational role on the F-22 is to discredit the superior engineering that is the secret to the F-22s agility, the F-119 has the oomph to make those pitch changes authoritative and sustainable, the F-22 has the ability to basically "Hover", pointed straight up, and to add power and using OVT to reduce pitch and fly away, whether one uses control surfaces alone or a combination of control surfaces and OVT, the OVT only adds to control authority----for you to imply that LOCKMART and the USAF are wrong, while acknowledging the superiority of the F-22 seems more than a little arrogant?


The fact that US doesn't retrofit its older fighters with TVC is very relevant. After all, if TVC provides so much advantages, the USAF wouldn't hesitate to retrofit all their aircraft with one. Money isn't an issue here, given how USAF plans on procuring large number of F-35s despite the high price tag. Dismissing this obvious indicator is nothing more than an attempt at cherry picking.

2.The USAF doesn't spend money to upgrade weapons systems that are approaching retirement, the F-22 is late in coming to the scene because of lack of money and the engineering and performance challenges that it represented at its initial inception, those engineering challenges and the technology required to maintain the stealth aspect of the F-22 are part of what has made this a very expensive aeroplane, but its mastery of the A2A regime is not in question, The USAF has decided to pursue "stealth and low observable technology at its core, something no modified 4 gen or 4.5 will ever provide, and something that is really not in the US thinking, the F-35 does not have OVT as a result of design philosphy for a Strike aircraft, it is expensive and unnecessary on an Attack aircraft, which was NOT designed as an air superiority fighter, but was designed to be low observable for following the F-22 after the high risk threats had been neutralized.


Lastly, super maneuverability is synonymous with post-stall maneuverability. It is something that gets the aircraft (even an F-22) killed faster. This has already been confirmed in the video as something you don't want to do in a dogfight. I don't need to go further.

3.Supermaneuverability is usefull and operational on the F-22 throughout its vast flight regime, it will maintain 6gs positive at 50,000 ft according to outgoing USAF Chief of Staff, Gen Norton Schwartz, who also asked the rhetorical question, "what other aircraft will do that? The implied answer is NONE, and he is in a position to "know", not a forum fanboy. To base your conclusions about OVT on an anecdotal video about a little horsing around, has led you to an untenable presupposition that has put you at odds with the engineers at LOCKMART, and the folks at USAF who have put a lot of money on this pony, and she is a winner. I have NO doubt Dr. Song would rap your knuckles with his slide rule, and I would love to see it, and yes I am smiling! Your Number One Fan here on Sino D, think about it bro, confession is good for the soul. Brat

 

[Engineer]

Re: J-20 The New Generation Fighter Thread IV

1.OVT most certainly contributes to the F-22s ability to make rapid pitch transitions, to deny its foundational role on the F-22 is to discredit the superior engineering that is the secret to the F-22s agility, the F-119 has the oomph to make those pitch changes authoritative and sustainable, the F-22 has the ability to basically "Hover", pointed straight up, and to add power and using OVT to reduce pitch and fly away, whether one uses control surfaces alone or a combination of control surfaces and OVT, the OVT only adds to control authority----for you to imply that LOCKMART and the USAF are wrong, while acknowledging the superiority of the F-22 seems more than a little arrogant?

2.The USAF doesn't spend money to upgrade weapons systems that are approaching retirement, the F-22 is late in coming to the scene because of lack of money and the engineering and performance challenges that it represented at its initial inception, those engineering challenges and the technology required to maintain the stealth aspect of the F-22 are part of what has made this a very expensive aeroplane, but its mastery of the A2A regime is not in question, The USAF has decided to pursue "stealth and low observable technology at its core, something no modified 4 gen or 4.5 will ever provide, and something that is really not in the US thinking, the F-35 does not have OVT as a result of design philosphy for a Strike aircraft, it is expensive and unnecessary on an Attack aircraft, which was NOT designed as an air superiority fighter, but was designed to be low observable for following the F-22 after the high risk threats had been neutralized.

3.Supermaneuverability is usefull and operational on the F-22 throughout its vast flight regime, it will maintain 6gs positive at 50,000 ft according to outgoing USAF Chief of Staff, Gen Norton Schwartz, who also asked the rhetorical question, "what other aircraft will do that? The implied answer is NONE, and he is in a position to "know", not a forum fanboy.

First, you are pulling a

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, since I never denied the F-22 as a good aircraft. However, the F-22 being a good aircraft and that super maneuverability/post-stall maneuver being useful are different concepts. The aircraft having high performance does not automatically means TVC being useful, as there are other known contributors of high performance.

Second, you essentially accused me of asserting USAF as wrong. This couldn't be further from the truth. I couldn't care less whether they are right or wrong, but I do value their opinion. This is why I used USAF's own behavior to illustrate how USAF didn't think as highly of TVC as you do. Once again, stop pulling strawman arguments.

Thirdly, USAF upgrades its old aircraft with new avionics like expensive AESA radars. In light of this, your argument about how USAF doesn't want to spend money to upgrade outdated equipments is hardly a strong argument.

To base your conclusions about OVT on an anecdotal video about a little horsing around, has led you to an untenable presupposition that has put you at odds with the engineers at LOCKMART, and the folks at USAF who have put a lot of money on this pony, and she is a winner. I have NO doubt Dr. Song would rap your knuckles with his slide rule, and I would love to see it, and yes I am smiling! Your Number One Fan here on Sino D, think about it bro, confession is good for the soul. Brat

I will respond with

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, which is a concrete example that illustrates real world and sale brochure claims are far apart. Meanwhile, you cannot draw an opposite real world example which supports your view; one where an aircraft used post-stall maneuverability to defeat an opponent.

You also need to realize that a mom always think her kids are beautiful. Having sunk so much money into F-22, USAF will naturally tell you all the related technologies are the best. Likewise, Lockheed Martin will always say it made the right decisions and that its products are superior to everyone else. That is also an attitude of a good salesman. This is why whether USAF retrofit their older aircraft with TVC is an important gauge in the actual capabilities of TVC.