Performance of these aircraft are very specifically and finely engineered sets of complex interacting parameters, not point tallies you can add up from some arbitrary feature counts.
J-20 5th Generation Fighter VII
- Thread starter siegecrossbow
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Even Vipers can splash Raptors in DACT depending on the many variables. No one (including yourself) would seriously claim the Eurofighter is in the same class as the Raptor. So this is a moot point.
You're using the same bad argument that many Americans use against China's military.
If I go to Italy and admire the aqueducts, am I "perpetuating the mythical pedestal" of Rome's propaganda?
Or am I admiring the kool stuff yet another empire built at its peak, before stupidity caused its inevitable collapse?
(hint: it's the latter.)
It is impossible to have a serious comparison with systems and logistics, because a lot of critical infos are confidential.
Of course. Which is why these comparisons are difficult at best and quite frowned upon on this forum.
Quickie
Colonel
It's a given a higher AoA entails a higher lift coefficient and higher drag coefficient as well.
As your for your comment on
with respect to the F-22 I guess, there is no proof that that is really the case without the availability of technical data. In the absence of available info, it is also possible the J-20 has a relatively lower drag coefficient (for a certain AOA relative to F-22).
Yeah we can't tell one way or another without relevant data from both planes, just that I personally don't hold expectation that J-20 can beat F-22 in STR, nor do I think J-20 needs to.... I mean it would be nice but it is not that important.
The only thing we can infer from J-20 having a higher max lift coefficient is that J-20 has a lower corner speed.
Quickie
Colonel
My expectation is opposite of yours for the reason that the stall condition is very much related to the drag coefficient i.e how fast drag increases with AOA. The high Alpha capability of the J-20 gives the aircraft a wider range of AOA to go through as the turbulent flow increases causing the increase in drag and finally the stalling.
I recall that the WS-10 powered J-20 was timed to have a STR of 18 degrees/ sec during some demo flight. Someone here even commented about it a while ago.
Long reply incoming, so will need to split this in two. Here's Part 1:
Wrt canard vs conventional layouts and how they compare on sustained turns, the framing itself is problematic. To put out an analogy, it’s like debating whether front wheel drive or rear wheel drive is better when comparing the handling and speed performance of two cars, or debating whether one boxer's left hook is better than another boxer's uppercut in a boxing debate. Neither tells you more than general characteristics or tendencies of the things you're trying to describe. It’s how you leverage those characteristics or tendencies that then translate to performance capabilities.
To break this down further, I think it's first necessary to understand that what your sustained turn rate is for a design is itself *not* a constant. For any given design a plane's kinematic attributes vary depending on flight conditions, and specifically altitude, speed, and angle of attacks, and the extent to which flight performance improves or worsens for each parameter (angle of attack btw refers to the pitch angle of the object of interest relative to the direction of airflow, or what is sometimes referred to as the "free stream"). At the most fundamental level what this means is that your lift coefficient and drag coefficient changes depending on altitude *and* speed *and* angle of attack, and the degree and trend of changes for each parameter is *different* and *independent* for each. In turn how those relationships between your lift and drag coefficients are defined depends the ways the free stream interacts with your plane's physical shape. Outside of some very general principles where we can derive some basic sense of what's going on aerodynamically, those relationships have to be determined experimentally if we really want to know them with enough precision to make meaningful relative comparisons.
Furthermore, different wings, fuselages, and other aerodynamically relevant shapes will typically bring different levels of gain or degradation to performance at different flight envelopes and conditions. I think getting to this point, it's typically useful to stop thinking about the attributes of the plane itself as conferring specific performance properties, and start to think about what's actually going on, which is how the physical shape(s) of the plane is interacting with the flow of air around it. In other words, what really matters here isn't so much "what does the plane have" but "what is the plane doing to the air around it". After all, the way planes work is that you're converting an opposing force from air pushing against your plane's movement and converting the force from that opposing flow of matter into a positive upward force rather than an opposite lateral force. And specifically, what's happening is that as the shape is pushing against the direction of mass flow pressure gradients will form around the shape, and if you can get the pressure gradients to be distributed in a way where one side of a shape has higher pressure than the other side then of course you will generate a positive force pushing in the direction from the higher pressure side toward the low pressure side.
If you think about it from that standpoint, what should then stand out pretty quickly is that well of course a complex shape is going to have different interactions with the flow of air when rotated to show a different cross section to the direction of flow. And of course the amount of pressure you can generate for each cross section is going to be different depending on the speed and density (and viscosity) of the air. And of course different shapes are going to create different cross sections at different rotations and will also interact with changes in speed and density of flow differently. And to further complicate the matter, the conjunction of different shapes and geometries aren't always additive in effect but often translate to those joined shapes being its own unique shape with its own unique interactive relations with the flow field, and once you add movable control devices and other aerodynamic features like strakes and LERXes etc etc, that picture gets even more complicated.
To illustrate this point with a concrete example think about how a high aspect ratio wide span wing. That kind of geometry tends to have very good lift to drag ratios at very low speeds, and thus have pretty good relative turn rates in low speed regimes. Why is that? Well think about what's going on with the shape of the wing in terms of its integration to the airflow around it. The wide span means you are essentially maximizing the amount of length that the flow of air is interacting with to convert the flow's opposing horizontal force into an upward vertical force. But this span wise exposure also means that as you go to higher speeds, keeping altitude the same, you're also increasing the amount of wing length that's exposed to drag, and air resistance goes up as a square of speed. And then the moment you start to hit the transsonic range, the compression shocks in the airflow also begin to interact with that whole wing span, causing drag to go up even more. How might you improve upon that situation? What if you reduced the aspect ratio (made the wing narrower), but tried to preserve the same surface area? Well, now you have a delta. You've traded away some positive lift generation at the low speed, but your drag profile is now much better at the high speed because the total span of the wing exposed to air resistance is a lot less. Meanwhile you've still preserved the same surface area so at least the amount of surface that your positive pressure gradient generating the lift is the same, even if the deeper wing itself probably also changes what the pressure gradient over the surface of your wing look like. Take this example, and think about what the lift coefficient curve in relation to speed, altitude (thickness of air), and angle of attack might look like for one shape vs another shape.
No, I do have some engineering background (and if I couldn't say that a few years before I can now), but wrt to aerodynamics it's a lot of self study. It's not all pieced together internet knowledge either though. If you want to understand anything properly you have to tackle the subject seriously from a fundamentals up approach, actually have a sound foundation of the physics involved and not just recite facts and rules of thumb, ideally with a goal of being able to usefully reconstruct some practical effect or prediction from the knowledge. The knowledge needs to be functional. If you can't reconstruct what is likely going on physics wise mechanism by mechanism you don't really know what you're talking about. I was very fortunate to have grown up with quite a bit of technical education before diverging from that track in college, and also fortunate to have opportunities to close the loop after college too, to understand both a lot of the basic science, and also to acquire good principles for learning new subjects. It also helps me a lot now to have had hands on experience with the engineering, R&D, and product development process. That said I would never profess to have perfect or authoritative knowledge here. I only know enough to know what's probably BS and what's actually realistic or plausible, and to do some casual analysis for fun. So take what I say on these things as informed (to the best of my ability) opinion and understanding, not concrete facts of reality.
Wrt canard vs conventional layouts and how they compare on sustained turns, the framing itself is problematic. To put out an analogy, it’s like debating whether front wheel drive or rear wheel drive is better when comparing the handling and speed performance of two cars, or debating whether one boxer's left hook is better than another boxer's uppercut in a boxing debate. Neither tells you more than general characteristics or tendencies of the things you're trying to describe. It’s how you leverage those characteristics or tendencies that then translate to performance capabilities.
To break this down further, I think it's first necessary to understand that what your sustained turn rate is for a design is itself *not* a constant. For any given design a plane's kinematic attributes vary depending on flight conditions, and specifically altitude, speed, and angle of attacks, and the extent to which flight performance improves or worsens for each parameter (angle of attack btw refers to the pitch angle of the object of interest relative to the direction of airflow, or what is sometimes referred to as the "free stream"). At the most fundamental level what this means is that your lift coefficient and drag coefficient changes depending on altitude *and* speed *and* angle of attack, and the degree and trend of changes for each parameter is *different* and *independent* for each. In turn how those relationships between your lift and drag coefficients are defined depends the ways the free stream interacts with your plane's physical shape. Outside of some very general principles where we can derive some basic sense of what's going on aerodynamically, those relationships have to be determined experimentally if we really want to know them with enough precision to make meaningful relative comparisons.
Furthermore, different wings, fuselages, and other aerodynamically relevant shapes will typically bring different levels of gain or degradation to performance at different flight envelopes and conditions. I think getting to this point, it's typically useful to stop thinking about the attributes of the plane itself as conferring specific performance properties, and start to think about what's actually going on, which is how the physical shape(s) of the plane is interacting with the flow of air around it. In other words, what really matters here isn't so much "what does the plane have" but "what is the plane doing to the air around it". After all, the way planes work is that you're converting an opposing force from air pushing against your plane's movement and converting the force from that opposing flow of matter into a positive upward force rather than an opposite lateral force. And specifically, what's happening is that as the shape is pushing against the direction of mass flow pressure gradients will form around the shape, and if you can get the pressure gradients to be distributed in a way where one side of a shape has higher pressure than the other side then of course you will generate a positive force pushing in the direction from the higher pressure side toward the low pressure side.
If you think about it from that standpoint, what should then stand out pretty quickly is that well of course a complex shape is going to have different interactions with the flow of air when rotated to show a different cross section to the direction of flow. And of course the amount of pressure you can generate for each cross section is going to be different depending on the speed and density (and viscosity) of the air. And of course different shapes are going to create different cross sections at different rotations and will also interact with changes in speed and density of flow differently. And to further complicate the matter, the conjunction of different shapes and geometries aren't always additive in effect but often translate to those joined shapes being its own unique shape with its own unique interactive relations with the flow field, and once you add movable control devices and other aerodynamic features like strakes and LERXes etc etc, that picture gets even more complicated.
To illustrate this point with a concrete example think about how a high aspect ratio wide span wing. That kind of geometry tends to have very good lift to drag ratios at very low speeds, and thus have pretty good relative turn rates in low speed regimes. Why is that? Well think about what's going on with the shape of the wing in terms of its integration to the airflow around it. The wide span means you are essentially maximizing the amount of length that the flow of air is interacting with to convert the flow's opposing horizontal force into an upward vertical force. But this span wise exposure also means that as you go to higher speeds, keeping altitude the same, you're also increasing the amount of wing length that's exposed to drag, and air resistance goes up as a square of speed. And then the moment you start to hit the transsonic range, the compression shocks in the airflow also begin to interact with that whole wing span, causing drag to go up even more. How might you improve upon that situation? What if you reduced the aspect ratio (made the wing narrower), but tried to preserve the same surface area? Well, now you have a delta. You've traded away some positive lift generation at the low speed, but your drag profile is now much better at the high speed because the total span of the wing exposed to air resistance is a lot less. Meanwhile you've still preserved the same surface area so at least the amount of surface that your positive pressure gradient generating the lift is the same, even if the deeper wing itself probably also changes what the pressure gradient over the surface of your wing look like. Take this example, and think about what the lift coefficient curve in relation to speed, altitude (thickness of air), and angle of attack might look like for one shape vs another shape.
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Part 2:
You may have noticed that up to this point I have essentially been answering most of your original inquiry by not really answering it. As I'm sure you're starting to gather, the actual realities of how fighter planes perform is extremely complex, and not as easily settled by rule of thumb arguments like canards always have worse sustained turn rates. But to make an attempt at a more direct answer, whether a canard configured fighter can have better sustained turn rates than a traditional configured fighter is going to be completely dependent on 1) what are the other shapes and features employed by the planes in comparison 2) what flight envelopes and flight conditions we're talking about in relation to the *entirety* of the plane's shape, rather than any individual set of features.
Sustained turn rates are ultimately determined by the combination of your optimal lift to drag flight profile and conditions along with your thrust. Insofar as you have a more optimal lift to drag ratio at a particular flight profile and conditions than another plane at equivalent or better engine power, you will have better sustained turn rates than your point of comparison. There is nothing inherently advantageous or disadvantageous about a canard configuration vs a traditional configuration however. Canards put your pitch control surfaces in front, which means that you have to mind downwash effects from the canards oto the wings, but those can be worked around, or even leveraged for positive effect. On one hand you might get some additional drag by having another set of surfaces outside of your wing exposed to the free stream, but on the other hand the canards might be smaller than your horizontal tales and then that helps reduce a bit of drag. Or perhaps the drag the canards add are negligible in comparison because the traditionally configured plane you're comparing to needs bigger tails to add some control authority that your canards are providing you more competently. It's really hard to say, and ultimately if you want to make comparisons you're going to have to look at the designs you want to compare holistically. There are no iron laws here.
Are canards superior to traditional configurations in the supersonic regime? Well...sort of. It's more precise to say that they provide some beneficial attributes to designs that want to optimize supersonic performance, but those benefits aren't only attainable with canards, and depending on how you're employing and what you're doing with that particular feature, the converse, that the way you're using those canards may not provide those benefits, can also be true. What canards do really nicely for designs that want optimal performance in the supersonic regime is that as you get into the supersonic regime, the aerodynamic center (the centerpoint where the lift force is pushing on the plane's body) will tend to shift backwards. This increases the leverage arm of the canards relative to where the aerodynamic center is in lower speed regimes, which can improve their control authority. Furthermore, a shift in the aerodynamic center during supersonic flight can also lead to natural pitching deviation from level flight, so you need to "trim" your control surfaces to keep the nose level, which can induce further drag. Longer lever arm means less trimming for pitch authority.
*However* whether these factors matter in a comparison will depend on a whole host of other details, like what the static stability margin of the planes in comparison are (how far is the aerodynamic center from the center of gravity), etc. Whatever benefits a canard may bring to this set of problems in theory can also be resolved with some other combination of features and design choices. The general takeaway here, as with the question about sustained turn rates, is that cherry picking physical features to try to draw broad conclusions about kinematic performance in comparisons between different planes is almost a meaningless exercise if you don't actually know all the particular balance of features and details that went into each plane design and how that in turn influenced the force parameters involved in flight in precise ways.
So, this is probably a *much* longer reply than you were expecting, and also a much longer reply than I had anticipated writing, but what you were asking was touching on a whole host of misconceptions about how most people here *think* about fighter aerodynamics and kinematics, and what that means for comparisons between two different designs. There is actually a whole other much longer conversation about how fighters use their particular kinematic advantages and disadvantages in different domains of combat and the tactical implications they have on engagement dynamics and outcomes (for example the Eurofighter may not be able to match the F-16's STR at its most optimal envelope, but it hardly matters because other aspects of the EF's maneuvering capacities all but guarantee that the F-16 is *probably* toast, or at least will be fighting with a significant disadvantage most of the time in WVR engagements) but without wading into that even longer discussion I thought it might be worthwhile to lay out something explanatory and in depth about the basics (which are still quite complex!) here in the hopes that it encourages far more thoughtful engagement from *everyone* about these kinds of questions,
So when we talk about "good" turn rates, it's useful to recognize that there are essential conditions around those "turn rates" that must be defined and qualified. A plane with wide span high aspect ratio wings might have even greater sustained turn rates than the F-16! But if it's at 200 mph and those turn rates plummet well after those speeds, is that really a meaningful statement? Similarly the F-16 is supposed to have the best sustained turn rates of any 4th gen fighters! But if the F-16's lift curve slope is at its optimum relative to other designs at 10k ft altitude, but flattens more sharply going up to and beyond 20k ft than other fighters (say in comparison with a Flanker) because of higher wing loading/smaller wing area, is that claim to having the best sustained turn rates of any 4th gen fighter actually categorically true across the board? Is that seemingly considerable kinematic advantage as comprehensive as it sounds? And wrt to G-limits, FWIW, in large portions of any fighter jet's total maneuvering envelope, past some combination of speed and altitude, they are not actually able to do maneuvers that reach 9Gs. There are some parts of the flight envelope where the airframe would be pushing what it can do at 5-6Gs. One of the main points of 5th gen fighter development was to expand that flight envelope to push out maneuvering capability at higher altitudes and speeds, by advances in aerodynamic design, and/or by features such as TVC (this btw is why despite some common notions that the J-20 doesn't need TVC, it will probably get it just to help it expand the range of its maneuvering envelope well past what the airframe's aerodynamics alone could accomplish).
You may have noticed that up to this point I have essentially been answering most of your original inquiry by not really answering it. As I'm sure you're starting to gather, the actual realities of how fighter planes perform is extremely complex, and not as easily settled by rule of thumb arguments like canards always have worse sustained turn rates. But to make an attempt at a more direct answer, whether a canard configured fighter can have better sustained turn rates than a traditional configured fighter is going to be completely dependent on 1) what are the other shapes and features employed by the planes in comparison 2) what flight envelopes and flight conditions we're talking about in relation to the *entirety* of the plane's shape, rather than any individual set of features.
Sustained turn rates are ultimately determined by the combination of your optimal lift to drag flight profile and conditions along with your thrust. Insofar as you have a more optimal lift to drag ratio at a particular flight profile and conditions than another plane at equivalent or better engine power, you will have better sustained turn rates than your point of comparison. There is nothing inherently advantageous or disadvantageous about a canard configuration vs a traditional configuration however. Canards put your pitch control surfaces in front, which means that you have to mind downwash effects from the canards oto the wings, but those can be worked around, or even leveraged for positive effect. On one hand you might get some additional drag by having another set of surfaces outside of your wing exposed to the free stream, but on the other hand the canards might be smaller than your horizontal tales and then that helps reduce a bit of drag. Or perhaps the drag the canards add are negligible in comparison because the traditionally configured plane you're comparing to needs bigger tails to add some control authority that your canards are providing you more competently. It's really hard to say, and ultimately if you want to make comparisons you're going to have to look at the designs you want to compare holistically. There are no iron laws here.
Are canards superior to traditional configurations in the supersonic regime? Well...sort of. It's more precise to say that they provide some beneficial attributes to designs that want to optimize supersonic performance, but those benefits aren't only attainable with canards, and depending on how you're employing and what you're doing with that particular feature, the converse, that the way you're using those canards may not provide those benefits, can also be true. What canards do really nicely for designs that want optimal performance in the supersonic regime is that as you get into the supersonic regime, the aerodynamic center (the centerpoint where the lift force is pushing on the plane's body) will tend to shift backwards. This increases the leverage arm of the canards relative to where the aerodynamic center is in lower speed regimes, which can improve their control authority. Furthermore, a shift in the aerodynamic center during supersonic flight can also lead to natural pitching deviation from level flight, so you need to "trim" your control surfaces to keep the nose level, which can induce further drag. Longer lever arm means less trimming for pitch authority.
*However* whether these factors matter in a comparison will depend on a whole host of other details, like what the static stability margin of the planes in comparison are (how far is the aerodynamic center from the center of gravity), etc. Whatever benefits a canard may bring to this set of problems in theory can also be resolved with some other combination of features and design choices. The general takeaway here, as with the question about sustained turn rates, is that cherry picking physical features to try to draw broad conclusions about kinematic performance in comparisons between different planes is almost a meaningless exercise if you don't actually know all the particular balance of features and details that went into each plane design and how that in turn influenced the force parameters involved in flight in precise ways.
So, this is probably a *much* longer reply than you were expecting, and also a much longer reply than I had anticipated writing, but what you were asking was touching on a whole host of misconceptions about how most people here *think* about fighter aerodynamics and kinematics, and what that means for comparisons between two different designs. There is actually a whole other much longer conversation about how fighters use their particular kinematic advantages and disadvantages in different domains of combat and the tactical implications they have on engagement dynamics and outcomes (for example the Eurofighter may not be able to match the F-16's STR at its most optimal envelope, but it hardly matters because other aspects of the EF's maneuvering capacities all but guarantee that the F-16 is *probably* toast, or at least will be fighting with a significant disadvantage most of the time in WVR engagements) but without wading into that even longer discussion I thought it might be worthwhile to lay out something explanatory and in depth about the basics (which are still quite complex!) here in the hopes that it encourages far more thoughtful engagement from *everyone* about these kinds of questions,
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Don't get what you're trying to say here, elaborate?
18degree/s if true makes a decent lower bound of J-20's abilities but it doesn't settles it vs F-22. Anyhow I'd be very happy to be proven wrong if there is evidence.
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