Re: Chinese Engine Development
Eyeballing aerodynamics of something as complex of a fighter aircraft ain't cool yo.
Eyeballing aerodynamics of something as complex of a fighter aircraft ain't cool yo.
Aerodynamics thread
- Thread starter siegecrossbow
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Re: Chinese Engine Development
Manueverability or agility? Agility=nose pointing and ITR, which is something the J-20 should excel at, it being a delta canard. Maneuverability=STR, which depends more on lift coefficients and L/D ratios (plural because that changes at different speeds, alphas, and altitudes). That's hard to eyeball, because modern day fighters depend on vortex lift to increase their lift coefficients.
Manueverability or agility? Agility=nose pointing and ITR, which is something the J-20 should excel at, it being a delta canard. Maneuverability=STR, which depends more on lift coefficients and L/D ratios (plural because that changes at different speeds, alphas, and altitudes). That's hard to eyeball, because modern day fighters depend on vortex lift to increase their lift coefficients.
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thunderchief
Senior Member
Re: Chinese Engine Development
Partially you are right, but canards on fighter like this are used more for control (J-20 is inherently unstable ) then for rapid change of direction (to increase ITR) . Of course, J-20 could deflect its canards almost to 90 degrees, but that would result in rapid loss of speed. Compared to other fighters of 5. and 4.5 gen, J-20 has relatively high wing loading, and I doubt it is configured for low speed turning combat. Be advised that generating vortex lift increases lift but actually also increase drag .
Partially you are right, but canards on fighter like this are used more for control (J-20 is inherently unstable ) then for rapid change of direction (to increase ITR) . Of course, J-20 could deflect its canards almost to 90 degrees, but that would result in rapid loss of speed. Compared to other fighters of 5. and 4.5 gen, J-20 has relatively high wing loading, and I doubt it is configured for low speed turning combat. Be advised that generating vortex lift increases lift but actually also increase drag .
SamuraiBlue
Captain
Re: Chinese Engine Development
Just because you have a delta canard does not insure agility. J-20's overall length compared to other fighter becomes a problem. Flying at high speed and suddenly trying to change direction (nose pointing) wings suddenly becomes a resistant surface in changing direction. You can easily experiment this with a row boat. A row glides in the water with it's winged surface horizontal to the water surface but when you try to twist the surface into it's upright position to row further you'll feel a strong force growing stronger as you twist it. Now imagine the surface of the row wing twice the length. I believe you can imagine easily that the strength will become twice as strong.
Don't try to complicate the problem when principle can easily be explained.
Just because you have a delta canard does not insure agility. J-20's overall length compared to other fighter becomes a problem. Flying at high speed and suddenly trying to change direction (nose pointing) wings suddenly becomes a resistant surface in changing direction. You can easily experiment this with a row boat. A row glides in the water with it's winged surface horizontal to the water surface but when you try to twist the surface into it's upright position to row further you'll feel a strong force growing stronger as you twist it. Now imagine the surface of the row wing twice the length. I believe you can imagine easily that the strength will become twice as strong.
Don't try to complicate the problem when principle can easily be explained.
Re: Chinese Engine Development
Sorry to step in and even if I did not follow the whole discussion ... why again a problem regarding length ??? We all know the J-20 is actually even slightly shorter than a Flanker, so what's Your point !??
So I really do not get this argument !
Deino
Sorry to step in and even if I did not follow the whole discussion ... why again a problem regarding length ??? We all know the J-20 is actually even slightly shorter than a Flanker, so what's Your point !??
So I really do not get this argument !
Deino
Re: Chinese Engine Development
With regards to decoy tactics and speed and altitude, as I've indicated in the thread arguing about the F-22, high speed might be undesirable when it comes to 5th gen aircraft warfare due to its effects on IR signatures. While with 4th gen aircraft with the radar being the dominant sensor against enemy aircraft, coming into the combat zone with high energy is a plus, with 5th gen aircraft supercruising into a fight will likely just get you spotted and tracked by IRSTs.
Altitude is of course still a good thing, giving your fighter greater potential energy, but sustaining high altitudes without high speeds might be impossible, depending on the airframe.
Thus, I don't see that much of a trade-off if your WS-15 J-20s are pretending to be Al-31 J-20s. And I think you're still underestimating the value of having baited your opponent into making a mistake.
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With regards to Thunderchief, mixing with J-11s and J-10s sounds plausible provided that the J-20s have LPI mode radars; the J-20s specialize in killing opponents from BVR, especially those tasked to engage the 4th gen fighters, while the fourth gens will cover the J-20s' escape when the combat reaches WVR distances.
With regards to decoy tactics and speed and altitude, as I've indicated in the thread arguing about the F-22, high speed might be undesirable when it comes to 5th gen aircraft warfare due to its effects on IR signatures. While with 4th gen aircraft with the radar being the dominant sensor against enemy aircraft, coming into the combat zone with high energy is a plus, with 5th gen aircraft supercruising into a fight will likely just get you spotted and tracked by IRSTs.
Altitude is of course still a good thing, giving your fighter greater potential energy, but sustaining high altitudes without high speeds might be impossible, depending on the airframe.
Thus, I don't see that much of a trade-off if your WS-15 J-20s are pretending to be Al-31 J-20s. And I think you're still underestimating the value of having baited your opponent into making a mistake.
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With regards to Thunderchief, mixing with J-11s and J-10s sounds plausible provided that the J-20s have LPI mode radars; the J-20s specialize in killing opponents from BVR, especially those tasked to engage the 4th gen fighters, while the fourth gens will cover the J-20s' escape when the combat reaches WVR distances.
vesicles
Colonel
Re: Chinese Engine Development
Yeah, people seem to be fixated on the length of the J-20. The measurement the J-20 from actual satellite photos with both J-20 and Flankers side-by-side shows that the J-20 is obviously shorter than several Flanker variants. I guess the PLA got tired of the length myth and decided to put the J-20 side-by-side with other fighters, knowing that someone will see the satellite images and pick up the hint...
Sorry to step in and even if I did not follow the whole discussion ... why again a problem regarding length ??? We all know the J-20 is actually even slightly shorter than a Flanker, so what's Your point !??
So I really do not get this argument !
Deino
Yeah, people seem to be fixated on the length of the J-20. The measurement the J-20 from actual satellite photos with both J-20 and Flankers side-by-side shows that the J-20 is obviously shorter than several Flanker variants. I guess the PLA got tired of the length myth and decided to put the J-20 side-by-side with other fighters, knowing that someone will see the satellite images and pick up the hint...
Re: Chinese Engine Development
Not a length but a surface area problem, primarily in the form of drag, which is why I mentioned lift to drag coefficient. It's not that straightforward at supersonic speeds either because of the mach cone. This isn't high school physics.
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Re: Chinese Engine Development
The relative long fuselage and canard-delta design imply that the J-20 was designed to providing a superior supersonic maneuverability - it's all about retaining kinetic energy to control the range of the engagement.
Something which would make state-of-the art engines even more crucial.
The relative long fuselage and canard-delta design imply that the J-20 was designed to providing a superior supersonic maneuverability - it's all about retaining kinetic energy to control the range of the engagement.
Something which would make state-of-the art engines even more crucial.
Re: Chinese Engine Development
That IR signature still probably won't matter until the merge with the current state of electro optical sensor. BVR will still be dictated by radar and WVR will still be dictated by kinematics. Getting a clear image at long range is not the same as getting a lock, which is also not the same as getting a kill. Assuming that your IR signature can get you a lock at BVR when your opponent fires mraams at you your survivability will still depend on how fast you can out turn the missile. Furthermore your IR missiles will still probably be range limited. Finally if you're both traveling at supersonic speeds we''re not taking a world of difference in IR detectability. This decoy thing is a bit fanciful by half. If it were so great then what's to stop an F-22 mimicking an F-15? We're not even talking about visual detection here. Ultimately it seems like you're suggesting that an opponent would sandbag if they thought they were facing a lesser threat, which just isn't how militaries conduct their business.
The F-22 is designed to supercruise at high altitude. If the J-20 can't (which would be odd because when they talk about supercruising at mach 1.8 that's a mach regime that's only practical at high altitude) it will be outmatched.
That IR signature still probably won't matter until the merge with the current state of electro optical sensor. BVR will still be dictated by radar and WVR will still be dictated by kinematics. Getting a clear image at long range is not the same as getting a lock, which is also not the same as getting a kill. Assuming that your IR signature can get you a lock at BVR when your opponent fires mraams at you your survivability will still depend on how fast you can out turn the missile. Furthermore your IR missiles will still probably be range limited. Finally if you're both traveling at supersonic speeds we''re not taking a world of difference in IR detectability. This decoy thing is a bit fanciful by half. If it were so great then what's to stop an F-22 mimicking an F-15? We're not even talking about visual detection here. Ultimately it seems like you're suggesting that an opponent would sandbag if they thought they were facing a lesser threat, which just isn't how militaries conduct their business.
The F-22 is designed to supercruise at high altitude. If the J-20 can't (which would be odd because when they talk about supercruising at mach 1.8 that's a mach regime that's only practical at high altitude) it will be outmatched.
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