J-20 5th Gen Fighter Thread VI

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jobjed

Captain
I don't think you can say that. The two types of wings have completely different shapes. You cannot eyeball the size the wings. You need to measure the surface area.

Wing surface area only tells part the story. There's also the lifting body which often gets discounted. Also, the pressure differential (lift force) between the lower and upper surfaces of the wing and lifting body can vary depending on how the wing interacts with the freestream, e.g. if the leading edges generate energetic vortexes, the lift force will be greater than a wing with conventional laminar flow, and if they generate vortexes well into an AOA regime where normal wings won't even have laminar flow but turbulent boundary layer separation, then it'll generate magnitudes more lift than a conventional wing.

Considering the J-20 pilot said the J-20's subsonic manoeuvrability was pretty good while its supersonic manoeuvrability was unmatched by anything in the PLAAF fleet, I'd hazard the J-20's canards, LERX and chines excite enough vortexes that during supersonic high-alpha manoeuvring, the J-20's lifting body and wings continue generating lift when conventional wings suffer boundary layer separation due to the low air density. In other words, it's not so much the J-20's manoeuvrability improves during supersonic manoeuvring, it simply doesn't go to shit like with most other airframes currently in service.
 

latenlazy

Brigadier
So i guess then the Flanker besides has somethink like 100m~2 metrs haha
specially if i add the LEX of the Flankers and part of the tail boom
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No. The Flanker has a wing area of 62 m^2.

In case you didn't know, this is how you measure wing area mister plane expert.

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You're supposed to calculate the entire area between the wings. So much for all that "studying".
 

Engineer

Major
Here it is:


To admit I’m disappointed with that report since it draws a few – IMO misleading or even wrong - conclusions based on quotes that were put into the wrong context:

Why are you surprised? That's how media works in the West. A conclusion is formed first, and then quotes are selective mined or distorted to support the conclusion.

In this case, people still don't want to accept the fact that J-20 is a stealth fighter. So to exclude J-20 from fighter classification, they claim the aircraft to be big, then they have to do mental gymnastics like calling a weapon bay that has shown less capacities as bigger than F-22's weapon bay.

It is a Propaganda 101 tactic that our resident Russian fanboy engages in all the time. Satellite photos that capture J-11 and J-20 side-by-side clearly show J-20 to be smaller. To our fanboy, the satellite camera is "a fanboy" and "in a club".
 
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latenlazy

Brigadier
Wing surface area only tells part the story. There's also the lifting body which often gets discounted. Also, the pressure differential (lift force) between the lower and upper surfaces of the wing and lifting body can vary depending on how the wing interacts with the freestream, e.g. if the leading edges generate energetic vortexes, the lift force will be greater than a wing with conventional laminar flow, and if they generate vortexes well into an AOA regime where normal wings won't even have laminar flow but turbulent boundary layer separation, then it'll generate magnitudes more lift than a conventional wing.

Considering the J-20 pilot said the J-20's supersonic manoeuvrability was unmatched by anything in the PLAAF fleet, I'd hazard that the J-20's canards, LERX and chines excite enough vortexes that during supersonic high alpha manoeuvring, the J-20's lifting body and wings continue generating lift when conventional wings suffer boundary layer separation due to the low air density. In other words, it's not so much the J-20's manoeuvrability improves during supersonic manoeuvring, it simply doesn't go to shit like with most other airframes currently in service.
While in terms of what's happening aerodynamically this is right, the entirety of that is encapsulated into the lift and drag coefficient curves, which are experimentally determined and specific to the geometry of the plane. Technically though wing area includes the part of the fuselage in between the two wings, because the primary lifting force generated by the wings acts on that whole section.

Of course wing area and wing loading is actually a simplification of what you actually care about in determining a plane's aerodynamic performance, which is the overall pressure distribution above and below the plane, and the net pressure differential. It's that net pressure differential that generates the lifting force, and ultimately what you care about isn't how much wing area you have or how much wing loading there is, but the the quantity of force acting on the quantity of mass per area. You could have a highly loaded wing and it may still outperform a lowly loaded one if that wing has a much greater lift coefficient and better lift to drag ratio, and thus generates more lifting force per area for less drag.

In real life though the wing isn't some separate element from the rest of the plane that lifting forces act on in isolation. The entirety of the plane's surface is where the lifting force is acting on, so the entirety of the plane's surface is technically the "wing". In real life the lift and drag coefficient curves for a plane aren't for its wings, but for the whole air frame. Lifting forces act on the whole geometry of the plane as a holistic system, not just on the wings. This is why eyeballing a plane's performance is a exercise in stupidity and futility. You need to know how the airstream acts on the entirety of the plane's shape, and not just on its parts, because how the airstream acts on one part cascades and affects how the airstream acts on other parts. Without either experimentally determining the plane's lift and drag coefficients at every flight envelope or modeling it with a computer you won't know a thing about its actual performance characteristics.
 
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BlueSeadragon

Just Hatched
Registered Member
The great value of the J-20 lies in its shape. The heart of effective (radar) stealth (there are other kinds of stealth, e.g. heat) lies in shape. The largest stealth aircraft is also the most stealthy - shape really matters. As China masters coatings, its J-20 will become even more stealthy, because the base platform is so well shaped. Over time, no doubt more power will become available - and that should give the J-20 the ability to supercruise. It is an impressive basic design.
 

Engineer

Major
If you want to understand why they say that you have to understand the size of the machine it self, consider the size of the weapons bays, if you just look at the main landing gear to the inlet lip you will notice the F-22 has a shorter size weapons bays, also it is no mystery the J-20 by having a longer nose to nozzle section it will be able to carry more fuel.
By weapons bays and fuel tanks you can easily guess with economical engines will have longer range and very likely bigger weapons inside the bays.
F-22 and J-20 have weapon bays that are nearly the same size. The weapon bay begins just after the inlet for both aircraft. For J-20, the weapon bay ends near the wing-root leading edge. For F-22, the end of weapon bay goes pass the wing-root leading edge all the way to the mid-chord of the wing.
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From the nozzle to nose section you can see they are packing more volume than F-22, without TVC nozzles and a 1.4 TWR at combat it is unlikely it will be a match to F-22, thus it it will operate over the sea operation with lower TWR then it is more or less like an F-35.
There is no need for J-20 to have TVC before classifying J-20 as a fighter, just as there is no need for F-35 to have TVC to classify F-35 as a fighter. Furthermore, TVC is considered so important on Russian jets only because Russia lacks behind in applying aerodynamics.
 
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