Chengdu J-20 pictures, analysis and speculation Part II

chuck4

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Just noticed the thing has at least 4 other pitot tubes besides the one at the tip of the nose radome. 2 below the radome, two besides cockpit.

It also seem to have a small angle of attack sensor sticking out the side of the nose radome.

This suggest the flight control system needs a lot of air data to compare, and the plane is more unstable than is usual.

What I thought was a window for distributed aperture sensor right in front of the cockpit, it's not there in this better picture.

There is still that diamond shaped window on the side the fuselage behind the radome. May be part of MAW system?

I also notice the side of the acturator blisters under the wings for the flapperons don't merge into the wing at the same angle as fuselage side as on the F-22. Instead they seem to merge into the wing at close to 90 degrees. So at least in this part they didn't pay as much attention to stealth as they might have.
 

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Chengdu J-20 cockpit mockup on display at Airshow China 2012 2010.

Source:
http://chinesemilitaryreview.blogspot.com/2012/01/cockpit-of-j-20-mighty-dragon-stealth.html

IMAGE REMOVED: Believed it was taken at this year's China Airshow
 

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I think the weapons display is a bit off - it shows the rough outline of an F-22.
 

Deino

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Can anyone please explain me how on earch such a BS can make it into a JDW report ??? ? :eek:

That's simply a J-20 RC model - and at least anyone who would do a bit of research would easily find out ! ??? - but to assume a twin engined VTOL-type being under development in China based on the J-20
.... what the hell became of Jane's ??? ??

Deino
 

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Janes turned into a mere compiler of other peoples work and press releases long ago. Only the books they publish for other authors are any good anymore.
 

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lancer21 said:
Perhaps this is a cockpit mock-up for J-31 then...
correct. it matches 1/4 scale model cockpit almost 100%
 

totoro

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chuck4 said:
I also notice the side of the acturator blisters under the wings for the flapperons don't merge into the wing at the same angle as fuselage side as on the F-22. Instead they seem to merge into the wing at close to 90 degrees. So at least in this part they didn't pay as much attention to stealth as they might have.

Maybe they thought they're safe regardless of shape, if they made the better part of that blister, as you call it, of RA material. I really don't see any other reason why the actuator fairings are so huge. Even on j10, which has similar configuration and is cheaper design a was made 13 years earlier the actuators are much, much smaller. Even when taking into account larger plane and larger control surface, the actuators themselves don't have to be even a quarter of the size of fairings seen on j20. I am not saying it is so, but if one wanted to, one could easely fit 3-5 cm thick RA material on each side of that actuator within that fairing size limit.
 

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What are those little stubs sticking out from the nose radome? AOA sensors?
 

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2IDSGT said:
Pitot tubes (some of them).
The ones that bend around to point forward are pitot tubes. The 4 that sticks out sideways from the radome can't be ordinary pitot tubes. They seem to some other air data sensor that, judging from their location, are part of the airplane's permanent equipment, not just flight test suite.
 

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chuck4 said:
2IDSGT said:
Pitot tubes (some of them).
The ones that bend around to point forward are pitot tubes. The 4 that sticks out sideways from the radome can't be ordinary pitot tubes. They seem to some other air data sensor that, judging from their location, are part of the airplane's permanent equipment, not just flight test suite.
They could be directional sensors of some kind to feed data to the flight computer, but they look too delicate to be a permanent part of the flight control system (easily damaged by ice or other rigors). Their positioning also seems awkward in relation to where one might assume the radar goes. We'll just have to see if the things disappear later on to be sure.
 

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Zoom in and it's very easy to see that they're AoA sensors; swept angular fins that sit on circular bases.

Undoubtedly, they'll be removed in later airframes, and would simply be there now for flight envelope testing.
 

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If they are temporary AOA sensors for test purposes only, then they would work better and more cleanly, and can be arranged more efficiently, on a long instrumented nose probe characteristic of many other prototype or development airframes, instead on the side radome.
 

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You would imagine so, but with a lack of such sensors on the nose probe, I stand by my view.

If 2002 has a working radar, wouldn't having moving fins, in the centre of the array's FOV prove troublesome?
 

chuck4

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Dragon029 said:
You would imagine so, but with a lack of such sensors on the nose probe, I stand by my view.

If 2002 has a working radar, wouldn't having moving fins, in the centre of the array's FOV prove troublesome?
Not necessarily. The sensors are fairly close to the rear edge of the radome. Due to stealth shaping of the radome edge, the rear edge of the radome on j-20 would not define the location of radar bulkhead. The actual bulkhead must lie some small distance ahead of the radome edge. So these probes on the radome might well be mounted near the radar bulkhead, and out of the field of view of the radar antenna.
 

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The reason they're mounted in that arrangement is most likely because they're being used to calibrate the FCS. When the stealthy sensors replace them they work partly due to the pressure patterns around the nose and by knowing the pressure distribution with respect to alpha, sideslip, and q they can deduct where the aircraft is within its flight envelope.
 

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Sundog said:
The reason they're mounted in that arrangement is most likely because they're being used to calibrate the FCS. When the stealthy sensors replace them they work partly due to the pressure patterns around the nose and by knowing the pressure distribution with respect to alpha, sideslip, and q they can deduct where the aircraft is within its flight envelope.
That would make sense if the location of the current sensors are the same as those intended for future production pressure sensors. If they are purely development sensors to provide calibration data on actual alpha and sideslip, then they would work better in a nose probe where the airflow is clean and undisturbed.
 

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chuck4 said:
That would make sense if the location of the current sensors are the same as those intended for future production pressure sensors. If they are purely development sensors to provide calibration data on actual alpha and sideslip, then they would work better in a nose probe where the airflow is clean and undisturbed.

I'm talking about calibration at their current locations. A nose probe can't do that, which is why that isn't what they are. The earlier prototypes had the nose probe for that purpose. Also, there are other ways you can do it without the nose probe, like the B-2 did with the drag drogue, but that's most likely just for subsonic speeds.
 

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Found at the SDF .... interesting satellite image :eek:






Truely an interesting image but again the author forgot that Xi'an is not only the home of XAC but even more important the CFTE !!!
 

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Would be nice if they gave latitude and longitude
 

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I think this is a good photo to see that the J-20 is smaller than a J-11/15.
A rough estimate: length: 19.2...20.7m, span: 12.8...13.8m.
 

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Once again - and hopefully finally in regard to "laarger than 23m !" - I played around a bit with the latest image from Xi'an-Yanglian !

What do You think ?

Deino
 

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LowObservable

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Nice on. RAF Medmenham will be calling.

However, it is still important to remember that dimensions are not size. The J-20 is pretty monolithic from nose to jetpipe, while the Su has the skinny cobra-like nose in front and is all jetpipes and tails behind the wing.
 

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Wonder how the J-20s volume compares to a Foxhound or F-111. There's probably a lot of fuel in that sucker.
 

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Much of the volume is undoubtedly taken up by serpentine intake ducts and the 3 internal weapon bays. It's not clear how much is left for fuel. Assuming the Chinese aim for similar overall lift characteristics in combat weight as other maneuverable fighters, one ought to be able to guess at its intended combat weight by making some assumptions about its fuselage lift characteristics (I imagine that to be similar to F-22, due to similar geometry) and looking the size of the wings.

My overall impression is the wings are not that large, compared to F-22, this suggests to me the aircraft isn't meant to be much heavier than F-22. Also, both the thrust of WS-10 engines (~13,000 KgF with AB), and the rumored thrust of the rumored WS-15 engines (~18,000 KgF, presumably with AB), does not suggest this to be an exceptionally heavy fighter, unless the Chinese are willing to accept unusually low T/W ratio. It suggests to me this fighter is about as heavy as F-22, possibly even a little lighter.

It's lengthy fuselage might suggest it is designed to either cruise or burst faster than F-22, or cruise supersonically on less thrust than F-22.

So I would guess either J-20 is lighter than everyone seem to think, or not meant to be very maneuverable by G4 or G5 fighter standards.
 

sferrin

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chuck4 said:
Much of the volume is undoubtedly taken up by serpentine intake ducts and the 3 internal weapon bays. It's not clear how much is left for fuel. Assuming the Chinese aim for similar overall lift characteristics in combat weight as other maneuverable fighters, one ought to be able to guess at its intended combat weight by making some assumptions about its fuselage lift characteristics (I imagine that to be similar to F-22, due to similar geometry) and looking the size of the wings.

My overall impression is the wings are not that large, compared to F-22, this suggests to me the aircraft isn't meant to be much heavier than F-22. Also, both the thrust of WS-10 engines (~13,000 KgF with AB), and the rumored thrust of the rumored WS-15 engines (~18,000 KgF, presumably with AB), does not suggest this to be an exceptionally heavy fighter, unless the Chinese are willing to accept unusually low T/W ratio. It suggests to me this fighter is about as heavy as F-22, possibly even a little lighter.

It's lengthy fuselage might suggest it is designed to either cruise or burst faster than F-22, or cruise supersonically on less thrust than F-22.

So I would guess either J-20 is lighter than everyone seem to think, or not meant to be very maneuverable by G4 or G5 fighter standards.
The YF-22 had ~25,000lbs of internal fuel. The J-20 has more internal volume than it did.
 

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knowing more or less the dimensions of j20, one can superimpose the pice of it and f22 taken from the front and then one can tell the frontal cross section is pretty similar to one of f22. however, fuselage length difference is noticeable. f22 has quite an overhang of its control surfaces behind the engine nozzles. j20 has less of an overhang. all in all, j20 has fuselage that is easely 2 meters longer. Plus a more tapered belly towards the engine nozzles.


I would be surprised if j20 doesn't end up having at least some 4-5 cubic meters of internal fuselage volume more than the f22. Weapons bay seems to be some 20% bigger, so part of the extra volume is spent there. Perhaps ws15 engines are planned to be of somewhat greater dimensions... or/and they use more fuel per thrust given. who's to say. but the plane certainly has plenty of room for fuel. that is, of course, both good and bad at the same time.
 

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totoro said:
knowing more or less the dimensions of j20, one can superimpose the pice of it and f22 taken from the front and then one can tell the frontal cross section is pretty similar to one of f22. however, fuselage length difference is noticeable. f22 has quite an overhang of its control surfaces behind the engine nozzles. j20 has less of an overhang. all in all, j20 has fuselage that is easely 2 meters longer. Plus a more tapered belly towards the engine nozzles.


I would be surprised if j20 doesn't end up having at least some 4-5 cubic meters of internal fuselage volume more than the f22. Weapons bay seems to be some 20% bigger, so part of the extra volume is spent there. Perhaps ws15 engines are planned to be of somewhat greater dimensions... or/and they use more fuel per thrust given. who's to say. but the plane certainly has plenty of room for fuel. that is, of course, both good and bad at the same time.
I simply don't think the likely engine thrust and wing area suggests a versatile and maneuverable fighter capable of handling an exceptional internal fuel capacity.
 

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Way back when the first J-20 pics came out, I thought stealthy interceptor/light bomber/anti-ship with a little bit of fighter agility in there too but not much. Depending on how big the bomb bay volume is. It's at least as big as the f-22s. A stealthy Mig-31/F-111 with some added agility.


Mig-31 type Interceptor to supercruise patrol those vast Chinese borders, anti-ship/anti US carrier, and some light stealthy bombing missions. Actually, the Chinese would deem the f-22 as inadequate for those functions. they wanted more fuel volume and a bigger weapons bay and they got it. but obviously they like the canard heritage of the j-10 and the frontal stealth aspect of the f-22. Its going to be perfect for their needs.


The j-31 if it gets to production will fill their low-end needs and export. the Chinese are doing really good commercially, and their aerospace industry is pragmatic and cost effective. They might even outsell the f-35 because of affordabilty. We will see. Makes me wonder what their next Gen design is going to look like.


As far as stealth, i would even say the J-20 is Stealthier than the Sukhoi T-50.
 

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Assuming the reference image I used to calculate wing area was fairly accurate, I arrived at these approximate figures for overall reference wing area based on the speculated dimensions provided above:

Length - Wing Area
19.2 meters (63 feet) - 71 square meters (763 square feet)
20.35 meters (66.75 feet) - 79.9 square meters (860 square feet)
20.7 meters (67.9 feet) - 82.6 square meters (889 square feet)

For comparison, the F-22 has a length of slightly above 18.9 meters (62 feet) and a wing area of 78.4 square meters (840 square feet).

If (and this is a big if) the J-20 has a similar weight per unit length as the F-22, the following wing loadings can be calculated. These figures may not be that unreasonable since the two are in roughly the same size range and have similar design elements (the boxy fuselage, closely-spaced engines, low aspect ratio wings, fixed inlets, internal weapons, same canopy, etc). Take note that I did some rounding with the numbers.

Length - Loaded Weight - Wing Loading

19.2 meters (63 feet) - 29,700 kilograms (65,400 pounds) - 418 kilograms/square meter (86 pounds/square foot)
20.35 meters (66.75 feet) - 31,500 kilograms (69,300 pounds) - 394 kilograms/square meter (81 pounds/square foot)
20.7 meters (67.9 feet) - 32,000 kilograms (70,500 pounds) - 387 kilograms/square meter (79 pounds/square foot)

You may have noticed that the larger values for length generate lower values for wing loading. Due to scaling laws, this is almost certainly incorrect. Using the square-cube law (and using the lowest length value as a baseline) more realistic wing loadings may be calculated:

Length - Loaded Weight - Wing Loading

19.2 meters (63 feet) - 29,700 kilograms (65,400 pounds) - 418 kilograms/square meter (86 pounds/square foot)
20.35 meters (66.75 feet) - 35,400 kilograms (77,900 pounds) - 443 kilograms/square meter (91 pounds/square foot)
20.7 meters (67.9 feet) - 37,200 kilograms (82,000 pounds) - 450 kilograms/square meter (92 pounds/square foot)

For comparison, the F-22's loaded weight is 29,300 kilograms (64,460 pounds) and its wing loading in this state is 375 kilograms/square meter (77 pounds/square foot). All of these estimates put it at a higher wing loading than the F-22. However, I would also like to point out the the range of wing loadings calculated is still rather "fighter-like". Compare these values with those of the F-16C Block 30 (at 431 kg/m2 or 88.3 lb/ft2), the F-35A (at 526 kg/m2 or 107 lb/ft2), the F/A-18E/F (at 459 kg/m2 94 lb/ft2), and the Su-35S (at 408 kg/m2 or 84.9 lb/ft2).

It should also be remembered that there are many other factors that affect an aircrafts lift than just wing loading alone. There is also leading edge sweep, taper ratio, camber, airfoil profile, types and sizes of leading edge/trailing edge flaps/flaperons, wing interactions with other aircraft structures (such as LERX and canards), thickness ratio, how it is integrated with the fuselage, etc.

In the end, I believe that the J-20 was designed with agility as a high priority. Not just the theoretical wing loading calculations, but the all-moving canards, tails and the canopy design lead me to this conclusion as well. If speed, supersonic cruise and range were all they cared about, a tailless delta would probably have been both a stealthier and a less-draggy option than a canard-delta.
 

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kcran567 said:
Way back when the first J-20 pics came out, I thought stealthy interceptor/light bomber/anti-ship with a little bit of fighter agility in there too but not much. Depending on how big the bomb bay volume is. It's at least as big as the f-22s. A stealthy Mig-31/F-111 with some added agility.


Mig-31 type Interceptor to supercruise patrol those vast Chinese borders, anti-ship/anti US carrier, and some light stealthy bombing missions. Actually, the Chinese would deem the f-22 as inadequate for those functions. they wanted more fuel volume and a bigger weapons bay and they got it. but obviously they like the canard heritage of the j-10 and the frontal stealth aspect of the f-22. Its going to be perfect for their needs.


The j-31 if it gets to production will fill their low-end needs and export. the Chinese are doing really good commercially, and their aerospace industry is pragmatic and cost effective. They might even outsell the f-35 because of affordabilty. We will see. Makes me wonder what their next Gen design is going to look like.


As far as stealth, i would even say the J-20 is Stealthier than the Sukhoi T-50.
No one sticks canards onto a plane just because they like it. The chines, LERXes, and canards all indicate a plane that's optimized for maneuverability, so I'm dubious of the conclusion that it will have limited agility.

totoro said:
knowing more or less the dimensions of j20, one can superimpose the pice of it and f22 taken from the front and then one can tell the frontal cross section is pretty similar to one of f22. however, fuselage length difference is noticeable. f22 has quite an overhang of its control surfaces behind the engine nozzles. j20 has less of an overhang. all in all, j20 has fuselage that is easely 2 meters longer. Plus a more tapered belly towards the engine nozzles.


I would be surprised if j20 doesn't end up having at least some 4-5 cubic meters of internal fuselage volume more than the f22. Weapons bay seems to be some 20% bigger, so part of the extra volume is spent there. Perhaps ws15 engines are planned to be of somewhat greater dimensions... or/and they use more fuel per thrust given. who's to say. but the plane certainly has plenty of room for fuel. that is, of course, both good and bad at the same time.
I wonder about that. While the J-20's fuselage does seem longer, the F-22's horizontal and vertical tails are much bigger than the J-20's vertical tails and canards. That should offset some of the volume difference.

Kryptid said:
Assuming the reference image I used to calculate wing area was fairly accurate, I arrived at these approximate figures for overall reference wing area based on the speculated dimensions provided above:

Length - Wing Area
19.2 meters (63 feet) - 71 square meters (763 square feet)
20.35 meters (66.75 feet) - 79.9 square meters (860 square feet)
20.7 meters (67.9 feet) - 82.6 square meters (889 square feet)

For comparison, the F-22 has a length of slightly above 18.9 meters (62 feet) and a wing area of 78.4 square meters (840 square feet).

If (and this is a big if) the J-20 has a similar weight per unit length as the F-22, the following wing loadings can be calculated. These figures may not be that unreasonable since the two are in roughly the same size range and have similar design elements (the boxy fuselage, closely-spaced engines, low aspect ratio wings, fixed inlets, internal weapons, same canopy, etc). Take note that I did some rounding with the numbers.

Length - Loaded Weight - Wing Loading

19.2 meters (63 feet) - 29,700 kilograms (65,400 pounds) - 418 kilograms/square meter (86 pounds/square foot)
20.35 meters (66.75 feet) - 31,500 kilograms (69,300 pounds) - 394 kilograms/square meter (81 pounds/square foot)
20.7 meters (67.9 feet) - 32,000 kilograms (70,500 pounds) - 387 kilograms/square meter (79 pounds/square foot)

You may have noticed that the larger values for length generate lower values for wing loading. Due to scaling laws, this is almost certainly incorrect. Using the square-cube law (and using the lowest length value as a baseline) more realistic wing loadings may be calculated:

Length - Loaded Weight - Wing Loading

19.2 meters (63 feet) - 29,700 kilograms (65,400 pounds) - 418 kilograms/square meter (86 pounds/square foot)
20.35 meters (66.75 feet) - 35,400 kilograms (77,900 pounds) - 443 kilograms/square meter (91 pounds/square foot)
20.7 meters (67.9 feet) - 37,200 kilograms (82,000 pounds) - 450 kilograms/square meter (92 pounds/square foot)

For comparison, the F-22's loaded weight is 29,300 kilograms (64,460 pounds) and its wing loading in this state is 375 kilograms/square meter (77 pounds/square foot). All of these estimates put it at a higher wing loading than the F-22. However, I would also like to point out the the range of wing loadings calculated is still rather "fighter-like". Compare these values with those of the F-16C Block 30 (at 431 kg/m2 or 88.3 lb/ft2), the F-35A (at 526 kg/m2 or 107 lb/ft2), the F/A-18E/F (at 459 kg/m2 94 lb/ft2), and the Su-35S (at 408 kg/m2 or 84.9 lb/ft2).

It should also be remembered that there are many other factors that affect an aircrafts lift than just wing loading alone. There is also leading edge sweep, taper ratio, camber, airfoil profile, types and sizes of leading edge/trailing edge flaps/flaperons, wing interactions with other aircraft structures (such as LERX and canards), thickness ratio, how it is integrated with the fuselage, etc.

In the end, I believe that the J-20 was designed with agility as a high priority. Not just the theoretical wing loading calculations, but the all-moving canards, tails and the canopy design lead me to this conclusion as well. If speed, supersonic cruise and range were all they cared about, a tailless delta would probably have been both a stealthier and a less-draggy option than a canard-delta.
How are you calculating the wing area? Are you just using the dimension of the wings, or are you including the fuselage area between the wings? If the former, are you doing the same with the F-22, or did you get pull that number from a reference? Regardless, good thorough work!

I think we've tried to calculate the wing area of the F-22 before just using the wing dimensions and got results that didn't match the reference.
 

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chuck4 said:
I simply don't think the likely engine thrust and wing area suggests a versatile and maneuverable fighter capable of handling an exceptional internal fuel capacity.
Do you think a Flanker is going to be flying Cobras etc. with a full internal fuel load? (That's a rhetorical question, because of course it's not.)
 

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Kryptid said:
Assuming the reference image I used to calculate wing area was fairly accurate, I arrived at these approximate figures for overall reference wing area based on the speculated dimensions provided above:

Length - Wing Area
19.2 meters (63 feet) - 71 square meters (763 square feet)
20.35 meters (66.75 feet) - 79.9 square meters (860 square feet)
20.7 meters (67.9 feet) - 82.6 square meters (889 square feet)

For comparison, the F-22 has a length of slightly above 18.9 meters (62 feet) and a wing area of 78.4 square meters (840 square feet).

If (and this is a big if) the J-20 has a similar weight per unit length as the F-22, the following wing loadings can be calculated. These figures may not be that unreasonable since the two are in roughly the same size range and have similar design elements (the boxy fuselage, closely-spaced engines, low aspect ratio wings, fixed inlets, internal weapons, same canopy, etc). Take note that I did some rounding with the numbers.

Length - Loaded Weight - Wing Loading

19.2 meters (63 feet) - 29,700 kilograms (65,400 pounds) - 418 kilograms/square meter (86 pounds/square foot)
20.35 meters (66.75 feet) - 31,500 kilograms (69,300 pounds) - 394 kilograms/square meter (81 pounds/square foot)
20.7 meters (67.9 feet) - 32,000 kilograms (70,500 pounds) - 387 kilograms/square meter (79 pounds/square foot)

You may have noticed that the larger values for length generate lower values for wing loading. Due to scaling laws, this is almost certainly incorrect. Using the square-cube law (and using the lowest length value as a baseline) more realistic wing loadings may be calculated:

Length - Loaded Weight - Wing Loading

19.2 meters (63 feet) - 29,700 kilograms (65,400 pounds) - 418 kilograms/square meter (86 pounds/square foot)
20.35 meters (66.75 feet) - 35,400 kilograms (77,900 pounds) - 443 kilograms/square meter (91 pounds/square foot)
20.7 meters (67.9 feet) - 37,200 kilograms (82,000 pounds) - 450 kilograms/square meter (92 pounds/square foot)

For comparison, the F-22's loaded weight is 29,300 kilograms (64,460 pounds) and its wing loading in this state is 375 kilograms/square meter (77 pounds/square foot). All of these estimates put it at a higher wing loading than the F-22. However, I would also like to point out the the range of wing loadings calculated is still rather "fighter-like". Compare these values with those of the F-16C Block 30 (at 431 kg/m2 or 88.3 lb/ft2), the F-35A (at 526 kg/m2 or 107 lb/ft2), the F/A-18E/F (at 459 kg/m2 94 lb/ft2), and the Su-35S (at 408 kg/m2 or 84.9 lb/ft2).

It should also be remembered that there are many other factors that affect an aircrafts lift than just wing loading alone. There is also leading edge sweep, taper ratio, camber, airfoil profile, types and sizes of leading edge/trailing edge flaps/flaperons, wing interactions with other aircraft structures (such as LERX and canards), thickness ratio, how it is integrated with the fuselage, etc.

In the end, I believe that the J-20 was designed with agility as a high priority. Not just the theoretical wing loading calculations, but the all-moving canards, tails and the canopy design lead me to this conclusion as well. If speed, supersonic cruise and range were all they cared about, a tailless delta would probably have been both a stealthier and a less-draggy option than a canard-delta.
This is a very interesting bit of analysis. If you don't mind I am porting it to sinodefence and see what the gents there think of it.

Thank you in advance.
 

Sundog

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The simple answer is that the J-20 is optimized for supercruise where as the F-22 isn't, as it's designed to supposedly do everything well. Unfortunately, the F-22s fuel fraction was marginal to begin with, you want a fuel fraction greater than .25 for a supercruise fighter, but due to weight increases the F-22 is now below that number. Providing the Chinese were able to control the weight of their aircraft well it should prove to be a very capable supercruise fighter if they can get engines up to the task..
 
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