Striker or Interceptor? Assessing commentary on J-20's role

Bltizo said:

I think it is very likely that J-20's weapon bay is poorly suited for carrying strike weapons, and I think PAK FA's weapon bay may be more suited for carrying strike weapons yes, based on their respective depth, position and geometry. I never said I knew what their actual dimensions, only their depth relative to each other.

And yes, based on rumours and collective consensus I do believe WS-15 exists and is intended for J-20 as its primary powerplant.
I never claimed a date for when WS-15 will appear.




You've made a whole heap of assumptions as well, about J-20's role in the chinese air force based on the viability of other projects, assumptions about their supporting force multipliers, the way they may want to conduct strike, and the capability of the adversary.

No one is claiming to know the actual specifications of the aircraft, but based on what little reliable information we do have, we can infer a reasonable conclusion which is what I think I have done. I'm not claiming this conclusion is final or not subject to change, but at present with the information we have I think my position is well supported.

And just for the record I believe J-20 is multirole as well, in the same way that F-22 is multirole and other modern fighter aircraft are also multirole.

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Jeff Head said:

Based on that...while we may not be able to get an exact measurement...we can certainly get measurements easily to within a half a meter and less.

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b787 said:

That is relative, because even he or any one thinks it is 20.3 meters if you add less us say a small margin of error of 70 cm it can reach 21 meters or as small as 19.4 meters.

Specially on grainy pictures where pixels might eat up 50 cms of real size, and by the way, the Su-27 is as large as 21.9 meters

So i will not elaborate its size so well let us leave it, no point for more conjectures it might be 20.3 meters it might not be, so let us wait and see

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Bltizo said:

I've never claimed my position is unassailable, but I think I've clearly outlined the various premises for my position and the logical leaps between them.




We have enough evidence to make an estimate that J-20 is no more than 20.5m long, and likely a little shorter.

Its internal volume is no doubt larger than F-22s.




Yes, estimates of its weight is even more difficult to make than length and volume.



We have enough information about WS-15 to make an estimated guess, and we have enough official sources to guess that it's almost definitely meant to be competitive in ACM.




Incorrect -- any offensive strike action does not need to only depend on strike aircraft. Cruise missiles, conventional ballistic missiles would all be part of any action.

J-20 will be part of that action, yes, and I've never denied that J-20 could be a useful striker, but it is almost certainly not a dedicated striker.




J-20 will be multirole without physical changes -- it can likely be able to launch PGMs from its internal weapons bay.

The issue I have with your position is that you believe it is easy for J-20 to be developed into an effective striker like Su-34 was from Su-27... when in reality J-20 is hindered by the fact that it is a stealth fighter and to be a more dedicated striker it will require larger weapon bays which will require substantial modification to the airframe if not a whole new airframe to begin with.

Again, this isn't to say J-20 can't be a viable striker with its current weapons bay configuration, but to think that they'll develop a "strike J-20" variant at this stage is very unlikely given the limitations of its weapons bay depth.
If they develop a "strike J-20" it will be forced to carry weapons outside its bays, meaning it will have to compromise its RF stealth.

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vesicles said:

Using a known object as a reference to estimate the measurement of an unknown object is very valid. Yes, there are margins of error. However, you have to assume the same margins of error for the known object, as well as the unknown. This is because you are analyzing objects in the same image. You can't have "double standards" for different objects in the same image. If you underestimate the length and assume a "-70 cm" margin for the J-20, you will have to do the same to the Su-27. Similarly, if you want to over-estimate and add "+70 cm" to your measurement of the J-20, you will also need to do it to the Su-27. Since we know the exact dimension of the Su-27, we can effectively calibrate the whole system and minimize the margins of error to almost the level of accuracy. This is a proper and valid engineering and physics technique to measure objects otherwise unmeasurable. The key is that you have to have an object with exact known measurements to calibrate the system. In this case with the J-20, we happen to have it.

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Jeff Head said:

b787, this is turning into a senseless arguement.

Bltizo has written a good article about the aircraft. Better than most.

The fact is, we have ample photos of the J-20 next to vehicles and other aircraft that we know the exactly dimensions of.

Based on that...while we may not be able to get an exact measurement...we can certainly get measurements easily to within a half a meter and less.

Once we know the overall length and width to that degree...it is relatively easy to come up with dimensions for the weapons bay to the same degree. We have pictures of the open wepaons bay, and can use proportional methods to come up with those dimensions. This is all very straight forward.

Not an exact measure it is true...but well within reason.

There is simply no need to argue against that. Bltizo has not said he has an exact measurement. But his figures are going to be very close and certainly good enough for the basis of the discussion and the things he is projecting based on them.

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Engineer said:

My belief have been, and still is, that the J-20 will not have thrust vectoring. To elaborate:

• Designing and building a F119-class engine is difficult enough as it is. Chinese engineers are not going to make life more difficult for themselves by incorporating thrust vectoring.
• The term "super manoeuvrability" is misleading, as it conjures up the thought that thrust vectoring could make the aircraft more manoeuvrable on top of being manoeuvrable. The correct term to use is actually "post-stall manoeuvrability". Here comes the problem: stall is a bad thing, and an aircraft in a stall can lose a lot of energy in very short time. It makes no sense to get into a stall, then having to use post-stall manoeuvrability, especially in a dog fight.
• Modern fighter aircraft can already turn at 9 G's. If you can make an aircraft turn at, let say, 13 G's, what then? Then you have a dead pilot. Ironically, adding more manoeuvrability is not desirable; but that isn't the purpose of thrust vectoring anyway.

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