please link me to the SDF thread if possible

your picture links are not working for me 🙁

http://www.sinodefenceforum.com/air-force/discussion-j-20s-aerodynamics-comparison-f-22-some-guesswork-5603.html
I think the talk about canards/aerodynamics start around the 40 page mark or slightly beyond.


Do the pictures work now?

but you’re right, the WS-10 on J-11s could simply mean that its not an issue of production capacity, but that CAC is pleased with the AL-31FN in its J-10 and currently has no intention of adopting the WS-10 yet.

I think he’s saying SAC’s flankers have to use WS-10 out of necessity.

But really we don’t know that, and it’s just as possible WS-10 production can’t keep up with airframes.

I’m talking about limitation in Control and stability.

I’m sorry I still do not quite understand — are you saying there is a limitation in being able to use FCS to compensate for removing, say, the ventral fins on the J-20, and that the J-20 somehow circumvents this limitation?

Because that’s assuming there is a limitation in the first place with removing said strakes. Of course we don’t know whether there will be or not — but the impact of the removal of those fins would be far less, say than that of the canards or V tails. My belief is that they could be removed on production aircraft especially if the FCS on the prototypes aren’t fully developed.

Umm i think not.
While you can do great with improved FBW(U mean the Flight control system, FCS?)
It does not change anything in the overall performance.
The layout of this prototype tells us the current aerodynamic configuration NEED those Carnards.

Yeah the canards will remain, I was talking about the ventral fins when talking about “strakes”. That shouldn’t change the overall aerodynamic config too much would it?
I thought you were talking about that too?
(i meant fcs when i said fbw, yea)

If The FCS is so improved on this bird, why havent they managed to remove the huge airbrake(which is adding weight!) like the case on both the Su-35S and Pak-Fa prototypes, and instead just use the verticals as airbrakes(both inverting inwards)!?

That’s the thing, I don’t think the FCS/FBW has been completed (prototype). The airbrake could be one of the things which we wont’ see on the production version along with the strakes.

I’m not bashing anything here, i’m only responding to the vids and pics shown in this thread..

Yeah me too 😮
I’d like to see some of the pictures with the massive deflection of canards that were mentioned by overg as well.

Can anyone show a picture of the J-20 taking off or landing with massive canard deflection? And what qualifies “massive”?

This?

or this?

Cause if it’s the latter, I certainly haven’t seen such a great deflection before. If it’s the former… well that isn’t exactly massive imho.

A new missile (for me at least) that has appeared on a J-11 or J-15 (it looks like it’s in PLANAF grey?)

Now I don’t think it’s PSed, and I also think it’s new, but I’m not sure whether it’s a completely new model or a development of PL-12 or PL-11, though I’d imagine it’s the former.
Of course this raises some questions, because PL-12C is supposed to be the “compact” version, but the drawing/timeline we saw a while ago showed it only had foldable rear fins where as this one looks more like the compact AMRAAM with clipped fins rather than folding ones. It’s possible they chose to go for the AMRAAM approach rather than fold fins.
thoughts?

Overall, the stealth shaping of the J-20 prototype design is without doubt considerably better than that seen in the Russian T-50 PAK-FA prototypes and, even more so, than that seen in the intended production configuration of the United States’ F-35 Joint Strike Fighter

Surprise surprise, more refined shaping is not worth the trouble, and is not even more efficient.

So you have a big design issue here

To choice a determined shape, sacrificing structural hardeness (increasing structural weight), aerodynamic efficiency, internal space, and other factors

Or to get a more conventional shape, reaching RCS demands through RAM, but compensating the extra-weight with the benefits above.

Loockeed original JSF concepts had far better shapping for RCS requirements, the F-35 did end with a far more aerodynamic design

Guess what…the F-35 is actually more advanced than the F-22.

Sorry but are you saying the F-35’s stealth shaping is more advanced than the F-22? Or that shaping just isn’t important?

This is why I have mixed feelings over the J-20, the overall configuration is OK, but it seems they are doing exactly the same mistakes the LM team did over the F-22, as some guy in a magazine pointed out ‘the thing looks like it was designed in the 80’s’, well he was right…the things philosophy design is pretty close to the F-22’s one.

What mistakes were those, if you could clarify?

Shaping works nice, but in real life does have a limit, because shapping have a nice performance in static testing, the problem is that an aircraft is not static by nature.

So for the real life, the sacrifice of shaping, adding more RAM probably will give you a worse performance in a lab, but a much better performance in battle, and I’m talking about the RCS performance.

And this is why, a moder strike plane that was meant to overcome SAM defences has less ‘stealth’ shape than a old fighter that was never meant to challenge a S-300 battery.

So.. you’re saying an F-15 is more stealthy than an F-22? (old plane never meant to challenge SAM vs modern strike plane meant to overcome SAM)

Correct me if I’m wrong, but it seems like you’re saying RAM is more important than shaping for VLO.

Can somebody tell me why this plane does need such deflection on its canards, for landing AND take off?, is impressive , not even the J-10 demands such deflection.

No even the Mig-1.44 did, as far i recall.

From the videos and pictures I’ve seen I can’t seem to make out massive deflection?

http://www.youtube.com/watch?v=kiUNxETwICs

Detailed Analysis of J-20’s RCS by Carlo Kopp.

http://www.ausairpower.net/APA-2011-03.html

Opinions?

I’m not sure about the technical side of the analysis, but I agree with this statement

Overall, the stealth shaping of the J-20 prototype design is without doubt considerably better than that seen in the Russian T-50 PAK-FA prototypes and, even more so, than that seen in the intended production configuration of the United States’ F-35 Joint Strike Fighter

And also their conclusion

If the production J-20 retains the axisymmetric nozzles and smoothly area ruled sides, the aircraft could at best deliver robust Very Low Observable performance in the nose aspect angular sector.

If the production J-20 introduces a rectangular faceted nozzle design, and refinements to fuselage side shaping, the design would present very good potential for robust Very Low Observable performance in the S-band and above, for the nose and tail aspect angular sectors, with good performance in the beam aspect angular sector.