J-20 5th Gen Fighter Thread IV (Closed to posting)

[vesicles]

Looks like the 2011 may be twelve to sixteen inches longer than the earlier prototypes.

It looks that they only stretched out the tail section while maintaining the other parts the same. So it is not a proportional lengthening. Why did they do that? To hide the engines?

 

[Deino]

It looks that they only stretched out the tail section while maintaining the other parts the same. So it is not a proportional lengthening. Why did they do that? To hide the engines?

YES, I think it was at the Secret-Projects Forum where one member suggested - in mind of the same radome-like-colour, which is also used for other EW- and dielectric parts around the front fuselage - that it might contain something of a rearward facing radar ??!

Deino

 

[tphuang]

when facing enviroment with awacs, ground/ship based radar etc radiating from various directions it doesn't matter if youre in j20 or f22, both planes would suffer the same problems. that's why vlo design is made in accordance with planned operational use patterns.

vlo design is concentrated on ingress, and somewhat on egress. it can't also provide small rcs from most angles most of the time when f22/j20 actually get in combat and start manouvering left and right. which is why, as any fighter in history did really, vlo planes pick their fights, pick their ingress routes, do their job quikcly and then get the hell out of there. in real world its hard to have a bunch of opposition everywhere, all the time.

also, it'd be nice to know the author of the alleged academic paper. is it a random student from a random university? or an engineer with known experience working for avic?

It seems like a bigger issue with J-20, because it does have more moving surfaces than F-22. Especially since something like canards, which can move to create 90 degree angle with rest of the aircraft. But then again, that's probably why you don't see any other 5th gen aircraft with it.

 

[shen]

It seems like a bigger issue with J-20, because it does have more moving surfaces than F-22. Especially since something like canards, which can move to create 90 degree angle with rest of the aircraft. But then again, that's probably why you don't see any other 5th gen aircraft with it.

J-20 has exactly the same number of moving surfaces as F-22.
Canards will only be in the 90 degree position when acting as speed brakes, probably only on the ground. flight control system will never move the canards to anything approaching 90 degree when J-20 is maneuvering in the air.

 

[tphuang]

J-20 has exactly the same number of moving surfaces as F-22.
Canards will only be in the 90 degree position when acting as speed brakes, probably only on the ground. flight control system will never move the canards to anything approaching 90 degree when J-20 is maneuvering in the air.

Cleary my point wasn't that canard will form 90 degree angle for large quantity of time.

you are acknowledging the existence of canad, which can move in flight so that it's at an angle to the the wings. Those are certainly moving surfaces that are not on F-22, that the CAC engineers will have to account for when they are trying to minimize all aspect stealth.

 

[kyanges]

Cleary my point wasn't that canard will form 90 degree angle for large quantity of time.

you are acknowledging the existence of canad, which can move in flight so that it's at an angle to the the wings. There is also the moving tailfin. Those are certainly moving surfaces that are not on F-22, that the CAC engineers will have to account for when they are trying to minimize all aspect stealth.

They're *different* surfaces, not *more* surfaces.

 

[tphuang]

They're *different* surfaces, not *more* surfaces.

so you are telling me that the CAC engineers don't have to account for the RCS affect on canard when it moves?

 

[kyanges]

so you are telling me that the CAC engineers don't have to account for the RCS affect on canard when it moves?

.

I'm just saying Shen's point is that it's a different moving surface, not an extra one.

 

[Totoro]

but shen's point was that canard won't get close to 90 degrees ever. in flight. the moving tails are also just different surfaces from fixed tails with movable parts. number of surfaces that move is the same, just as number of corners that move.

actually, if one wanted to be meticulous about it, raptor's tails might in some instances produce more radar reflections, precisely because they have more gaps and edges. they have the leading edge, then the gap between the fixed part of tail and the rudder leading edge, then the trailing edge of the rudder. Compared to that, j20 has just the leading edge and the trailing edge. Of course, j20 might have issues with the base of the all moving tails with the swivel mechanism which may produce different (and possibly bigger) radar returns than simpler mechanisms for rudder movements on f22. but that's really speculation territory, no way to know.

 

[Blitzo]

Cleary my point wasn't that canard will form 90 degree angle for large quantity of time.

you are acknowledging the existence of canad, which can move in flight so that it's at an angle to the the wings. Those are certainly moving surfaces that are not on F-22, that the CAC engineers will have to account for when they are trying to minimize all aspect stealth.

technically Shen is still right, because there are still only as many moving surfaces on J-20 as F-22...

Leading edge, trailing edge, V rudders, and canards for J-20 and horizontal tails for F-22. Whether there is any major difference between the returns of a canard versus the horizontal tails is another matter.
But the original statement that J-20 has more moving surfaces is clearly wrong.



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Also I'm not sure why there was the mention of canards doing 90 degrees. Like you said, canards won't ever be doing 90 degrees in flight (if it is even physically possible) And furthermore, the horizontal tail of F-22 probably has the same range of motion in flight anyway.
So unless you're saying canards will generate greater returns because it is in front of the wing, there is no reason why canards are more disadvantageous to RCS reduction than having horizontal tails that hold a similar range of rotation.