J-20 5th Gen Fighter Thread VI

[taxiya]

Maybe after TVC is incorporated.

TVC can help the yaw control. But removing the ventral fins will expose the round nozzles to radar beams on the side. The flat surfaced fins reflect the radar beam away from the source.
The ventral fins are not only meant to be yaw stability, but also contribute to radar stealth on the side for the round nozzle. If one goes for F-22 style, the fins can be eliminated for stealth purpose, but one must then increase the area of the vertical stabilizer for yaw control, in turn increase returning radar signal strength in a fan shaped area. It is all about compromise.

 

[Air Force Brat]

TVC can help the yaw control. But removing the ventral fins will expose the round nozzles to radar beams on the side. The flat surfaced fins reflect the radar beam away from the source.
The ventral fins are not only meant to be yaw stability, but also contribute to radar stealth on the side for the round nozzle. If one goes for F-22 style, the fins can be eliminated for stealth purpose, but one must then increase the area of the vertical stabilizer for yaw control, in turn increase returning radar signal strength in a fan shaped area. It is all about compromise.

Only Russian 3D OVT is able to "yaw" the aircraft, the flat nozzles of the F-22 are 2D and have no influence over aircraft "yaw", and while you are right, if those vents weren't needed for "yaw" control, they would be gone very shortly, a shorter "stubby" might be retained to minimize L/O, but I would be very skeptical,, as nowhere in the J-20 design analysis was that suggested??

In any regard, I rather doubt that the J-20 will ever fly without those ventral fins?? they also act to "depitch" the post stall aircraft once positive pitch input has ceased.

 

[Totoro]

Yaw can be achieved without any TVC if using two engines. When left engine outputs more thrust than right, plane will yaw to the right.

 

[taxiya]

Only Russian 3D OVT is able to "yaw" the aircraft, the flat nozzles of the F-22 are 2D and have no influence over aircraft "yaw", and while you are right, if those vents weren't needed for "yaw" control, they would be gone very shortly, a shorter "stubby" might be retained to minimize L/O, but I would be very skeptical,, as nowhere in the J-20 design analysis was that suggested??

In any regard, I rather doubt that the J-20 will ever fly without those ventral fins?? they also act to "depitch" the post stall aircraft once positive pitch input has ceased.

Actually I was not suggesting that the fins will be gone if they are not needed for "yaw" control.

Maybe the "yaw" control is not the right wording. It is more appropriate to say they are meant to maintain "yaw" (that vector or axis) stability when the vertical stabilizers are blocked by the main wings in high AoA.

Only the Russians can do without the fins on J-20 or big vertical stabilizers on the F-22 by employing 3D OVT.

As of the L/O aspect of the fins, it is only my speculation, not from any readings. But that is a point easy to see, a flat surface reflect radar beams to a very narrow direction, while the round nozzles with lots of grooves will scatter radar beams everywhere. It is the same principle why F-22 has its nozzles buried.

So my guess is that the fins will stay even if J-20 is equipped with 3D nozzles.

 

[noone536]

Yaw can be achieved without any TVC if using two engines. When left engine outputs more thrust than right, plane will yaw to the right.

yep same principal used in the b-2

 

[Air Force Brat]

Yaw can be achieved without any TVC if using two engines. When left engine outputs more thrust than right, plane will yaw to the right.

that's not operationally safe or practical, say you are post-stall and have lost directional stability, how are you going to modulate throttles,, twin engine aircraft are always operated with the throttles in one hand, and operated in unison, recipe propeller driven aircraft do have a "synchronizer", where you incrementally increase or decrease thrust on one engine to "sync your props"..

Multi engine aircraft are accelerated beyond best climb speed to "blue line", that airspeed where if you lose an engine, you will not lose yaw control, because the rudder has enough control authority to maintain directional control. so NO that's not a practical means for directional control, if your multi engine examiner found you messing around with that, he would "bust your check ride"!

Yes, I do realize that in extreme situations, such as the Sioux City DC-10 crash, that differential throttle was used for yaw/roll control, but you see the results of that landing attempted in those conditions where the complete destruction of the aircraft, and the loss of many lives.

 

[Air Force Brat]

yep same principal used in the b-2

actually the B-2 uses a split flap to create drag, yawing the aircraft to the right or left,, those split flaps are controlled by the yoke/FCS computers...

please post an authoritative source for your assertions,, not saying the FCS may not modulate throttles,, to be very honest I'm not familiar with all the particulars of the B-2, because I find tail-less to be kinda half- axed, not really suitable for fighter type aircraft,,

in any regard the J-20 will be maintaining those ventral fins for primary directional control,,, like a 4 fletched arrow, the J-20 is directionally very stable, and I for one, "Highly Approve" of the ventral fins, they make the J-20 a very safe aircraft to fly, and one that continues to handle very well even at very low airspeed.... that gentlemen is the idea!

 

[Air Force Brat]

actually the B-2 uses a split flap to create drag, yawing the aircraft to the right or left,, those split flaps are controlled by the yoke/FCS computers...

please post an authoritative source for your assertions,, not saying the FCS may not modulate throttles,, to be very honest I'm not familiar with all the particulars of the B-2, because I find tail-less to be kinda half- axed, not really suitable for fighter type aircraft,,

in any regard the J-20 will be maintaining those ventral fins for primary directional control,,, like a 4 fletched arrow, the J-20 is directionally very stable, and I for one, "Highly Approve" of the ventral fins, they make the J-20 a very safe aircraft to fly, and one that continues to handle very well even at very low airspeed.... that gentlemen is the idea!

actually after re-reading this, those split flaps are no doubt controlled by the "rudder pedals", even though the B-2 has no verts or actual "rudder"!

I'd still be very much interested to read the source, for your assertion that differential thrust is part of that equation, and I'll make an attempt to do a little digging on my own..

the XB- version of the Northrupp flying wing was abandoned due to poor flying characteristics,, it was initially powered by turbines, later turbo-jets and was a gorgeous thing, but had some very dangerous areas of the envelope that were unmanageable until the advent of computer aided FCS...

 

[SinoSoldier]

Newest rumor from Hui Tong:

山东日照民航机场惊现J-20隐身战机，估计连空管都搞不清楚它什么时候降落的

不知道此行是否与海军有关？

图片来源见水印。

Said to be a (land-based?) naval variant of the J-20

 

[SinoSoldier]

Newest rumor from Hui Tong:



Said to be a (land-based?) naval variant of the J-20
View attachment 44868

Actually, this is not confirmed yet; some people are saying it's just an exhibit. Or maybe one of the earlier prototypes?