F-22 vs PKA-FA thrust vectoring

Anything goes, as long as it is about the Lockheed Martin F-22 Raptor
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alloycowboy

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Unread post26 Jan 2018, 01:18

gta4 wrote:YF-23 MANEUVERS AS GOOD AS YF-22?

This is what I have read:

"YF-22 demonstrated 60 deg controllable AOA. YF-23 claimed to have very high controllable AOA but only demonstrated 22 deg. USAF emphasized so much on maneuverability so it chose YF-22."


Given the large vertical tail surfaces on the YF-23 I would say you are greatly mistaken.

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rheonomic

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Unread post26 Jan 2018, 01:22

sprstdlyscottsmn wrote:with the V shaped TVC it can produce Yaw, and yes there will be an accompanying roll moment. The roll is likely desired and if not then a proper FCS can counter the roll moment with inside (direction the nose is yawing) aileron dropping to hold the wing up which in addition also increases the asymmetrical drag pulling the nose in the desired direction for pure yaw.


Expanding on this, as the control effector suite becomes more complicated it results in the control allocation problem, where the FCS determines the best way to use the effectors to achieve the commanded moments based on the model of the aircraft's control effectiveness.

I'd really like to see what kind of allocator the PAK-FA/Su-57 uses, as it seems like there are some, uh, interesting deflections:
Image

I'd guess the LEFs are scheduled, but the other surfaces appear to be allocated.
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hythelday

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Unread post26 Jan 2018, 07:29

alloycowboy wrote:
gta4 wrote:YF-23 MANEUVERS AS GOOD AS YF-22?

This is what I have read:

"YF-22 demonstrated 60 deg controllable AOA. YF-23 claimed to have very high controllable AOA but only demonstrated 22 deg. USAF emphasized so much on maneuverability so it chose YF-22."


Given the large vertical tail surfaces on the YF-23 I would say you are greatly mistaken.



When I said YF-23 maneuvered as good as YF-22, I meant first and foremost the fact that both aircraft satisfied USAF requirements for maneuverability. F-22 achieved high angles if attack only after it was declared a winner (which wasn't because of its greater agility). YF-23 engineers were confident it could expand envelope past the bounfaries achieved during ATF fly-off. I.e. F-35 can do 50 deg AoA without TVC - and that is only a software limitation on operational machines. Test aircraft were flown in a controllable fashion at greater AoAs.
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gta4

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Unread post26 Jan 2018, 13:33

botsing wrote:
XanderCrews wrote:Image

https://www.youtube.com/watch?v=YV3zE6yZviE :mrgreen:


These picture clearly shows that the nozzle can not deflect laterally. It just deflects vertically in a "V" pattern.
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gta4

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Unread post26 Jan 2018, 13:35

hythelday wrote:gta, let me get this straight, you define 3D vectoring as "ability of nozzle to deflect in any direction of 360 deg circle freely just because it is cool" as opposed to "ability to deflect nozzle in a way that assists aircraft maneuver in pitch, roll and yaw"? Because according to your definition there are no operational aircraft with "3D" thrust vectoring, and Raptor is a "1D" TVC aircaft.

I may be illiterate, but I do know how simple vector math works. By deflecting left nozzle UP and LEFT, and right one DOWN and LEFT pilot assists plane in yawing to the left (as seen in Xanders picture up&right corner).


You are making the same mistake again.

It can not assist yaw because it generates ROLL MOMENT. The aircraft will roll instead of yaw.
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gta4

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Unread post26 Jan 2018, 13:40

And, why do you keep ignoring the fact that 20 deg > 15 deg?

Given the presence of "V" pattern, the maximum useful deflection is even inferior than 15 deg. It could be only 13-14 deg.

However, I strongly doubt you can understand this due to your limited math and physics knowledge.
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gta4

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Unread post26 Jan 2018, 13:49

sprstdlyscottsmn wrote:with the V shaped TVC it can produce Yaw, and yes there will be an accompanying roll moment. The roll is likely desired and if not then a proper FCS can counter the roll moment with inside (direction the nose is yawing) aileron dropping to hold the wing up which in addition also increases the asymmetrical drag pulling the nose in the desired direction for pure yaw.

However, aileron loses effect at low speed. There is no way to counter the ROLL moment.
Aileron don't even generate roll moment at high AOA. It generates yaw moment (proverse yaw effect).
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f-16adf

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Unread post26 Jan 2018, 16:19

The F-22's tail booms would probably be in the way for a 3D nozzle. And to put an extension on the engine would be heavy and costly aka F-14D F110. LM engineers probably thought the Raptor doesn't need 3D nozzle. Maybe not cost effective in the long run, and probably not very stealthy (and might further expose IR signature from rear).


Notice in videos the F-22 (and from what I was told) TV nozzle is linked with stab deflection (from the stick imput).

https://www.youtube.com/watch?v=ZH1gufgmopA

https://www.youtube.com/watch?v=XfPsF6KnR34



Su-35 is a button-

Here is Su-30:

https://www.youtube.com/watch?v=hYi1e4pOQJw
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popcorn

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Unread post27 Jan 2018, 00:46

Why entail the penalties of 3D TVC ( eg. weight, cost, complexity)when you can achieve the same performance with 2D TVC plus generous control surfaces and sophisticated CLAWs?
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juretrn

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Unread post27 Jan 2018, 00:53

popcorn wrote:Why entail the penalties of 3D TVC ( eg. weight, cost, complexity)when you can achieve the same performance with 2D TVC plus generous control surfaces and sophisticated CLAWs?

Does "3D" TVC really weigh that much more than "2D"?
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rheonomic

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Unread post27 Jan 2018, 01:06

popcorn wrote:Why entail the penalties of 3D TVC ( eg. weight, cost, complexity)when you can achieve the same performance with 2D TVC plus generous control surfaces and sophisticated CLAWs?


TBH TVC is pretty overrated except in limited circumstances.
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hythelday

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Unread post27 Jan 2018, 01:20

gta4 wrote:
sprstdlyscottsmn wrote:with the V shaped TVC it can produce Yaw, and yes there will be an accompanying roll moment. The roll is likely desired and if not then a proper FCS can counter the roll moment with inside (direction the nose is yawing) aileron dropping to hold the wing up which in addition also increases the asymmetrical drag pulling the nose in the desired direction for pure yaw.

However, aileron loses effect at low speed. There is no way to counter the ROLL moment.
Aileron don't even generate roll moment at high AOA. It generates yaw moment (proverse yaw effect).


But does sprstdlyscottsmn also have limited math and physics knowledge, like me? I mean, he's only an aerospace engineer.

gta4 wrote:And, why do you keep ignoring the fact that 20 deg > 15 deg?


I am ignoring it because I never made any statements regarding "the fact that 20 deg > 15 deg" either in this thread or any other.
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zero-one

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Unread post27 Jan 2018, 11:06

Someone correct me if I'm wrong. I talked to a military journalist once and he said that the Raptor doesn't need TVC for yaw control because of its canted tail design.

The canted tails capture the high pressures generated by the vortecies in the chined forward fuselage allowing the vertical stabilizers to affect control at near zero airspeed or even when falling belly first.

This is why the F/A-18 and F-35 can still do Flat spin maneuvers even without yaw TVC.
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basher54321

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Unread post27 Jan 2018, 13:50

zero-one wrote:
This is why the F/A-18 and F-35 can still do Flat spin maneuvers even without yaw TVC.


Partly I think because this AFAIK only applies to the FA-18E/F, not the FA-18A/C. The Super was designed with a goal to elliminate the high AoA handling issues the Legacys had - which required an increase in control surface size and a full up fly by wire system (the magic that brings it all together).
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Unread post27 Jan 2018, 16:03

Greets Zero-One.......first, IMO, I think the complexity of developing 3D tvc for the 22 in its current configuration would have been interesting. I also think that once it was found to have superior yaw rates throughout it really wasn’t needed.

Now the Russkies decided for some reason that they “neede” 3d tvc for the PAK. I can tell you from this pilot’s perspective that you aren’t hiding those tailpipes from anything!, especially in the rear 180 degree corridor. The heat signature would be extreme and from what I see, all the “stealth” is frontal only. Not sure how that benefits you with the ability of today’s sensored platforms?

Basher, I agree with you, I only think it applied to the echo/foxtrot, but I believe the engine upgrade alone provided a significant boost in this area.......my 2 cents
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