Did this actually happen or is it just propaganda nonsense?

[Pilotasso]

Roll is reversed and extremely slow for example. It doesnt provide enough controlability. A fighter caght flying up there would be unable to change course in usefull time.

[Echo38]

Period.

 

It doesnt have to be down low and slow where the boudary layer is divergent. At high altitudes and high speeds aerodynamic surfaces are useless.

 

This is a simplistic take. One problem with using one's VTC to overcome aerodynamic limits at high speeds is G. Try a supermaneuverable high-alpha pitch-up ("cobra-like") at 500 M.P.H. and you're gonna break your airplane (and probably yourself). Extra true at Mach 1+.

 

Also, aerodynamic surfaces are very far from useless at high speeds, unless you've got a hydraulic failure or something--barring such an event, aerodynamic surfaces in the modern fighter are quite effective at a high speed--to the point where, at very high speeds (e.g. Mach 2+), you'll want to be careful not to over-control and thus over-G.

[Pilotasso]

This is an aerodynamic limitation not the aircraft per se.

[Echo38]

I'm not following. What aerodynamic limitation are you referring to? If you mean the cobra breaking the bird at Mach 1, yeah--it isn't specific to any aircraft. It's true of any aircraft with the ability to perform such a supermaneuverable, erm, maneuver. Laws of physics, yo'. High alpha at high speeds = high G. High enough G = broken airplane.

 

Also, reversed ailerons at high speed? I don't think that modern fighters have that problem. It was around the Korean War when aircraft started to be designed to not have problems with compressibility.

Edited August 31, 2012 by Echo38

[Pilotasso]

When speaking TVC everybodies imaginations go straight for cobras and stuff, not this case.

 

Maybe a language barrier but Im not implying dogfighting at 80000 feet. Simply changing course where others basically cant in that regime.

 

The limitation is due to air flow (I dont have all theory im memory), your roll and pitch are reversed and extremely slow like I said.

Edited August 31, 2012 by Pilotasso

[Echo38]

As far as I can think of, the only conditions in which TVC can do something that aerodynamic surfaces can't are when there is insufficient airflow over those surfaces, which happens only at extremely high altitudes, "super" high AoA, and/or very low speeds. (In WWII fighters, it could also happen at transonic speeds because of compressibility stall, but this doesn't happen to modern fighters because of wing, body, and stabilizer design.)

 

From Mach 2 all the way down to 400 knots, at 0 to 20,000 feet, the control surfaces should be able to do the same job as the vectored thrust. Only thing the VTC'll let you do there that the the conventional controls won't is over-G your airframe more easily. (Those are conservative limits I listed, because I don't know exactly how high/slow/high-AoA you have to go before you cross the point where VTC is more effective than control surface. Correct me if I'm wrong.)

 

See, the thing is, under most conditions with a modern jet fighter, your big limiter is G, not alpha--and a fighter being supermaneuverable doesn't change that one bit. The vectored thrust can make the fighter pull more Gs at most speeds, yes, but it doesn't change the G limit itself--and under most conditions, the elevator alone can reach that G limit just as well as TVC. It's just the low-IAS where TVC is really useful, and that sort of low IAS may not be a good thing in real air combat. Which isn't to say that TVC isn't useful--it is (even if only as a safety feature!). But you're grossly overstating its usefulness in normal air combat.

Edited August 31, 2012 by Echo38

[RagnarDa]

Well I guess you should maybe e-mail Lockheed Martin and Sukhoi and tell their engineers that thrust vectoring isnt really worth it... ;)

[Echo38]

See previous post: "Which isn't to say that TVC isn't useful--it is."

[aaron886]

Well F-22 loosing too much energy because of using TVC is not an issue with Russian birds with TVC, they are still very agile in dogfight like this and I am sure in close combat 1 for 1 latest Russian TVC fighters do have manouverability advantage.

 

Clearly you don't understand the concept of "energy." :huh:

[Echo38]

Gotta agree with Aaron here. Performing any "supermaneuver" pretty much pulls the drain plug on your E, regardless of what kind of airplane you're flying.

Edited August 31, 2012 by Echo38

[RagnarDa]

See previous post: "Which isn't to say that TVC isn't useful--it is."

(even if only as a safety feature!).

:music_whistling:

 

I'm tired and stupid enough to argue over semantics... Sorry about that.

[Pyroflash]

For those who are still arguing about how TVC can help with high altitudes. Surely because you are going at around M2.5 at 80,000', you won't have any airflow issues for your control surfaces right? Well, the problem with that is that Mach is relate able to true airspeed and temperature, however control surfaces are largely dependent on INDICATED airspeed, which drops significantly at higher altitudes, even though true airspeed continues to climb, and temperature, in general, drops.

 

So at higher altitudes you are going faster, but there is still less air moving over your controls, leaving you with reduced authority. TVC helps with this by somewhat alleviating the dependency on control surfaces for maneuvering.

 

The other thing about energy is that once you are in a stall, there is pretty much 0 energy for your aircraft to use. Much like the F-15C is more maneuverable than the Su-27S at higher speeds, the F-22A can still turn faster than most planes when it is flying in its own regime. The minute it is caught down in low speed turning fights with the Tiffies or Sucke.. ahem, Sukhois, it is done. However that does not mean that the F-22A is lacking in its ability to turn, or that its TVC is useless, however there is a time and place to use it, because once you lose all of your energy you end up having to drag yourself out of a stall, then back up to combat speed, before you can stand a chance at winning again.

 

The Su-35S has the SAME problem. The only difference is that it doesn't have as much speed that it needs to pick up, whereas the F-22A has a lot of smash it needs to generate afterwards. However the F-22A has some pretty big engines to help with this. But what for lack of available information, I'd say that the Su-35S will have an easier time climbing out of that hole than the F-22A will.

Edited August 31, 2012 by Pyroflash

[marcos]

When speaking TVC everybodies imaginations go straight for cobras and stuff, not this case.

 

Maybe a language barrier but Im not implying dogfighting at 80000 feet. Simply changing course where others basically cant in that regime.

 

The limitation is due to air flow (I dont have all theory im memory), your roll and pitch are reversed and extremely slow like I said.

Well I'm not following that for one. Planes can manoeuvre at high speed it's just that the thrust required to sustain a high-speed, high-g turn is immense and the turning radius will still be large due to the speed involved.

 

TV will probably slow you down and provide AOA faster allowing you to escape being killed with a tighter turn radius. Turning that into a kill however is probably something for the film industry but one shouldn't overlook the importance of not being killed in combat.:)

 

AFAIK TV allows you to control the aircraft when recovering from stall but a nice high TTW also allows you to recover through immense accceleration to re-gather airspeed in whatever direction your aircraft is pointed.:D

[marcos]

For those who are still arguing about how TVC can help with high altitudes. Surely because you are going at around M2.5 at 80,000', you won't have any airflow issues for your control surfaces right? Well, the problem with that is that Mach is relate able to true airspeed and temperature, however control surfaces are largely dependent on INDICATED airspeed, which drops significantly at higher altitudes, even though true airspeed continues to climb, and temperature, in general, drops.

 

So at higher altitudes you are going faster, but there is still less air moving over your controls, leaving you with reduced authority. TVC helps with this by somewhat alleviating the dependency on control surfaces for maneuvering.

I think that's what I was getting at in post 25. High speed itself is not an issue for aerodynamic surfaces but high altitude is because of low air density (0.365kg/m^3 at 11000m vs 1.225kg/m^3 at SL). So it's really low speeds at high altitude that are the problem, even though the problems will arise at higher speeds than they do at SL, if you get my drift. Stall is still the issue.

 

The other thing about energy is that once you are in a stall, there is pretty much 0 energy for your aircraft to use. Much like the F-15C is more maneuverable than the Su-27S at higher speeds, the F-22A can still turn faster than most planes when it is flying in its own regime. The minute it is caught down in low speed turning fights with the Tiffies or Sucke.. ahem, Sukhois, it is done. However that does not mean that the F-22A is lacking in its ability to turn, or that its TVC is useless, however there is a time and place to use it, because once you lose all of your energy you end up having to drag yourself out of a stall, then back up to combat speed, before you can stand a chance at winning again.

 

The Su-35 has the SAME problem. The only difference is that it doesn't have as much speed that it needs to pick up, whereas the F-22A has a lot of smash it needs to generate afterwards. However the F-22A has some pretty big engines to help with this.

Ah, you see, the YF-23 just wouldn't have had these problems to begin with. 54lb/ft^2 wing loading, 1.36 TTW. Low speed, high speed, it was all covered minus TV.:)

[Echo38]

I'm tired and stupid enough to argue over semantics... Sorry about that.

Not sure if English is your primary language, but, at least in U.S.A., "even if only X" is generally used to mean, "X is true, and there may be more than X as well, but at least X," and that is what I was trying to say. Let me clarify further:

 

Vectored thrust is good for a safety feature, because it provides additional redundancy to the flight controls and because it can work even at zero airspeed. There are also other advantages to vectored thrust, but even if there were no others, the added safety alone is worth it.* However, although, as I said, there are advantages to [vectored thrust + conventional control surfaces] over [conventional control surfaces only], my previous point remains: some here are grossly overstating the value of VTC in air combat, even though VTC is indeed useful in various situations (potentially including some combat situations).

 

* Although if it's vectored thrust only, and no conventional control surfaces at all, that's a terrible idea--a complete power failure here equals complete inability to control the aircraft. I believe there was at least one proposed aircraft of this VT-only sort, and even a prototype built? Waste of resources, I.M.O.

 

For those who are still arguing about how TVC can help with high altitudes

 

I might've missed something, but I don't think anyone in this thread suggested that thrust vectoring wouldn't help at high altitudes. Not that I disagree with anything you wrote in your post.

Edited August 31, 2012 by Echo38

[EtherealN]

Gotta agree with Aaron here. Performing any "supermaneuver" pretty much pulls the drain plug on your E, regardless of what kind of airplane you're flying.

 

It seems you're not quite following what Pilotasso is saying.

 

"Supermaneuverability" is not to do a cobra at Mach 1 or silly airshow stunts. It does usually confer some fun airshow stunting capabilities too, but this is about as much "the point" as the Cobra is useful in real-world combat... That is: not at all. It is simply to do things that are not possible with control surfaces only. Consider for example reduced efficiency in ailerons etcetera due to shock waves or whatever (I'm not an aerodynamicist so); a conventional aircraft will then have a very hard time rolling at those speeds, because aileron movements don't give adequate control authority in that regime.

 

However, tilting one engine nozzle up, and one down, does give roll authority. This is what Pilotasso is talking about; not things like doing the cobra or executing airshow-style ultra-tight turns. It is simply that you are able to maneuver in ways that would not be possible without TWC. Forget the airshow movies you see on youtube, they are not what this is about.

[Pilotasso]

Exactly. I said repeatedly NOT A COBRA, to no avail. :)

[RagnarDa]

Not sure if English is your primary language, but, at least in U.S.A., "even if only X" is generally used to mean, "X is true, and there may be more than X as well, but at least X," and that is what I was trying to say.

Yes, I must have misunderstood you. I read it like you meant that TVC is only for safety. And no, English is not my primary language. Never knew that is the meaning of that expression, but good to learn something new!

[Echo38]

It seems you're not quite following what Pilotasso is saying.

 

Look at the post I was replying to: http://forums.eagle.ru/showpost.php?p=1540854&postcount=34

 

Kuky was talking about cobra-like maneuvers, unless I am greatly mistaken. He's talking about losing too much energy from using the VT, and that won't occur from your VT roll boost example--only from things like the crazy maneuvers you see at air shows. I can't stress enough that I'm not saying that VT isn't useful, and I'm not even saying that it isn't useful in air combat--I'm only saying that it isn't the Holy Grail of air combat maneuvering, the way some people are (e.g. Kuky saying that Russian VT aircraft are able to regain lost E after a cobra better than the Raptor can).

 

In short (and I'm hoping we can wrap this up, because it's starting to look less like an exchange of knowledge and more like a contest of some sort): vectored thrust has its uses, and these make it worthwhile for an aircraft to have vectored thrust, but over-using VTC in air combat can be a very bad idea. Some people do not realize this--for those who do, I apologize for preaching to the proverbial choir.

Edited August 31, 2012 by Echo38

[RagnarDa]

Ahh! You edited your post making my really long one totally unecessary. Yes wrap this thread up PLEASE!

Edited August 31, 2012 by RagnarDa
Post replied to was edited.

[EtherealN]

Echo, here's the thing I was indicating:

 

This is a simplistic take. One problem with using one's VTC to overcome aerodynamic limits at high speeds is G. Try a supermaneuverable high-alpha pitch-up ("cobra-like") at 500 M.P.H. and you're gonna break your airplane (and probably yourself). Extra true at Mach 1+.

 

This in response to Pilotasso indicating that "supermaneuverability" as a concept is NOT about pulling cobras.

 

Just so you see where I was coming from. :)

[Echo38]

Roger that. Sorry if I misread you, Pilotasso.

[marcos]

I'm only saying that it isn't the Holy Grail of air combat maneuvering, the way some people are (e.g. Kuky saying that Russian VT aircraft are able to regain lost E after a cobra better than the Raptor can).

That depends on good old TTW. Even non-TV aircraft occasionally stall deliberately in air-combat and a high TTW is a way to begin moving again. TV gives you some control over attitude during stall, TTW helps you recover and regain energy.

[4c Hajduk Veljko]

Well, on paper (if one is actually available), is F-35 turn rate and climb worst then Su-35? I mean, that was what that movie in the first post was all about, right?

[aaron886]

Ohhhh my god, here we go. Thanks for those barely relevant numbers.