F35 debate thread- enter at your own risk.

[Peregrinefalcon]

Watch the direction of travel and velocity of exhaust condensation. It is obvious the engines are at idle. Idle engines cannot produce the control moments needed to overcome the interia of a 50K lb airplane. Also, F-22's control laws do not allow the engines to operate differentially because the moment arm from the centerline is very small and tolerances are tight in torsion due to differential thrust.

At the same time, you can see the huge horizontal tails at work.

I asked because direction of the exhaust condensation looked deflected to me.



But when I looked closer I saw that F-22 is actually sinking (probably in every single instance) so maybe direction of the "wind" can cause exhaust condensation to look deflected. Any way, maybe you are right regarding TVC and I do agree with everything else you just said.

At air show F-22 is not going over 40° at level flight when we look at Slow Speed Pass Parameters.

http://webcache.googleusercontent.co...=firefox-a#199

Maneuver Description. Following the Tail Slide, begin a turn in the direction to set
up the Slow Speed Pass into the wind. If wind is negligible or predominantly a crosswind,
set the pass up for a crowd right to left flow. Maintain 150 KCAS in the reposition turn and
fly to a point ~3,000’ from the start of the crowd line. Hit the line at 90 degrees off pass
heading at 150 KCAS, 800 feet AGL and in MIL power. Execute a soft stop pull to align the
jet on the desired heading and catch 36 degrees angle of attack. Do not exceed 40 degrees
angle of attack. Manipulate power and pitch to maintain 800 feet AGL and 36 degrees angle
of attack on show line heading. After passing the crowd on the opposite side, select full
afterburner and climb to 4,000 feet AGL to set up for the Split-S.
7.18.2. Abnormal Procedures. If 40 degrees angle of attack is exceeded, immediately add
power and push forward to catch and sustain 36 degrees. If the aircraft descends below
700 feet AGL terminate the maneuver and recover the aircraft. Do NOT select afterburner at
any time unless greater than 75 KCAS and less than 36 degrees angle of attack. If the
aircraft slows below 75 KCAS, add power (up to MIL) and decrease angle of attack. If an
engine fails, select full afterburner on both engines and immediately break the angle of attack
to less than 30 degrees and obtain 150 KCAS while arresting any sink rate

In contrast to that Su-30MKI is doing ~70° AoA in sustained level flight at air shows.

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

2:34 sec of the video.

[LmRaptor]

All high AoA testing above 20-30 degrees is technically a controlled stall TooCool_12. A Cobra or a Kulbit are both examples of instantaneous controlled stalls. The nose down pitching moment during the recovery from one of these manoeuvres is the result of aerodynamic hysteresis. Its magnitude can give you a clue as to how refined the aircraft's aerodynamic design is, and how effective its control authority is.

A stalled wing still provides lift however. The lift generated in this post-stall environment can be mathematically modelled as a dynamical system which sometimes composes of Hopf Bifurcations and their associated limit cycles.

The limit cycles define the coefficient of lift in stalled air flow. This means for a given AoA, Reynolds Number, Mach No, Altitude etc... the coefficient of lift is time dependent. The coefficient of lift at a given point in time has a potential maxima and minima, which is bounded by the limit cycle. The coefficient of lift could also be anywhere in between these maxima and minima at any point in time

Aerodynamicists are mainly interested in the potential maxima and minima of stalled flow coefficient of lits .

[TooCool_12f]

we agree on that, the fact is that you don't aerodynamically control your aircraft in such positions (at least, not enough to put it through any manouvers other than straight line)... the only really efficient way to manouver it is through thrust vectoring (which is how Sukhois manage their "awesome" maneuvers )

[Tu22m]

Controllability at 50 is right there in the presser

In other words, they are designed to be controllable up to 50 AoA.

There i a distinction between surviving those AoAs and sustaining them. For instance many modern fighterns without thrust vectoring can reach AoA of 90 degrees and get back safely to the flight envelope. The Su35 can even reach 180 degrees and still be controllable both horizontally and vertically. Needless to say it still cant be maintained so its not a number they are boasting about.

Whats interesting is sustained G, turn radius and instantaneous turn radius.

[LmRaptor]

I asked because direction of the exhaust condensation looked deflected to me.



But when I looked closer I saw that F-22 is actually sinking (probably in every single instance) so maybe direction of the "wind" can cause exhaust condensation to look deflected. Any way, maybe you are right regarding TVC and I do agree with everything else you just said.

At air show F-22 is not going over 40° at level flight when we look at Slow Speed Pass Parameters.

http://webcache.googleusercontent.co...=firefox-a#199



In contrast to that Su-30MKI is doing ~70° AoA in level flight at air shows.

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

2:34 sec of the video.

While admittedly impressive, the Su-30MKI is not actually sustaining that maneuver. It is using a combination of thrust vectoring and canards to balance the aircraft in a position where its thrust is used to maintain altitude. The forward motion of the aircraft is actually coming from its initial momentum, and when that is bled off it is forced to roll or climb out. It is therefore an instantaneous maneuver, which is prolonged by the relatively low drag force at 70 km/h.

[Peregrinefalcon]

While admittedly impressive, the Su-30MKI is not actually sustaining that maneuver. It is using a combination of thrust vectoring and canards to balance the aircraft in a position where its thrust is used to maintain altitude. The forward motion of the aircraft is actually coming from its initial momentum, and when that is bled off it is forced to roll or climb out. It is therefore an instantaneous maneuver, which is prolonged by the relatively low drag force at 70 km/h.

I disagree, look at this video http://www.youtube.com/watch?v=53iQbz-TQGU at 1:31 sec. It is combination of AoA and throttle modulation that can give you sustained level flight.

You can also look at this video http://www.youtube.com/watch?feature...&v=F2WUlc5-ww8 at 11:50 sec. Su-35S is doing sustained horizontal turn at high AoA. Even more impresive than Su-30MKI high AoA level flight.

[Spitfire9]

High AOA testing is done at idle and relatively low airspeed. If the airspeed was faster, the structural G limit would be exceeded and the wings would break off.

Understood.

The purpose of high AOA testing is to demonstrate care-free handing is a post-stall environment. This gives operational pilots the confidence to take their airplanes to the edges of the flight envelope without fear of losing control.

Understood.

Question: why is a high AOA ability portrayed as being highly desireable for a combat aircraft if it cannot be used at combat speeds (since the resulting G force would incapacitate the aircraft / incapacitate the pilot)?

[LmRaptor]

Ok, then on that basis the F-22 routinely sustains 90 degree AoA maneuvers at airshows. Whenever the F-22 performs the 'hover' maneuver with its nose pointed vertically, any lateral movement would count as a 90 deg AoA.

All that is happening is careful throttle modulation as you kindly pointed out. But again the critical thing is the bulk of the aircrafts mass is being 'lifted' by the engines. That is the same with all of the sustained ultra high AoA maneuvers (except for when the aircraft is virtually falling) I have seen at airshows

[Peregrinefalcon]

Ok, then on that basis the F-22 routinely sustains 90 degree AoA maneuvers at airshows. Whenever the F-22 performs the 'hover' maneuver with its nose pointed vertically, any lateral movement would count as a 90 deg AoA.

All that is happening is careful throttle modulation as you kindly pointed out. But again the critical thing is the bulk of the aircrafts mass is being 'lifted' by the engines. That is the same with all of the sustained ultra high AoA maneuvers (except for when the aircraft is virtually falling) I have seen at airshows

F-22 can sustain 90° AoA for very short period of time when performing a tail slide. At 90° AoA he is standing still and he can control only pitch angle. Stronger crosswind could cause sideslip and F-22 doesn`t have means to control sideslip angle at 0 speed, only planes with 3D tvc can do that. In other words F-22 can`t sustain 90° AoA. Only when he starts to fall (he starts to build up speed) he can use elevators for directional control.

This is what happens when F-22 starts to roll at high/critical AoA http://www.youtube.com/watch?v=VOro3MDF_sI . He goes to spin.
And this is what happens when Su-35S starts to roll at high AoA http://www.youtube.com/watch?v=oTypIHLqG2I at 10:40 sec. He uses directional TVC control to finish high AoA 360° roll without any problem.

[Peregrinefalcon]

Question: why is a high AOA ability portrayed as being highly desireable for a combat aircraft if it cannot be used at combat speeds (since the resulting G force would incapacitate the aircraft / incapacitate the pilot)?

Of course it can be used at combat speeds.
For example, F-16MATV can use TVC till 5Gs and F-15ACTIVE can use TVC till 6,5Gs. I don`t have data on Russian plans but it is clear that Su-35S is doing some very violent post stall maneuvers at relatively high speed. You can`t exit at high AoA when you are doing 9G turn because your AoA limiter is preventing you from damaging the plane. When your G load drops you can gradually increase your AoA.
The point is, you will hardly find "photo kill" at 9G load when you have good pilots at the controls.















Here we have planes such as F-22, EF2000 and Rafale who are known to be very/most effective at high speeds, yet you can see at what speeds, G loads and AoA they made "kill" or being "killed". Very low values of speeds and G loads at relatively high AoA´s.
There are plenty of room for TVC/high AoA maneuvering usage in such situations.

[TooCool_12f]

to be honest, chances of hitting anything with your gun at 9G are pretty much close to 0, and even lower to record it on camera, as at such G-load, your target would be somewhere below your nose (unseen on camera).

[obligatory]

There was one man that could do it
http://en.wikipedia.org/wiki/Hans-Joachim_Marseille

mere demi-gods like Erich Hartmann was better advised doing something simplified.

As operational cost keep going up, chances are nil that we will ever see
a real expert again.

[TooCool_12f]

he could shoot very accurately, but not at "9G"... again, at sucvh load factors, it's a matter of luck rather than aim to hit something

[Tu22m]

Depends on whether or not your aircraft uses the radar to automatically align you correctly fot the gun kill. Those systems do exist.

[TooCool_12f]

we're talking about humans firing...

if you have automatic (radar) guidance, with a computer to do the calculations for a successful aim, it's another story...

[Sens]

As a matter of fact, high AoA handling can give you great advantage in the low airspeed, high AoA arena.

.. as long as you find someone doing you that favor. In reality it is more an attribut of carefree handling and a safety margin in flight corners. See the F-18s and the carrier landings about that f.e..

[Sens]

Here we have planes such as F-22, EF2000 and Rafale who are known to be very/most effective at high speeds, yet you can see at what speeds, G loads and AoA they made "kill" or being "killed". Very low values of speeds and G loads at relatively high AoA´s.
There are plenty of room for TVC/high AoA maneuvering usage in such situations.

That is no "real" combat, just pilots honing their skills and bring their fighters to the limit as well as their own abilities. They met at a given time, at a given area, stick to given rules and none will die from doing a mistake in that "sport" contest. The main purpose is to built confidence in the own training and ability from that as the weapon-system at hand. To get the most from that you will train worst case scenarios. Just in the end you have learned all tricks to survive such situations. Well trained pilots will avoid unfavorable tactical situations whenever possible. Not doing so a "F-22" will defeat a "Rafale" or the other way around. Every fighter is a compromise and can not be top-end everywhere by that.

[CastleBravo]

As your speed goes down, you need more alpha in order to load the jet to 9g. At very low speeds where you can pull lots of alpha without going over your g limit, being able to maintain control of the jet at 50° AoA means you can not only pull more g to change velocity vector that much faster, but you can also point your nose that many degrees farther from your vector than a jet with a lower AoA limit. An extra 20° AoA is potentially 20° less the jet needs to change the direction it is moving in order to bring its gun to bear.

However, not only do you need to get down to a slow airspeed in order to use this capability, you also pay for it with significantly increased drag while at an extreme angle of attack. I suspect the F-35 will have a bitch'n first turn somewhere between the F-18 and the F-22, but will not be able to sustain such maneuvering as well as the F-22 can due to it's lower thrust.

Also, none of this is particularly useful outside a 1v1 guns-only engagement that is not likely to happen in real combat since no one ever intentionally goes into combat without missiles and a wingman, much less without either. The same can be said about all the post-stall maneuvering some of the sukhoi/raptor fanboys like to talk about.

[LmRaptor]

F-22 can sustain 90° AoA for very short period of time when performing a tail slide. At 90° AoA he is standing still and he can control only pitch angle. Stronger crosswind could cause sideslip and F-22 doesn`t have means to control sideslip angle at 0 speed, only planes with 3D tvc can do that. In other words F-22 can`t sustain 90° AoA. Only when he starts to fall (he starts to build up speed) he can use elevators for directional control.

This is what happens when F-22 starts to roll at high/critical AoA http://www.youtube.com/watch?v=VOro3MDF_sI . He goes to spin.
And this is what happens when Su-35S starts to roll at high AoA http://www.youtube.com/watch?v=oTypIHLqG2I at 10:40 sec. He uses directional TVC control to finish high AoA 360° roll without any problem.

The F-22 can sustain what is effectively 90 deg AoA, irrespective of sideslip while lacking 3D TVC. A skilled pilot in the 'hover' maneuver can use pitch vectoring to generate a forward force while maintaining the same altitude by using throttle modulation and variable stick inputs. This would be a sustained maneuver by the definition you have been using.

In practical terms I would consider these types of maneuvers to be instantaneous or perhaps transient. This is because the aircraft's mass is almost wholly supported by the engine thrust, resulting in extremely (and I stress extremely) low speed maneuvers.

[LmRaptor]

I can't watch the videos you have provided because my internet connection is currently too slow, while at work I will have similar problems for different reasons.

What I will say is that I have seen the F-22s departure testing videos and they have no bearing on whether it can roll at extreme AoA. It can, while maintaining controlled flight at. It just won't be doing it at close to the rate a 3D TVC equipped fighter.

[Sign]

in fact, 360° AoA is 0° AoA (pretty much going ballistic... )

good point...
sustained 90 deg AoA fighter, would be our reference for now on.

[haavarla]

This is what happens when F-22 starts to roll at high/critical AoA http://www.youtube.com/watch?v=VOro3MDF_sI . He goes to spin.
And this is what happens when Su-35S starts to roll at high AoA http://www.youtube.com/watch?v=oTypIHLqG2I at 10:40 sec. He uses directional TVC control to finish high AoA 360° roll without any problem.

Damn.. That F-22 vid!
The way the F-22 lost control and went spinning looked quite voilent to me.. and by the sound of the F-22 pilot too!

[Peregrinefalcon]

.. as long as you find someone doing you that favor. In reality it is more an attribut of carefree handling and a safety margin in flight corners. See the F-18s and the carrier landings about that f.e..

One question!
Are you smarter or do you know more than people who are real fighter pilots and do you think that all people that invest so much money and time in TVC are ordinary fools? Because judging by your words the only thing they wait in order to win in the dog fight is someone`s favor.

[Peregrinefalcon]

That is no "real" combat, just pilots honing their skills and bring their fighters to the limit as well as their own abilities. They met at a given time, at a given area, stick to given rules and none will die from doing a mistake in that "sport" contest. The main purpose is to built confidence in the own training and ability from that as the weapon-system at hand. To get the most from that you will train worst case scenarios. Just in the end you have learned all tricks to survive such situations. Well trained pilots will avoid unfavorable tactical situations whenever possible. Not doing so a "F-22" will defeat a "Rafale" or the other way around. Every fighter is a compromise and can not be top-end everywhere by that.

You are right, that was not real fight!
In real fight people are prone to do irrational things because of fear from death. In other words more chance to make a mistake (drain the speed, hit the ground, enter the spin etc.)

http://www.youtube.com/watch?feature...&v=XGimTMpEMiU

http://www.youtube.com/watch?feature...&v=oOa9eWgFllE

Here you have some videos where the fight was not staged. You can find much more videos on that subject.
Pay attention to speed loss rate, G load and AoA. This is the closest thing you can get to death. It coincides with everything I posted earlier.

[Peregrinefalcon]

Also, none of this is particularly useful outside a 1v1 guns-only engagement that is not likely to happen in real combat since no one ever intentionally goes into combat without missiles and a wingman, much less without either. The same can be said about all the post-stall maneuvering some of the sukhoi/raptor fanboys like to talk about.

There is open source data on F-16MATV 1V1 and 1V2 engagements. In every single instance plane with TVC had advantage.
There are numerous simulated fights with TVC planes in 1V1, 1V2 and many V many conducted by Russians using guns as well as missiles.
You think that these people are fanboys?

[CastleBravo]

Oh it's an advantage, just not one that will be of use in combat very often.

[Peregrinefalcon]

The F-22 can sustain what is effectively 90 deg AoA, irrespective of sideslip while lacking 3D TVC. A skilled pilot in the 'hover' maneuver can use pitch vectoring to generate a forward force while maintaining the same altitude by using throttle modulation and variable stick inputs. This would be a sustained maneuver by the definition you have been using.

Sorry man, you are talking about tail slide all the time (at least that is what i think you mean by "hover" maneuver).
What that has to do with sustained level flight at high AoA? By that definition ordinary Su-27 and Mig-29 can sustain 90° AoA.
Give me some video that can prove that F-22 can sustain 70° in level flight without height drop or 90° AoA.

In practical terms I would consider these types of maneuvers to be instantaneous or perhaps transient. This is because the aircraft's mass is almost wholly supported by the engine thrust, resulting in extremely (and I stress extremely) low speed maneuvers.

I am not sure what are you trying to prove?
I gave you examples of planes sustaining level flight at 70° AoA or more. You can consider what ever you like, but if the plane flies for prolonged time at high AoA without height drop and in perfect control that is what is called sustained level flight. Is it important if the flight is done almost wholly supported by the engine thrust with 3D TVC nozzles or by any other means?

[Peregrinefalcon]

I can't watch the videos you have provided because my internet connection is currently too slow, while at work I will have similar problems for different reasons.

What I will say is that I have seen the F-22s departure testing videos and they have no bearing on whether it can roll at extreme AoA. It can, while maintaining controlled flight at. It just won't be doing it at close to the rate a 3D TVC equipped fighter.

I hope you will get better connection. . .

This particular video is example of F-22 rolling at extremely high AoA. And there is no doubt that Russian planes with 3D TVC have better rolling characteristics at much greater AoA. After passing some AoA F-22 will enter spin in the roll, while Russian planes can maintain control.
Compared to any other plane F-22 has much better high AoA characteristics aside from Russian 3D TVC equipped planes.

[obligatory]

The aerodynamic advantages derived from the close coupled canard configuration,
foremost its good vortex flow stability up to high angles of attack (AOA),
that can be translated into a very high instantaneous turn rate, and which in conjunction with pivoting canards that are
automatically trimmed to give optimal lift-to-drag (L/D) ratios for all cg positions,
Mach and AOA, were not technically feasible for the Viggen generation of fighters.
Only full span slotted flaps on the canards were present on the Viggen, for further improvement of its
already excellent Short Take Off and Landing (STOL) characteristics).
.
.
High angle of attack

The topic of air combat at high angles of attack has gained much interest since the seventies,
when it made reappearance, perhaps helped by the not-so-reliable air-to-air missiles of that era.
Air combat seemed to end up like a classic dog-fight, with decreasing speed and subsequent high AOA.
Many early supersonic fighters had a tendency to stall out of the sky when entering this region of the flight envelope,
to the dismay of its pilots, as recovery was often difficult, if not impossible.

The Viggen aircraft had gone through a program of spin testing in the late seventies,
that verified the rather benign high AOA characteristics of the canard layout,
a fact contrary to what was known on some contemporary aft-tailed foreign fighters.
So this was also an argument favouring the Gripen canard layout.
Early investigations in vertical spin tunnels and tests in different rotary rigs and subsequent simulations,
also pointed to acceptable spin behaviour.

A very substantial flight test program that recently was concluded for both the single as well as the two seat Gripen versions has
also fully verified the excellent recovery capability, both in manual test mode and in the normal automatic mode.
There exists a requirement in the Gripen project specification for a spin recovery capability, and if this can not be shown,
a spin prevention system must not allow a departure to happen.
Flight testing has also verified that the EFCS matches this additional demand. Double insurance might be said to exist.

As remarked previously, the only externally visible “fix” to the airframe are a pair of small strakes behind the canard surfaces.
This type of “flow augmentation system”, often serving the purpose of directional and lateral stability enhancement at high AOA,
is not uncommon on fighters; suffice to mention the Eurofighter and the Mirage 2000.

A spectacular Gripen aircraft departure and ensuing crash at a public air display in 1993,
was the cause of modifications and revisions to the EFCS control laws in order to cure certain ailments there,
one example being pilot induced oscillations (PIO).
Among the changes was one pertaining to canard deflection angles at high AOA in combat mode,
to increase margins for the trailing edges surfaces to run into a geometrical limitation,
and thus possible longitudinal stability loss and eventual departure.

Yaw and roll stability at high AOA is strongly dependent on canard incidence, and slightly above the MLL boundary,
stability drops off rapidly, becoming unstable earlier for canard deflections in the region of minus 10 to minus 25 degrees.
Obviously, this incidence range was avoided.
Instead small positive values of canard deflection were used in the control law’s schedules.
This was beneficial, as it meant that the trailing edge surfaces were positive, that is rear end down,
thus giving more positive lift. But now it was realized that in some conditions,
a physical, geometrical limitation to the elevons might be encountered, which momentarily caused loss of stability.

A low speed wind tunnel program had immediately been instigated,
and for the first time the large low speed wind tunnel model’s electrical engines,
that normally were used only to provide discrete incidence changes to facilitate operations,
where now deflected continually during a run.

A bunch of “fixing devices” was tried, and success was instant with several of these.
The earlier rapid drop of stability was now completely over-bridged, and the plots showed good, continuous behaviour,
indicating at dramatic improvement of the flow characteristics in that a delay of separation occurred to slightly higher alphas.
A new canard trim schedule could now be introduced that eliminated the risk of the control surfaces being limited in its travel.

The flow phenomenon, commonly called “dynamic lift”, perhaps more aptly called aerodynamic hysteresis,
has been the object of intense interest in some countries for decades, not the least has this been the case in Russia.
Its best public known, practical application may well be the awesome aerobatic display performed by test pilot V.G. Pugachev and his
“cobra” turn in a Sukhoi Su-27.

When these hysteresis effects manifested themselves during high AOA/spin tests in the specially modified second Gripen prototype,
they came as no surprise. Years prior,
low speed wind tunnel tests with pitching motion of the model had already demonstrated the presence of marked unsteady flow effects,
hysteresis, in the post stall alpha regime. Normal force hysteresis was most evident,
but all the other components, except side force, had their share.

In the high AOA and spin tests that has taken place since 1996 and recently concluded successfully,
the normal tactic was to initiate the tests with a near vertical climb with speed dropping off to near zero and a
rapid increase of AOA up to extreme angles, and the aircraft could then be “parked” at 70 to 80 degrees of alpha.
When giving adverse aileron input there,
a flat spin with up to a maximum of 90 degrees per second of yaw rotation started and could then be stopped by pro aileron input.
Recovery followed, whenever commanded.

A very recent test performed in a specially high AOA equipped twin seat Gripen version has recorded a
noticeable increase in maximum normal force coefficient over the static data base value, jumping up to 3.2,
nearly doubling the static number 1.8.

Wind tunnel and flight test data correspond reasonably well,
but it must still be said that modelling these effects are difficult, so normally in high AOA simulations they are neglected.
In the future, their inclusion will hopefully improve simulations of more complex behaviour, like departure entrance.


http://www.mach-flyg.com/utg80/80jas_uc.html

[Jaidyn24]

This discussion has become an exercise in silliness. There is not 1 thing a su can do that the F-22 cannot. We have plenty of things a F-22 can do that the Su planes dream about. Bacck to topic please.

http://www.youtube.com/watch?v=oTypIHLqG2I