Su27 inverted depart is realistic?

[Esac_mirmidon]

No.

 

The AoA line from left to right:

 

Air Condition System On-OFF - Cockpit calefaction AUTO-HOT-COLD - Air Intake Protection Covers AUTO-CLOSED - AoA + G limiter ON-OFF - Noose Wheel Steering - Lights LANDING-TAXI-OFF - Flaps IN-OUT.

 

And yes Fox One, my mistake. Reading again the manual this switch is an emergency SAU Autopilot disconnection from the SDU system.

 

Now i´m guessing if there is a manual switch to turn off-on the SDU or is a full automatic system.

[amazingme]

So, the conclusion is, the Su27 PFM is pretty badly implemented.. At low speeds (~300km/h) the Flanker in DCS is acting like a brick no matter the AoA, as oppse to the RL Su-27 which can do the cobra.. q.e.d.

[GGTharos]

Who made that conclusion?

 

Cobra is done at 400-500kph. Any modern jet fighter at 300kph will fly like a brick. Even an A-10.

 

So, the conclusion is, the Su27 PFM is pretty badly implemented.. At low speeds (~300km/h) the Flanker in DCS is acting like a brick no matter the AoA, as oppse to the RL Su-27 which can do the cobra.. q.e.d.

[amazingme]

This is pretty relevant.. if true of course

 

Not to sound like I'm not happy with the Su-27 module (I'm really enjoying it) but it seems like the S key is just implemented so you can do "out of envelope maneuvers" such as the cobra. The cobra requires turning off more than one switch,not the limiter only, as per the following account of an F-18 pilot :

 

We discussed the Cobra in our flight brief. It went something like this:

Me: "I would like you to show me the Cobra maneuver."

Kvochur: "Yes, sure."

Me: "What entry airspeed and altitude should we use?"

Kvochur extended the fingers of both hands in a calming gesture and said: "I show you."

That was it. I looked toward our interpreter for a read on this physical punctuation, but she returned the internationally universal shoulder shrug. So I took his brevity as an admonition against prying too much into this top-secret aerobatic phenomenon and made a mental note to be prepared to absorb as much technical data as I could during his demo.

When I was ready for the demo, he had me turn off the angle of attack limiter and another fly-by-wire switch that was never explained completely to me. Then he said, "I do one. We do one. You do one." The setup was 350 kilometers per hour (approximately 190 knots) in straight and level flight. He pulled the stick all the way back, and the airplane pitched nose up past vertical. In a little more than one second, we were more than 90 degrees nose up after the stick pull. He recovered the plane back to straight and level, and the maneuver was complete. The speed was about 90 knots as the nose approached the horizon. During the "We do one," I was again surprised at the non-aggressive control inputs. He used large pedal displacements during the first half of the pitch-up then transitioned to differential throttle control to keep the roll and yaw minimized. For the nose-down recovery, the stick was moved well forward but not all the way. Differential throttle that gave way to rudder-pedal activity essentially kept us wings-level throughout. My turn: I replicated what I had just ridden through, and the results were the same. I didn’t get past 90 degrees nose up like Kvochur, but I was awed anyway. Despite the radical attitude change, the entire maneuver was completed under 3G. Throughout this seemingly suicidal contortion, the engines never complained, and there was no implication of an impending loss of control.

Fun complete, I switched the limiter and fly-by-wire switches back to their normal positions, and we headed back.

 

If this is true, then the DCS Flanker is nowhere near the real thing.. Just try and see for yourself.

[amazingme]

Who made that conclusion?

 

Cobra is done at 400-500kph. Any modern jet fighter at 300kph will fly like a brick. Even an A-10.

 

And here is the mistake.. Cobra is done BELOW 400Km/h and this is what is really bothering me (and others too) :)

 

So, imho, ED should tweak the PFM to allow this maneuvre at a slightly lower speed which will mimic the real life Flanker: "Russian emphasis on close-range slow-speed supermaneuverability runs counter to Western Energy–maneuvrability theory, which favors retaining kinetic energy to control the range of the engagement." wiki.

 

With the current PFM the F15C (which is a flying brick also in RL) will outturn the Flanker..which I find it pretty STUPID and UNEALISTIC. I mean Su27 is built to be supermaneuvreble at those low speeds and high AoA.

[GGTharos]

And here is the mistake.. Cobra is done BELOW 400Km/h and this is what is really bothering me (and others too) :)

 

The mistake is all yours. It can be done under 400kph, and that fact doesn't mean what you think it means with respect to the aircraft's performance at slow speed/high AoA.

 

So, imho, ED should tweak the PFM to allow this maneuvre at a slightly lower speed which will mimic the real life Flanker: "Russian emphasis on close-range slow-speed supermaneuverability runs counter to Western Energy–maneuvrability theory, which favors retaining kinetic energy to control the range of the engagement." wiki.

And you're wrong.. And so is wiki.

 

With the current PFM the F15C (which is a flying brick also in RL) will outturn the Flanker..which I find it pretty STUPID and UNEALISTIC. I mean Su27 is built to be supermaneuvreble at those low speeds and high AoA.

That's actually incorrect. The F-15 won't out-turn the flanker, unless you get yourself into a situation where you reduce your DPS (by flying slow, let's say) which is FACT OF LIFE when flying an aircraft ... and the other guy stays fast enough to sustain a higher TR.

 

I don't think you understand what you're talking about, either. The Su-27 isn't 'supermaneuverable', it's just maneuverable. F-15's aren't flying bricks in RL - they were never in danger of being such a thing.

 

Your problem is that you don't know what you're talking about, and as a consequence you don't know what you're doing.

Edited January 6, 2015 by GGTharos

[amazingme]

Hmm..I already knew your answers..

 

The mistake is all yours. It can be done under 400kph, and that fact doesn't mean what you think it means with respect to the aircraft's performance at slow speed/high AoA.

 

And you're wrong.. And so is wiki.

 

That's actually incorrect. The F-15 won't out-turn the flanker, unless you get yourself into a situation where you reduce your DPS (by flying slow, let's say) which is FACT OF LIFE when flying an aircraft ... and the other guy stays fast enough to sustain a higher TR.

 

I don't think you understand what you're talking about, either. The Su-27 isn't 'supermaneuverable', it's just maneuverable. F-15's aren't flying bricks in RL - they were never in danger of being such a thing.

 

Your problem is that you don't know what you're talking about, and as a consequence you don't know what you're doing.

 

1. You try doing the Cobra under 400km/h and show us the trk.

2. I didn't say Su27 is "supermaneuvarable". Supermaneuvrability is achieved with thrust vectoring, which is not the case here.. but still, F15 IS a brick compared to MiG29 and Su27 (in real life).

3. I perfectly know what I'm talking about. For example.. can you show me a video footage with a low speed, high AoA of a... F15?

Case closed.

[amazingme]

Can anyone do this with the current DCS Su27? Too bad we don't know the exact speed.. but it's below 400km/h. My Su27 just falls down when I try that maneuvre.. It only work @ speeds > 500km/h..

[Ironhand]

And here is the mistake.. Cobra is done BELOW 400Km/h and this is what is really bothering me...I mean Su27 is built to be supermaneuvreble at those low speeds and high AoA.

FWIW, there's no problem performing Pugachev's cobra at airspeeds between 350 & 400 k/h and it works very much like in the quoted article that you re-quote. You take direct control. Stabilize the aircraft. Pull the stick full back. As the nose comes through, the stick goes to neutral. As the nose drops, a quick short pull on the stick stops the nose just below the horizon. Advance throttles as necessary to regain airspeed. Once in stable flight, reengage FBW.

 

I prefer doing it in the slower speed regimes simply because the aircraft is easier to control while in direct control mode.

 

As far as maneuverability is concerned, you can perform a reasonable replication of any Flanker air show maneuvers you can see online--those done with the none-thrust vectoring Flankers, that is--even the climbing "S" which is evidently extremely difficult for any aircraft to accomplish. The sim's aircraft is every bit as maneuverable as you see in those shows. And keep in mind that, often, when you see references to the Flanker's maneuverability in combat, that's assumed maneuverability based on what's displayed in air shows. Some sources actually go so far as to admit that. The issue is that the Flanker's maneuverability is very much tied to gross weight, changes in CG as fuel is burned, and the added drag of anything hanging on its wings.

 

I don't think the flight model is perfect but I also don't think it's as screwed up as you seem to believe. Far from it.

 

.. You try doing the Cobra under 400km/h and show us the trk.

Check the track here: Cobra. And, I suppose you can take a look at this one, too: 2013 Radom Air Show

 

I have to say that I now perform the cobra differently, since making that track. Back then, I was turning the FBW system back on to recover. I've since discovered a video that shows the maneuver from inside the cockpit and you can see when the system is turned off and back on. I now do it according to the video--as described in the my first paragraph.

Edited January 6, 2015 by Ironhand

[GGTharos]

but still, F15 IS a brick compared to MiG29 and Su27 (in real life).

 

No, it isn't, and it isn't in danger of being such.

 

3. I perfectly know what I'm talking about. For example.. can you show me a video footage with a low speed, high AoA of a... F15?

Case closed.

 

No, you're still clueless. The F-15 will happily fly around at high AoA. It won't turn as well as a flanker below M0.4, but other than that, you can control it down to 100-110kt which is around 180kph.

The sooner you divest yourself of this dumb idea that F-15's are bricks, the sooner you'll fight better against them.

[Ironhand]

Can anyone do this with the current DCS Su27? Too bad we don't know the exact speed.. but it's below 400km/h. My Su27 just falls down when I try that maneuvre.. It only work @ speeds > 500km/h..

 

Then I have to suggest that something is wrong on your end. A high AoA, low speed pass? It's easy to do at 200 k/h--level flight, high AoA--and I'm guessing that's around the airspeed its normally performed at. It remains easy at 170 k/m. And I've managed to control it for an extended period at speeds as low as 150k/h but you are pressed right up against the critical AoA at that speed and, if you some much as sneeze, you'll fall out of the sky. And completing the maneuver with the climb out and rolling turn is not especially difficult. EDIT: it's all a matter of airspeed and you don't attempt any maneuver unless you're at the speed to do it. Entry and exit airspeeds are not an accident. The more I've practiced air show routines, the more I've come to appreciate that.

Edited January 6, 2015 by Ironhand

[amazingme]

Thanks for the tips. I'll watch and try it too.

Don't get me wrong here.. ED did and it surely does a magnificent job with DCS but I'm frustrated of these last changes of the Su27. I can't "feel" it as before especially at those low speeds and my heart cries when it gets busted by the "brick".

[amazingme]

Then, ED must change the F15's FM too.. to match it with the new Su27.

[GGTharos]

That's not how things are done.

 

The Su-27 gets its own FM from Su-27 documentation and SMEs.

The F-15 gets its own FM from F-15 documentation and SMEs.

 

If you can show where the F-15 or Su-27 performance diverges significantly from documentation, myself or another moderator or tester will be happy to report it.

 

If you can't show such a thing, then I suggest you stop claiming that you know something about their flying capabilities.

 

Then, ED must change the F15's FM too.. to match it with the new Su27.

[GGTharos]

QFT

 

it's all a matter of airspeed and you don't attempt any maneuver unless you're at the speed to do it. Entry and exit airspeeds are not an accident. The more I've practiced air show routines, the more I've come to appreciate that.

[Ironhand]

Thanks for the tips. I'll watch and try it too.

Don't get me wrong here.. ED did and it surely does a magnificent job with DCS but I'm frustrated of these last changes of the Su27. I can't "feel" it as before especially at those low speeds and my heart cries when it gets busted by the "brick".

I'm trying to put together a tutorial for the cobra. But it's very much as I stated above.

 

The low speed, high AoA pass is only difficult to enter. Once in it, you can fly there all day. It's the transition that's tricky. Slow down. Extend the speed brake. Throttle back even more and, as you begin to slow toward your target speed, raise your nose to maintain level flight as your AoA increases. Use your throttles to maintain an AoA of 20*. That'll actually give you a higher pitch angle than you see in most airshows. From then on, you're controlling level flight with your throttles--advancing them a bit, retarding them a bit. Remember that each AoA has it's corresponding airspeed. Fly faster and the AoA decreases. Fly slower and it increases accordingly.

 

EDIT: Once you are stable and enjoying the thrill of victory, slowly reduce your airspeed by 10 k/h. Observe the change in AoA. Maintain stable flight. You can get as slow as 150 k/h and your AoA will be pushed right up against the critical AoA of 31*. If you push past it...you will start to descend dramatically. :) Don't panic. Advance your throttles but keep your nose pointed where it is. You will regain sufficient airspeed to fly again. If you practice this and other things enough, you'll start to notice that you fall out of the sky much less frequently because you begin to understand what keeps the aircraft flying in the first place.

Edited January 6, 2015 by Ironhand

[theropod]

I didn't say Su27 is "supermaneuvarable". Supermaneuvrability is achieved with thrust vectoring, which is not the case here..

 

in fact supermaneuverability also includes su-27 and mig-29 as leader.

 

http://en.wikipedia.org/wiki/Supermaneuverability

[GGTharos]

Read the first paragraph of that article and see if you can spot the funny.

 

Follow up with what's written in the rest of the wiki article, then, if you dare inject reality into your suggestion, read the flight manuals for those aircraft and spot how much BS there is in that article.

 

The lesson here is, don't believe everything that's written on Wikipedia.

 

in fact supermaneuverability also includes su-27 and mig-29 as leader.

 

http://en.wikipedia.org/wiki/Supermaneuverability

Edited January 6, 2015 by GGTharos

[Ironhand]

Read the first paragraph of that article and see if you can spot the funny.

 

Follow up with what's written in the rest of the wiki article, then, if you dare inject reality into your suggestion, read the flight manuals for those aircraft and spot how much BS there is in that article.

 

The lesson here is, don't believe everything that's written on Wikipedia.

Or believe... :) According to their clarifying example of the definition, the sim's Flanker is, indeed, supermaneuverable: "In a supermaneuverable aircraft, the pilot can maintain a high degree of maneuverability below corner velocity, and at least limited attitude control without altitude loss below stall speed." Both are perfectly true in the sim.

[GGTharos]

Then I would submit that the A-10 is also super-maneuverable (or better yet, the F-18!). :)

 

What-ever they're trying to make up in that article, it isn't even consistent.

 

Super-maneuverability has always been about post-stall maneuvering AFAIK. None of the aircraft in-game can do that - you can do some 'in-stall' maneuvers, but if you try to do anything that resembles maneuvering outside the script, your next stop is six feet under.

 

There's no lack of aircraft that have very good high AoA performance - it's just part of the flight envelope and there's nothing strange or new there. These aircraft weren't called 'super-maneuverable' before ... why now?

 

I think some peeps just like their labels, and they like to apply their favorite labels to their favorite things, even if the labels don't apply. ;)

 

As for no altitude loss after the stall as a parameter errr .. really? Is a rocket super-maneuverable? There are some seriously hokey things going on with those definitions. Keep it in the stall and see if you can keep altitude. Just saying! (Ok, ok, I know. They say 'limited'. It's a nice excuse.)

 

Or believe... :) According to their clarifying example of the definition, the sim's Flanker is, indeed, supermaneuverable: "In a supermaneuverable aircraft, the pilot can maintain a high degree of maneuverability below corner velocity, and at least limited attitude control without altitude loss below stall speed." Both are perfectly true in the sim.

Edited January 6, 2015 by GGTharos

[theropod]

Read the first paragraph of that article and see if you can spot the funny.

 

Follow up with what's written in the rest of the wiki article, then, if you dare inject reality into your suggestion, read the flight manuals for those aircraft and spot how much BS there is in that article.

 

The lesson here is, don't believe everything that's written on Wikipedia.

 

thanks for comment, you enlightened me because i've always suspicions about wiki informations.

when first days of su-27 beta release,i had mistaken about cobraturn issue which is also mentioned on wiki.

http://forums.eagle.ru/showthread.php?t=134057

 

this is weird but now with 1.2.14 patch flanker can perform this maneouvre:)

maneouvre is not certain like su-35 but su-27 is about to perform that maneouvre.

i noticed that, with 1.2.14 patch ,yaw rotation increased and that allows us to move aircraft both sides at high aoa when asc off

this is my cobra turn test track, not perfect but i'm about to perform it.

_LastMissionTrack2.trk

[Ironhand]

...As for no altitude loss after the stall as a parameter errr .. really? ...

:) The problem is that you're not reading carefully enough. It's why I love language. It's kind of like statistics. They don't say that you can maintain level flight while in a stall. They say you can maintain level flight below stall speed. Which you can do. Our Flanker's stated stall speed is, what 230? 240? k/h. Of course there are a lot of variables but, anytime you look it up, those are the numbers the references will spit out. You can actually maintain level flight down to about 150 k/h (depending on weight and configuration) at which point you will push past the critical AoA and bad things start to happen.

 

EDIT:

...i've always suspicions about wiki informations.

when first days of su-27 beta release,i had mistaken about cobraturn issue which is also mentioned on wiki.

http://forums.eagle.ru/showthread.php?t=134057

 

...

One issue is that most of us don't fly with a split throttle. If we did, controlling taxi speeds would be much easier and I wonder if you could actually perform the cobra turn--or a reasonable facsimile. Just thinking out loud because I've read that differential thrust is used during the cobra to control any yaw.

 

Looking forward to viewing your track.

Edited January 6, 2015 by Ironhand

[GGTharos]

:) The problem is that you're not reading carefully enough. It's why I love language. It's kind of like statistics. They don't say that you can maintain level flight while in a stall. They say you can maintain level flight below stall speed. Which you can do.

 

No IH, you can't. Stall it and show me maintained altitude. I mean maintained, not 'hung in the air for the duration that the existing momentum carried me for', otherwise we might not be talking about the same meaning of the word. The Cobra does not maintain altitude - the fact is that you climb, and then return to the altitude you climbed out from, but you're not going to be doing a 'level flight' Cobra ... because you're not flying. This isn't like throwing the aircraft into a High-AoA sustained turn where you actually maintain altitude. The Cobra isn't even an energy-neutral maneuver.

 

Not even 'supermaneuverable' aircraft can really do that, but they can certainly stall AND point the nose around with apparent impunity ... and that's what super-maneuverability is all about. Flankers can't do that. If you deviate from the script, you deepen the loss of control. To be clear, the Cobra, Tail-slide etc - those are OOC maneuvers - you put the aircraft out of control, but it's relatively benign and you can regain control easily as long as you follow the script. Deviate from the script, and at best you waste time (can be deadly in combat), and at worst you're unrecoverable.

 

Our Flanker's stated stall speed is, what 230? 240? k/h. Of course there are a lot of variables but, anytime you look it up, those are the numbers the references will spit out. You can actually maintain level flight down to about 150 k/h (depending on weight and configuration) at which point you will push past the critical AoA and bad things start to happen.

And you are stalled when you pass critical AoA, usually not before :)
Edited January 6, 2015 by GGTharos

[GGTharos]

I don't believe you can do a Cobra-Turn in the 27, or at least, I don't believe you can do it safely.

 

The reason is what you mentioned: The rudder has become useless, and you've just induced yaw. That's prime spin territory, and all you've got to try and counter it with is a slow-adjusting (by comparison to the rudder) jet engine.

 

One issue is that most of us don't fly with a split throttle. If we did, controlling taxi speeds would be much easier and I wonder if you could actually perform the cobra turn--or a reasonable facsimile. Just thinking out loud because I've read that differential thrust is used during the cobra to control any yaw.

 

Looking forward to viewing your track.

[Ironhand]

I think we might be talking past each other in regards to stalls and level flight. We both agree that, once stalled, there is no such thing as level flight. But, again, that's not what the article quote seems to be saying. They specify stall speed as one criterion. I take that to mean the published stall speed for the aircraft. Nothing more. Nothing less. If they don't, then I'd have to agree with you. We know that you can fly at slower speeds without stalling and maintain level flight and much higher speeds and still stall. Everything hinges on pushing past the critical AoA at whatever airspeed that occurs.

 

You're probably right about differential thrust. I think it'd be fun to try, though, in the sim just to see what happened. Any takers?