"Pitch Up"

[Shadow KT]

Mkay guys I have couple of tracks for you to check out with some things which really bug me about the Su-27. I don't know if it has to be this way(no other aircraft handles like that from what I have flown (A-10C, F-15, TF-51 and the Ka-50 but that doesn't count :D )). I am posting these so somebody can check em out if it s just me and I have to get used to it or is it something that has to be addressed.

 

 

Tracks ".trk" and "2.trk" are me trying out some of the new missions added in the game. I was in a hurry so I just wanted to check em out wasn't really going for precision flying.

 

Track "Level.trk" is me taking off with a light payload and trying to make the plane flying straight with trim and without trim and letting off any Joystick input.

 

Track "taxi.trk" is a quick one. Accelerating from 0 to 50 kph and breaking ( full payload ). The resuls just makes me go :?

 

Press "RCnrl + Enter" so the input graph shows up so you can monitor my stick input. That is for the firstr two tracks. I have it on for the other two.

 

[ATTACH]109090[/ATTACH]

 

[ATTACH]109091[/ATTACH]

 

[ATTACH]109092[/ATTACH]

 

[ATTACH]109093[/ATTACH]

 

P.S: These Tracks only work with 1.2.12.34915.571(or the original 1.2.12 ver)

Edited December 12, 2014 by Shadow KT

[Shadow KT]

Just so you know this is not some random flights I've put on thinking I am Maverick....

 

These are possible bugs which I am trying to find if they are or not

[Ironhand]

I'm at work and, so, can't view the tracks. Concerning trimming, though: (EDIT: Ignore the following if you have a FFB stick as that seems to be its own special issue. :EDIT END) For most of us, FBW means "point the nose and that's where she'll go" but it's not necessarily true. The Su-27's ACS design adds a logic law to the longitudinal channel to make it behave like a conventional aircraft with positive speed stability. Translated that means that as your speed increases, your pitch will increase. As it decreases, your pitch will decrease.

 

So you need to approach trimming a bit differently than you might think. If you pick a speed and, then, try to trim to it, it'll be an exercise in frustration. Instead, trim for a particular angle of attack (AoA) and fine tune your speed to it. I usually settle in on an airspeed and, then, trim until the controls feel light in my hand. If the AoA I've set is for a slightly slower airspeed, the nose will want to drop. If higher, the nose will want to rise. In either case, I'm needing to adjust lightly with the stick. I'll nudge the throttles forward or backward a bit depending on where I have the stick and level the aircraft again. Normally I'm very close a that point and, depending on how much I want to play with it, I'll tune it finer or not. I can often let the stick go (assuming calm weather) for the better part of a minute or more without gaining or losing much altitude. You do have to be settled in on an airspeed.

 

An interesting thing about aircraft with positive speed stability is that, since every AoA has a speed it wants to fly for (in simplistic terms) the weight of the aircraft, it'll seek that speed. If you are close to the right speed and let go of the stick your nose will rise or fall accordingly but as you pass through the speed it wants to fly the nose will slowly reverse direction. These oscillations will continue but become increasingly smaller until you end up at the speed the AoA setting requires--probably at a different altitude (air density) than you started. Depending on how far off you were to start, it could take awhile--or not.

Edited December 9, 2014 by Ironhand

[Shadow KT]

I'm at work and, so, can't view the tracks. Concerning trimming, though: (EDIT: Ignore the following if you have a FFB stick as that seems to be its own special issue. :EDIT END) For most of us, FBW means "point the nose and that's where she'll go" but it's not necessarily true. The Su-27's ACS design adds a logic law to the longitudinal channel to make it behave like a conventional aircraft with positive speed stability. Translated that means that as your speed increases, your pitch will increase. As it decreases, your pitch will decrease.

 

So you need to approach trimming a bit differently than you might think. If you pick a speed and, then, try to trim to it, it'll be an exercise in frustration. Instead, trim for a particular angle of attack (AoA) and fine tune your speed to it. I usually settle in on an airspeed and, then, trim until the controls feel light in my hand. If the AoA I've set is for a slightly slower airspeed, the nose will want to drop. If higher, the nose will want to rise. In either case, I'm needing to adjust lightly with the stick. I'll nudge the throttles forward or backward a bit depending on where I have the stick and level the aircraft again. Normally I'm very close a that point and, depending on how much I want to play with it, I'll tune it finer or not. I can often let the stick go (assuming calm weather) for the better part of a minute or more without gaining or losing much altitude. You do have to be settled in on an airspeed.

 

An interesting thing about aircraft with positive speed stability is that, since every AoA has a speed it wants to fly for (in simplistic terms) the weight of the aircraft, it'll seek that speed. If you are close to the right speed and let go of the stick your nose will rise or fall accordingly but as you pass through the speed it wants to fly the nose will slowly reverse direction. These oscillations will continue but become increasingly smaller until you end up at the speed the AoA setting requires--probably at a different altitude (air density) than you started. Depending on how far off you were to start, it could take awhile--or not.

 

 

Aha, I do understand what are you talking about with the difference in trim... but still you will see what happens when you chekc out the tracks. I can handle that.

 

The first two and the last tracks are the ones which concern me more.

 

I am glad that you will take a look at them. Glad to see someone taking off their time to check out something for the community. Thank you

[SilentGun]

When they were building the su-27, the extra "blended wing" put the center of lift in front of the center of mass resulting in an unstable aircraft, and that's where your "pitch up" problem comes from.

[Shadow KT]

When they were building the su-27, the extra "blended wing" put the center of lift in front of the center of mass resulting in an unstable aircraft, and that's where your "pitch up" problem comes from.

 

Did you see the tracks especially the first two ? and what happens. You can see I am trying everything to try and recover the aircraft

[SilentGun]

I'm on my phone right now so I can't watch them but there have been many cases of su-27's loosing or gaining speed putting there center of gravity way off.

[SilentGun]

Also take in mind it's a beta

[Shadow KT]

I know it is beta. I am not bashing on it. That is why I am asking if it is how it's supposed to be

[Ironhand]

...

 

Track "taxi.trk" is a quick one. Accelerating from 0 to 50 kph and breaking ( full payload ). The resuls just makes me go :?

 

 

I'd post taxi.trk in a separate thread and ask the devs to look at it. Something isn't right. (EDIT: I want to add that I have yet to blow a tire. So it's interesting that this does it. I used your TRK file and tried myself. I didn't create a new mission to see if it could be reproduced. Before posting it, you might want to try that just in case there's something flakey about this particular mission.)

 

Concerning the others:

 

Not sure what you were trying to do in "level.trk" You never settled on an airspeed and, so, needed to constantly play with trim--which is fine--but, then you reset trim to neutral while traveling at combat speeds and... So, anyway, I'm not sure what you were trying to do. I watched the track a 2nd time and took over after your first significant pitch up. You'll find a copy of the track attached below. I don't know what airspeed you were aiming for, since I don't think the throttle ever moved from your takeoff setting. But since you ended up in the high 700's, I went there.

 

Please see the attached. Most of what I did after I took over was done with slight trim inputs and the throttle to settle on the airspeed for the AoA I had set. If you look closely, you'll see an occasional gentle nudge of the stick to get the aircraft's momentum going in the direction I wanted so it could settle.

 

As far as the two A2A tracks are concerned, you didn't have the airspeed to be doing what you were trying to do. You were OK until you turned your 23 ton aircraft into a 115 ton aircraft by loading additional Gs onto the airframe. Turning further complicated the issue by transferring some of the limited energy your airspeed provided from the work of holding you up to the work of creating lateral movement. What was left of your E continued to hold the aircraft up...for a short time.

 

Your aircraft said: OK. I'll do that for you and responded in the only way she could--by increasing the AoA to increase lift, since you weren't allowing her an increase in airspeed to compensate. You then ignored her when she began complaining that, if you didn't give her more airspeed, you were going to turn her into a brick. You then let even more of her speed decay and she finally said in frustration: OK. Have it your way. :)

 

Long story short. You were slow and needed to drop your nose and slice through the turn in burner. Then you would have been OK--more or less. Fly the aircraft first. Use her as a weapons platform second. It doesn't work so well the other way around. :)

 

 

Rich

Edited December 10, 2014 by Ironhand
To make a statement clearer.

[Shadow KT]

I'd post taxi.trk in a separate thread and ask the devs to look at it. Something isn't right. (EDIT: I want to add that I have yet to blow a tire. So it's interesting that this does it. I used your TRK file and tried myself. I didn't create a new mission to see if it could be reproduced. Before posting it, you might want to try that just in case there's something flakey about this particular mission.)

 

Concerning the others:

 

Not sure what you were trying to do in "level.trk" You never settled on an airspeed and, so, needed to constantly play with trim--which is fine--but, then you reset trim to neutral while traveling at combat speeds and... So, anyway, I'm not sure what you were trying to do. I watched the track a 2nd time and took over after your first significant pitch up. You'll find a copy of the track attached below. I don't know what airspeed you were aiming for, since I don't think the throttle ever moved from your takeoff setting. But since you ended up in the high 700's, I went there.

 

Please see the attached. Most of what I did after I took over was done with slight trim inputs and the throttle to settle on the airspeed for the AoA I had set. If you look closely, you'll see an occasional gentle nudge of the stick to get the aircraft's momentum going in the direction I wanted so it could settle.

 

As far as the two A2A tracks are concerned, you didn't have the airspeed to be doing what you were trying to do. You were OK until you turned your 23 ton aircraft into a 115 ton aircraft by loading additional Gs onto the airframe. Turning further complicated the issue by transferring some of the limited energy your airspeed provided from the work of holding you up to the work of creating lateral movement. What was left of your E continued to hold the aircraft up...for a short time.

 

Your aircraft said: OK. I'll do that for you and responded in the only way she could--by increasing the AoA to increase lift, since you weren't allowing her an increase in airspeed to compensate. You then ignored her when she began complaining that, if you didn't give her more airspeed, you were going to turn her into a brick. You then let even more of her speed decay and she finally said in frustration: OK. Have it your way. :)

 

Long story short. You were slow and needed to drop your nose and slice through the turn in burner. Then you would have been OK--more or less. Fly the aircraft first. Use her as a weapons platform second. It doesn't work so well the other way around. :)

 

 

Rich

 

 

Thank you for the feedback. I'll check out the track you have attached.

 

Concerning the taxi. I am pretty sure it is not just the mission. They were generated by instant action and for me to even have the idea of doing it, means I've epxrienced it before, so I just wanted to confirm. Also I have some buddies which have reported the same.

 

In the "level.trk" you can see after intially trimming it. I just put my hands off the controls and watch what happens. The trim reset was just to show, something I find very funny, how the aircraft does a full loop without me even putting any controls in. So much pitch up ^.^

 

About the two A2A. I know it is a different aircraft, but I have put so muc Gs dat the aircraft just can't keep up with me how am I not blacking out ? Also, you can see when it wants to pitch up just before stall you can see I am pushing the strick as much as I can to make the nose go down or to roll the aicraft over so it can gain some speed.

 

What concerns me more is what happens after the stalls. Yea it might be just me and my flight controls making the planes stall, but how is it possible dat I cannot recover the plane ? As if the planes has a perfect center of gravity and just falls as a piece of paper. The roll or rudder input does anything ? Pretty sure if the plane stalls it will want to go nose down directly byitself and not just stay almost perpendicular to the ground and not accpeting any input. I was trying to make the nose go down so I can gain speed, didn't work. Tried putting couter input to the planes rotation so it can stop, nothing happend. As if the planes has no elerons at all and is not effected by input of anykind. I even tried dissengagin the assists or w/e it is ( the S button)

[Ironhand]

...

 

In the "level.trk" you can see after intially trimming it. I just put my hands off the controls and watch what happens...

:) You can take my comments for whatever value you'd like to place on them. :)

 

I guess my point is that you were trimmed momentarily but then you allowed your airspeed to steadily increase and, so, were once again well out of trim. And the result is what you'd expect. EDIT: But... trimming is done to allow you a light hand on the stick, not to make flying hands free. You can fly hands-free in the sim because, unless you make changes to the default settings in the ME, there is no air movement. That's not the case in the world.:EDIT

 

About the two A2A...[if] I have put so muc Gs dat the aircraft just can't keep up with me how am I not blacking out ?

You can't pull more Gs than your airspeed can provide. The most Gs you could pull in either track was around 5 but, with your limited airspeed, it was enough to do you in because you didn't manage your airspeed.

 

Also, you can see when it wants to pitch up just before stall you can see I am pushing the strick as much as I can to make the nose go down or to roll the aicraft over so it can gain some speed.

But by that time you had too little speed for the control surfaces to be effective.

 

What concerns me more is what happens after the stalls. Yea it might be just me and my flight controls making the planes stall, but how is it possible dat I cannot recover the plane ?

:) Operator error? :) FWIW, I took control of the aircraft right after each stall and recovered without a problem. Take track 2 as an example. You stayed in full afterburner for almost half the ride to the ground. The very first thing you should do when you stall and, especially in a spin, is to throttle back to idle. It's counterintuitive but it's also in the manual. Edited December 10, 2014 by Ironhand

[Shadow KT]

:) You can take my comments for whatever value you'd like to place on them. :)

 

I guess my point is that you were trimmed momentarily but then you allowed your airspeed to steadily increase and, so, were once again well out of trim. And the result is what you'd expect. EDIT: But... trimming is done to allow you a light hand on the stick, not to make flying hands free. You can fly hands-free in the sim because, unless you make changes to the default settings in the ME, there is no air movement. That's not the case in the world.:EDIT

 

 

You can't pull more Gs than your airspeed can provide. The most Gs you could pull in either track was around 5 but, with your limited airspeed, it was enough to do you in because you didn't manage your airspeed.

 

But by that time you had too little speed for the control surfaces to be effective.

 

:) Operator error? :) FWIW, I took control of the aircraft right after each stall and recovered without a problem. Take track 2 as an example. You stayed in full afterburner for almost half the ride to the ground. The very first thing you should do when you stall and, especially in a spin, is to throttle back to idle. It's counterintuitive but it's also in the manual.

 

I want to see those recovers....

 

First time hearing that you have to tune down the throttle to recover... Guess the Flanker is just too different.

 

Also when I let my hands of the stick the planes pitches up and then goes down ( which I think is on eof the systems trying to maintain it stable) I know the trim is not for making it possible to fly with hands of the stick.... I am just doing it so I can show my point

[Nedum]

:) You can take my comments for whatever value you'd like to place on them. :)

 

I guess my point is that you were trimmed momentarily but then you allowed your airspeed to steadily increase and, so, were once again well out of trim. And the result is what you'd expect. EDIT: But... trimming is done to allow you a light hand on the stick, not to make flying hands free. You can fly hands-free in the sim because, unless you make changes to the default settings in the ME, there is no air movement. That's not the case in the world.:EDIT

 

 

You can't pull more Gs than your airspeed can provide. The most Gs you could pull in either track was around 5 but, with your limited airspeed, it was enough to do you in because you didn't manage your airspeed.

 

But by that time you had too little speed for the control surfaces to be effective.

 

:) Operator error? :) FWIW, I took control of the aircraft right after each stall and recovered without a problem. Take track 2 as an example. You stayed in full afterburner for almost half the ride to the ground. The very first thing you should do when you stall and, especially in a spin, is to throttle back to idle. It's counterintuitive but it's also in the manual.

 

About this AB thingie!

Where is all this AB energy going to? Energy will never be lost. The engine is at the plane, the engines producing thrust, thust is energy, but there is no reaction. This is against all physically behaviors I know.

If the engine is running and you put energy out there, there must be a reaction! But the Su27 does nothing. No spin, no acceleration, nothing.. even the stall was not really flat, most of the time the nose shows +20° to the ground.

Yes you can get out of this stall, but the AB behavior is very strange for me.

Where is all this energy going?

Flat stalls are mostly a energy problem after an stall (blow out) but the Su27 has two engines with full AB running and nothing happened. This can't be right!

Action -> reaction! A simple physic law!

The Su27 behaves like she is in her own physic bubble.

[Shadow KT]

About this AB thingie!

Where is all this AB energy going to? Energy will never be lost. The engine is at the plane, the engines producing thrust, thust is energy, but there is no reaction. This is against all physically behaviors I know.

If the engine is running and you put energy out there, there must be a reaction! But the Su27 does nothing. No spin, no acceleration, nothing.. even the stall was not really flat, most of the time the nose shows +20° to the ground.

Yes you can get out of this stall, but the AB behavior is very strange for me.

Where is all this energy going?

Flat stalls are mostly a energy problem after an stall (blow out) but the Su27 has two engines with full AB running and nothing happened. This can't be right!

Action -> reaction! A simple physic law!

The Su27 behaves like she is in her own physic bubble.

 

+1

[Ironhand]

I want to see those recovers....

Hopefully I'll have some time tomorrow morning to run your TRKs again. If not, it might be the weekend. Regardless, I'll post them to this thread for you.

 

First time hearing that you have to tune down the throttle to recover... Guess the Flanker is just too different.

Really? I've always thought of it as SOP. I could be wrong but I've always found it easier to recover with throttle at idle. If you have split throttles, you might be able to use a single engine to counteract a spin.

 

Also when I let my hands of the stick the planes pitches up and then goes down ( which I think is on eof the systems trying to maintain it stable) I know the trim is not for making it possible to fly with hands of the stick.... I am just doing it so I can show my point

I know you were trying to make a point. I used the same technique when I took over in your track. My point is that you still hadn't arrived at the airspeed your throttle setting was going to take you to. So any trim setting would only be momentary.

About this AB thingie!

Where is all this AB energy going to? Energy will never be lost...

Never really stopped to think about it. A stall does create a great deal of drag. Whether or not it's enough to negate that thrust, I really don't know. The answer requires more knowledge than I have.

[Nedum]

 

Never really stopped to think about it. A stall does create a great deal of drag. Whether or not it's enough to negate that thrust, I really don't know. The answer requires more knowledge than I have.

 

There is no path change, with or without AB. The Su27 falls straight down.

The Su27 can go straight to the sky with full AB. At stall the fall down speed is about 260 kph (landing speed), that's not enough drag to eliminate the power of the AB completely, even the AB energy vector is changing slowly between -20° and +10°. The length of the amplitude (nose up and down) must be change at full AB, because if the nose goes down, there is less drag and so there is more acceleration and the energy impluse must show a longer amplitude. With each up and down, the amplitude must be longer and the nose must show more and more to the ground till the Su27 gets out of the stall and this very fast.

And near the ground is also no change at this amplitude and the fall speed, but the air drag is much greater. The whole stall over there is no change at the stall behavior. How could this be if the AB is still running at full power? The energie at full AB is more or less the same, the air drag is changing every meter, so there must be any change, but there is non. The stall behavior is the same from the beginning till the end.

There is something extrem strange and I doupt that the Su27 behavior is physically ok.

Edited December 10, 2014 by Nedum

[Nedum]

I want to see those recovers....

 

First time hearing that you have to tune down the throttle to recover... Guess the Flanker is just too different.

 

Also when I let my hands of the stick the planes pitches up and then goes down ( which I think is on eof the systems trying to maintain it stable) I know the trim is not for making it possible to fly with hands of the stick.... I am just doing it so I can show my point

 

Tune up or down the throttle is a must have in a flat spin with a prob AC (spin direction matters). Even if you are in a stall, a change of the energie vector can help to prevent a flat spin and to stabilize the AC.

But if I see in your tracks there is no need for this, because there is no fast flat spin. The fall down vector is more or less stable, so the AB power should had helped you to get out of this stall!

[Ironhand]

There is no path change, with or without AB. The Su27 falls straight down.

The Su27 can go straight to the sky with full AB...

Only because of lift. I'd like to suggest that, without lift (a stall condition), the aircraft is going nowhere but down.

[Chief1942]

Definitely not an aeronautic engineer, but since there is no lift to take-off until the energy from the engines/afterburners apply forward motion, then how can the same engines/afterburner forces not have the slightest effect on the aircrafts motion in a flat spin? Whether upright or inverted, the sheer energy produced by full afterburner should have some physics effect. I appreciate the loss of control due to the absence of forward movement (lift) of the airframe, but I agree with Nedum, where is all the energy going?

[Shadow KT]

Also, you can see I am trying to put the nose down trough the whole time falling down so I can gain speed. No matter what input I put in there is no effect from any of it. Like even if that doesn't save me from a flat spin ( which dose weren't , the nose was actually pointing quite a bit down) there should be some noticable change in the spin's speed, angle of the planes or something

[Ironhand]

So...I'm finding this whole topic very interesting. Unfortunately, I lost power overnight due to the snow storm and wasn't able to run through those tracks again this morning to monitor what's happening more closely. Hopefully my power will be back on by the time I get home tonight.

 

Now, I'm going to risk looking like a fool...

 

But I have a question to all involved in this discussion: What's the difference between a stalled wing attempting to fly parallel to the horizon and one attempting to fly perpendicular to it as the aircraft falls? So far, no one has asked where all the energy from the afterburner has gone, if the aircraft stalls parallel to the horizon. Why is that question such a concern here?

 

This is where I wish I had my home computer available. I'd really like to take a very close look at the paths of the aircraft in those 2 tracks and compare them to those tracks with power set to idle. The HUD, IIRC, is showing a forward airspeed of X. I don't recall if it varies. I have no idea of how fast the aircraft is actually falling, since that's not being measured, is it? At least I don't think it would be in a flatter spin. Perhaps there should be rapid variations in IAS which the modeling isn't showing.

 

It doesn't actually matter where the nose is pointing. What matters is the direction of the relative wind--it's going to approach the aircraft (and wing) from a direction parallel to but opposite the flight path at any given moment. A stalled wing continues to be "stalled" until the relative wind approaches at an angle less than the critical AoA. Then, with sufficient forward speed, the wing can start flying again.

 

From inside the cockpit, everything looks much as it should to my eye. It seems the objection to what's happening occurs when the view is shifted outside. BTW, I'm not arguing that the modeling is absolutely correct. Just thinking out loud.

Edited December 11, 2014 by Ironhand

[Shadow KT]

Can't we use the the rate of climb for fallin speed ? Or just calculate it by monitoring the altitude drop for a period of time ( a min probably ).

 

What do you mean it doesn't matter where the nose is pointing. The nose points to the relative position you aircraft wants to go. If you pointing directly down the less drag you will be producing, combined with the gravitational pull that means you should have a easier time regaining control of the aircraft (cuz of increased airspeed) , right ?

 

The cool thing about this thread is that we are all not experts and we are just trying to figure out what is happening and should it be like this. Nobody is arguing about anything ^.^. We are just discussing, so we can reach a conclusion

[Ironhand]

... Or just calculate it by monitoring the altitude drop for a period of time ( a min probably ).

This was what I was thinking. Check altitude and time at the start of the stall. Follow it to the ground. Check time and altitude. Then do the math. If you have some spare time... :)

 

What do you mean it doesn't matter where the nose is pointing. The nose points to the relative position you aircraft wants to go. If you pointing directly down the less drag you will be producing, combined with the gravitational pull that means you should have a easier time regaining control of the aircraft (cuz of increased airspeed) , right ?

Yes and no. The wing doesn't care which way the aircraft's nose is pointing. It only cares which direction the wind is coming from. Take slow flight, for example. Slow down enough and your nose can be pointing quite high, while you're still traveling horizontally. The relative wind would be coming from straight ahead because that's the direction opposite the flight path. Or consider a spin. Your nose can be pointing toward the ground but you aren't flying. Why? Because the wind across the wing isn't coming from where your nose is pointing. As far as drag is concerned, "The drag incurred by an airfoil is the net force produced parallel to the relative wind" [Aerodynamics for Naval Aviators, pg 22]. (I'll probably live to regret citing this text.) So, again, it's not where your nose is pointing that's important. Exiting a stall with your nose pointing down might be important. But while in a stall, where your nose is pointing doesn't necessarily mean anything.

 

The cool thing about this thread is that we are all not experts and we are just trying to figure out what is happening and should it be like this. Nobody is arguing about anything ^.^. We are just discussing, so we can reach a conclusion

:) There are two things in life that especially please me. 1) Learning new things and 2) helping others to learn new things. Here we might be accomplishing both. I'm certainly getting a much better understanding of some concepts that I hadn't considered too fully in the past.

Edited December 11, 2014 by Ironhand

[Shadow KT]

That is why I said that it is the relative position of where your plane wants to go ^.^