Su-27 Flight Model Discussion

[Svend_Dellepude]

Playing around with this FM after wading through this discussion. What is the:

 

"stick to trimmer control mode" in the Options Flight control settings ?

 

Its an unassigned key as default. Enabling it results imo in a sort of pseuedo Auto trim in pitch in the higher IAS range .... though I have only briefly looked at it.

 

You use the stick to trim instead of the hatswitch. Last time i tried it didn't work very well.

[Rikus]

The flight model is Beta, isn´t it?

 

I mean, ED still have to work on it.

 

We will have in future DCS patch, or we will have it in the DCS SU27 Stand Alone Full DCS Cliclable

[Weta43]

The flight model is Beta, isn´t it?

 

I mean, ED still have to work on it.

They are, but I think it's not likely to change radically..

 

We will have in future DCS patch, or we will have it in the DCS SU27 Stand Alone Full DCS Cliclable

Full system modelling and clickable cockpit is a big, big job. Bigger than a patch :)

[FubarBundy]

Latest Su-27 open beta pfm

 

I'm finding the open beta version of the Su-27 a real joy to fly. As far as I can tell, many of those strange little behaviours seem to have gone away.

[Dell_Murrey-RUS]

Greetings to all fans of the Su-27! :D

 

And sorry for my bad english, I'm russian. :)

 

For a while I was watching this thread, views and opinions PFM Su-27.

Basically, my letter is addressed to those who're skeptical about the reliability of the PFM Su-27 and those who wish to study for a high level of its flight dynamics and combat capabilities.

PFM - professional model and approach to the study of the dynamics of flight and combat capabilities must be with the same professional approach.

Virtual pilot before beginning to practice flights, shall study the theory.

Theory of Su-27 DCS manual attached to the simulator, as well as try to explore the available documents (Flight Manual and Technique Manual). These documents describe the behavior of the Su-27 at different flight modes, its capabilities and most importantly - fly management technique (aerobatics and their parameters).

So it is necessary to understand what the aircraft steady speed and control laws such aircraft. Without this, it would be difficult to understand how the Su-27 is flying and how to tame this thoroughbred stallion. :)

 

In addition to the Su-27 I like the F-15C. And what would the full capabilities of the F-15C, I had to carefully read the FM F-15C/D/E. With the Su-27 is the same story - read the documentation on it.

Now the Su-27 is very similar to the prototype. All changes in its dynamics (according to the developers of the russian thread) will be minimal (cosmetic). Global changes in the dynamics will be gone.

 

Me and my wingman (MI1T) have about 110-120 hours on PFM Su-27 (and more 3000 hours with SFM). Yes, PFM hardly SFM. However, and flight-combat capabilities with PFM are growing. Now with PFM Su-27 is much more maneuverable its predecessor with SFM. In some ways, the Su-27 can fly as the Su-35, of course, with some reservations, however, he can. :)

 

About balancing (trim) - we can say this, set on the ground balancing position minus 2/5 (away from you). This balancing to a speed of about 750 km/h, it allows the virtual pilot did not have a problem when performing solo and group aerobatics.

Of course, to carry out precise maneuvers requires a good joystick.

I use Cobra M5 (without external trottle), it is cheap, but allows you to have precise control on the roll and pitch axes. My wingman using G940.

Both of these require tuning curves joystick axis roll, pitch and yaw.

For very precise (real) control of the Su-27 you will have to stick with a speculum shoulder. Whatever the length of the control knob of the order of 40-50 cm. Then there is no need for the curves and the virtual pilot can enjoy incredibly precise control and perform extremely high-quality aerobatics.

 

Below is some video examples of group and solo aerobatics.

 

Group aerobatics - low and medium level.

 

Flying with flight-training bot on our server (example):

 

This recovery mission after a break of a week (it is clear that the retention rate of wingman position and accuracy of the figures leading steel worse) :cry::

 

 

Some videos of close combat (guns only):

DCSW v1.2.11

 

DCSW v1.2.15

 

If you have questions, please write here or through private messages.

 

Good luck to master this is not a simple fighter - Su-27. :thumbup:

[Ironhand]

Greetings to all fans of the Su-27! :D

 

And sorry for my bad english, I'm russian. :)

 

For a while I was watching this thread, views and opinions PFM Su-27.

Basically, my letter is addressed to those who're skeptical about the reliability of the PFM Su-27 and those who wish to study for a high level of its flight dynamics and combat capabilities.

PFM - professional model and approach to the study of the dynamics of flight and combat capabilities must be with the same professional approach.

Virtual pilot before beginning to practice flights, shall study the theory.

Theory of Su-27 DCS manual attached to the simulator, as well as try to explore the available documents (Flight Manual and Technique Manual). These documents describe the behavior of the Su-27 at different flight modes, its capabilities and most importantly - fly management technique (aerobatics and their parameters).

So it is necessary to understand what the aircraft steady speed and control laws such aircraft. Without this, it would be difficult to understand how the Su-27 is flying and how to tame this thoroughbred stallion. :)

 

In addition to the Su-27 I like the F-15C. And what would the full capabilities of the F-15C, I had to carefully read the FM F-15C/D/E. With the Su-27 is the same story - read the documentation on it.

Now the Su-27 is very similar to the prototype. All changes in its dynamics (according to the developers of the russian thread) will be minimal (cosmetic). Global changes in the dynamics will be gone.

 

Me and my wingman (MI1T) have about 110-120 hours on PFM Su-27 (and more 3000 hours with SFM). Yes, PFM hardly SFM. However, and flight-combat capabilities with PFM are growing. Now with PFM Su-27 is much more maneuverable its predecessor with SFM. In some ways, the Su-27 can fly as the Su-35, of course, with some reservations, however, he can. :)

 

About balancing (trim) - we can say this, set on the ground balancing position minus 2/5 (away from you). This balancing to a speed of about 750 km/h, it allows the virtual pilot did not have a problem when performing solo and group aerobatics.

Of course, to carry out precise maneuvers requires a good joystick.

I use Cobra M5 (without external trottle), it is cheap, but allows you to have precise control on the roll and pitch axes. My wingman using G940.

Both of these require tuning curves joystick axis roll, pitch and yaw.

For very precise (real) control of the Su-27 you will have to stick with a speculum shoulder. Whatever the length of the control knob of the order of 40-50 cm. Then there is no need for the curves and the virtual pilot can enjoy incredibly precise control and perform extremely high-quality aerobatics.

 

...

 

Good luck to master this is not a simple fighter - Su-27. :thumbup:

Thanks so much for taking the time to post. Wonderful videos!

 

Like you, I usually trim nose down before beginning my takeoff role. But clearly, I could use a better stick. :)

[wasserfall]

Thank you for your input here Dell_Murrey-RUS!

 

So if I understand well, a stick extension (which I ordered but not received yet) will increase flying controllability

[WildBillKelsoe]

I have a question regarding stick to trim mode: When I depress that mode, and move the stick a mm forward nothing happens. When I move it halfway, it starts to trim heavily in that direction. My stick is CH and no I don't use curves.

 

Is that normal behaviour?

 

P.S. I use hat for trimming as well, but assigned both trim reset, direct control and stick to trim to HOTAS.

[Ironhand]

I have a question regarding stick to trim mode: When I depress that mode, and move the stick a mm forward nothing happens. When I move it halfway, it starts to trim heavily in that direction. My stick is CH and no I don't use curves.

 

Is that normal behaviour?

 

P.S. I use hat for trimming as well, but assigned both trim reset, direct control and stick to trim to HOTAS.

This is ShuRugal's take on it: Stick to Trimmer Control Mode. Unless I'm using it wrong--entirely possible since I'm not sure how it works--it's much as he describes. There may be a very good reason why it's not assigned a key combo. But I hope to play around with it a bit more in the near future.

[Weta43]

My understanding - It's for people flying with the keyboard - it effectively turns the stick (or rather the up,down,left,right keys) into a trimmer control and you fly by trimming to a stick deflection - in this mode the virtual stick doesn't center when you stop pushing the keys

Edited April 7, 2015 by Weta43

[nickexists]

I wish it had a helicopter style trim-to-stick-position mode but I know that's probably not very realistic.

[Dell_Murrey-RUS]

Could be possible some of you guys that have already control well the Su-27 show in this thread the AXIS CONFI and the Joy you have for the actually Su-27????

 

This is one of the most frequently asked questions in our community. :)

 

Here's URL to our site, where there is a screen with my settings axes for Cobra M5.

It is common settings such as airplanes: Su-25(T), Su-27/33, MiG-29A/C, F-15C, P-51D (TF-51) (this aircraft on which I fly aerobatics and combats (WVR/BVR)).

 

So if I understand well, a stick extension (which I ordered but not received yet) will increase flying controllability

 

Yes, the control will be extremely accurate and will create very precise aerobatics and generally will be useful in the management of air combat.

 

 

 

I have a question regarding stick to trim mode: When I depress that mode, and move the stick a mm forward nothing happens. When I move it halfway, it starts to trim heavily in that direction.

 

Do not quite understand the problem. ((((

 

My stick is CH and no I don't use curves.

 

If the length of the stick <250 mm, for the precise control necessarily requires tuning curves.

[Esac_mirmidon]

So the ED recommendation for linear curves on every AFM module?

[Weta43]

I think it always has been - if they thought it should be something else that's the way they'd have made it....

[Dell_Murrey-RUS]

So the ED recommendation for linear curves on every AFM module?

 

Each user chooses to fly with some curves. :)

However, linear curves are perfect when the user stick around 40-50 cm long.

If the length of the stick less than 25 cm, for precise control in a range of basic movements stick requires tuning curves. This is simple physics. :)

 

Can you give me post (message) where ED recommended that? Perhaps there's a certain some context.

[Bourrinopathe]

Imho, the response curves settings really depends on the control stick, precision, position, resistance and such.

 

All it does is sending your muscular inputs to the aircraft flight control system (even virtual). The length of the stick is the r component of an angular motion: the longer the stick, the longer the arc length for the same input.

It may be why even the modern russian fighters use a central column control stick instead of a lateral ministick (except for the familiarization factor, and other considerations).

 

For example, I use my Black Mamba as a lateral stick and at first I tried linear response curves with the PFM. The problem was the BM was so precise it transferred some "noise" due to my breath and the micromovements from my arm (near the center position). I had to raise the curves to 20 (X and Y) to avoid holding my breath during precise maneuvers ;)

 

Of course, a longer stick will provide a better control but it will also change the movements/piloting style (as seen in the Flankers pilots videos). The transition should be fast but it must be different. Something to consider (in my opinion).

 

The best thing should be to experiment both and try our best to fly as precisely as our fellow Dell_Murrey-RUS :thumbup:

[Ironhand]

My understanding - It's for people flying with the keyboard - it effectively turns the stick (or rather the up,down,left,right keys) into a trimmer control and you fly by trimming to a stick deflection - in this mode the virtual stick doesn't center when you stop pushing the keys

Experimented with it this morning for a bit with the controls indicator pulled up and it works the same way for both the stick and the keyboard. If you push forward with the stick or corresponding keyboard key and then, press "stick to trimmer", additional trim is continuously added until you either stop pressing "stick to trimmer" or let the stick go to "neutral" (or take your finger off the keyboard arrow key. There's a bit of dead zone built in, too. So, unless you have the controls indicator pulled up, it's hard to know what's actually happening.

 

In the air, it would be extremely frustrating to use. But, if you fly like me and set some nose down trim before you start to roll, it's another way to do it. What I didn't think to do was use the normal trim keyboard controls with the keyboard arrow keys to see if that had the same effect as the "stick to trimmer control" for those only flying with the keyboard. And, unfortunately, I have to work today instead of play.

 

[EDIT]Forgot to mention that, once have have added trim, in order to move the trim in the opposite direction you have to first move past the dead zone AND the amount of trim you've added before the "stick to trimmer' will move your trim toward where you want it. This makes it even more frustrating, not to mention dangerous, to use in the air.[/EDIT]

Edited April 7, 2015 by Ironhand

[wilsonov]

amen, and amen.

[kobac]

As I see it, you are focusing on the joystick, but I think that something is not completely done well with FM. In fact how is it possible when turning at low speeds (turn left or right doesn't matter), plane suddenly raise his nose, take the opposite side, and then just fall back into a tailspin, and does not respond to any commands?! Too often DCS Su-27 falls back into this tailspin.

[karambiatos]

I think it happens because when you roll, rudder gets automatically applied.

[Dell_Murrey-RUS]

As I see it, you are focusing on the joystick,

 

Just because precise control is important!

 

but I think that something is not completely done well with FM.

 

What do you "think" this is very subjective.

You could test showed that the prototype behaves while ED model behaves differently? This will objectively.

 

In fact how is it possible when turning at low speeds (turn left or right doesn't matter), plane suddenly raise his nose, take the opposite side, and then just fall back into a tailspin, and does not respond to any commands?! Too often DCS Su-27 falls back into this tailspin.

 

I do not really understand what you mean, I have no such problems.

Apply your track with the situation that you describe. So it will be more clear about what you say.

 

As already mentioned, we must clearly understand that the Su-27 aircraft static instability in the longitudinal channel with providing artificial stability.

Su-27, the art of making steady speed (sustained speed). To manage such a plane, it is necessary to understand the logic (laws) control such aircraft.

If the virtual pilot tries to master its maneuverability without understanding the basics, the very specific behavior of the Su-27 will seem unreal. Although these are the real prototypes. Fighter pilots in the schools teach the theory of 4 years, and then another practice. And there is just practice on the same simple aircraft sustained speed (steady speed).

 

We have't any problem with aerobatics on Su-27.

 

Some russian info about T-10 (Su-27):

Важнейшей особенностью Т-10 впервые в отечественной истребительной авиации СССР должна была стать реализация концепции продольной статической неустойчивости самолета на дозвуковых скоростях полета с обеспечением его продольной балансировки в полете посредством автоматики четырехкратно резервированной электродистанционной системы управления (ЭДСУ). Принятие концепции продольной статической неустойчивости (иначе - "электронной устойчивости") сулило серьезные преимущества: для балансировки самолета на больших углах атаки требовалось отклонение стабилизатора носком вверх, при этом его подъемная сила складывалась с подъемной силой крыла, что давало существенное улучшение несущих свойств истребителя при незначительном росте его сопротивления. Благодаря использованию интегральной статически неустойчивой компоновки Су-27 должен был обрести исключительные маневренные характеристики, позволяющие ему выполнять в воздухе эволюции, недоступные самолетам обычной схемы, и иметь большую дальность полета без подвесных баков.

Edited April 7, 2015 by Dell_Murrey-RUS

[Ironhand]

As I see it, you are focusing on the joystick, but I think that something is not completely done well with FM. In fact how is it possible when turning at low speeds (turn left or right doesn't matter), plane suddenly raise his nose, take the opposite side, and then just fall back into a tailspin, and does not respond to any commands?! Too often DCS Su-27 falls back into this tailspin.

As suggested, you might want to post a track. But I will say that once you get into the low speed range, you need to be very cautious in how you handle the aircraft. That said, you can turn her at airspeeds as low as 190 km/hr IAS (perhaps even less) as long as you are very, very careful and do it, very, very slowly. Otherwise your wing will stall and then...

 

What you describe sounds very much like stalling a wing in the turn.

[Bourrinopathe]

[…] That said, you can turn her at airspeeds as low as 190 km/hr IAS (perhaps even less) as long as you are very, very careful and do it, very, very slowly. Otherwise your wing will stall and then... […]

 

What's frustrating is that most of us are very ignorant about the real Su-27 capabilities (at least I am).

I was about to create a thread asking about the lowest speed sustained in a linear flight. I was fooling around with the Flanker and I reached a stable 170 km/h IAS with a 25° AoA, low altitude (below 500 m) (I think it was a winter mission with about 0°c).

I was wondering if it was realistic, but I have no clue (the "official" stalling speed is 200 km/h if I'm not mistaken).

 

More studying ahead, for sure! :book:

[theropod]

As suggested, you might want to post a track. But I will say that once you get into the low speed range, you need to be very cautious in how you handle the aircraft. That said, you can turn her at airspeeds as low as 190 km/hr IAS (perhaps even less) as long as you are very, very careful and do it, very, very slowly. Otherwise your wing will stall and then...

 

What you describe sounds very much like stalling a wing in the turn.

 

ironhand, that is weird!

 

you always want to see the track which includes anomalies but no one post it!

and i dont know which aircraft do they compare su-27 and how can be easy to scribble the FM.

guys, this aircraft is not an any aircraft to compare with!

what i have learned about su-27 is studying and adaptation for is more needed than any dcs aircraft!

and for me, with or without ASC it is very stable in flight!

 

and yes there are issues, but dont forget its beta stage and i guess it will be longer than we expect.

Edited April 7, 2015 by theropod

[Ironhand]

What's frustrating is that most of us are very ignorant about the real Su-27 capabilities (at least I am).

I was about to create a thread asking about the lowest speed sustained in a linear flight. I was fooling around with the Flanker and I reached a stable 170 km/h IAS with a 25° AoA, low altitude (below 500 m) (I think it was a winter mission with about 0°c).

I was wondering if it was realistic, but I have no clue (the "official" stalling speed is 200 km/h if I'm not mistaken).

 

More studying ahead, for sure! :book:

I'm not sure that any of us are any more knowledgeable about the F-15C either. The real issue here is that our Flanker isn't handling according to our preconceived ideas of how she should handle. You have to keep trimming her, her constant desire to lift her nose up into the air, etc... The only reason I think this is probably close to correct is that it seems too wrong for it not to be right. (How's that for logic?) I have a hard time believing that this behavior wouldn't have been corrected a long time ago, if it wasn't reasonably accurate. (Rose colored glasses?) I also have received some input behind the scenes that suggests things are fairly correct.

 

I've seen varying citations for the Su-27's critical AoA ranging from 23-33 degrees. Beyond the critical AoA, the wing stops producing lift and bad things happen. I do notice, however, that the real world manual cites 24 degrees as a permissible AoA at .5 Mach for aircraft with nothing hanging off her wings.

 

BTW, the 200 km/hr (300 km/hr above 6000 m) figure you cite isn't the stall speed, it's the minimum speed for sustained level flight from the viewpoint of controllability. Below that airspeed, if you sneeze, bad things might happen.

 

...

 

you always want to see the track which includes anomalies but no one post it!...

Not necessarily an anomaly. Just something unexpected. It might well be wrong but, until people can check it out, it's hard to know what's happening.