Su-25T FM question

[tflash]

I've been flying the Su-25T a lot now, I really really like it but I still have an uneasy feeling about its FM.

 

The strangest thing is the way the aircraft hangs in the air. E.g. if you roll 90 degrees, so you just fly with your wings 90 degrees against the ground, you do not lose altitude? (be sure: I'm not misinterpreting the altitude meter above ground here) The simple fact is you fly straight, you roll 90 degrees and you do not lose altitude. If you put your wings back level, you often end up at a somewhat higher altitude!

 

The problem is that this behaviour is partly responsible for the fact that the Su-25T seems so unmanoevrable. Has nothing to do with the fact that it's AFM makes flight more "realistic": in my view quite the opposite: it is because it does NOT fly realistic in this case. If you do not loose hight immediately while banking, a turning manoevre just takes much longer to complete.

 

The whole idea of turning that way is: you roll, your aircraft immediately drops down and while gaining speed in the dive you complete the turn.

 

This is exactly what you cannot do in the AFM'ed S-25T.

 

So flight gurus on these forums, just how wrong am I about this? ;)

[Laivynas]

Proove this statement with a track. ;)

(90 bank flight w.o altitude loss on Su-25/25T)

[Vati]

I've said in the past and I will repeat again.. Su25T AFM is not realistic at all. If real Su25T flew like that, it would never been accepted into service.

Some aspects of AFM are improvement others are step backwards from the old model. But since most of folks here do not know how real aircraft fly, they are happy with their illusion of having an 'Advanced' FM :)

 

(pops flares and chaff :) )

[britgliderpilot]

I've said in the past and I will repeat again.. Su25T AFM is not realistic at all. If real Su25T flew like that, it would never been accepted into service.

Some aspects of AFM are improvement others are step backwards from the old model. But since most of folks here do not know how real aircraft fly, they are happy with their illusion of having an 'Advanced' FM :)

 

(pops flares and chaff :) )

 

That's a bold statement ;)

 

 

Back to topic . . . .

 

I've been flying the Su-25T a lot now, I really really like it but I still have an uneasy feeling about its FM.

 

The strangest thing is the way the aircraft hangs in the air. E.g. if you roll 90 degrees, so you just fly with your wings 90 degrees against the ground, you do not lose altitude? (be sure: I'm not misinterpreting the altitude meter above ground here) The simple fact is you fly straight, you roll 90 degrees and you do not lose altitude. If you put your wings back level, you often end up at a somewhat higher altitude!

 

I went and had a look in Flaming Cliffs - I roll to 90 degrees, try to hold the aircraft at constant altitude . . . . . couldn't do it, the aircraft yawed towards the ground.

 

I can't hold the aircraft at level altitude at 90 degrees bank.

 

With increased pitch angle it might be possible to get enough lift from engines and tail, but I dunno . . . . like the others said, provide a track and let's see.

 

 

The problem is that this behaviour is partly responsible for the fact that the Su-25T seems so unmanoevrable. Has nothing to do with the fact that it's AFM makes flight more "realistic": in my view quite the opposite: it is because it does NOT fly realistic in this case. If you do not loose hight immediately while banking, a turning manoevre just takes much longer to complete.

 

The whole idea of turning that way is: you roll, your aircraft immediately drops down and while gaining speed in the dive you complete the turn.

 

This is exactly what you cannot do in the AFM'ed S-25T.

 

This is a new and interesting way of flying that I haven't heard of before . . . . where'd you learn it from?

[Pilotasso]

ME thinks hes flying on 1.02 and mistakening the vanilla Su-25 with the T in Flamming Cliffs.

[TekaTeka]

The problem is that this behaviour is partly responsible for the fact that the Su-25T seems so unmanoevrable.

Did you setup your joystick properly? This is a quote from 1.1 readme.

 

Joystick setting for Su-25 and Su-25T

 

When setting the joystick response pitch curve for aircraft with Advanced Flight Model (Su-25 and Su-25T), it is recommended that you remove any joystick insensitivity near the neutral / centering area (the so-called “dead zone”). You should also have a linear response curve; meaning that the joystick pitch setting curve should be a straight line from corner to corner of the response field. This is recommended because any nonlinearity will distort the correct balancing of the aircraft. This AFM balancing consists of angle of attack, G-loading, and control stick longitudinal diversion. A dead zone would create a “flat” response area (local control insensitivity zone) when balancing the dependencies in the mid-angle of attack range (5 - 10°). This would make angle of attack and G-loading control difficult.

 

 

To Vati, this is a quote from a details report of AFM.

-Flight tested by a Russian Su-25 pilot.

http://forum.lockon.ru/showpost.php?p=25344&postcount=1

[Force_Feedback]

Uh ugh, flight tested doesn't mean 'fixed and made as realistic as possible'

 

Didn't the su-25T have slightly uprated engines? Beyond that, I don't think either of us could judge wether the su-25T perfroms as it should, same applies even more to others, but they lack AFM so are inherently less realistic.

[TekaTeka]

Uh ugh, flight tested doesn't mean 'fixed and made as realistic as possible'

So, do you think the pilot said "Su25T AFM is not realistic at all" like Vati said and ED didn't care at all? If ED is such a company, they released BS a year ago in an imperfect condition and got some money...

[tflash]

I think indeed that it has to do with joystick settings, like TekaTeka says in post #7. I didn't set my roll and pitch completely flat. Still, when I do, I wonder if the effect is strong enough. I included a track (I'm not good at it, so maybe you can make a better one.

 

I guess what in fact happens is that I automatically compensate the roll with rudder. This can explain why the aircraft doesn't drop as expected, together with inertia.

 

Look at the last part of the track, with external views, than you have a more reliable (I suppose) indication of altitude.

 

Brittglider, what I mean is the kind of manoevre WWII dive-bombers do when they break up formation and roll into the target.

 

Thanks for putting your time in this question!

BankingSu-25T.zip

[britgliderpilot]

I think indeed that it has to do with joystick settings, like TekaTeka says in post #7. I didn't set my roll and pitch completely flat. Still, when I do, I wonder if the effect is strong enough. I included a track (I'm not good at it, so maybe you can make a better one.

 

I guess what in fact happens is that I automatically compensate the roll with rudder. This can explain why the aircraft doesn't drop as expected, together with inertia.

 

Look at the last part of the track, with external views, than you have a more reliable (I suppose) indication of altitude.

 

Brittglider, what I mean is the kind of manoevre WWII dive-bombers do when they break up formation and roll into the target.

 

Thanks for putting your time in this question!

 

 

Have had a look at the track and don't see anything immediately wrong.

 

Perhaps a better indication of what's happening is given by looking at the vertical velocity indicator . . . as you roll to the vertical and lift is lost, the aircraft slowly begins to accelerate downwards. Once lift is removed, it takes a while for vertical velocity to build, in accordance with Newton etcetera.

 

In a couple of your maneuvres you're not rolled fully over - perhaps 70 or 80 degrees. In this case, the wing is still generating a lift component in the upwards direction, AND you're getting some lift from the tail surface as well. This could be why the aircraft isn't dropping as fast as you think it should.

 

In order to judge the effect better, it might be better to set up a flight alongside an AI aircraft at fixed altitude and repeat the exercise in F5 view from that aircraft - I bet you'll see the drop in altitude better that way.

[Yo-Yo]

The strangest thing is the way the aircraft hangs in the air. E.g. if you roll 90 degrees, so you just fly with your wings 90 degrees against the ground, you do not lose altitude? (be sure: I'm not misinterpreting the altitude meter above ground here) The simple fact is you fly straight, you roll 90 degrees and you do not lose altitude. If you put your wings back level, you often end up at a somewhat higher altitude!

 

 

So flight gurus on these forums, just how wrong am I about this? ;)

 

Are you ready to perform it at 15 m altitude level flight? :)

 

To be serious, the only way you can hold your altitude is to fly about 700 kph with full rudder applied ("knife edge flight") and it is usual for a big number of planes. In this case the side force (the force that provides FLAT TURN in normal flight if full rudder is applied and the bank due to yaw is compensated with ailerons) becomes the lift force .

[S77th-konkussion]

All I have to say is if the 25 flies like it does in lock on.....mannnnn I feel sorry for the pilot.

 

no doubt... :joystick:

[ericinexile]

I don't know if the Su25 flys like THE real airplane because I have never flown one. I do know that the Su25 does fly like A real airplane because I have 11,000 hours flying real airplanes and it comes closer than any other sim, including MS and X-Plane in getting the experience about right. There are some faults, wheel friction and yaw stability being the most irritable, but overall its pretty hard to complain.

 

As to knife-edge flight, most high performance jets (the Su25 is not in this category) are able to maintain altitude for a sustained period of time. This is mostly a function of thrust overcoming gravity but the vertical stabilzer(s) do provide lift as well. Same principal as a missile: Give it enough thrust and/or speed and it needs little if any wing.

 

Smokin' Hole

[tflash]

With heavy fuel load and draggy Vikhr pods, I doubt it would even be suitable for combat. I'm now concentrating on flying it clean, with medium fuel load.

 

You can reach good speeds, but the wing feeling is so strange. I still do not manage to turn like I want to. I would want to take advantage of the aircrafts speed. It doesn't seem to be an aircraft that you can throw into a turn like that.

 

The good news is that for some reason the standard SEAD loadouts like 2 x Kh-58 and 4 x Karen seem to produce no extra drag at all.

[tflash]

I don't know if the Su25 flys like THE real airplane because I have never flown one. I do know that the Su25 does fly like A real airplane because I have 11,000 hours flying real airplanes and it comes closer than any other sim, including MS and X-Plane in getting the experience about right. There are some faults, wheel friction and yaw stability being the most irritable, but overall its pretty hard to complain.

 

As to knife-edge flight, most high performance jets (the Su25 is not in this category) are able to maintain altitude for a sustained period of time. This is mostly a function of thrust overcoming gravity but the vertical stabilzer(s) do provide lift as well. Same principal as a missile: Give it enough thrust and/or speed and it needs little if any wing.

 

Smokin' Hole

 

Sorry, our posts crossed. This is valuable input, since I have no real flight experience at all. Do you have any suggestion how I could best approach a sharp turn in the Su-25T? With the yaw stability, do you mean the fact that it doesn't seem to stabilize in the yaw axis depending on speed?

[Vati]

So, do you think the pilot said "Su25T AFM is not realistic at all" like Vati said and ED didn't care at all? If ED is such a company, they released BS a year ago in an imperfect condition and got some money...

Fact is we do not know what the pilot had said :)

And secondly, I did not say anywhere that ED did not care at all, so please try to avoid putting your words into my mouth.

 

What I wanted to point out is that, just because there is A in AFM, it does not mean now that everything is OK. And it also does not mean, we should not try to strive for better FM.

While being said that... while there is still a lot of room in improvement in plane's FM in lockon, I look forward to BS. Looking how FM is evolving from Flanker 1.0 to BS, I am still optimistic that along the road we will get better plane's FM :)

[TekaTeka]

What I wanted to point out is that, just because there is A in AFM, it does not mean now that everything is OK. And it also does not mean, we should not try to strive for better FM.

 

Well, your original statement is much much stronger than that. Say what you want to say more reasonably.

[ericinexile]

With heavy fuel load and draggy Vikhr pods, I doubt it would even be suitable for combat. I'm now concentrating on flying it clean, with medium fuel load.

 

You can reach good speeds, but the wing feeling is so strange. I still do not manage to turn like I want to. I would want to take advantage of the aircrafts speed. It doesn't seem to be an aircraft that you can throw into a turn like that.

 

The good news is that for some reason the standard SEAD loadouts like 2 x Kh-58 and 4 x Karen seem to produce no extra drag at all.

 

Turns require rudder. Jets with swept wings have some natural yaw stability usually aided by a yaw-dampening system which, when combined, allow for feet-on-the-floor flying. For whatever reason, the Su25 (as simulated by LO:FC) needs lots of foot-work to fly properly. Check the "ball" both during turns and after non-symmetrical ordinance drops. If it isn't centered then the plane, just like the real thing, will fly poorly--even dangerously.

 

As for the Vikhr, imagine all the combat jets you've seen. Have you ever seen anything so draggy on a plane before? Of course it's going to slow the jet down. Double the speed, parasite drag QUADRUPLES. Again, I think this is an accurate simulation of a plane that has been tasked to do something it's original designers didn't intend when they first thought it up in the 70's. I'm enjoying the hell out of it!

 

Smokin' Hole

[ericinexile]

Sorry, our posts crossed. This is valuable input, since I have no real flight experience at all. Do you have any suggestion how I could best approach a sharp turn in the Su-25T? With the yaw stability, do you mean the fact that it doesn't seem to stabilize in the yaw axis depending on speed?

 

Sorry, we crossed again ;). The best way to fly it is to buy rudder pedals if you don't already have them. Using the stick's twist feature is much harder to do with precision. When you apply aileron, also apply some rudder in the same direction. There is a "ball" below the attitude indicator that should be kept fairly close to center. Don't stare at and don't get too wrapped around keeping it perfectly centered--just be aware that it is there as a guide. Again, every time you apply aileron, also apply rudder. Usually the slower the speed, the more rudder that will be required to maintain coordinated flight. When you drop or launch a single bomb, missile, or rocket, you will notice the ball will be well out of center. This will either require a constant rudder application or rudder trim. Just keeping the wings level with aileron and with the ball uncentered will mean that you are flying in a side-slip which does very bad things for both the flying qualities and the stall characteristics of the jet.

 

All of this only applies to the Su25(t). The other jets can be flown "feet-on-the-floor".

 

Hope this helps.

 

Smokin' Hole

[tflash]

I don't have pedals yet, but I reconfigured so as to remove the rudder from the joystick's Z-axis. And indeed, I think I start to see what you mean. I totally misjudged the ball's function, and using it as a guide while applying aileron and rudder properly seems to hold the promise I will finally be able to control this beast! Will take some time though to adjust from bad habits.

[MBot]

All I have to say is if the 25 flies like it does in lock on.....mannnnn I feel sorry for the pilot.

 

Keep your payload under 2000 kg, better under 1000 kg. And dump the -T for the vanilla :) A Frog with 4 B-8 launchers has excellent firepower and flies like a blast.

[Force_Feedback]

Yes, but if your engines do get hit by something, they will burn, wether you turn them off or not, and after a while your plane will say 'boom', on the su-25T, you can turn off the burning engine, and the fire will extinguish itself, guess it's some bug on the vanilla Frog.

[Yo-Yo]

I don't know if the Su25 flys like THE real airplane because I have never flown one. I do know that the Su25 does fly like A real airplane because I have 11,000 hours flying real airplanes and it comes closer than any other sim, including MS and X-Plane in getting the experience about right. There are some faults, wheel friction and yaw stability being the most irritable, but overall its pretty hard to complain.

 

As to knife-edge flight, most high performance jets (the Su25 is not in this category) are able to maintain altitude for a sustained period of time. This is mostly a function of thrust overcoming gravity but the vertical stabilzer(s) do provide lift as well. Same principal as a missile: Give it enough thrust and/or speed and it needs little if any wing.

 

Smokin' Hole

 

Yaw dynamic stability is the main issue for real Su-25 so the special damper was implemented (look at the small rudder as it automatically turns counter yaw angular velocity). If you turn off main electric switch you can feel how it flies WITHOUT it.

Stability did tune using real Su-25 characteristics. So here it is...

[GGTharos]

Yo-Yo, out of curiosity - why does Su-25 not slow down much during landing? Gear, flaps, and airbrakes out - it does not want to slow down!

[Force_Feedback]

Yo-Yo, out of curiosity - why does Su-25 not slow down much during landing? Gear, flaps, and airbrakes out - it does not want to slow down!

 

That is a very interesting question, when coming in on absolute minimums, 800-900kg of fuel, the thing needs 1.2km to stop (no chute, 220kph landing speed, perfect flare)?