Learn About Trimming

[lockon2015]

Does anyone have any introductory videos or tracks about trimming used within the context of dogfighting? I understand on a basic level what trimming does; if the plane is unstable you can "trim" controls to not have to keep using the joystick to correct for pitch and roll, but how do people use trimming in a dogfight? For example, you got a bandit red hot, you're flying after him, the radar is going and missiles are everywhere, you turn, do you trim here?, then maybe you turn again, trim here? Then pitch down. Trim? I guess that's what I'm confused about. Or, do you set a trim just as the dogfight begins and not worry about it until everything is over?

 

I also couldn't tell too easy if trim remains after I push a trim button once, say for pitch, and if it stays on Trim until I hit LAlt-9, or if the trim goes away after I stop pushing the Trim button. I know it will take practice but what happens for trimming the nose, and then the roll, so you have a combined trim?

[Bourrinopathe]

LAlt-9 only resets the autopilot, not the trim.

The trim acts like a flight stick permanent default input correction. Once you've set the trim, the flightstick (and rudder pedals) will recenter in that corrected position (pitch, roll, yaw, combined) until you reset the it (but iirc the navigation autopilot will reset the roll axis trim - not sure).

 

I don't know how real pilots use the trim during close range combat, but I'd suggest you reset the trim before a dogfight. The reason is your trim setting limits the axes manual range (in the opposite direction).

(e.g. trim full pitch down = limited maximum pitch up flight stick (and control surfaces) range - with a flight stick fully trimmed to pitch down, you won't be able to reach the maximum pitch up capability by fully pulling the stick)

 

The best way to get familiar with it is to test it. You can test the trim, the trim lights and the effect on the control surfaces and flight stick motion range, before take-off.

Don't take my word for it, just go test it :thumbup:

[Ironhand]

I assume we are talking about the Su-27. First, understand that the need to trim in this bird is placed there artificially by the aircraft designer. It's written into the fly-by-wire control laws. Without getting into the whys and wherefores, every time you increase or decrease your airspeed, you need to trim. If you trim for an airspeed of 500 km/hr and, then increase your airspeed to 700 km/hr (for example) you need to retrim.

 

That being said, in a turning fight, you do not need to keep retrimming because, as long as you are putting Gs on the airframe, this artificial trimmer law disconnects. So your increasing or decreasing airspeed in a turning fight has no effect on trim. If you then get back into a straight line chase, for example, you will need to start trimming again.

 

There are several l-o-n-g threads in this Su-27 forum concerning trimming and its requirements and this aircrafts flight model. You might want to give them a read. It'll help you understand what you are dealing with.

[DarkFire]

I'd very much recommend reading pages 110 - 117 of the Su-27 flight manual which contains a pretty comprehensive discussion of how the flight control system works. Also as Ironhand said, during ACM, particularly WVR, trim is irrelevant as the system-imposed trim behaviour is essentially turned off.

 

The Su-27 flight model is apparently very nearly totally working as intended. There are some quirks that diverge from the behaviour described in the manual but you probably won't encounter them unless you try using the autopilot at very high altitude or at very low speeds.

 

A big +1 for Ironhand's Flanker Training videos. Made for an older version but still 100% relevant.

 

I'd suggest these threads as being very helpful to learn about the flight behaviour of the Su-27:

 

A lengthy discussion about trim:

http://forums.eagle.ru/showthread.php?t=150650

 

Huge, ultimate flight model discussion thread:

http://forums.eagle.ru/showthread.php?t=137234

 

A long discussion about edge-of-envelope flight:

http://forums.eagle.ru/showthread.php?t=143425

 

A somewhat technical thread about flight performance at various altitudes:

http://forums.eagle.ru/showthread.php?t=147556

 

Another somewhat technical thread about possible range at various altitudes:

http://forums.eagle.ru/showthread.php?t=151731

 

Anyway, hope this all helps, & good luck with learning the Su-27 :)

Edited March 3, 2016 by DarkFire

[lockon2015]

Yes, this is what I was looking for. I will go through those links. Thanks for putting them up.

[Hummingbird]

That being said, in a turning fight, you do not need to keep retrimming because, as long as you are putting Gs on the airframe, this artificial trimmer law disconnects. So your increasing or decreasing airspeed in a turning fight has no effect on trim. If you then get back into a straight line chase, for example, you will need to start trimming again.

 

Sadly not so, I find I have less positive pitch authority available in a turn fight the higher the subsonic speed the aircraft was initially trimmed for.

 

i.e. trimmed for level flight at 500 km/h I have far more positive pitch authority than when trimmed for level flight at 800 km/h.

 

That's one of the reasons I don't fly the Su-27 anymore, the way the SAS is simulated just doesn't make sense, both in terms of the amount of positive pitch it applies with changes in speed as well as the fact that it limits max pitch authority in the opposite direction in the process.

[winchesterdelta1]

I have issue's with this trimming in close combat as well. If i start a turning fight i do what you guy's suggest and don't trim. But that makes my plane a wobbly wobbly in a turning fight. How to counter this?

 

See my vid: [ame]

[/ame] at 14:03

As you can see my plane go's all left right left right if i make these kind of turns and i continuously have to correct (I think my corrections make it all wobbly) . Any way to prevent that?

[DarkFire]

I have issue's with this trimming in close combat as well. If i start a turning fight i do what you guy's suggest and don't trim. But that makes my plane a wobbly wobbly in a turning fight. How to counter this?

 

See my vid:

at 14:03

As you can see my plane go's all left right left right if i make these kind of turns and i continuously have to correct (I think my corrections make it all wobbly) . Any way to prevent that?

 

Good kills! Was one of those F-15's trying to shoot at you with his gear down??!! Loved the music by the way, what is it?

 

For smooth control, firstly I'd recommend using control axis curves, somewhere between 15 and 25 units for both pitch and roll. This will help you make precise but smooth inputs. Next, feet off the rudder! The ACS on the Su-27 will perform co-ordinated turns for you, you don't need to touch the rudder. Nearly the only time I ever touch the rudder in the Su-27 is when I'm on final approach for a cross-wind landing.

 

I'd also recommend flying more slowly for conducting WVR combat. The corner speed for the Su-27 is roughly 700 - 770 Km/h depending on weight & load. Flying above 1100 Km/h will give you a very large turning circle & also makes it much easier to over-G the airframe. Finally, the ACS on the -27 doesn't react well to making inputs in multiple axes simultaneously, i.e. roll then pull rather than doing both at once.

 

Hope this helps. Great video!

[winchesterdelta1]

Thank you for the advice. I think i make inputs on different axis on accident. Might have to take care of that more. I'm used to F-15 and there it does not have this behavior in dogfights. Might have picked the bad habit from there.

 

Good question on the music in the vid. I lost all my data on a corrupted disc. So i have no clue anymore. If you find out please tell me :)

[gsjman]

about DCS Wold 2.5 Problem

 

I downloaded from here https://www.digitalcombatsimulator.com/en/

Use the rocker is Logitech - Shining titanium wing second generation rocker

Use the Z and X keyboards to adjust the deviation of the Su-25T aircraft on the runway

It is difficult to correct the deviation of aircraft taxiing

When the throttle is fully open, the aircraft deviation is difficult to correct. Finally the plane was destroyed.

 

This Whether the joystick is not set or what key

to be pressed can lock the airplane to prevent the airplane from deviating while coasting ?

Aircraft lift off Also uncontrollable Will deviate from left to right or Up / Down

[Ironhand]

I downloaded from here https://www.digitalcombatsimulator.com/en/

Use the rocker is Logitech - Shining titanium wing second generation rocker

Use the Z and X keyboards to adjust the deviation of the Su-25T aircraft on the runway

It is difficult to correct the deviation of aircraft taxiing

When the throttle is fully open, the aircraft deviation is difficult to correct. Finally the plane was destroyed.

 

This Whether the joystick is not set or what key

to be pressed can lock the airplane to prevent the airplane from deviating while coasting ?

Aircraft lift off Also uncontrollable Will deviate from left to right or Up / Down

First of all, welcome. Looks likes you've been a member for awhile but this is your first post?

 

Secondly, anytime odd things like this start happening, go into the CONTROLS settings for the aircraft and make sure that axis inputs and other inputs of concern are only assigned to one location. For example, I have a joystick, throttle, and rudder pedals. The sim, by default, assigns the rudder axis to all 3 of these and roll and pitch to both the throttle and stick. You have to go in and remove what you don;t want.

[Cik]

trim is just for comfortable level flight while moving between fights

 

 

once you are in the fight, it's irrelevant. if you need to pull on the stick, just pull on the stick.

[gsjman]

Dcs World 2.5 Su-25T Problem

 

Is there a related setting the movie to provide a reference?

Edited July 6, 2018 by gsjman
Repeated questioning

[Ironhand]

Rather than a lot of writing back and forth, I've created a short video the I'm currently uploading to Youtube (very slowly because of my pathetic internet connection). Hopefully that will help us figure this out for you. Should be ready in about an hour. I'll post it along with the mission it was created from as soon as it's ready.

That took a lot longer to upload than I expected...

 

Hopefully, this will be of some help. Try using only the keyboard rudder controls set up as shown in the video--be sure there are no other rudder assignments. The video then goes on to show an Su-25T taxi and takeoff with the Controls Indicator showing so that you can see how the aircraft should respond to rudder input.

 

 

 

 

I've attached the mission I used for this. If you download it and use it, you'll have the same environmant I had. Try taxiing and taking off using only the keyboard rudder assignments. If that works as you see in the video, then the problem is either in your Logitech or in the axis assignments for your gear.

Su-25T Butami-Kutaisi.miz

[gsjman]

Show throttle and rudder at the bottom right of the movie Mark

is Which keyboard is used ?

After the plane is raised, the posture cannot be maintained. It is always left or right. Up and down

Is there which key can To adjust the flight attitude ?

Edited July 10, 2018 by gsjman

[draconus]

Show throttle and rudder at the bottom right of the movie Mark is Which keyboard is used ?

RCtrl+Enter shows controls' current state - be it keys, stick, pedals and thorottle - make sure it is centered when you're not touching anything. If it's not centered you may want to increase deadzone in axis tune. Trimming can also center the controls it was trimmed before. Make sure one key (or one direction on the stick) moves only one axis!

 

After the plane is raised, the posture cannot be maintained. It is always left or right. Up and down

Left/right is unusual after take off - thus deadzones suggestion above.

Up/down is common - just trim it. In fact you have to do it all the time (due to airspeed changes). Default keys:

Rctrl + . = Trim UP

Rctrl + ; = Trimp Down

Assign it to your stick's hat switch or whatever you're comfortable with - some sticks have dials for that.

 

Is there which key can To adjust the flight attitude ?

You can use autopilot but it won't solve the problem. Default key:

Alt + 1 = AP Attitude Hold (maintains bank and pitch angle)

` (~) = override AP

A = Autopilot (follows waypoints)

Edited July 10, 2018 by draconus