Autopilot issue

[Tomahawk674]

Hello everyone. I recently purchased DCS and FC3 on Steam. Everything is going well as I'm relearning the simulator, I used to have the first FC.

 

Currently I have an issue with the Su-27 and the autopilot. Basically, I can't get it to work; pressing A seems to barely do anything, and trying to use the straight and level feature does nothing as well (Alt+3). The funny thing is that the features work perfectly in the Su-33.

 

I haven't touched the default key assignments for it, I can still go to Controls/Su-27/Autopilot and see all the default autopilot commands, which I have not mapped to my MS Sidewinder 2 stick.

 

I am trying to use Autopilot in the SIM difficulty setting, on instant missions and create fast mission. I have everything on realistic except the English HUD.

 

I welcome any suggestions.

[Tomahawk674]

PS: I did do a search and read the whole thread about the Su-27 autopilot issues; I'm not sure I'm having an oscillation problem, I can't get it to do anything, but I will try again at a low altitude and high rate of speed.

[holimoli]

Do you trim before u engage the autopilot ? Are any of the autopliots lights on? (next to the weapon loadout display)

[DarkFire]

PS: I did do a search and read the whole thread about the Su-27 autopilot issues; I'm not sure I'm having an oscillation problem, I can't get it to do anything, but I will try again at a low altitude and high rate of speed.

 

The various autopilot mode lights are forward of where your throttle appears. When you turn on your autopilot are any of them illuminated?

[Tomahawk674]

I will need to check the lights, but yes, I trim before I engage the autopilot. I only want to use the autopilot to maintain course and altitude while I fiddle with the radar.

[DarkFire]

I will need to check the lights, but yes, I trim before I engage the autopilot. I only want to use the autopilot to maintain course and altitude while I fiddle with the radar.

 

When you're scanning with your radar, altitude hold mode is your friend :) So much so that it's worth binding the key, and the "autopilot off" key, to HOTAS buttons.

[Tomahawk674]

Alright, here is what I have discovered:

 

In the Su-33 the autopilot works as programmed. I actually don't get the lights in the buttons, but when I press "A" I can see the buttons being "pressed down".

 

In the Su-27 I can also see the buttons being pressed down, but nothing happens. I have tried accelerating to over 800Kph, have it trimmed for level flight, then try A or Alt+3 and while I see the button animation work, the autopilot is not working.

 

Any help is appreciated.

[DarkFire]

Alright, here is what I have discovered:

 

In the Su-33 the autopilot works as programmed. I actually don't get the lights in the buttons, but when I press "A" I can see the buttons being "pressed down".

 

In the Su-27 I can also see the buttons being pressed down, but nothing happens. I have tried accelerating to over 800Kph, have it trimmed for level flight, then try A or Alt+3 and while I see the button animation work, the autopilot is not working.

 

Any help is appreciated.

 

Could you post a track file showing the problem? That might help us figure out what's going wrong.

 

When you try engaging the autopilot, is there a red warning light illuminated under the HUD?

[JunMcKill]

Could you post a track file showing the problem? That might help us figure out what's going wrong.

 

When you try engaging the autopilot, is there a red warning light illuminated under the HUD?

 

It's possible that this autopilot options are the ones of the real aircraft? remember that SU-27 have PFM and SU-33 dont

[Tomahawk674]

I will try to post a track.

[Tomahawk674]

Is there a way to reset DCS to factory defaults by deleting some config file? Maybe I messed something up during setup.

[DarkFire]

Is there a way to reset DCS to factory defaults by deleting some config file? Maybe I messed something up during setup.

 

Try running start --> Eagle Dynamics --> Repair DCS World

 

That should sort out any corrupted files that might be causing a problem.

 

I think the keyboard bindings for the Su-27 are stored in this file:

 

C:\...\DCS World OpenBeta\Mods\aircraft\Flaming Cliffs\Input\su-27\keyboard\default.lua

 

I'd save a copy of it before deleting it though because I'm not sure if the game will re-create a default file when you re-start DCS world after deleting it.

[Tomahawk674]

Hello everyone, I have attached a track of the Su-27 autopilot issue. I take off, retract gear and flaps. I trim nose down, throttle back so you can see the autopilot lights. I press A and it engaged. I do not touch anything else and it disengages on its own seconds later. I try engaging Alt+3 again and nothing happens.

 

Any help would be appreciated. I deleted all my keyboard/joystick assignments and was back to default mapping.

Autopilotnotworking.trk

[Ironhand]

Watched your track. Route Following Mode, which is what you engaged with the "A" key, will maneuver you to keep your aircraft on the course track as well as at the assigned altitude. That last is important. In this case your assigned altitude was about 2000m above your altitude when you engaged it. As you nosed up, you let your airspeed drop so that your AoA increased to the point where the AP was forced to disengage because you were about to lose control of the aircraft.

 

I ran the track a 2nd time but took control after you engaged the AP but before it disengaged and pushed the throttle forward to keep my airspeed up and it remained engaged. You might want to fly that track yourself and take control at the same point, increase thrust and see what happens.

 

EDIT: Flew this mission one more time taking control as soon as you entered the cockpit. Based on the continual roll to the left your track had displayed, I expected a wind pushing me to the left as I rolled down the runway. Instead I was surprised to find myself rolling straight down the centerline and remained wings level as I climbed out. So you need to check your hardware. At a minimum you might need to add a bit of "dead zone" in DCS's Su-27 control panel for the roll axis. Something is not right with your setup but I don't think that's actually the culprit in this particular case.

 

That being said, I experimented with the various AP functions and each performed correctly including attitude, baro altitude, radar altitude, panic, and route following. Each did what it was supposed to do.

Edited August 17, 2016 by Ironhand

[Tomahawk674]

Thanks for reviewing my track. I recently did a calibration on my stick; the FF spring seems to not be perfectly centered, so it's a hair off. I have added enough dead zone to counter for it. I also added a curve to the sensitivity.

 

I will try taking control of the track at full throttle and see what happens. I only throttled back so we could see the autopilot lights, I'm not sure if there's another way to check them.

[Ironhand]

...

 

I will try taking control of the track at full throttle and see what happens. I only throttled back so we could see the autopilot lights, I'm not sure if there's another way to check them.

:) Always remember that you are ultimately responsible for maintaining control of your aircraft. :)

 

A lot of people have a tendency to let the aircraft speed up or slow down on its own rather than maintaining a constant airspeed. That can lead to a lot of unnecessary pain. Anyway, I'll be interested in hearing about your results.

[DarkFire]

Thanks for reviewing my track. I recently did a calibration on my stick; the FF spring seems to not be perfectly centered, so it's a hair off. I have added enough dead zone to counter for it. I also added a curve to the sensitivity.

 

I will try taking control of the track at full throttle and see what happens. I only throttled back so we could see the autopilot lights, I'm not sure if there's another way to check them.

 

Dead zone should correct the slight left roll. I'd also definitely recommend using a curvature of between 15 & 25 units in both pitch and roll. This will allow you to make precise, small changes but will still allow for drastic inputs when you need them.

 

It's important to remember that the Su-27 doesn't have a traditional autopilot rather an "automatic control system" that works via trim inputs. The ACS on the Su-27 does not have any control over the throttle input, so if you use ACS functions such as the 'panic button' or route following mode, it's important to remember that you as the pilot must still manually control the throttle to maintain the desired airspeed.

 

Pages 44-46 and 110-117 of the Su-27 flight manual are well worth reading.

[Tomahawk674]

Hello, I have more tracks for your review. I have 5% dead zone and 25% curvature on both axis.

 

First is the Su-27. I take off and accelerate, retrack flaps and gear, trim nose down, press A and.... nothing.

 

I then tried the same in the Su-33 and all works normal.

Autopilotnotworking.trk

AutopilotWORKINGwithSu33.trk

[Ironhand]

Hello, I have more tracks for your review. I have 5% dead zone and 25% curvature on both axis.

 

First is the Su-27. I take off and accelerate, retrack flaps and gear, trim nose down, press A and.... nothing.

 

I then tried the same in the Su-33 and all works normal.

 

I think there is something odd going on when you trim and that might be the problem. Note the difference in stick positions when I take control. I don't recall ever seeing this before with anyone else's track. As soon as I take control, the stick jumps to the new position:

 

EDIT: One thing I did notice in playing around with this... at one point, if I was pulling on the stick while at 45 degree bank angel or greater, the AP would not engage. FWIW, I normally have the stick in a neutral position, when I engage any AP function. I don't think you were doing that in the Su-27 track. The Su-33 is a different animal entirely in that it still uses the old flight model which is much more forgiving.

 

EDIT 2: OK. I'm at work and can't check but the difference in stick position might have more to do with how I have DCS set up than anything on your end. But consider my first edit.

Edited August 18, 2016 by Ironhand

[Tomahawk674]

Hello, I don't know if you have a Force Feedback stick, but in case you don't let me describe something: With my FF stick, trimming "nose down" actually moves the "spring force" forward so that the stick's center is much forward vs a non-FF stick.

 

If I didn't trim up the Su-27 would be trying to climb at 45 degree climb. The manual says there can't be more than 20% stick input to engage the autopilot. Is this causing an issue?

 

However, the manual says I can have more than 20% stick and engage the flying level and straight mode, ALT+3. That mode isn't working either. What I can do is try unplugging my joystick and see if AP works without it.

[Ironhand]

Hello, I don't know if you have a Force Feedback stick, but in case you don't let me describe something: With my FF stick, trimming "nose down" actually moves the "spring force" forward so that the stick's center is much forward vs a non-FF stick.

 

If I didn't trim up the Su-27 would be trying to climb at 45 degree climb. The manual says there can't be more than 20% stick input to engage the autopilot. Is this causing an issue?

 

However, the manual says I can have more than 20% stick and engage the flying level and straight mode, ALT+3. That mode isn't working either. What I can do is try unplugging my joystick and see if AP works without it.

Didn't realize you have a FF stick. That probably explains what I was seeing. And also might have something to do with the problem. Try unplugging the stick and see if the situation changes.

[DarkFire]

Hello, I have more tracks for your review. I have 5% dead zone and 25% curvature on both axis.

 

First is the Su-27. I take off and accelerate, retrack flaps and gear, trim nose down, press A and.... nothing.

 

I then tried the same in the Su-33 and all works normal.

 

OK, I watched the AP not working track twice then tried taking over control. Something is deeply wrong there: as soon as I took control I experienced massive amounts of left roll. I think it's quite possible that the AP wouldn't engage because the existing trim settings were outside of permitted maximum. I also had the ACS reset light illuminate after I trimmed out which means that the system went outside of 80% maximum deflection of the control surfaces.

 

Try disabling the force feedback on your stick: FF is known to cause all sorts of issues with controlling DCS aircraft.

[Ironhand]

...as soon as I took control I experienced massive amounts of left roll. I think it's quite possible that the AP wouldn't engage because the existing trim settings were outside of permitted maximum. I also had the ACS reset light illuminate...

Same thing happened to me unless I took control before he trimmed. The stick still moved but only a little.

[DarkFire]

Same thing happened to me unless I took control before he trimmed. The stick still moved but only a little.

 

Yep, I think this is another force feedback problem. I'd definitely recommend disabling it for pretty much everything in DCS.

[Tomahawk674]

Bingo, unplugged the joystick and autopilot works.

 

Now moving forward, my Microsoft Sidewinder 2 stick is not defective, I've used it with other sims just fine. I don't want to go out and get a different stick just for DCS. Are there any steps I can take to make this joystick work with the sim? I already have deadzone and sensitivity curve settings.