Think I might finally understand Trim problem!

[Suchacz]

Trim bump is not an issue.

 

The issue is the autopilot over-correcting during trim, illustrated in the following 8-second clip:

 

...

 

See how the 'trim bump' is barely noticeable even on the input graph.

Meanwhile the autopilot exaggerates the trim by a full ten degrees.

 

Yeah, this exactly happen, when you trim after the big change of collective input. And it is the right behaviour. Because autopilot is fighting with your input with its 20% authority. But when you press trimmer button, in this moment AP input is off and helo acts like this. When you are doing some "wild" maneuvering, such as turning, going into dive, pulling nose up to stop etc, you should be using a "push & hold" trimming method. "Click - click" method is suitable only for small corrections of attitude.

 

Watch this video and listen for the Trim clicks...

 

 

I hope, you will understand, what I want to say with my poor English... :smilewink:

[PeterP]

Yeah, this exactly happen, when you trim after the big change of collective input.

... and don't use the collective brake while alt-hold AP is engaged.

 

To make a smooth transition you have to use the collective brake.

collective brake = rotor-pitch-Trim

 

 

>> Is it even possible to maintain speed and/or altitude?

Edited January 8, 2013 by PeterP

[159th_Viper]

"Click - click" method is suitable only for small corrections of attitude.

 

 

As it applies to an non-FFB controller, this statement is incorrect. The click-immediate-release can be used very successfully when you engaged in 'wild' maneuvering as this vid illustrates:

 

/4l_LhCRIRgo

 

Alternatively, do not use trim at all when flying like a hooligan as in the above vid - trim not needed with a non-FFB controller, provided you are trimmed correctly to begin with :)

[MTFDarkEagle]

Alternatively, do not use trim at all when flying like a hooligan as in the above vid - trim not needed with a non-FFB controller, provided you are trimmed correctly to begin with :)

 

Aye. When I lift-off, I always trim for the hover and go from that. Whenever I need to do long distance flying I'm trimming for level flight, but in combat I'm (nearly) always trimmed for the hover.

[Suchacz]

As it applies to an non-FFB controller, this statement is incorrect. The click-immediate-release can be used very successfully when you engaged in 'wild' maneuvering as this vid illustrates:

 

...

 

Alternatively, do not use trim at all when flying like a hooligan as in the above vid - trim not needed with a non-FFB controller, provided you are trimmed correctly to begin with :)

 

If you fly mosltly random airshow-like maneuvers like in the vid, you dont need to trim at all, but I noticed, that in 1:23 you held the trim button when you wanted to precisely enter the level flight. And that's what I ment with my previous post :smilewink:

 

P.S.> I use a G940 FF stick

[doveman]

Thanks B25Mitch and Suchacz, finally someone understands the point Brainless and myself were making, that this is caused by the AP being disengaged when clicking Trim and not because of having the "wrong" joystick :music_whistling:

[mmaruda]

Click trimming actually works as it is supposed to, without bumps and other unintended behaviour, but you need to use small inputs and trim every time. I had this problem too, but I changed my curves to about 30% and was able to fly without issues. Try manoeuvring and trimming without exceeding a 5 degree angle each time you move the stick, you will see the difference.

[doveman]

Click trimming actually works as it is supposed to, without bumps and other unintended behaviour, but you need to use small inputs and trim every time. I had this problem too, but I changed my curves to about 30% and was able to fly without issues. Try manoeuvring and trimming without exceeding a 5 degree angle each time you move the stick, you will see the difference.

 

I normally have my curves set to 20-30% but someone suggested that the problem might be caused by having non-default curves, so I tried resetting them but it didn't help.

 

I've also tried making very small adjustments and trimming but that didn't seem to help either. I'll try again with both sets of curves though. In theory it makes sense as then the AP won't be trying to pull so much in the opposite direction and so there won't be such a bump when it disengages when pressing Trim.

[TurboHog]

Watch the promo video for my KA-50 JTAC mod. Follow link in sig.

 

Watch and Listen how I trim. No FFB and no special settings such as center trimmer mode. I'm using a Thrustmaster T16000 and I have used a Logitech 3D Pro in the past. Never had problems with either of them. (But the T16000 feels a million times better though :))

 

There shouldn't be a reason to complain. It may sound a bit harsh and arrogant, but I think it's a matter of your flying skills and not the sim.

 

In the video there are no large changes in stick position. However, there is also no bumping for me when I take off and set to virtual stick from hover to FFF position after accelerating with the trimmer held down.

[doveman]

I've made two tracks showing the problem, one with Central Trimmer mode on and the other with it off. I trim with FD off and on to show how it's almost impossible to get the helo to trim where I point it with FD off, due to the stick jumping and the resultant over bank/pitch, even if I align it straight and hold it steady for a while before clicking Trim, whilst with FD on there's little to no bump and it Trims to where I'm pointing it, more or less. I think I did a long bank using the hold Trim technique as well, where it settles nicely where I'm pointing once I straighten up and release.

 

I made a video of the test with Central Trimmer mode on (although I forgot to start it straightaway, so missed the take-off and hovering where the problem was perhaps the most extreme) but I'll have to edit it before uploading as it's quite long and boring and can't be sped up to skip as easily as the Track can. The video I made with Central Trimmer mode off didn't work properly so I'll have to replay the Track and video that.

 

I don't think I noticed the Trim behaving much differently in either mode, other than that the controls are locked out until re-centering of course.

 

I've set HelicopterTrimmerTauInverse = 4.5 in Mods\aircrafts\Ka-50\FM\FMOptions.lua which supposedly should give me a bit longer to center the stick with Central Trimmer mode disabled but I'm not taking my time to do so anyway and pretty much releasing the stick as soon as I click Trim.

 

So if anyone could take the time to watch the tracks and see if they think what's happening is normal, I'd appreciate it. I can't imagine it is, as it would seem any pilot trying to use a Trim that works like this whilst landing on a ship would just get slammed sideways into the deck!

 

If no-one can see a problem in the Track, I'll upload the video so you can see if what happens on my system isn't reflected in the Track when played on your system as I understand they don't always play back exactly the same on different systems.

Trimming Problem (Central Trimmer Mode on).trk

Trimming Problem (Central Trimmer Mode off).trk

[cltmmm]

There was an old profile I used to use with my Cougar that Viper made that would somehow virtually trim the joystick external to BS2 and make it think the joystick was "stuck" in place like a FFB or real cyclic. I never had the trim bounce or the wrestling with the trim like I do now. You would lose the nice hover indicator in Auto-Hover mode, though. Viper changed the profile to use the standard trimming method and I thought I should get with the times. Now I want to go back and can't find the old profile.

[Daniel M]

Trim bump is not an issue.

 

The issue is the autopilot over-correcting during trim, illustrated in the following 8-second clip:

 

 

See how the 'trim bump' is barely noticeable even on the input graph.

Meanwhile the autopilot exaggerates the trim by a full ten degrees.

 

center position on or off

[LordLobs]

Watch the promo video for my KA-50 JTAC mod. Follow link in sig.

 

It sounds like you hold down the trim button while doing some turns or when you wanna enter level flight. If that's true, that's pretty much how I fly... I don't think it's the correct way, but works like a charm for non-FFB users and it is really smooth. No bumpy trimming:D!

[Pizzicato]

It sounds like you hold down the trim button while doing some turns or when you wanna enter level flight. If that's true, that's pretty much how I fly... I don't think it's the correct way, but works like a charm for non-FFB users and it is really smooth. No bumpy trimming:D!

 

I'm the same. I hold down the trim button for the entirety of any maneuver, only releasing it when the helicopter is in the desired attitude. No bumps at all.

[TurboHog]

It sounds like you hold down the trim button while doing some turns or when you wanna enter level flight. If that's true, that's pretty much how I fly... I don't think it's the correct way, but works like a charm for non-FFB users and it is really smooth. No bumpy trimming:D!

 

That is realistic...

[Ich666]

Last I heard russian pilots were trained to click it...

[LupinYonder]

Sorry for copying this from another thread but I can't be assed to try and re-word it and I want to get your opinions :

 

I find the central method the best way ( for me ) to avoid trimmer bumps. One behavior I have noticed that control inputs made under a trim that is far from the centre of the red control indicator box are much more sensitive. Also the input seem to snap out of trimmed flight more violently. I believe this is due to the input axis curves being applied using the in game input values ( the red box )to judge centre rather than the actual joystick position.

 

This means that as I speed up and need to apply more trim to keep strait and level flight, my control inputs seem to be interpreted using the sensitivity values further towards the edge of the axis tune settings.

 

I have had this suspicion for a long time, does this seem correct to anyone else or is the increased input sensitivity due to aerodynamic effects?

 

This could also be an example of this instead

 

Yeah, this exactly happen, when you trim after the big change of collective input. And it is the right behaviour. Because autopilot is fighting with your input with its 20% authority. But when you press trimmer button, in this moment AP input is off and helo acts like this. When you are doing some "wild" maneuvering, such as turning, going into dive, pulling nose up to stop etc, you should be using a "push & hold" trimming method. "Click - click" method is suitable only for small corrections of attitude.

:

[ronht]

It's a shame there simply aren't any good force feedback joysticks out on the market on the level of the Thrustmaster Cougar/Warthog, especially considering the level of detail Thrustmaster went to in their design of the Warthog, around the DCS stand-alone release.

 

I have a TM Warthog and a Logitech G940 force feedback joystick. When flying the KA50, I use the G940 joystick, with my Warthog throttle and my Simped rudder pedals. The difference in flying the KA-50 with a force-feedback joystick versus a TM Warthog or Cougar joystick is night and day. I's simply a different game all-together and in my opinion, one of the most enjoyable aspects of DCS flying that there is.

 

Since there has been a bug with force-feed back in the last couple of DCS World releases, I've been using a work-around to get the force-feedback to work in the sim which you can find in the Input/Output section of the forums. But even with that inconvenience, you will never find a better more precise and immersive way to fly the KA-50 than with a force-feedback joystick that physically holds it's position after the trim button is released, where ever you release it.

[doveman]

Sorry for copying this from another thread but I can't be assed to try and re-word it and I want to get your opinions :

 

I find the central method the best way ( for me ) to avoid trimmer bumps. One behavior I have noticed that control inputs made under a trim that is far from the centre of the red control indicator box are much more sensitive. Also the input seem to snap out of trimmed flight more violently. I believe this is due to the input axis curves being applied using the in game input values ( the red box )to judge centre rather than the actual joystick position.

 

This means that as I speed up and need to apply more trim to keep strait and level flight, my control inputs seem to be interpreted using the sensitivity values further towards the edge of the axis tune settings.

 

I have had this suspicion for a long time, does this seem correct to anyone else or is the increased input sensitivity due to aerodynamic effects?

 

This could also be an example of this instead

 

Hi Lupin

 

I'd invite you to take a look at my tracks and see if my movements fit into the category of "wild" maneuvering as described by Suchacz. I don't think much of it did, such as shortly after take-off when trying to achieve a hover (I think with the track you can ffwd over the boring startup before takeoff) but still the shark oversteers.

 

If that's too much trouble I'll try and work out how to edit the video I recorded and upload that :)

[doveman]

It's a shame there simply aren't any good force feedback joysticks out on the market on the level of the Thrustmaster Cougar/Warthog, especially considering the level of detail Thrustmaster went to in their design of the Warthog, around the DCS stand-alone release.

 

I have a TM Warthog and a Logitech G940 force feedback joystick. When flying the KA50, I use the G940 joystick, with my Warthog throttle and my Simped rudder pedals. The difference in flying the KA-50 with a force-feedback joystick versus a TM Warthog or Cougar joystick is night and day. I's simply a different game all-together and in my opinion, one of the most enjoyable aspects of DCS flying that there is.

 

Since there has been a bug with force-feed back in the last couple of DCS World releases, I've been using a work-around to get the force-feedback to work in the sim which you can find in the Input/Output section of the forums. But even with that inconvenience, you will never find a better more precise and immersive way to fly the KA-50 than with a force-feedback joystick that physically holds it's position after the trim button is released, where ever you release it.

 

Yes I'm sure FFB sticks are great but that's besides the point as unless using one somehow makes the shark behave differently (which I doubt but it's possible there's some weird code that changes how it acts depending on the stick being used) then you'll have the same problem with a FFB stick, with the stick jerking on click-release Trim to mirror the in-cockpit stick and the FFB holding it in that oversteer position.

[Ich666]

While I was actually sceptical about any trim bumps, today I decided to give it a try myself, so I left my FFB stick on the shelf and just used my keyboard (and later my X-52) for some helicopter action. To ensure theres no manipulating input I set the Trim method to center. My track is attached to this post.

 

So here are the observations of my keyboard flight: At first I didnt notice anything wrong, any weird autopilot behaviour or the "trim bump". But near the end of my flight I transitioned from a situation where I had the cyclic pulled back into one where the cyclic was pushed forward. After I established a level flight I pressed T to trim to the new attitude. Immediatly after the helicopter pitched down to -10 degrees without my input changing (as I saw on the Input Indicator Box). So I waited a second for the helicopter to stabilize and pressed it again. Similar behaviour, I was now at -20. I repeated this some more, all tries with the same result. When only doing slight adjustments I found the Trimmer to be reacting just perfect, it held my position where I wanted it to be, in turns as in pitch up and downs.

 

So I decided to plug in my X-52 (which is what I flew my track with, since the previous observation took place near the end of the flight), to try if this was also true for joysticks, and, what I previously had not experienced, in changes in roll. The Result: Both YES. It is not obvious at first, everything is normal if you trim after small corrections. However if you are doing, for example, a left turn (45°), trim, and, after the flight attitude has stabilized, turn right (45°), again trim, you see the exact same "spring" effect.

 

My conclusion: There seems to be a spring effect implemented in the simulation, effectively simulating the change of force on the pilots hand. For example, if the pilot goes from full cyclic back to half forward, the pilot would have to act against a significant counterforce, that suddenly released, would cause his hand to "overshoot", inputting mor e input than at first commanded. This is, while realistic for Non-FFB controllers, effectively a "double simulation" of the user's input on FFB controllers. Moreover the effect is not easily explainable for the Non-FFB joystick pilots, it just makes it harder to fly the aircraft. Thus it should be removed (unless someone here can explain, why this is all correct).

 

tl;dr: Theres some spring effect simulated on the virtual cyclic that should not be there.

 

 

Trimming.trk

[doveman]

Thanks for testing Ich666, it's good to have some observations from someone with both types of joystick. I'll take a look at your track.

[doveman]

Ich666, I do see the over-pitching caused when clicking Trim in your track. It was also useful to watch your rapid trim clicking in places, to see exactly what is meant by "rapid".

 

I just noticed this, which might be complete nonsense of course but it's in the BS User FAQ thread so I presume someone decided it wasn't. http://forums.eagle.ru/showpost.php?p=572028&postcount=34

 

"You may trim in either discreet presses/releases of the button or by holding the button down while you maneuver the helicopter into the desired position. Once the helicopter is stable, you can release the trim button to command the FCS to stabilize the current flight parameters. In reality, the second method is not advised or typically used by Ka-50 pilots, because holding down the trimmer button while maneuvering the helicopter can easily lead to oversteering."

 

So that's saying that hold-release trim is not typically used in reality, as it can lead to oversteering, yet the click-release method in BS2 is causing oversteering also, which seems to leave us no method to use that doesn't (in fact it's much less of a problem, in my experience, with the hold-release trim method in BS2, the only problem with that is it makes the shark more unstable/twitchy due to the AP/stabilisation being disengaged)

 

It also says:

 

"In reality, the trim button is used very often and you would be advised to do the same. Trim the helicopter whenever your flight parameters change, but be sure to only trim when the helicopter flight path is stable. Trimming in increments may help you avoid undesired control input when trimming."

 

I've seen similar advice elsewhere but it seems rather contradictory as one can't trim very often, whenever the flight parameters change and also only trim when the flight path is stable. I don't think the sections of Ich666's track where he's rapidly clicking trim are with the shark in a stable flight path, the whole point is he's making a large adjustment and is rapidly clicking trim to avoid banking/pitching a large amount and then clicking trim only once.

[ZaltysZ]

If you have FFB stick and are constantly clicking trim while moving stick, you should get slight over-steer on the first click, but not on successive clicks (granted clicking is frequent enough). This is because it seems that AP manages to remove its influence almost instantly, but lags in applying it. So, fast clicking is like always having stick in trimmed position and AP stabilization off. In other words, you don't noticeably fight AP if you are clicking with enough frequency.

 

This is almost impossible with non FFB stick, because such stick needs too much delay between clicks caused by requirement to recenter it. That delay leaves enough room for AP to catch with you and cause over steer on successive click. This is with center based method. If you use delay based method, it is possible to use such technique: you want to push stick 50%, however you just push it very slightly (lets say 5%) and keep it there, then you just click trim button n number of times, until it reaches that 50%.

 

Click-click is recommended by some manuals from MIL. Reasoning is simple: it is easier for the hand (click-click is like climbing a staircase, and move-move-click is like climbing inclined plane - ramp) and it is safer than click-hold-move because trim forces are not removed for prolonged time, and that means less chance for accidents caused by vibration or wind gusts.

[doveman]

Thanks for the suggestions ZaltysZ, I'll try the move the stick 5% then click n times to reach 50% idea.

 

I'm not clear what you mean by Click-click though. Click-hold-move is obvious but Click-Click has no move in the sequence, so it suggests just clicking without trying to move! Not really sure what move-move-click means either, as that implies trying to move twice before clicking, so if you could clarify what you mean that would be great.