trim when not in FD mode

[flyinfriend]

I don't mean to beat a dead horse but...

 

I have read all of the endless trim threads...

 

I completely understand how trim works, in both center and non-centering modes. What I have noticed is that if while moving forward between 150 and 200 knots (any speed really) and then I pitch up 5 degrees an additional 8-10 degree pitch up occurs. The same happens if I pitch down, an additional 8-10 degrees of down pitch is added. I have the stick/trim indicator showing on the bottom left and I can see that the stick's position does not change, it is just the heli adding the additional pitch up or down in its attitude.

 

If I put the heli in Flight Director mode this additional pitching does not occur. The heli remains in the attitude I trimmed. This additional input of control also occurs in the roll axis.

 

Does anyone know how to get rid of this additional input that is occurring upon trimming? It only happens with FD off. With FD on the additional pitch is not added when trimming.

 

I am using the Warthog HOTAS.

 

Thanks for any ideas.

[Fishbreath]

Hold the trimmer down while changing attitude if you aren't in FD mode.

 

The pitch change doesn't happen in the real helo because the pilots 1) trim almost constantly (there's a video around of a flight over Moscow; you can hear him tapping the trimmer almost constantly) and 2) don't have to recenter their stick when they do. In the sim, the pitch change happens because the Ka-50 autopilot can't distinguish external deviations from the set attitude (wind, change in ground effect, etc.) from control inputs, and we without FFB sticks can't trim as the real guys do.

[Sylvan]

I think what is causing the behaviour you describe is the autopilot attitude hold. (ATTitude, not ALTitude.) You seem to understand the trimmer but not the autopilot. The trimmer button gives input to both systems at the same time.

 

Here's how attitude hold works: With FD off, every time you release the trimmer you are setting your desired attitude, meaning a level of pitch, roll and a heading that you want the autopilot to hold for you. For instance, when you are trimmed for forward flight, you have pitched the nose down and told the attitude hold autopilot to maintain this attitude, and the autopilot will use its 20% authority to try and maintain the nose down. When you pull back and then re-trim, the releasing of the trimmer button supplies the attitude hold mode with new constraints and starts to apply it's authority to attain that attitude. Those extra 8-10° of pitch is probably the autopilot ceasing to try to push the nose down and starting to try and hold the attitude you just told it to hold.

 

The solution, like Fishbreath mentioned above, is changing the way you trim. Either perform constant presses on the trim button through the entire manouver, like most russian pilots do, or press and hold the trimmer button when you manouver, like most western pilots do. I prefer the latter. The pressing and holding of the trimmer button will temporarily disable the attitude hold mode (effectively the same as enabling the FD) while the button is held and re-engage it when you release it.

Edited January 9, 2014 by Sylvan

[Davis0079]

if trimmed in flight and you move the stick forward to a new position and tap the trimmer, it will add 20% more pitch then you hoped for....

 

Now...if trimmed in flight and you hold the trimmer then move the stick forward to a new position, then release the trimmer, it trims perfectly...

 

the trimmer only has 20% authority, so in the first example, when you move the stick forward, you are pushing it 20% further then you would in the second example to get the same pitch.....at this point in the first example you click the trimmer...the trimmer releases 20% authority....the game thinks you are 20% further...then the trimer kicks back in...all in a micro second (the click of the trimmer)...this leads to you seeing this as a "Out of no where rock forward too far".....but its not out of no where...its out of the trimmer system...and it can be up to a 20% difference (if not pushing the stick far one way you are not fighting the full power of the trimmer), short throws equal a small jump....big changes equal a big jump.....change to the "Hold trimmer, maneuver, release trimmer" method for a better gaming experience

 

So like stated above...real Ka-50 pilots dont have this effect when using the "Clicky, clicky" trimmer method....so in the game the "Hold, maneuver, release " method is a better way...

[flyinfriend]

Thanks all for the helpful replies. I understand now. With FD off I have to overcome the 20% 'effort' that the ap/trim system is applying to keep my current attitude. When I click trim the new 'zero' is really whereever the stick is PLUS the 20% I had to overcome. I did notice that the smaller my pitching movement with the stick the less the additional pitching the heli self-applied.

 

I'll try clicking and holding or constantly clicking to see which works best for me. I think click and hold-move-release will seem most natural. When I am really trying to maneuver quickly I am in FD which doesn't fight me with the additional 20%.

 

Thanks so much for the help guys!

[-MadCat-]

[...]

when you move the stick forward, you are pushing it 20% further [...] the trimmer releases 20% authority....the game thinks you are 20% further...then the trimer kicks back in [...] this leads to you seeing this as a "Out of no where rock forward too far".....but its not out of no where...its out of the trimmer system

[...]

If this really is the cause for the "trimming too far" when using just one click to trim, I wonder why ED doesn't fix this?

Should be so easy to do, the game already knows how much authority the AP applies (and therefor how much you "oversteer" to get to a desired cyclic position).

That known information can easily be used for the new center position calculation.

 

(displaced joystick position) - (AP authority currently applied) = (new center position once the trim button is pressed)

 

Tada, we got rid of the trim "oversteer", easy isn't it ?!

 

Please ED have a look into this issue!

 

Greetings

MadCat

[Dr_Arrow]

If this really is the cause for the "trimming too far" when using just one click to trim, I wonder why ED doesn't fix this?

Should be so easy to do, the game already knows how much authority the AP applies (and therefor how much you "oversteer" to get to a desired cyclic position).

That known information can easily be used for the new center position calculation.

 

(displaced joystick position) - (AP authority currently applied) = (new center position once the trim button is pressed)

 

Tada, we got rid of the trim "oversteer", easy isn't it ?!

 

Please ED have a look into this issue!

 

Greetings

MadCat

 

This is not an issue, this is how the real thing works. In the real helo without pressing the trim button the stick is hard to move. Pressing the trim button removes forces acting on the stick and disengages the attitude autopilot allowing you to move the stick freely. After releasing the trim button the stick is kept firm in its current position and new commanded attitude is maintained. If you have an FFB stick and use simffb program, it works exactly the same. So it really is not an issue but a feature.

[-MadCat-]

Sorry to disappoint:

How does the trimmer work and how am I supposed to use it?

 

Now we bring together, you saying the "oversteer is correct", and from an official source that "trimming in discrete presses" is advised to real pilots.

That would mean, the real pilots do have the same oversteer as when we trim in discrete presses.

How come I highly doubt that, until confirmed by an official ? !:music_whistling:

 

I'll give you that we don't know how the real trimmer works (on the software level).

 

I was about to write a rather long thought experiment, but then noticed another little detail in that linked post.

[...] it's important to understand that the FCS is commanded by the trimmer when the button is released, not when it's pressed [...]

Now how I understand that quote, is that the press of the button does nothing else than to take away control forces.

However it does not interfere with the 20% control authority in any way.

Only when it is released, the new center position should be updated to the AP and the control forces are reengaged.

The control authority is never ever disengaged at any point, only updated.

 

That would mean, temporarily disabling the AP authority upon pressing the button is all wrong to even begin with!

Doesn't this make more sense than what we have now ?

Switching from "compensated controls" to "raw stick input" upon pressing (and holding) the trim button ?

 

Think about it.

 

And I would really appreciate an official statement on this!

There are so many misconceptions about the Ka-50 trim system out there, and this may be the cause for many (or even all) of them.

 

Greetings

MadCat

Edited January 30, 2014 by -=MadCat=-

[doveman]

If this really is the cause for the "trimming too far" when using just one click to trim, I wonder why ED doesn't fix this?

Should be so easy to do, the game already knows how much authority the AP applies (and therefor how much you "oversteer" to get to a desired cyclic position).

That known information can easily be used for the new center position calculation.

 

(displaced joystick position) - (AP authority currently applied) = (new center position once the trim button is pressed)

 

Tada, we got rid of the trim "oversteer", easy isn't it ?!

 

Please ED have a look into this issue!

 

Greetings

MadCat

 

Yes, there's been plenty of threads about it but no official response from ED.

 

http://forums.eagle.ru/showthread.php?t=99981&highlight=trim

 

http://forums.eagle.ru/showthread.php?t=96398&highlight=trim

 

http://forums.eagle.ru/showthread.php?t=94833&highlight=trim&page=3

 

http://forums.eagle.ru/showthread.php?t=80992&highlight=trim&page=13

 

The problem is most of us don't have FFB sticks, as there aren't many decent ones available but ED hasn't implemented a decent system of accomodating non-FFB users.

 

I made a suggestion for an alternative trim method about a year ago, which would avoid non-FFB users having to do this annoying re-centre stick dance constantly when using trim, here:

http://forums.eagle.ru/showpost.php?p=1661763&postcount=76

 

and more recently re-posted it here:

http://forums.eagle.ru/showpost.php?p=1987204&postcount=302

 

"I still think it would work better if stick movements away from the centre were still registered after clicking Trim (which would emulate the real behaviour, where after the pilot clicks Trim he can still move the stick further and click Trim again (or not), without any timeout or having to re-center the stick) but stick movements towards the centre were ignored until the stick had re-centered, which would allow us to release the stick, as is necessary when using a non-FFB stick as we can't hold it in position all the time, without any unwanted input."

 

I really don't understand all these explanations about the AP's 20% authority causing us to oversteer, so that when we click Trim the stick's too far from where it actually needs to be and the AP then releases it's 20% authority and the helo lurches and Trims to the wrong position.

 

If this is the case, I would think it would affect FFB users and indeed real pilots, as regardless of whether the stick starts in the real centre or a FFB-held position, we move the stick to point the helo where we want and if the AP is trying to counteract this by 20% and this 20% is only released when clicking Trim, causing the helo to lurch and the AP to Trim to this attitude instead of the one we were holding the helo at when we click-release Trim, I can't see why this wouldn't happen to all pilots, real or virtual. The only difference I can imagine is that with FFB and real pilots, they feel the AP release it's authority and the stick lurching and counteract that themselves by pulling it back but it's hard to imagine them being able to do that before releasing Trim as it's meant to be a rapid click-release, not click, correct stick, release.

 

As you said a few posts back, the sim should know about this potential to oversteer, if that is indeed accurate modelling and counteract it automatically for non-FFB users who have no way to do so themselves.

[doveman]

This is not an issue, this is how the real thing works. In the real helo without pressing the trim button the stick is hard to move. Pressing the trim button removes forces acting on the stick and disengages the attitude autopilot allowing you to move the stick freely. After releasing the trim button the stick is kept firm in its current position and new commanded attitude is maintained. If you have an FFB stick and use simffb program, it works exactly the same. So it really is not an issue but a feature.

 

It's an issue for non-FFB stick users for whom the Trim system doesn't work properly.

 

The real stick can't be that hard to move without pressing Trim, if the proper Russian method of flying is "move the stick, click-release Trim, repeat" and not "hold Trim, move the stick, release"

[Fishbreath]

If this is the case, I would think it would affect FFB users and indeed real pilots

 

It does—it's just that real Ka-50 pilots (as you can see in that one Ka-50 HUD over Moscow video) use the trimmer lots, as in multiple times per second. There's no time for enough deviation to cause noticeable oversteering to build up if you're doing it that way.

 

You're right, though. It is a problem, even if it's one which only arises because it's next to impossible to trim that rapidly without a FFB stick.

[Wizard1393]

I would like to add a question on this topic. I do understand the trimming principle, but people vaguely mentions speed.

 

I always fly with FD OFF and pitch, roll, heading channels on AP. When I trim people say I'm telling the autopilot to hold my pitch, roll and heading. But, it seems to me that airspeed also has something to do with it all. Is it so, that it holds those 3 channels, at the current speed held when the trimmer is released?

 

/C

[PFunk1606688187]

I would like to add a question on this topic. I do understand the trimming principle, but people vaguely mentions speed.

 

I always fly with FD OFF and pitch, roll, heading channels on AP. When I trim people say I'm telling the autopilot to hold my pitch, roll and heading. But, it seems to me that airspeed also has something to do with it all. Is it so, that it holds those 3 channels, at the current speed held when the trimmer is released?

 

/C

 

Speed is largely determined by your pitch angle. When you command a fixed pitch you are also commanding a roughly fixed speed, so long as you don't alter too many other variables significantly. Changes in pitch will lead to immediate increasing or decreasing, or sometimes oscillating speeds, however, eventually the aircraft will always settle at a given speed at a given pitch angle (assuming you aren't crashing, experiencing battle damage to controls or stability, non normal situations, excessive input in other channels, etc).

 

In this way you can deliberately set your speed by setting your pitch, which is a pretty basic concept for real pilots, rotary or fixed wing alike.

 

Basically the autopilot follows instructions to control your aircraft attitude, but as a pilot you are responsible and able to conceptualize what that total commanded attitude will result in with respect to speed, vertical velocity, side slip, etc.

Edited February 14, 2014 by P*Funk

[Wizard1393]

trim when not in FD mode

 

Speed is largely determined by your pitch angle. When you command a fixed pitch you are also commanding a roughly fixed speed, so long as you don't alter too many other variables significantly. Changes in pitch will lead to immediate increasing or decreasing, or sometimes oscillating speeds, however, eventually the aircraft will always settle at a given speed at a given pitch angle (assuming you aren't crashing, experiencing battle damage to controls or stability, non normal situations, excessive input in other channels, etc).

 

In this way you can deliberately set your speed by setting your pitch, which is a pretty basic concept for real pilots, rotary or fixed wing alike.

 

 

I'm not sure I want to agree with you here. (I still may be wrong however) Because when changing collective during trimmed flight the AP changes your pitch. This I question! Is it to maintain speed or altitude? Your saying it does not take current velocity into account when trimming. But it seems to me that it does. It "should" not be altering pitch to maintain ALT, as ALT channel is OFF right? So for what other reason than maintaining speed, is it changing my pitch when I alter collective? I think I would rather have the AP not touch my trimmed pitch when I change collective.

 

To be an even more annoying questioning rookie :) I'd also like to add another thing to the table regarding trim. You say, when trimming, I tell the AP to maintain aircraft attitude. Sure, it does. But if I'm using rudder when trimming, it actually seems bugged to me. Some times in windy conditions I need to apply a bit of rudder to fly straight trimmed. But sometimes, especially when turning with rudder at low speeds, I come around to the heading I want, release trim button, and the darn thing keeps turning and turning. Seems like it's sometimes deciding to maintain heading where the nose is pointing when I release the trim button, and some times it decides to maintain current rudder input when released. I find this extremely annoying. Thoughts and reflections on this?

 

:) Chris

Edited February 14, 2014 by chrisofsweden

[PFunk1606688187]

I'm not sure I want to agree with you here. (I still may be wrong however) Because when changing collective during trimmed flight the AP changes your pitch. This I question! Is it to maintain speed or altitude? Your saying it does not take current velocity into account when trimming. But it seems to me that it does. It "should" not be altering pitch to maintain ALT, as ALT channel is OFF right? So for what other reason than maintaining speed, is it changing my pitch when I alter collective? I think I would rather have the AP not touch my trimmed pitch when I change collective.

The AP channels are given a 20% total authority to retain the commanded attitude. This means that on either side of your commanded position they have 10% input authority to maintain position. If you make a strong collective input you can easily force the AP to exceed its 10% input at which point the axis will begin to shift in whichever direction the AP can no longer control it.

 

This functions identically with the Altitude hold channel as well. Using the Collective Brake you assign an alt. If you pull back sharply on the Cyclic you will see the vertical velocity indicator begin to rise because the upward force created by the cyclic input has exceeded the 10% that the Collective channel has to hold its station.

 

Its my understanding that while in any of the autopilot channels, with FD off, if you see them beginning to move, without depressing the trimmer button, its because they've run out of input authority to maintain position.

 

To be an even more annoying questioning rookie :) I'd also like to add another thing to the table regarding trim. You say, when trimming, I tell the AP to maintain aircraft attitude. Sure, it does. But if I'm using rudder when trimming, it actually seems bugged to me. Some times in windy conditions I need to apply a bit of rudder to fly straight trimmed. But sometimes, especially when turning with rudder at low speeds, I come around to the heading I want, release trim button, and the darn thing keeps turning and turning. Seems like it's sometimes deciding to maintain heading where the nose is pointing when I release the trim button, and some times it decides to maintain current rudder input when released. I find this extremely annoying. Thoughts and reflections on this?

 

:) Chris

Can't be sure without seeing a track of you flying, but proper trimming technique is essential to ensuring that the shark flies as you intend. Have you enabled "Center Trim Function" in the Special section or not?

 

Also your trim is only good for a given altitude and speed. As soon as one or both of those changes the required trim to maintain straight and level flight will change slowly. Rudder especially changes as speed changes. There's also the possibility that you simply trimmed an imperfect attitude. I often find myself slipping a bit and need to make only a rudder correction to my trim.

 

The Black Shark is not my forte, but I'm confident in what I've posted so far. Better advice can come form more experienced players.

[ZaltysZ]

I always fly with FD OFF and pitch, roll, heading channels on AP. When I trim people say I'm telling the autopilot to hold my pitch, roll and heading. But, it seems to me that airspeed also has something to do with it all. Is it so, that it holds those 3 channels, at the current speed held when the trimmer is released?

 

Speed is a function of nose pitch angle and rotor pitch (blade angle). This means, if you fix nose pitch and blade angle, aircraft will settle at certain speed, and you will be stuck at that speed unless you change either nose pitch angle (using cyclic) or rotor blade angle (using collective). So, if you tell AP to hold certain nose pitch angle and stay at certain altitude, it may look like it is also holding the speed. However, this is only a side effect, and AP does not care about the speed.

 

If you want AP to keep certain speed, you must tell it not to keep nose pitch angle, but vary it accordingly to speed instead . This is possible in ROUTE mode. If you need to keep flying at precise speed while not on flight plan route, make sure you have no waypoint selected. This way you will be using so called "route without task" mode, and AP will try keeping commanded speed for straight flight.

 

Always remember that AP is intended for fighting small oscillations and deviations only. It needs aircraft to be in roughly correct attitude before it can make it into precisely correct attitude. This means, that it won't hold 50km/h if you release trim button while cyclic is in pretty far forward position and so on ;) It does not have authority to overcome that.