Trim/AP operation

[Olmba]

The trim function has a occilation bug that hopefully would be fixed soon. 

 

Edited June 30, 2021 by Olmba
Added link.

[zerO_crash]

Yeah I know about it, but this is a FFB force-trim issue. It’s likely that it needs a separate solution.

[jotaele]

Edited:  wrong thread.

 

Edited July 6, 2021 by jotaele
wrong thread

[KoN]

On 6/18/2021 at 3:38 PM, Nealius said:

The behavior has been very inconsistent for me, often times working fine other times giving an overcorrection. I move the stick where I need it, tap the trim button, then immediately release the stick so it centers. 80% of the time it holds with no fuss. 20% of the time it will overcorrect. For me, the overcorrection is consistently when descending (overcorrection down) or when slowing down to a hover and giving a lot of aft stick, in which case tapping the trim and centering the stick results in pitch oscillations until she settles down. 

Noticed this too coming into land , if I trim were i want too on a landing , the hind over reacts causing crash into ground , Now I don't trim when coming in on final .

I'm more or less using the stick and rudder to guide me down . Slow decent approach with out push trim . 

[fjacobsen]

I really can´t see what's wrong with the AP, also not the Yaw channel.

 

I use a Joystick with a spring, thus I use the "Center trim" option, and don´t have Tailrotor trim (rudder trim) enabled.

 

Pitch and Roll channels work as expected and mostly adds a dampening effect to the inputs.

With a deadzone of 5% for my rudder pedals (Tailrotor pedals), the Yaw channel works as expected too.

 

Before takeoff I turn on the Yaw channel.

I set my trim for pitch and roll, slightly right and appr. 25-30% aft.

I then slowly increase colective and correct any yaw, while still in contact with the ground , with the pedals.

As soon as the helicopter get's off the ground I center my pedals, and the Yaw channel will keep  the heading.

You can see the Yaw channel indicator adjusts the Tailrotor and on the control indicator the pedel input will move without touching the pedals.

 

As long as the pedals are centered, the Yaw channel will try to keep the actual heading.

 

What happens when You start pressing the pedals left or right is that the Yaw channel indicator will center and only provide dampening.

Once the pedals are centered again, the Yaw channel will start keeping the heading where on when centering the pedals.

 

The problems some people have with the Yaw channel might be caused by not having a deadzone for the pedals, thus the Yaw channel will not sense this an act up.

 

It really seems that the developers has simulated the pedal switch, most probably found on the real Mi-8, by sensing when the pedals ar pressed off center.

 

Note that the Yaw channel is reset when the Trim reset button is pressed.

Also remember that Pitch and Roll can be trimmed with the Trim hat, hwich in most cases is easier and more precise than using the Trim button.

 

Also remember to do a Roll trim with thw Trim hat after firing weapons, cause this can lead to assymetric weight.

 

For landing I slowly bring the trim to the same position as for takeoff (slightly right and 25-30% aft), this way landing becomes very easy and precise.

I also keep the Yaw channel on for landing, but mostly it will only dampen the input, due to constant adjustment of heading with the pedals.

 

Edited July 12, 2021 by fjacobsen

[ZeroReady]

How does a Hip pilot remove their feet from the pedals to actuate switches? Aren't they strapped into them? Serious question. 

[Lurker]

2 hours ago, ZeroReady said:

How does a Hip pilot remove their feet from the pedals to actuate switches? Aren't they strapped into them? Serious question. 

 

Which switches? The microswitches in the pedals are activated by moving the pedals. 

[ZeroReady]

On 6/24/2021 at 5:33 AM, VitMax said:

In the real helicopter there are special disconnectors on the pedals. When pilot puts his feet on the pedals, yaw channel temporarily disconnects, so it's possible to do a coordinated turn without fighting the AP. After the turn pilot can remove feet from pedals, which will cause AP to reengage and keep new heading. The same system is found on the Mi-8.

 

This makes it sound like the pilot takes their feet off the pedals.

[zerO_crash]

6 hours ago, Lurker said:

 

Which switches? The microswitches in the pedals are activated by moving the pedals. 

 

IRL: The microswitches are pressed in when the pilot rests his feet on the rudder pedals.

In DCS (for reasons of microswitches lacking on most pedals): The function of the microswitch is disabled when the pilot moves the pedals. Otherwise the heading-AP will work.

[ZeroReady]

3 hours ago, zerO_crash said:

 

IRL: The microswitches are pressed in when the pilot rests his feet on the rudder pedals.

In DCS (for reasons of microswitches lacking on most pedals): The function of the microswitch is disabled when the pilot moves the pedals. Otherwise the heading-AP will work.

This is my question. IRL the pilots feet are strapped to the pedals. It doesn't seem like it would be easy to remove one's feet from them in flight, then get strapped back in when it's time for pedal work. So I'm just curious how the switches are actuated. 

[zerO_crash]

1 hour ago, ZeroReady said:

This is my question. IRL the pilots feet are strapped to the pedals. It doesn't seem like it would be easy to remove one's feet from them in flight, then get strapped back in when it's time for pedal work. So I'm just curious how the switches are actuated. 

 

Pilots don´t strap their feet, the pedals do have straps on them, but they are typically strapped to a position that doesn´t lock the foot on the pedal. It´s one of those designs that makes "it" possible, but is practically never used. Thus, the pilot puts his feet on the rudder pedals thereby activating the microswitches which put the heading-hold AP on standby (the AP heading light remains lit on the crew chief´s central panel). If the pilot wants to engage the heading-hold AP, he takes his feet off the pedals, depressing the microswitches, and the AP holds the heading nice and steady.

 

Keep in mind, this is exactly how the system works with Mi-8 and Mi-24, however not Ka50. On Ka50, there are no microswitches on the rudder pedals. There, it´s the trimmer button the pauses and changes the heading-hold AP. This is a good-to-know.

Edited August 4, 2021 by zerO_crash

[ZeroReady]

OK got it thanks for the explanation!

[Scofflaw]

Does anyone know if the "fix" was included in this patch?  I don't see it in the patch notes.

[sylkhan]

On 8/12/2021 at 1:53 AM, Scofflaw said:

Does anyone know if the "fix" was included in this patch?  I don't see it in the patch notes.

Not fixed (only partially)

[PHMAC]

I know the developers are aware of this issue but I really hope this trim bug is fixed soon with some priority. Trim is a basic function in this helicopter that needs to work properly. I have seen it mentioned several times in different threads.

This problem is making precise maneuvering very frustrating. The sudden nose down respons after trimming has caused me to crash already several times while trying to hover or taxi at low altitude.

I’m confident the bug will be addressed but I hope that it will have some priority because it’s taking away from the fun of flying.

[PHMAC]

Anybody notice an improvement since yesterdays update?

Personally I noticed a change in trim behaviour. The nose down pitch change that occured after pushing the trim button seems to be gone or decreased.  But now I noticed a small bank to the right instead.

Overall it feels like a small improvement but trim operation in the Hind is still not as precise as in the Mi-8.

[cow_art]

Yes I noticed something very similar. The last update definitely made it much better, but it's not entirely gone. Sometimes the trimmer still makes the Mi-24 do wonky things I didn't expect. But now we are at a point where I as a player who has never flown a real Mi-24 can't decide if that's still a bug or just how the thing behaves in real life...

[PHMAC]

Well, according to user sLYFA, in another thread related to this issue, the way the AP and trim interact in the Hind is different than in the Mi-8:

22 hours ago, sLYFa said:

Thats because there is a fundamental difference in how the AP behaves in this two helicopters. In the Mi-8, the AP servos are unaffected by trim while in the Mi-24 they are reset to zero whenever the trim button is pushed. So imagine you are hovering and just found the sweet spot for the cyclic. Before you trim, your total input is your stick position+whatever the AP puts in (which can be up to 20% IIRC). When you press the trim button, the AP input is "taken away" and your total input is not what it was before trimming, even without moving the stick. Thats why it is important to trim a lot and thus minimize AP input, especially when transitioning from/to hover.

 

21 hours ago, sLYFa said:

The AP implementation in DCS is true to real life for both helicopters. I'm not sure why Mil decided to implement it that way for the Hind but I suppose its because in the Hind, there is no flight engineer which can adjust the AP servos for you if they hit their authority limits, unline in the Mi-8.

If you turn AP off entirely then yes, the over/undertrimming effect should go away. But you loose AP stabilization which IMO is worse than having to re-trim a lot.

I tried turning of the AP entirely and indeed the trim gets more stable/ predicatable.

I'm still not sure why Mil decided to implement it differently in the Hind and the Mi-8.

 

Nevertheless,...I feel the Hind is better managable now with the updated trim system. Especcially combined with the default trimmer setting in the Special menu.

If it feels true to life?...I can't say

 

Edited October 22, 2021 by PHMAC
added text

[River]

Can anybody tell me if the trim bug is still there? Thank you

[cow_art]

21 hours ago, River said:

Can anybody tell me if the trim bug is still there? Thank you

The situation has been somewhat improved. It is much less noticable now, but there are still situations where pressing the trim button makes the Hind do things I didn't expect (AP still seems to induce some oscillations, just a bit less than before). As an armchair pilot I can't say if that's still a bug or how the real helo works. But I find it pretty annoying and currently try to keep my use of the trim button to a minimum (the 4-way directional trim works fine and does not show this behaviour btw).

Edited January 17, 2022 by cow_art

[River]

thank you, yes I find it too still weird. The Mi 8 flies like a dream, wish the Hinds trim gets an update soon. 

[River]

On 6/25/2021 at 12:44 PM, Rogue Trooper said:

A lot of people seem to Trim when turning, I never do this unless I intend to hold a wide turning pattern around something.

I just roll and pull slightly whilst levelling the nose on the Horizon with the Pedals (Yaw AP neutralises when I take pedal in). The Hind seems to turn and come out of the turn very cleanly for me.

I do the same, trim mostly after a hard maneuver but the AP bug remains. Still no fix, just flew her for an hour. Such a bummer... 

[AeriaGloria]

10 hours ago, River said:

I do the same, trim mostly after a hard maneuver but the AP bug remains. Still no fix, just flew her for an hour. Such a bummer... 

that post you replied was almost a year ago. What trim bug? 
 

The issue that started the thread is not an issue but a realistic feature. Where the AP is set to nuetral when trim is pressed, causing the airframe to jump/jerk if AP is doing a lot at the time trim is pressed. Solved by trimming twice or trimming with smaller changes In Attitude. Also fixed by holding the trimmer button for a while and re adjusting cyclic 

The issue of pitch oscillations also raised in this thread has been worked on and is better then it used to be 

The Hip probably flies better for you becuase it’s trim doesn’t interact with AP. The Hind upgraded the Mi-8 AP becuase the Mi-8 AP requires a flight engineer to constantly turn wheels to keep the AP from running out of authority, or needs the pilot/engineer to turn AP off and on when they change attitude/flight mode. 
 

In the Hind, like Ka-50, trim re centers the AP so instead of messing with control spindle dial wheels and pressing AP button lights constantly, you can make sure the AP has max authority by just pressing trim, and therefor also using the trim button to tell the AP what attitude you want it to hold (like Kamov)

Edited October 26, 2022 by AeriaGloria

[River]

I know what you mean by now, that doesn't change the fact that the Hind kicks uncontrolable at certain situations. I don't buy that we have to trim in small increments only, neither do I believe we have to hold the trim button pressed during a maneuver. 

If you hold trim pressed you get the wobble at the beginning (AP disconnects) and not on the exit when you release.

Tell a RL Mi 24 pilot he only can trim in small increments and / or keep pressing the trim button till he has done his maneuver. He will have a good laugh.

And no Hind kicks up or down after trimming IRL, it's dangerous and not correct. 

The AP in DCS should reset to the current attitude after trimming but it still uses the attitude before trimming. Reading this is already weird and wrong. 

Edited October 26, 2022 by River

[sylkhan]

2 hours ago, River said:

I know what you mean by now, that doesn't change the fact that the Hind kicks uncontrolable at certain situations. I don't buy that we have to trim in small increments only, neither do I believe we have to hold the trim button pressed during a maneuver. 

If you hold trim pressed you get the wobble at the beginning (AP disconnects) and not on the exit when you release.

Tell a RL Mi 24 pilot he only can trim in small increments and / or keep pressing the trim button till he has done his maneuver. He will have a good laugh.

And no Hind kicks up or down after trimming IRL, it's dangerous and not correct. 

The AP in DCS should reset to the current attitude after trimming but it still uses the attitude before trimming. Reading this is already weird and wrong. 

 

+1

Great description of the weird/inaccurate behaviour of the AP/TRIM