Nodding/tilting/jolting when trimming

[Donglr]

HI, 

 

I am currently testing the Hind (two weeks (TM)). I would consider myself an experienced DCS helicopter pilot, having all other helos and flying them frequently. Flight model wise I would consider the Mi8 my love and expected the Hind to be similar.  However I feels the trim function to not be what I expected.

I have a regular Warthog stick with spring and extension and have set the trimmer mode to "central position trimmer" in the special options as I do with every helo. I fly, put the Hind in the flight position I want, press&release the trim button and then recenter the stick, the aircraft then has a tendency to add tilt/nod in the direction I was holding the stick. This is not how I know it from other helicopters. If I compare this to the Ka50 in flight director mode for example, if I briefly press&release the trim button the helo maintains its attitude without jolting in any direction, even if the new stick postion is far away from the new one.

If I try to trim the Hind in "maneuver mode" as I call it, i.e. press and hold trim, position the Hind how I want it and once stable release trim button, I do not experience this jolt. In general it feels like the longer I hold down the trim button the less wobbly/jolty is the Hind when I release the trim button. 

I have pitch, roll and yaw channels active. Am I doing something wrong? How do I get rid of the tilting/nodding tendency when pressing the trim button only briefly?

 

[admiki]

2 hours ago, Donglr said:

I fly, put the Hind in the flight position I want, press&release the trim button and then recenter the stick, the aircraft then has a tendency to add tilt/nod in the direction I was holding the stick.

This is your problem.

Unlike Mi-8, Hind's trim will reset autopilot. In Mi-8, flight engineer is re-setting autopilot in coordination with pilot flying. In Hind, reset is instant.

Picture this: you are flying nose level, not holding trim. You push nose down. Autopilot will try to bring your nose back up to its trimmed position. Your new attitude is a result of your stick input and autopilot input. When you press trim, that autopilot input is gone and only input is from your stick pushing nose down. That's your "nodding".

Best way to fly the Hind is to hold down trim release until you are happy with your new attitude. You will lose stabilisation, but Hind is quite stable with any forward speed. Even in hover, you will quickly learn to anticipate inertia.

Other option is to trim often. Autopilot input is directly proportional to departure from its trimmed position. More you trim, less autopilot input you will lose- less nodding.

Unfortunately, there is no real good way to make springed stick work with this kind of autopilot.

I don't fly Ka-50 and I'm not quite sure how its trim works, but Hind was first Soviet helicopter that got rid of flight engineer setting autopilot using analog system.

My guess is what you are experiencing in Ka-50 is a result of experience from the Hind.

Edited January 2, 2024 by admiki

[Ornithopter]

24 minutes ago, admiki said:

I don't fly Ka-50 and I'm not quite sure how its trim works, but Hind was first Soviet helicopter that got rid of flight engineer setting autopilot using analog system.

My guess is what you are experiencing in Ka-50 is a result of experience from the Hind.

 

When its flown like it is supposed to be flown, the Ka-50 trim works just like the Hind:  The trim button will reset the autopilot, and you need to hold the trim button down while establishing a new attitude.  The Shark will jolt and jump just like the Hind, if the pilot doesn't hold in the trim.  However, he is referring to "Flight Director Mode", which is more just a three axis damping system to the pilot inputs, not full on autopilot.  When in this particular mode, the trim button will act exactly like it does on a Huey, or the Mi-8, so you can just click it once, and it will lock the stick.  In a game, we can fly it however we want, but I've read that in real life, that isn't a standard operating mode.  As for me, I've just gotten used to holding the trim button down on both the Shark and the Hind, but it will mess me up a little bit after flying the Mi-8 or Huey, most especially when going into a hover.

Edited January 2, 2024 by Ornithopter

[AeriaGloria]

I don’t like holding trim button down becuase I use FFB, I prefer to just trim 2-3x in quick succession to get rid of “nodding.”

[admiki]

12 hours ago, AeriaGloria said:

I don’t like holding trim button down becuase I use FFB, I prefer to just trim 2-3x in quick succession to get rid of “nodding.”

Why not? If anything, FFB should push you towards trim hold?

[average_pilot]

35 minutes ago, admiki said:

Why not? If anything, FFB should push you towards trim hold?

Talking for myself, but may be the same for other FFB users. When you hold down the trim button there are no FFB effects at all (yes, I know the centering force must go away), hence the stick has no resistance at all. Fine control becomes quite difficult in this situation.

That's why a very long time ago I suggested adding friction and/or damping effects to FFB, which my MSFFB2 at the time could reproduced quite convincingly when not abusing the intensity of the effects. In fact the added effects provided a really nice feeling to the stick, like if it were connected to a much more complex mechanism, which without really knowing I can imagine it may be closer to how it feels in a real helicopter. But unfortunately nothing came out of my suggestion.

I switched to the diametral oposite of FFB and I'm using a Force Sensing stick now, so, not much affected anymore.

Edited January 3, 2024 by average_pilot
Inb4

[AeriaGloria]

Yeah with FFB force goes away with trim button, making precision hard. Easier with Ka-50 where autopilot stills dampens with trim held 

[Ornithopter]

When I paid closer attention to how I actually use the Hind trim, I see that I hold in the trim for coarse attitude changes, but in hover, I see I also tend to quick-click, after tiny corrections.  I also don't hesitate to use the "other" trim, on the directional hat, to tune it as necessary.  At some point, its just whatever works to get the precision you need.

 

[admiki]

10 hours ago, AeriaGloria said:

Yeah with FFB force goes away with trim button, making precision hard. Easier with Ka-50 where autopilot stills dampens with trim held 

Can't you set dampening effect to be always on?

IIRC, Rhino FFB let you set mutliple effects to your liking, so trim release will only affect spring force, "hydraulic" feel can always be present.

[average_pilot]

10 hours ago, Ornithopter said:

I also don't hesitate to use the "other" trim, on the directional hat, to tune it as necessary.

It always makes me so happy when I suddenly remember I have that available. 

[AeriaGloria]

19 hours ago, admiki said:

Can't you set dampening effect to be always on?

IIRC, Rhino FFB let you set mutliple effects to your liking, so trim release will only affect spring force, "hydraulic" feel can always be present.

I’m sure with Rhino SW you can. With SimFFB software, setting any effect automatically disables any input from DCS 

I could get it so trim still works the same, but not sure I can program it so that the trim hat works the same as in DCS 

[Sobakopes]

Autopilot on hind produces it's own cyclic input but when you trim you reset it's input to zero momentarily. That's why you get uncomfortable. Keep your eye on autopilot input in the channels and when you see that it's near the maximum expect the nodding when you trim because it's going to be instantly reset to zero for a moment 

You can compensate for it by trimming the second time quickly in the opposite direction of nodding

It usually happens during transition from flight to hover

Edited February 26, 2024 by Sobakopes

[zerO_crash]

On 1/2/2024 at 7:16 PM, Donglr said:

HI, 

 

I am currently testing the Hind (two weeks (TM)). I would consider myself an experienced DCS helicopter pilot, having all other helos and flying them frequently. Flight model wise I would consider the Mi8 my love and expected the Hind to be similar.  However I feels the trim function to not be what I expected.

I have a regular Warthog stick with spring and extension and have set the trimmer mode to "central position trimmer" in the special options as I do with every helo. I fly, put the Hind in the flight position I want, press&release the trim button and then recenter the stick, the aircraft then has a tendency to add tilt/nod in the direction I was holding the stick. This is not how I know it from other helicopters. If I compare this to the Ka50 in flight director mode for example, if I briefly press&release the trim button the helo maintains its attitude without jolting in any direction, even if the new stick postion is far away from the new one.

If I try to trim the Hind in "maneuver mode" as I call it, i.e. press and hold trim, position the Hind how I want it and once stable release trim button, I do not experience this jolt. In general it feels like the longer I hold down the trim button the less wobbly/jolty is the Hind when I release the trim button. 

I have pitch, roll and yaw channels active. Am I doing something wrong? How do I get rid of the tilting/nodding tendency when pressing the trim button only briefly?

 

Much correct has already been posted here. The thing about DCS is; its modules are so realistic, that the bottleneck is not software, but rather the hardware that you use. In order for many of the flight-systems (trimming, AP, etc...) to make natural sense, you'd have to have a FFB setup with stick and pedals (I am using Brunner's stick base and pedals). With proper FFB, you would have to learn, and use, the trimmer correctly - either with the click-method, or click-and-hold. That way, you would naturally remove any unwanted jolting/movement/imprecision. Because your hardware isn't sufficient to replicate the actual behaviour of these complex machines, you are bound to making up for it with creativity. 
 

Now, while there are differences between the trim systems of Mi-8, Mi-24 and Ka-50 (pretty major differences as well), the trimmers are actually used in the same manner and, with the same techniques (even western helicopters trim in this way, with certain nuances depending on the specific airframe). You mention Ka-50. It has the FD-mode purely as an option to disable AP while retaining the dampening functions. If you are to practice hand-craft, you can use this mode, however in all practical applications (especially combat), there is a very good reason for why the Ka-50/52 have the most powerfull AP in the world. If you have taught yourself to fly Ka-50 only with FD-mode on, then you are doing it wrong. There is much misinformation on this matter online, which I imagine could have misguided you. People have a tendency to chose the easy/simple way out (most don't understand trimming & AP with helicopters), which is a mentality that tends to bite later on. Here you are "later", and having issues, because you never learned how to fly the Ka-50 properly, and according to its strengths. Even with your hardware, you should first read about the trimming in these helicopters, then practice flying in accordance with what manuals command as well as what pilots perform IRL.

 

Let me run it down for you: In order to remove the unwanted behaviour (mentioned above), with your hardware and its limitations, you want to click-and-hold trim button. That means - click and hold the trimmer, move the stick to the desired position and release the trimmer (quickly recenter your stick after letting go of the trim button, as the virtual position of the stick will magnify quickly (you have 0.5 seconds to recenter stick without any interference)). Since you know a little Ka-50, start by using the trimmer more actively. You have to trim every time you change the attitude of the helicopter. If you learn to fly like that (realistically and according to SOP), you will notice that the helicopter is a joy to fly, and that it does whatever you command it to, giving you room to focus more on the task at hand. Once you become accustomed to flying this way in the Ka-50, you'll transition to Mi-24 naturally, with your issues eliminated.

Edited February 28, 2024 by zerO_crash