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For those who trim by tapping the trim button


PeaceSells

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Hey,

 

I'm learning the Ka-50 and, man, what a pleasant aircraft to fly... so smooth! I want to get proficient in controlling it in all different modes: autopilot on, fight director on autopilot off.

 

Been reading a lot about the trim lately, as well as watching Youtube videos and experimenting with it. I now understand how the Ka-50 trim works, and the question I have is related to using the trim with autopilot ON and flight director OFF, and is independent of whether you use an FFB joystick, conventional joystick or joystick without springs and FFB (I use conventional stick with springs, btw).

 

Here's the deal: you have autopilot ON and flight director OFF, you move your joystick to a new position, (let's say slightly FWD), stabilize it and tap the trim button. In a time span of a few milliseconds, the following sequence of events happen, as I understand (please tell me if I understand something wrong):

 

1) upon pressing the trim button, autopilot stabilization gets turned off;

 

2) without autopilot, your FWD input gets amplified, even though you're still holding the stick at the same place and even though it's during only a few milliseconds;

 

3) upon releasing the trim button, the new amplified input gets saved and fixed by the flight control system, and autopilot gets re-engaged holding this new amplified input;

 

4) aircraft pitches down noticeably instead of holding the pitch you originally intended when you pressed the trim button.

 

Now I'm able to work around that by moving the stick while I keep the trim button depressed, and releasing the button when the aircraft is pointing where I want. But as I read the forums I see that many people trim by simply tapping the trim button. Doesn't it bump your aircraft slightly out of position when you do that? How exactly do you trim by tapping without getting this effect?

 

Thanks for your input!

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Crick trimming only works smoothly when re-trimming from a relatively small speed difference.

 

You can't be trimmed for a hover -> push stick forward to accelerate to 200 kph, then trim. The helicopters nose will violently pitch down when you depress the trim button as the autopilot was using 20% back stick to try to get you back to previously trimmed speed (hover) but when you depressed the button that 20% back stick force goes away instantly = nose drops.

 

What you want to do is either hold down the trim button while accelerating/decelerating to whatever speed you want then release it or click the trim button every 10-30 kph you gain/loose to reprogram the autopilot to new speed before it starts using more than a few % of it's authority.

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Otter

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Using the original trimmer option (not central) there is a time-based blending of the new input. With practice one can relax the input back to spring-neutral at the same rate to avoid any significant upset. If desired this value (tau, a common time constant Greek letter) can be lua-edited. The effect can be seen by the controls indicator.

 

Stabilization is always on when the channel button-lights are shining. The hold input (the thing that FD disables) is suspended (read: frozen) during trim button hold.

 

The tap method is no problem. You deflect the stick and hold it until the maneuver stabilizes and tap with a practice relax motion.

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PeaceSells, as it happens I too have tried to wrap my head around this issue as late as last night, with the same experience.

Especially when trying to establish a steady turn with AP on the nose drop.

Also if I let go of my cyclic after first trim click, and then press T repeatedly on my keyboard the nose drop slightly every time.

If I use the press'n'hold technique the nose tend to rise at release after established steady attitude.

Flight Director mode work, so does the Huey and Mi-8 trim.

 

I fly with a "without spring and FFB" stick, but have also tried a FFB one (spring removed) with the same fesult (FFB settings all correct and working otherwise).

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Crick trimming only works smoothly when re-trimming from a relatively small speed difference.

 

You can't be trimmed for a hover -> push stick forward to accelerate to 200 kph, then trim. The helicopters nose will violently pitch down when you depress the trim button as the autopilot was using 20% back stick to try to get you back to previously trimmed speed (hover) but when you depressed the button that 20% back stick force goes away instantly = nose drops.

 

What you want to do is either hold down the trim button while accelerating/decelerating to whatever speed you want then release it or click the trim button every 10-30 kph you gain/loose to reprogram the autopilot to new speed before it starts using more than a few % of it's authority.

 

hmm, it seems I have to practice more with this clicking method.

 

Using the original trimmer option (not central) there is a time-based blending of the new input. With practice one can relax the input back to spring-neutral at the same rate to avoid any significant upset. If desired this value (tau, a common time constant Greek letter) can be lua-edited. The effect can be seen by the controls indicator.

 

I have no problem with relaxing the input to neutral in time when using the original (Default) trimmer option, I used this method a lot in the Huey before. Now I discovered the Center trimmer option and it eliminates this problem 100%, as it waits until you've actually returned your joystick to center before it accepts any new input from you.

 

Stabilization is always on when the channel button-lights are shining. The hold input (the thing that FD disables) is suspended (read: frozen) during trim button hold.

 

Yes, you're right. When I said "autopilot stabilization gets turned off" during trim button hold, I was actually trying to say "autopilot input hold gets suspended" during trim button hold. My mistake...

 

The tap method is no problem. You deflect the stick and hold it until the maneuver stabilizes and tap with a practice relax motion.

 

The issue I'm specifically referring is not the relax motion back to the joystick center, it's what happens immediately before that: the "autopilot input hold" gets suspended even if you tap the trim. I expected this to happen only when you press and keep pressed the trim, but I was wrong.

 

If I use the press'n'hold technique the nose tend to rise at release after established steady attitude.

Flight Director mode work, so does the Huey and Mi-8 trim.

 

I fly with a "without spring and FFB" stick, but have also tried a FFB one (spring removed) with the same fesult (FFB settings all correct and working otherwise).

 

What trimmer mode did you choose under the "Special" tab in the "Options" screen of DCS?

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"joystick without springs and FFB" (or whatever it's called) for my PFT Lynx (non-FFB) with rather high friction applied for the cyclic to keep it in place.

 

"default" and "force feedback" checked under whatever the tab is called for my Cyborg Evo Force (FFB) with centering spring removed.

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I also have heard that the taping method should work better with FFB or "no spring,no FFB" sticks, while press'n'hold for others. But I don't see that.

 

Generally I use press'n'hold with "default" mode and decreased tau value (decreased = more time)

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"unnecessary" might be the wrong word. It's about springs and breaks holding the controls in place but in the same time causing uncomfortable forces for the pilot to fight against, so you need to be able to disable them when needed. Many real life helicopters do have it.

Ordinary joysticks with springs also benefit from it for the same reason.

But dedicated helicopter simulation controllers in general don't have any means to keep them in place, and often not possible (or at least difficult) to balance in center position. So you can't really take advantage of triming in that respect. But it is still usable to get the cyclic in a more comfortable position for your hand.

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hmm, it seems I have to practice more with this clicking method.

 

 

Good thing it's fun helicopter to practice in!

Try out Holbeach's mountain slalom mission in this thread: https://forums.eagle.ru/showthread.php?t=167089 It's a nice course for practice in any helicopter module with hard turns, elevation changes and low power lines to squeeze under as fast as you can.

HYXwfkdSfRQ

 

I thought force trim was unnecessary with dedicated heli controls. I'm still not clear on why it would be needed.

"unnecessary" might be the wrong word. It's about springs and breaks holding the controls in place but in the same time causing uncomfortable forces for the pilot to fight against, so you need to be able to disable them when needed. Many real life helicopters do have it.

Ordinary joysticks with springs also benefit from it for the same reason.

But dedicated helicopter simulation controllers in general don't have any means to keep them in place, and often not possible (or at least difficult) to balance in center position. So you can't really take advantage of triming in that respect. But it is still usable to get the cyclic in a more comfortable position for your hand.

It totally depends on the helicopters designer but in general in light and early made helicopters you wont find force trim systems and many pilots dislike them in these air frames if they are installed due to interfering with small balancing movements on the cyclic.

Bigger and more modern ones do mostly fly with a force trim system on all the time with some type of SAS/autopilot. With a force gradient on the controls they can be designed with a lot more advanced autopilot systems like on the ka-50 that makes hands off flying possible.

 

There are some sim equipment manufacturers do real trim in dedicated heli sim cyclics like this but I have no idea where you can buy or how much it would cost...

HjuD-_gSP4A


Edited by Penshoon

Otter

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Good thing it's fun helicopter to practice in!

Try out Holbeach's mountain slalom mission in this thread: https://forums.eagle.ru/showthread.php?t=167089 It's a nice course for practice in any helicopter module with hard turns, elevation changes and low power lines to squeeze under as fast as you can.

HYXwfkdSfRQ

 

Yes it is! Cool flying btw, I saw that video from you (and the Huey one too) many months ago!

 

Question: what's that knocking sound in the video? Is that you clicking the trim button?

 

EDIT: Never mind, I just saw the answer in the Youtube comments, that's the trim button...

 

EDIT 2: New question: it makes the sound both when you tap it AND when press and hold? Do you remember if the sound is produced when you 'press' or when you 'release', or both?

Question 3: I see you have autopilot on and flight director off... are you using 'route mode' or 'normal' autopilot?

 

Thanks for your input!!


Edited by PeaceSells

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Yes it is! Cool flying btw, I saw that video from you (and the Huey one too) many months ago!

 

Question: what's that knocking sound in the video? Is that you clicking the trim button?

 

EDIT: Never mind, I just saw the answer in the Youtube comments, that's the trim button...

 

EDIT 2: New question: it makes the sound both when you tap it AND when press and hold? Do you remember if the sound is produced when you 'press' or when you 'release', or both?

Question 3: I see you have autopilot on and flight director off... are you using 'route mode' or 'normal' autopilot?

 

Thanks for your input!!

Yeah its the trim button, it makes a click both when you first depress it and then when you release it, there is a tiny sound difference between them. I believe first click in the video is from pressing trim reset button though. Like 90% of the video I'm holding down the trim button to get FD controls behaviour.

Normal autopilot is on, no route mode.

Otter

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But as I read the forums I see that many people trim by simply tapping the trim button. Doesn't it bump your aircraft slightly out of position when you do that? How exactly do you trim by tapping without getting this effect?

 

Here's a donkeys-years old vid I made shortly after release. The point however remains the same - do whatever feels naturally to you. Both methods work - you just need to find the one that works for you :)

 

4l_LhCRIRgo


Edited by 159th_Viper
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I do most trimming including course corrections with flight director on. That way the heli isn't trying to fight me while i reorient. So, FD on, reorient, click trimmer, FD off. I dont' like click and hold method because i've found that sometimes the trimmer button will release if I'm not holding it tightly enough, and on my x-55 hotas my hand does tend to slip as I'm moving the stick around.

 

What really blew my mind about the trimming and autopilot system in the ka50, is that flight director off is also autopilot. It will not only remember the trim but also the heading and will fight to reorient to that heading if you move the stick. What the cyclic/collective display (if you're using it - right ctrl + enter to toggle) shows as the A is the route following autopilot. And by the way it follows your PVI waypoints, not your Abris waypoints - they aren't linked!!! *mindblown gif*

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I have to conclude that PeaceSells is right. You cannot fly the Ka-50 with the normal autopilot channels without an upset at every trim button press. Whatever input the channel hold was holding is removed at this time and there is an upset in the helicopter.

 

All you can do is live with it and minimize them by keeping the channel hold input closer to 0% than its 20% limit. Trim early and trim often.

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Here's a vid - listen closely for the trim inputs:

 

eq1kkvxAsd0

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I tested the click method earlier tonight, both with my FFB and my no-spring-no-FFB, with FD off and pitch and bank AP on, and with both heading AP on and off.

 

I do believe I actually got a grip on the technique now. As others have said, trim often and lead with triming, i.e. start trimming before attitude corrections and the initial jump of the nose is minimized. I found ridiculous amount of trimming was the key (much more than in the above IRL video).

At every click, the nose will jump, yes. But do a quick but small correction in the opposite direction (up/down, left/right) and click again. A small jump by the nose, quick and fast correction, click. Repeat, repeat, repeat!

Eventually the stick and AP will agree, and the nose no longer jump. You are in perfect trim. Works also in turns. Works for me in all above mentioned configurations. Needs some training to get used to.

 

Personally I like the press'n'hold better, more relaxed, but was curious about the "without spring and FFB" mode (with friction so I can let go of the stick without balance it in center position) which seems to me not realy work that well with the press'n'hold method (nose make unpredictable jumps at release)

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Yeah its the trim button, it makes a click both when you first depress it and then when you release it

 

I just noticed that I can hear the clicks too when I fly. Why? Because it's in the game!! *major facepalm* lol

 

Thanks for answering though!!

 

 

Here's a donkeys-years old vid I made shortly after release. The point however remains the same - do whatever feels naturally to you. Both methods work - you just need to find the one that works for you :)

 

4l_LhCRIRgo

 

Nice flying! I can see you are "lead trimming" as Holton said. Before I started the thread, I suspected this would be the way to do click-trimming efficiently, but I wasn't sure because it seemed kinda weird and un-intuitive to me. It's good to see that there are people that actually do this, thank for the demonstration!

 

 

Here's a vid - listen closely for the trim inputs:

 

eq1kkvxAsd0

 

Before I started the thread, I was wondering if the real Ka-50 would also have this "bump" when click-trimming. I suspected that, in the real one, you'd have to actually hold the trim button to disable the autopilot's counter-actions, so you could click-trim without having to "lead-trim". Watching the video, I can see that there seems to be some bumping indeed when he clicks, but not always. So I'm still not sure. This is a great curiosity of mine.

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Thanks for posting that, inspired me to do a similar flight right away. :D

qckM1S9xOEw

 

Lol you guys...

 

You even set the small FOV and the horizontal stripe in the lower part of the screen to simulate the camera in the cockpit! Lol

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I never noticed but the DCS HUD has major errors. The horizon-parallel lines aren't. The nose reference marker is moving relative to the nose at double the bank angle.

 

If anyone can demonstrate a channel-normal Ka-50 fight with airliner-type turns without any upsets in attitude on trim button presses I'd like to see it. I can't fly the helicopter 100% smoothly. No matter how smoothly I try every trim press has a transient impulse simply due to the channel authority being switched off suddenly. It has nothing to do with shifting stick position.

 

The real helicopter can't possibly act this way.

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I never noticed but the DCS HUD has major errors. The horizon-parallel lines aren't. The nose reference marker is moving relative to the nose at double the bank angle.

 

According to Chizh the Hud in the real video is supposed to be an early variant that was refused. The default hud in DCS is a later more modern variant.

I use a mod to changes the scales and bird mark too look more like in that video: https://forums.eagle.ru/showpost.php?p=3109972&postcount=46

If anyone can demonstrate a channel-normal Ka-50 fight with airliner-type turns without any upsets in attitude on trim button presses I'd like to see it. I can't fly the helicopter 100% smoothly. No matter how smoothly I try every trim press has a transient impulse simply due to the channel authority being switched off suddenly. It has nothing to do with shifting stick position.

 

The real helicopter can't possibly act this way.

The upsets in attitude in there in the real video, it's just comes with the system. The kamov is one of the few actual mil sim modules that ED managed to get to us consumers. If a critical system like autopilot behaviour during trimming wasn't accurate it wouldn't have been good enough for pilot training. With practice it's possible to be minimised.

 

In order to provide the most realistic experience of flying the Ka-50, Kamov has supplied us with a host of information not available to the general public. Once we had beta versions of the software available for testing, Kamov reviewed the software for accuracy (systems and flight dynamics) and helped us revise the simulation for greater realism.

Military contracts are not a license to print money, as often they are required to be done on a “cost plus” basis, and I can assure you that they are very demanding as the simulation has to be perfect so as not to introduce “negative training”.


Edited by Penshoon

Otter

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No matter what real pilots in the shark do or why they do it... holding the button during transient maneuver is better for me. I've tried both ways. There is no way to remove the jumps that occur with the press-release style but you CAN do so with the hold style. This in an of itself is enough for me to say the hold style is better. This is due to the tip touching issue at the edges of the performance envelope.

 

That said... I use a force sensing X65F (NOT force feedback) stick so my experience may be due in part to that.

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