[REPORTED]Pitch Excursions while using Trim Release

So, I decided to get back in the Ka-50 to try the Georgia Oil War campaign that I never finished years ago.

My cockpit is quite different than it was back then. It used to be a Saitek X-45, with Track IR3. Now, if you care, you can check out the specs in my sig, but only because it matters for finding this potential bug, I'll mention that I currently use a Brunner CLS-E in hardware trim mode for DCS. What this allows me to do is have trim release, and coolie hat trim outside of DCS, since the FFB functionality of the Brunner is still in the early stages.

When I was setting my controls back up, I decided to go with the trim option in the special tab for 'Joystick with no spring or FFB.' In addition, I mapped the trimmer button on the cyclic within DCS to the same button. My thought was that this would allow me to use hardware trim to hold the physical stick position, as well as reset trim functions for the autopilot on the Ka-50.

Everything seems to work fine (autopilot, and the loud clicks for trim release), but I started to notice something felt weird compared to the last time I flew the shark. I remember, even with my older spring loaded joysticks, if you held the trimmer, the aircraft was pretty smooth to fly. Now, if I press the trimmer, the nose pitches down, which must by manually arrested with aft cyclic, and then pitches up when the button is released, again, only arrested with opposite cyclic.

I tested this by getting the aircraft trimmed out straight and level, and just depressing the trimmer, without moving the stick. Without fail, the nose pitched down when the trimmer button was depressed, and pitched up when the trimmer button was released.

I then unmapped the trimmer from the cyclic, and only used the hardware trim function of the Brunner stick. Everything was smooth, as I remembered. No pitch excursions whatsoever. I remapped the trim release, and sure enough, the aforementioned behavior began anew.

Again, not sure if this is a bug, as maybe the actual aircraft behaves this way. If so, I'm glad it's not something I have to pilot for real, as it would drive me nuts. If it is a bug, it would be great to get it fixed, so those that use the trim option of no spring or ffb can actually map the trimmer button.

Pretty sure I found someone who had the same problem in this post, so I don't think I'm the only one:

https://forums.eagle.ru/showpost.php?p=3357762&postcount=10

Edit: Attached a .trk. In the .trk, I start out with hardware trim only, with the trimmer button unmapped. After I get everything straight and level, I actually depressed the timmer button quite a few times to demonstrate no pitch excursions. Then, I mapped the cyclic trimmer button to the same button that operates trim release on my Brunner CLS-E. I then used the trimmer multiple times, demonstrating how the nose will pitch down when the trimmer is depressed, and pitch up when the trimmer button is released.

I created a video through Nvidia Geforce experience, and attempted to voice over (drowned out by DCS mostly), but as its over 900mb, I'm still trying to figure out how to get it posted. I think the video would be more useful, as you can see when I change settings.

Edit again: Here's the video I made to go along with the .trk:

Ka-50 Trim Bug Test.trk

We discussed this issue a few weeks ago:

https://forums.eagle.ru/showthread.php?t=248239

I confirmed that it is indeed an issue:

https://forums.eagle.ru/showpost.php?p=4032455&postcount=19

We discussed this issue a few weeks ago:

 

https://forums.eagle.ru/showthread.php?t=248239

 

I confirmed that it is indeed an issue:

 

https://forums.eagle.ru/showpost.php?p=4032455&postcount=19

Ranma,

Thanks for the reply, but looking through the thread linked in your post, I believe we are talking about two different issues. It may have to do with my terminology, and as such, I edited my first post to make it more clear.

I'm not using the 'Trim Reset' (Lctrl-T) function at all. I'm using the standard cyclic 'Trimmer' (T) button, as can be seen being mapped in the video I posted.

Edit: From the looks of your video, we are indeed talking about the same issue. However, the thread that post is in is about a completely different issue related to the 'Trim Reset' (LCtrl-T) function, not the 'Trimmer' (T). If that's the case, I'm glad there's confirmation from another user, but it would be great if an ED rep would shed some light as to whether this is a bug being tracked, or a 'feature'.

I watched the video and looked at the track and I believe I know what the issue is. The trim is like a rubber band on the nose of the helicopter that tries to pull it back to the last-trimmed position:

What's happening is that the stick's position is in equilibrium with the AP force; the AP is trying to pull the helicopter's in one direction, but the cyclic's position is counter-acting that force. Imagine that the AP is trying to move the helicopter's nose 10 arbitrary units up, and your cyclic's position is pulling it 10 units down. The net effect is that the helicopter's nose stays where it is.

When you hold down the trimmer, the AP force is removed, but the cyclic position is still pulling the nose down 10 units, which is why it "jumps" when you hold down the trimmer but don't move the stick. You can confirm this by enabling Flight Director; it disables the AP force so with it on, holding down the trimmer without moving the cyclic should hold the nose steady.

Here's a video of me recreating the issue. I have the trim type set to "Joystick without spring or FFB" and I'm doing it on a FSSB R3, so apologies for the rough takeoff:

At 0:12 I tap the trim to set the AP attitude rather low, then pull the nose up to fly in the direction I want it to. At 0:20 I hold down the trimmer without moving the stick and you can see the nose rising. At 0:26 I tap the trim at a steeper angle this time, and at 0:36 I hold down the trimmer and the nose significantly rises up without me moving the cyclic.

Here's a video with Flight Director this time:

Tapping the trim doesn't set the AP attitude (aside from the indicator on the HUD), so holding down the trimmer later doesn't bob the nose.

The problem certainly does feel that way. It's seems as if the pitch attitude hold captures an attitude that's a couple of degrees off, in the up direction, from where the nose actually is when the trimmer button is released.

I think it would be enlightening to trim the aircraft so that the AP channels don't need to deviate from the trimmed stick location to keep the attitude.

Basically a SUPER stable flight envelope BEFORE you release the trim button. I still feel that the cause is the AP's CURRENT control authority magnitude and how that gets applied to a NEW trimmed state.

To elaborate...

The air-frame will oscillate around a trimmed attitude... and the AP channels are what's responsible for keeping the nose in the rubber-band...

So... Take a for instance...

You trim to a super stable hover and note the stick position and trim offset (in a FFB setup these will be the same... and they will be very close to the trimmed position.

Now... Press trim and VERY QUICKLY move the stick to somewhere else WITHIN the trimmer's 20% control authority and release trim. The attitude of the airframe won't change much (due to inertia) by the time you release trim. Because of this badly attained trim what you will end up with is the AP channels applying up to 20% control authority to maintain the air-frame's attitude when the trim was released. There will be a large offset between where you released trim and where the stick ends up based on the AP's interest in maintaining the attitude and not the stick position.

That offset is what I think is causing the movement you're seeing. And... I'm not sure it's a bug. If it is... It may be that the logic behind the FFB mode does the wrong thing with the AP channel's trim offset.

That said... I don't fly with FFB.

I think it would be enlightening to trim the aircraft so that the AP channels don't need to deviate from the trimmed stick location to keep the attitude.

 

Basically a SUPER stable flight envelope BEFORE you release the trim button. I still feel that the cause is the AP's CURRENT control authority magnitude and how that gets applied to a NEW trimmed state.

 

 

To elaborate...

 

The air-frame will oscillate around a trimmed attitude... and the AP channels are what's responsible for keeping the nose in the rubber-band...

 

So... Take a for instance...

 

You trim to a super stable hover and note the stick position and trim offset (in a FFB setup these will be the same... and they will be very close to the trimmed position.

 

Now... Press trim and VERY QUICKLY move the stick to somewhere else WITHIN the trimmer's 20% control authority and release trim. The attitude of the airframe won't change much (due to inertia) by the time you release trim. Because of this badly attained trim what you will end up with is the AP channels applying up to 20% control authority to maintain the air-frame's attitude when the trim was released. There will be a large offset between where you released trim and where the stick ends up based on the AP's interest in maintaining the attitude and not the stick position.

 

That offset is what I think is causing the movement you're seeing. And... I'm not sure it's a bug. If it is... It may be that the logic behind the FFB mode does the wrong thing with the AP channel's trim offset.

 

That said... I don't fly with FFB.

If this oscillation based on pressing and releasing the trimmer is normal for the ka-50, then it would definitely be a real pain to fly. No helo I’ve ever flown IRL has had this issue.

My ffb stick doesn’t utilize the in-game ffb functions. It’s entirely hardware based. That said, Ranma isn’t using a ffb stick. I’m about 99% sure this is a bug in the module.

I took another look and I agree, it does look like a bug, and the same bug as the trim reset one. When you press trim down without moving the stick, the aircraft's nose will dip down, and when you release it, the aircraft's nose will pop back up to the same position as it was in when you first pressed it down. As far as I understand the Ka-50's AP system, this is not supposed to happen.

I don't think either of you are understanding what I'm trying to say. No offense meant... maybe I'm not explaining it well.

All I'm asking is that you test with a very small trim offset (When the AP channels are exerting very small amounts of control authority to maintain trimmed attitude) and with a large trim offset (when the AP channels need to exert somewhere near their maximum control authority to maintain air frame attitude). This will be valuable information.

I'm just seeing both of you perform a minor test that doesn't prove anything and certainly doesn't prove any "cause" for what you're seeing.

I'm not saying "there is no issue here... move along...".

I'm saying "Test, test, Test. We'll find a bug IF it's there AND we'll have a good bit of info about what settings, procedures and even environmental factors affect it"

Until you do that... NOBODY will be convinced :). If you want someone to be convinced... you need to do the leg work :). That's all :).

Also...

The oscillation I'm talking about is not what you're talking about. I'm talking about any free body's natural tendency to oscillate around an equilibrium. It's basically the concept that no motorcycle or aircraft EVER can go straight. EVER. It doesn't happen. That's the oscillation I'm referencing. Not what happens here when you re-trim the KA-50. I'm going to stop trying to make the point though because I don't think that either of you have the background knowledge to get the reference. Please don't take offense..

That said... I'll try to find an explanation and I'll post it here.

Here... this is true for all unstable bodies... Motorcycles are one of these as well. The oscillation is never 0.

https://en.wikipedia.org/wiki/Flight_dynamics_(fixed-wing_aircraft)

Short-period pitch oscillation

A short input (in control systems terminology an impulse) in pitch (generally via the elevator in a standard configuration fixed-wing aircraft) will generally lead to overshoots about the trimmed condition. The transition is characterized by a damped simple harmonic motion about the new trim. There is very little change in the trajectory over the time it takes for the oscillation to damp out.

 

Generally this oscillation is high frequency (hence short period) and is damped over a period of a few seconds. A real-world example would involve a pilot selecting a new climb attitude, for example 5° nose up from the original attitude. A short, sharp pull back on the control column may be used, and will generally lead to oscillations about the new trim condition. If the oscillations are poorly damped the aircraft will take a long period of time to settle at the new condition, potentially leading to Pilot-induced oscillation. If the short period mode is unstable it will generally be impossible for the pilot to safely control the aircraft for any period of time.

 

This damped harmonic motion is called the short period pitch oscillation, it arises from the tendency of a stable aircraft to point in the general direction of flight. It is very similar in nature to the weathercock mode of missile or rocket configurations. The motion involves mainly the pitch attitude {\displaystyle \theta }\theta (theta) and incidence {\displaystyle \alpha }\alpha (alpha). The direction of the velocity vector, relative to inertial axes is {\displaystyle \theta -\alpha }\theta -\alpha . The velocity vector is:

Sooo...

If you catch the oscillation (by releasing trim) at a place where some of the 20% control authority in the AP channel is used... Then re-trim... We don't know what the shark's computer (and by that I mean the selected control logic ini the options really...) is doing WITH THAT EXERTED CONTROL AUTHORITY.

We need to.

I don't think either of you are understanding what I'm trying to say. No offense meant... maybe I'm not explaining it well.

 

All I'm asking is that you test with a very small trim offset (When the AP channels are exerting very small amounts of control authority to maintain trimmed attitude) and with a large trim offset (when the AP channels need to exert somewhere near their maximum control authority to maintain air frame attitude). This will be valuable information.

 

I'm just seeing both of you perform a minor test that doesn't prove anything and certainly doesn't prove any "cause" for what you're seeing.

 

I'm not saying "there is no issue here... move along...".

 

I'm saying "Test, test, Test. We'll find a bug IF it's there AND we'll have a good bit of info about what settings, procedures and even environmental factors affect it"

 

Until you do that... NOBODY will be convinced :). If you want someone to be convinced... you need to do the leg work :). That's all :).

 

 

Also...

 

The oscillation I'm talking about is not what you're talking about. I'm talking about any free body's natural tendency to oscillate around an equilibrium. It's basically the concept that no motorcycle or aircraft EVER can go straight. EVER. It doesn't happen. That's the oscillation I'm referencing. Not what happens here when you re-trim the KA-50. I'm going to stop trying to make the point though because I don't think that either of you have the background knowledge to get the reference. Please don't take offense..

 

That said... I'll try to find an explanation and I'll post it here.

Don't worry, no offense taken. I also perfectly understand your attempted explanation of the phenomenon. I just don't agree that it's correct behavior in the simulated aircraft system/flight model. Mainly the aircraft system, as the flight model acts just fine when I take the ka-50's trimmer out of the equation, and simply trim using the hardware feature of my joystick.

The oscillation is easily reproduced, and is shown many times within the already posted videos. The oscillation increases in magnitude directly proportional to the amount of time the trimmer button is depressed, to a certain degree that is able to be arrested by opposite pitch in the stick.

As for background, I assume you could mean engineering. Not sure if that's the case, and no, I don't have an engineering degree. I have been flying various helicopters for the last 13 years, though, admittedly not a ka-50. I have also been playing/flying the DCS Black Shark for almost the same amount of time (12 years IIRC).

In a no wind gust situation, in a stable hover, it is possible to get a near zero oscillation hover. The small corrections required to maintain a stable hover without gusts are quite negligible compared to the oscillations in pitch experienced in the current Beta version of the DCS Black Shark when using the trimmer. The oscillations are not something I remember when playing the game initially, or until recently.

Frankly, I'm not concerned about convincing you there's a bug. I would just like someone from ED to run their own test, and confirm whether or not it's a bug. The oscillation is there, whether you perform a small re-trim, within the 20% as you say, or if you just hold the trimmer button down for a few seconds.

"I also perfectly understand your attempted explanation of the phenomenon. I just don't agree that it's correct behavior in the simulated aircraft system/flight model. Mainly the aircraft system, as the flight model acts just fine when I take the ka-50's trimmer out of the equation, and simply trim using the hardware feature of my joystick."

No you don't.

As I said... "The oscillation I'm talking about is not what you're talking about. I'm talking about any free body's natural tendency to oscillate around an equilibrium. It's basically the concept that no motorcycle or aircraft EVER can go straight."

I'm talking about how you initially set the trim affecting what happens during a re-trim. You're talking about what happens when you re-trim.

The issue you're talking about isn't even an oscillation. It's a possibly errant control input coming from somewhere.

Again :)... I'm not convinced it's not a bug... I'm just trying to explain a method to isolate where it's coming from so we can go to the dev's with more info rather than less.

Let's stop the pretentious "I am so smart" bullshit. We're talking about an inconsistent behavior with the trimmer, not the natural oscillations that would occur in not only motorcycles and aircraft, but any moving mechanical device. It's like we're discussing an issue with bicycle handling, and you're trying to contribute by throwing out info on rubber adhesion to asphalt.

Getting back on topic, I looked into this some more and the pitching issue seems to only occur severely when the trimmer mode is set to Joystick without Spring and FFB. Here's a video of the the trimmer mode set to Default. I start by holding down the trimmer and changing the attitude significantly, then release when I have it stable. After that, I periodically hold down and release the trimmer without moving the stick, and the aircraft gradually pitches up each time towards the 0 pitch line, which I believe is just the aircraft's natural tendency to straighten out:

The same effect can be seen with trimmer mode set to Central Position Trimmer Mode, it gradually moves towards the 0 pitch lines and stays there:

It's only when the trimmer mode is set to Joystick without Spring and FFB where the aircraft starts to pitch significantly in either direction and is too large to be considered natural:

It seems that if the aircraft is going to pitch up, it will do so when the trimmer is released, and if it's going to pitch down, it does it when the trimmer is first pressed. I believe the bug is with how Joystick without Spring and FFB mode handles the trim presses.

Let's stop the pretentious "I am so smart" bullshit. We're talking about an inconsistent behavior with the trimmer, not the natural oscillations that would occur in not only motorcycles and aircraft, but any moving mechanical device. It's like we're discussing an issue with bicycle handling, and you're trying to contribute by throwing out info on rubber adhesion to asphalt.

 

Getting back on topic, I looked into this some more and the pitching issue seems to only occur severely when the trimmer mode is set to Joystick without Spring and FFB. Here's a video of the the trimmer mode set to Default. I start by holding down the trimmer and changing the attitude significantly, then release when I have it stable. After that, I periodically hold down and release the trimmer without moving the stick, and the aircraft gradually pitches up each time towards the 0 pitch line, which I believe is just the aircraft's natural tendency to straighten out:

 

 

The same effect can be seen with trimmer mode set to Central Position Trimmer Mode, it gradually moves towards the 0 pitch lines and stays there:

 

 

It's only when the trimmer mode is set to Joystick without Spring and FFB where the aircraft starts to pitch significantly in either direction and is too large to be considered natural:

 

 

It seems that if the aircraft is going to pitch up, it will do so when the trimmer is released, and if it's going to pitch down, it does it when the trimmer is first pressed. I believe the bug is with how Joystick without Spring and FFB mode handles the trim presses.

That’s the exact test I thought of today at work, suspecting it may have something to do specifically with the trim mode. Thanks for checking that out, and I’ll see if I can replicate.

Just tried it with the MSFFBII - no pitchup at all.

At a stable altitude and 240km/h, actually a very slow slight nose drop if the trimmer's held in, nothing else.

Do you have curves set on your controllers ?

No curves set, though it shouldn't matter since I'm not moving the stick. If the nose is dropping very slightly, it sounds like you're getting the same behavior as I am with trimmer mode set to default or central.

Maybe - it doesn't drop with a jerk though, it just slowly starts to drift down if I hold the trim in for more than a second.

No curves - Good (in that at least it eliminates something), but using curves does make a difference if you're actually using FFB, as the FFB is set to always assume no curves for providing the FFB for the trimmed position (the FFB assumes a linear relationship between real stick position and SIM stick position, but with curves that doesn't exist), and so the trimmed position & reported position of the stick end up misaligned if FFB is on and there are curves set on the pitch and roll axis.

That would mean there was a tension between the point the aircraft's AP was trying to align to and where the stick was trying to fly the aircraft to, and one side of that tension would be relaxed every time the trimmer was pushed...

There are threads about it and E.D.'s advice is no curves with FFB sticks...

No curves in my case either. My setup is currently (and has been throughout this conversation) force feedback disabled, using ‘Joystick with no springs or Forcefeedback’ trimming method.

Just tried it with the MSFFBII - no pitchup at all.

At a stable altitude and 240km/h, actually a very slow slight nose drop if the trimmer's held in, nothing else.

Can you confirm which trimming method you have selected?

Ranma, I just tried all three trimming methods, and can confirm the same results as what you posted. In addition, I tried disabling the 'Pitch Attitude' channel while using the 'Joystick without springs and FFB' method, and the pitch excursions disappeared. It seems to be an issue with that particular trimming method, and the Pitch Attitude hold function of the autopilot.

@RANMA

No pretentious "I'm so smart" bullshit going on at all. Also... thanks for suggesting that maybe it's in the way the trimmer mode handles the "trim offset"...

Just like I suggested a few posts before you...

Post #6

"That offset is what I think is causing the movement you're seeing. And... I'm not sure it's a bug. If it is... It may be that the logic behind the FFB mode does the wrong thing with the AP channel's trim offset."

and

"I still feel that the cause is the AP's CURRENT control authority magnitude and how that gets applied to a NEW trimmed state."

Post #10

"If you catch the oscillation (by releasing trim) at a place where some of the 20% control authority in the AP channel is used... Then re-trim... We don't know what the shark's computer (and by that I mean the selected control logic ini the options really...) is doing WITH THAT EXERTED CONTROL AUTHORITY.

We need to."

"We're talking about an inconsistent behavior with the trimmer, not the natural oscillations that would occur in not only motorcycles and aircraft, but any moving mechanical device."

No. Only motorcycles and aircraft and maybe a few other unstable yet self righting object. Anything on the ground with more than two wheels specifically does NOT fit in this category.

In any case... It's not my fault you don't understand the concept I'm trying to point out that could be effecting the results we're seeing based on where in that oscillation you're releasing trim. It is a motorcycle or airplane's natural tendency to oscillate back and forth on both sides of an equilibrium. Simply that.

So yeah... get off your high horse. I'm trying to help.

_______________________________________

Anyway... back on topic :)...

Yeah...

As I said... I'd like to see a few tests to isolate where the issue is coming from so we can decide if it's a problem with the trimmer mode.. Thanks for those :)

Nobody understands the concept you're trying to point out, hence why we're all ignoring you. Show evidence of what you're talking about, otherwise you're just quoting Wikipedia and yourself.

Well that's not my problem... I'm still making an excellent point :).

Also... you're obviously starting to get my point as you're starting to test better and starting to suggest the same things I have been :). What's more... the more you test and narrow down the likely cause of the issue... the more it points in the direction of what I've been saying for a while now :)... that the issue comes from how the current logic is applying or mis-applying the trim offset.

So yeah... Feel free to ignore but if you had listened to me and accepted that maybe there's things you don't know a LONG time ago and tried to understand what I was saying... we would ALL be a lot further ahead now.

Thanks for that :). It's been super amusing to watch through the course of these two threads :)

One more thing...

Sorry not sorry for switching to "tell it like I see it mode" regarding you... But you got under my skin when you decided to start dismissing what I was saying just because you decided I was wrong based on your own lack of understanding of what I was trying to say.

I general you seem to bring relatively good info and presence to the forum but as soon as I said "I'm not sure this is a bug" (or something like it) in the other thread you started being super dismissive and rude to anything I said later. That's on you. I'm still trying to help :). The Shark is my favorite sim toy :). Maybe the Lotus 79 in iracing is a close second :).

What (I think) he means is :

You put enough forward cyclic in to get the aircraft 10 degrees down, and as it passes through 5 degrees you let go of the trimmer.

The joystick stays where it's trimmed, and the control authority of the AP takes the aircraft back to 5 degrees (the nose rises after you let go of the trim).

But although the aircraft is flying at 5 degrees, the stick's deflection would generate 10 degrees if the AP weren't countering it.

At the point that you push the trimmer in, the AP stops fighting the stick, and the aircraft moves from 5 degrees nose down to 10.

To make sure that this isn't part of the problem, you'd have to make sure that the aircraft was stable in both pitch and airspeed before releasing the trimmer.

I use an FFB stick and the FFB trimming method, and if I do make sure the aircraft is stable before releasing the trimmer, I get the result I mentioned above.

If there is an offset in the autopilot pitch attitude hold from where the trimmed stick position is using "Joystick with no spring and no FFB" as a trimming method, then that is a bug, I believe, which is why I posted in the first place.

Although it may be hard to deduce from the videos that were posted, rest assured, the aircraft was in a stable state when the trimmer was released in all counts.

I've treated it as I've flown all the different models of helicopter I've flown IRL. Hold the trim release until you reach the state you want (in this case, level, with a fixed power setting, which equates to a specific airspeed, which is unimportant in this case), then release the trim. The attitude hold should hold that attitude unless you move the controls, unless the devs say this behavior is related to actual behavior in the aircraft, which I suspect isn't true, based on the fact that the behavior changes if you choose a different trimming method.

The oscillation down when the trimmer is pressed (which increases based on how long you hold the trimmer to some limit), and the oscillation up when the trimmer is released (which seems to be directly proportional to how long you hold it down) is nothing like anything I've ever seen on an actual aircraft. Thus my belief that it's a bug. In addition to the fact that the other trimming solutions work like this.

If you are trying to help, you could actually perform some tests yourself, and post the results.

Feel free to ignore

Done, added you to my ignore list.

Yes, as heloguy said, we're getting the aircraft into a stable state before releasing the trimmer. In one video I even press the trimmer repeatedly after getting it stable to make sure it's really "locked in". The uncommanded pitching only seems to happen with Joystick without Spring and FFB mode but not with the other 2 trim modes, so it's a bug with that specific implementation and not something inherent to the aircraft itself.

What (I think) he means is :

You put enough forward cyclic in to get the aircraft 10 degrees down, and as it passes through 5 degrees you let go of the trimmer.

The joystick stays where it's trimmed, and the control authority of the AP takes the aircraft back to 5 degrees (the nose rises after you let go of the trim).

But although the aircraft is flying at 5 degrees, the stick's deflection would generate 10 degrees if the AP weren't countering it.

At the point that you push the trimmer in, the AP stops fighting the stick, and the aircraft moves from 5 degrees nose down to 10.

 

To make sure that this isn't part of the problem, you'd have to make sure that the aircraft was stable in both pitch and airspeed before releasing the trimmer.

 

I use an FFB stick and the FFB trimming method, and if I do make sure the aircraft is stable before releasing the trimmer, I get the result I mentioned above.

Yes exactly :).