@Rob,

 

One additional thing to try is to manually fail the PFC's into Secondary Mode via the CDU aircraft options menu and simply leave your hardware setup as it normally is in terms of calibration/dead zone.      If this were to have a significant impact on the manual trimming issue in terms of precision, it would be revealing.

 

I have tried that before SP1......and as expected that worked fine.

 

Because it basically bypasses all that FBW stuff and the thing becomes a heavy B737.

 

I would think the same would happen if you did that in SP1, but I do no see that as revealing though. (but correct me if I not thinking straight here!)

I mean,....is it revealing that the default C172 or Baron, or NGX (do not have it installed, cant try) work just fine?

Once you disable the FBW gymmics the 777 becomes an airplane just like the others (not really of course.....because it still has a FBW system, but an un-augmented one)

That other aiplane work just fine, and the 777 does not only tells me something is wrong with my settings for the 777, or it has a bug.

 

And that is what we need to find out.

 

If I were to disable the Normal mode and the FBW trim would STILL not work correctly......by feel......that would maybe be more revealing no?

Because in secondary mode the trim inputs should go directly to the STAB and there is no FBW trim speed!

So the whole "reduced elevator authority system" that is used in the Normal mode by PMDG to simulate a FBW system, should be deactivated at that point.

If that does NOT give me normal trim by feel......THEN that is really wrong.

 

 

PS....Something came up today.....so I will not have time to try all this stuff untill later tonight (Europe time) :-(

 

Thx for the ideas Bruce.

@Rob

 

Sympathise with your problem, and admire your efforts to get to the bottom of why things are not working for you, and a few others.

 

I do not have the problem of trim activating only when returning the column to neutral. Tested this many times. If acceralting from an in-trim situation, and say wanting to maintain straight and level, I have to apply increasing forward pressure on yoke. While still holding that forward pressure, if I then trim nose down, I HAVE to release some of the forward pressure, or else start diving so trim is coming in for sure. As speed picks up I trim progressively nose down, till I "feel" I can realax all pressure on the yoke, and I am there and there abouts with the fbw marker at the desired speed at that stage. Diito for slowing down / back pressure.

 

So for Rob's research these are my settings, including some that I have not seen mentioned in this thread (nor in the PMDG manual, and I have tripple-checked, so Kyle does not jump on me).

 

• Saitek Pro Flight Yoke
• PMDG FMC Null zones: CTL Column Null zone 1%; CTL Wheel null zone 5%
• Trim buttons assigned in FSX to joystick Button 3 trim down, Button 4 trim up. No keyboard assignment to rule out any unintentional override.
• Under FSX calibration (Advanced) - Aileron and Elevator sensitivity Max (sliders full right)
• Small Null zone in FSX calib applied to both - (no number to this setting, but five right clicks with right arrow on keybord from the leftmost zero-null point). This gives me a slight area of no response, otherwise I find I have to hunt a bit to get the pitch I want. With this null setting, fingertip nudges on the yoke let me set the exact pitch I want (level or desired VS).
• In FSUIPC I have Control spike elimination on for rudders, elevators and ailerons (my yoke is getting old and the pots are spiking a bit.)

 

Now the one setting that I have not seen discussed, and I thought may not have been mentioned because PMDG "take control" of this, so it makes no difference. But I see it does make a difference - and that is the repeat setting on the trim buttons.

 

I experimented on the ground with the FCTL screen open to check this out.

 

If have zero repeat set for assigned trim buttons - Have to click 7 to 9 times before will register a 0.25 stab trim change EXCEPT if reversing trim direction, then one click will give 0.25 change. Clearly NOT what one wants (or else your repeated clicks are only registering sporadically, and holding the trim button does nothing).

 

At midrange repeat - timed on stop watch holding trim buttons 5secs give 1.75 stab trim change. One short push gives 0.25 trim change (I found this to be a bit erratic. If single flick of the button was too fast, no change registered)

 

At fast repeat (slider full right) - again holding 5secs on stop-watch gave 1.75 stab trim change, but this time even the quickest short push on a trim button gave me 0.25 change. So to me this was the setting to use for quick trim response, plus "blip trim".

 

With these settings have just done two full-manual flights, take off to 30000ft and back to landing, with FBW working as advertised, no sudden pitch changes, and a real pleasure to fly. All just Pitch, Power (handled by A/T), and Trim , usual aircraft procedure.

 

If fact off to have a beer or two I am so stoked up about the approach and landings I made! Not under any SOP so from now on I will be going manual whenever I feel like it!

 

So to Rob and others still battling, I really hope you find your solution soon!

 

Rob

@Robin Harris,

 

Thank you very much for taking the time to provide so many detailed settings for your hardware setup.      I will try your exact same settings with my Saitek hardware and report back here.     Both Rob Robson and I are experiencing the very same issues with manual trim at present, as well as the OP of this thread, among others.   

 

Testing your settings with a known-to-be properly working Saitek joystick on my own setup should help eliminate the issue some of us are collectively experiencing as being related to a hardware-specific problem.   

@Rob Robson @Robin Harris,

 

I just completed a test using R. Harris' settings for my Saitek joystick which I've previously not used with the PMDG 777 before.    I experienced the exact same results and the trim instability issue in as troublesome as ever.     So far, I've tried a CH Yoke, CH Fighterstick Pro, Saitek Yoke, and finally today a Saitek X-45 joystick.     I've carefully calibrated each device before use, used every null zone setting imaginable, and have also tried assigning controllers via both FSX and FSUIPC (separately of course).    Nothing I've tried towards this end has ever mitigated the manual trim issue in the least.

 

Therefore, I am very confident in concluding that whatever the issue is with those of us who continue to have this problem with trimming the 777, that the issue is not hardware related.      There are simply too many individuals having this problem, along with the utilization of a variety of controllers for this issue to be hardware related.    

 

Perhaps the eminent Rob Robson will arrive at a different conclusion after his own tests with his hardware, but I suspect that he will concur with my own observations.      In my tests today, I was able to trim by 'feel' at the desired airspeed, but then the aircraft gradually went from a  perfectly stable flight path and 'hands off' condition and slipped into some kind of delayed  phugoid oscillation for no perceptible reason.     At least one other user on the forum has related the same experience within the past few days - the aircraft is trimmed on reference speed, then after a few seconds goes into phugoid for no logical reason.     

 

If I can find a decent wall, I'm ready to bang my head against it right now.   

Sorry Ryan but your source is wrong :-(

 

The source is a ~30,000 hour captain - he said that trimming in the opposite direction of yoke input still caused a change in the control force/pressure when he tried it. What he did was put the airplane out of trim in the nose down direction so that he had to maintain back pressure on the yoke to remain level. While holding this back pressure, he started trimming nose down. This caused the amount of back pressure needed to increase over what he was already holding. I do trust this person - have you tried this in the real airplane?

Let me start with repeating two conclusions I made in my last post (I am going to call that PART I from now on) that are not confirmed by others yet:

(I am going to need some confirmation of my observations at some point from someone)

 

1) The yoke becomes extremely unsensitive when FBW trim is very much below actual speed (i.e. FBW trim ref speed = 220kt and act speed =310kt)

Even full yoke deflection hardly has any effect.

2) As actual speed is reduced again from the above situation, and gets closer to FBW trim ref speed, effectiveness gradually returns.

 

PART II

 

Now I just tried the opposite, so flying i.e. 220kt, I increased the FBW trim ref speed to 310kt while trying to maintain altitude.

And on my system the yoke became hyper sensitive!

So question nbr 3) is...DO YOU GUYS GET THE SAME RESULT?

 

I find this effect very illogical.

If PMDG sais that they have to reduce yoke effectivenes when out of trim to simulate the FBW system.....then I would have thought that in both out of trim situations (over trim/under trim) you should get a less effective yoke.

But that is not the case.

(Again, I am no programmer......but to me that seems inconsistent)

 

 

Try this:

same weights and everything (I told you to save that flight ;-) )

select - FBW trim ref speed displayed- option in FMC.

Level in 5000ft.

 

1)

This makes sence (to me):

Fly 310kt and level flight with AP and AT on.

My STAB trim showed 4.25.

(Do not worry about going through neutral or not with your yoke during the following experiment....it does not matter for now)

Disengage the AP.

Follow the FD to maintain 5000ft.

 

ready?

 

Now reduce FBW trim ref speed way way below actual speed. To about 210kt or so.

(it is difficult to get it spot on 210kt on my system......dont know why....213kt or whatever is fine too.)

(The nose will try to go up, so try to compensate with fwd yoke....just try to follow the FD.)

 

Fly like this for a minute or so untill the STAB trim setting has stopped increasing.

 

Result - STAB trim goes up (mine was at 5.00) and nose goes up. All ok.

At the same time yoke effectiveness is reduced gradually, and at the extreme (FBW trim ref speed =210kt and actual speed is 310kt) a lot of yoke deflection is required to keep the nose level.

(In the real aircraft full nose up STAB trim would also require a full fwd yoke deflection to keep the nose from going vertical.....I dont even know if such a deflection can be compensated by elevator alone - might have to roll over). Anyway, this could have been simulated by PMDG allowing a much greater STAB trim range (like plus 10) just the same. That would also require full fwd yoke. Why the choice for less yoke effectiveness? Ok that is their choice....I am no programmer......but here comes the weird part)

 

2)

This makes no sence but this is how the PMDG works (on my system):

Fly 210kt and level flight with AP and AT on.

(I know....well below the flaps up maneuvering speed at this weight (green up symbol), but don't worry)

My STAB trim showed 5.50

(Do not worry about going through neutral or not with your yoke....it does not matter for now)

Disengage the AP.

Follow the FD to maintain 5000ft.

 

Now increase FBW trim ref speed to 310kt, again just keep following the FD.

 

Fly like this for a minute or so untill the STAB trim setting has stopped decreasing.

 

Result - STAB trim goes down (in my case to 4.75) and nose goes down. At the same time though....yoke effectiveness is INCREASED to the point of hyper effectiveness at the extreme out of trim condition (flying i.e. 210kt, with FBW trim ref speed increased to 310kt.)

This condition (STAB (full?) down with strong tendency of the nose to want to drop) should just the same, require full yoke deflection (up) to compensate - right?

But it does not!

It requires just a tiny, little bit of yoke deflection!

 

And now finally we come to the first problem I have with the "trim by feel" thing!

 

Tell me.......how can you trim away a huge huge out of trim situation by feel....if you feel nothing to begin with?

I mean I had a yoke deflection of between 0 and 1cm in there to stay level in 5000ft.....1cm to compensate for that unreal out of trim situation!?

 

I then disabled the display of FBW trim ref speed and trimmed by "feel"

Ofcourse I felt nothing......all I could do is trim a bit......let go of the yoke.....oh, nose still drops.....trim some more.....let go of the yoke.....oh, nose still drops.....trim some more......ah getting close......a few short clicks and a blib effect later I displayed the FBW trim ref speed again, and I was in trim.

 

So yes, trimming without the FBW trim ref speed displayed worked......but in no means was that by trimming away a large yoke displacement by feel!

 

You guys dont have the same result/effect?

 

Ps..before everybody goes.....here see, it works, now stop complaining.....I have more.

Tomorrow I tend to find out (hope I can) why it sometimes takes for ever to get in trim by feel and at other times it worked quite quickly and well (even if not by feel like in the above example but by trial and error).

Trying different dead zones will be a part of that.

Rob..Nobody is disagreeing that there is a problem with trimming on your system or may be a couple of other. All we are trying to say is, when we trim, we have been trimming by feel rather than by trial and error.So we don't feel that FBW marker is absolutely necessary when trimming. When I made those couple of videos that day it was by feel.I would trim and slowly release to find it is yet out of trim and trim again and release..till i felt the aircraft was not reacting when i release it.And after your comments I watched my videos again and could see very well that trim was being applied even when elevator was not passing through neutral.

And to change 0.25 units of trim, we have to use several notches of up/down trim(unless its held repeatedly).So it could very well be the case that the trim change on FCTL page would have shown the moment the final notch was applied and my yoke would have been travelling through neutral.

 

 

check this video from 1:20 to 1:25.. You will see the elevator is not passing through neutral at 1:21 and 1.25. At 1:21 my elevator is still down and at 1.25 it is close to neutral(but still down)

The source is a ~30,000 hour captain - he said that trimming in the opposite direction of yoke input still caused a change in the control force/pressure when he tried it. What he did was put the airplane out of trim in the nose down direction so that he had to maintain back pressure on the yoke to remain level. While holding this back pressure, he started trimming nose down. This caused the amount of back pressure needed to increase over what he was already holding. I do trust this person - have you tried this in the real airplane?

I know you have very experienced Captains that help you out Ryan.......but everybody can be wrong.

 

Myself included.

 

But, yes, I did try this in the aircraft myself.

 

I just came back from Washington DC yesterday.

Did the take off myself and I did not trim during the clean up and acceleration phase.

So I am sitting there pushing the nose down right.

And now I trim UP (instead of down which would be normal).......and I sat there for a while like that......pushing and trimming UP.

And nothing happened Ryan.......the push force was never reduced, not by a milligram!

We had the FCTL page open during that experiment as well and we could see the elevators being deflected down a little bit the whole time.

That display is pretty rough though.....but if you ask me the elevators did not move either during trim in the opposite direction

(this is why I asked if you have better data abailable to you to support your conclusion) you would need actual FCTL data output in numbers......maybe from the maintanace pages.?)

 

I repeated the same thing again upon passing 10.000ft.

Same same..... I sat there and sat there pushing the yoke and trimming opposite, but the trim system did nothing......or, at least the artificial feel force remained the same.

 

 

But honestly Ryan.....this is just a detail of the FBW system.

Whether you are right or I am right......it does not matter that much because nobody will fly like that. It will not cause problems either way.

 

Way more important is that we figure out why some of us are having problems with trimming by feel and others not.

Possibly my hardware....or my settings (CDU dead zone)......I tend to find out tomorrow.

 

I found something today that I think is strange.

I would realy appriciate your opinion of my findings Ryan.

(You can read the long version above.)

 

Short version:

When FBW trim ref speed is (much) below actual speed - yoke effectiveness decreases

When FBW trim ref speed is (much) above actual speed - yoke effectiveness increases

 

Is this meant to be like this, or should yoke (elevator) effectiveness decrease in both situations (that would seem more logical to me and would give more consistant trim results).

 

Thx in advance.

So for Rob's research these are my settings, including some that I have not seen mentioned in this thread (nor in the PMDG manual, and I have tripple-checked, so Kyle does not jump on me).

 

Rob

Hi Rob.

 

Thx for all that data and sorry for the delayed reply, really appriciate you taking the time :-)

 

I am so busy with my experiments right now that I hardly have time to read up on this thread.

 

I will try your settings, if I cant fix things with a CDU or joystick deadband, while keeping my current FSUIPC settings.

I am also gonna try your scenarios tonight Rob. Let me see what I get on my system. Only issue is when i get home sometimes the big boss(WIFE...) takes over

I am also gonna try your scenarios tonight Rob. Let me see what I get on my system. Only issue is when i get home sometimes the big boss(WIFE...) takes over

Oh boy, dont get into trouble on my behalf ;-)

 

But yes, please do that if you can.

In passing, I wonder if this whole thing is perhaps the result of an overloaded Simconnect bus, and certain control inputs like pitch trim are being processed outside of the FSX platform with some kind of delay?      This would account for a tendency with users to over-trim in either direction, seemingly illogical aircraft responses, the phugoid oscillation popping up after the aircraft has already stabilized on flight path, and the general goofiness of the trim function in general, at least for some of us.      Would a saturated Simconnect bus also only affect a certain percentage of 777 customers with particular FSX installations?

 

I suppose someone could try a 'virgin' installation of FSX, with absolutely no add-ons whatsoever (not even FSUIPC), and test just the PMDG 777 add-on alone in that environment.       I personally bow down and admit defeat to this thing though.     I wish everyone else the very best and I hope you find a solution.     One year + at this trying to get the FBW system to behave is enough for me.      Au Revoir mes amis!  

There seems to be some contradictory statments here. But I am still getting a noticable 'bubble/bounce' the moment the yoke is returned to neutral and the moment I apply the smallest amount. 

 

When out of trim, the sudden pitch change when releasing the stick to achieve the trim ref speed seems odd.

 

Alex

There seems to be some contradictory statments here. But I am still getting a noticable 'bubble/bounce' the moment the yoke is returned to neutral and the moment I apply the smallest amount. 

 

When out of trim, the sudden pitch change when releasing the stick to achieve the trim ref speed seems odd.

 

Alex

can you try my experiment Alex (post 143)?

 

It should not take you more than 10minutes flying.

 

I would like to know if others get an oversensitive elevator response as well when FBW trim ref speed is well above actual speed.

 

thx.

can you try my experiment Alex (post 143)?

 

It should not take you more than 10minutes flying.

 

I would like to know if others get an oversensitive elevator response as well when FBW trim ref speed is well above actual speed.

 

thx.

 

 

I am doing it now, comparing sensitivity between low and high differences between trim speed and elevator pressure. I didn't find what you saw. Just a steeper and massively different auto elevator pitch when releasing the stick

I am doing it now, comparing sensitivity between low and high differences between trim speed and elevator pressure. I didn't find what you saw. Just a steeper and massively different auto elevator pitch when releasing the stick

Very very strange.....that would mean my system is doing things it totally should not be doing??

 

Just to make sure we are doing the same thing here:

 

I did not mean "sensitivity between high and low differences".....

(that would mean to me that you only checked the difference between having the FBW trim ref speed a little bit out if trim and having it a lot out of trim)

 

I meant

check sensitivity at an extrem + FBW trim speed (extreme ABOVE actual speed).

check sensitivity at an extreme - FBW trim speed (extreme BELOW actual speed)

 

It is best if you stick exactly to my instructions (post 141) .......to make sure we are comparing the exact same things!