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aceridgey

Still Trim issues with Sp1b

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[...] but I sometimes disconnect the stick from the USB connector when I notice axis noise/jitter. Disconnecting helps to get rid of residual volts in the pots and assures proper function while flying...  :blink:

 

Holy cow, amazing tip! I was close to ordering a new set ...

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Holy cow, amazing tip! I was close to ordering a new set ...

 

I can nevertheless highly recommend the Madcatz V1 Stick! Especially when using the PMDG T7 and its FBW.

It is the most permanent precise and durable stick (for an affordable price) I ever had (in 21 years!).

 

The residual volts "phenomenon" in the potentiometers is in no way Madcatz specific. It e.g. depends on how the USB connection is interrupted on PC shutdown. Although unloading residual volts from the USB device on PC shut down in this case would be desirable, it could gernerally cause problems if the currents of any USB device would flow back uncontrolled into the PC's electronic...

 

Fortunately the stick's control panel is able to indicate (on its "null zones" tab) even smallest potentials between the pots and the USB power supply. So you have a chance to unload potentials manually by once interrupting the connection.

 

Last but not least: I like the possibility to unmount the Madcatz V1 stick into two parts for easy transport in narrow cases. So I can take it everywhere with my laptop... 


Claus KUEPPER

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The primary issue I'm seeing with the manual trim issue described in this thread is the way PMDG has modeled the 777 FBW system with two separate modes.     If there is no input detected from the user's joystick (stick in neutral zone), the PMDG FBW system enters a path hold/speed stability mode and will autonomously pitch up or down to achieve the trim reference speed.      By contrast, if input is detected from the user's joystick AND the joystick is deflected completely outside of it's calibrated null zone, the PMDG FBW enters a manual maneuver demand mode.     Maneuver demand mode seems to completely bypass speed stability mode altogether if too much joystick displacement is implemented and this mode will furthermore be oblivious to the trim reference speed.     This latter mode scenario makes it impossible to trim by feel.     

 

What the user must do under the circumstances is to both create a proper null zone for their particular joystick (by trial and error), and trim in such a way that their joystick regularly falls back into it's neutral position during pitch changes.     In this way the PMDG FBW will stay in speed stability mode and provide constant feedback in terms of where the trim reference speed is set.      Again, if the user implements too much joystick deflection at once, the PMDG FBW will enter into and remain in maneuver demand mode which provides no feedback as to trim reference speed.    

 

I don't believe the real 777 FBW works this way; rather, I would assume a true C*U law system would always have a blended pitch rate/speed stability mode in which the pilot always has feedback (via artificial feel) as to how the trim reference speed is set.   PMDG may have had to model a dual mode FBW system to circumvent limitations inherent in the FSX engine, but I can't be sure.    

 

In any event, one must teach themselves how to properly interface with the PMDG FBW logic in order to precisely manage manual pitch trim.     The technique I personally use is to move my joystick in small increments to achieve pitch changes, trim, neutralize controls, then judge by how the aircraft is responding as to where the trim reference speed is set.     The trick is to make small, gradual changes and trim in such a way that your joystick is constantly neutralizing as part of a deliberate process.         

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Yep....you described the changeover between the two modes accurately.

But that is nothing new.

We have noticed this and been saying this for a while now.

 

And PMDG has confirmed it is the only way they could simulte a FBW system.

 

But you CAN trim by feel, and both modes ARE blended and you do not have to go through neutral for this AS LONG AS THE TRIM DEVIATION IS LARGE!

 

When you get close to in-trim........this is where you automatically start to get into and out of the neutral dead band and that is where you get that switch over behavior.

 

 

I have come up with an idea to prevent getting into that switch over region in post 307 (page 21) but nobody has replied to my question there.

 

Since you have noticed, understood and desribed the switchover between the modes so perfectly (mean that, not sarcastic)...... could you do me a favour and tell me what you think of my yoke mod idea in post 307?


Rob Robson

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I think the only way to trim her is have the trim ref speed on the speed tape, I just don't think it's possible to trim by feel 


Alex Ridge

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I think the only way to trim her is have the trim ref speed on the speed tape, I just don't think it's possible to trim by feel

 

yes it is......except for that last little bit of finetuning.

And I agree that displaying the FBW trim ref speed makes getting that last little bit a heck of a lot easier.

 

But dont forget that your system is still not working properly!

Your assymetric trim behavior is not how things are supposed to be.

 

I dont know how you can fix that other then by uninstalling and reinstalling till things are right (no virus scanner running)......till you are blue in the face....... :-(

Or ask PMDG with a support ticket.

But I would not (did not) give up untill I have/had symmetric trim behavior!

 

To be honest I am quite surprised that this lengthy thread has not tickled a bunch of users to giving some feedback as to whether they have symmetrical or symetrical trim behavior.

I would think that many would be interested in identifying such an important possible bug.

 

Maybe it is because most dont notice the difference anyway (autopilot all the way).

Maybe because some feel this thread has gone too deep for them.

If so.....then say so.....I have no problems describing again how to do that overtrim/undertrim flight check that will reveal an assymetric trim problem.

 

That the SP1b install routine does not work correctly for some has been proven by Martin you Aceridgey so far. And Kevin has said his was fine from the get go with SP1b.

But unless some more people start replying here with:

- "symmetrical trim behavior here"

or

- "unsymmetrical trim behavior here, but fixed/not fixed after reinstall of SP1b"

we will never know if many more have the problem, and thus we will never get a fix from PMDG :-(

 

I could care less at this point because mine is working as it should.

That may sound egoistic, but after all the time I have put into this thread if there is no more than two or three guys giving a feedback........then hey, that is the end of the assymetrical problem for me then.

 

I have moved on and will soon (in a few days) try to get the best possible trim by feel experience by messing with rubber bands and springs (yoke modding), dead zones and what not.


Rob Robson

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yes it is......except for that last little bit of finetuning.

And I agree that displaying the FBW trim ref speed makes getting that last little bit a heck of a lot easier.

 

But dont forget that your system is still not working properly!

Your assymetric trim behavior is not how things are supposed to be.

 

I dont know how you can fix that other then by uninstalling and reinstalling till things are right (no virus scanner running)......till you are blue in the face....... :-(

Or ask PMDG with a support ticket.

But I would not (did not) give up untill I have/had symmetric trim behavior!

 

To be honest I am quite surprised that this lengthy thread has not tickled a bunch of users to giving some feedback as to whether they have symmetrical or symetrical trim behavior.

I would think that many would be interested in identifying such an important possible bug.

 

Maybe it is because most dont notice the difference anyway (autopilot all the way).

Maybe because some feel this thread has gone too deep for them.

If so.....then say so.....I have no problems describing again how to do that overtrim/undertrim flight check that will reveal an assymetric trim problem.

 

That the SP1b install routine does not work correctly for some has been proven by Martin you Aceridgey so far. And Kevin has said his was fine from the get go with SP1b.

But unless some more people start replying here with:

- "symmetrical trim behavior here"

or

- "unsymmetrical trim behavior here, but fixed/not fixed after reinstall of SP1b"

we will never know if many more have the problem, and thus we will never get a fix from PMDG :-(

 

I could care less at this point because mine is working as it should.

That may sound egoistic, but after all the time I have put into this thread if there is no more than two or three guys giving a feedback........then hey, that is the end of the assymetrical problem for me then.

 

I have moved on and will soon (in a few days) try to get the best possible trim by feel experience by messing with rubber bands and springs (yoke modding), dead zones and what not.

 

Yesterday I did a full clean install of windows 7, still same issue.

 

Alex


Alex Ridge

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I have come up with an idea to prevent getting into that switch over region in post 307 (page 21) but nobody has replied to my question there.

Since you have noticed, understood and desribed the switchover between the modes so perfectly (mean that, not sarcastic)...... could you do me a favour and tell me what you think of my yoke mod idea in post 307?

 

Hi Rob,

 

Are you referring to increasing yoke tension in order to have a stronger centering force?     I can tell you from personal experience that control yokes like the CH Products models that are designed with a fluid centering mechanism (i.e. do not tightly center) are very difficult to use with the PMDG 777.     Tightly centering controllers on the other hand lend substantially more precision with 777 trimming.      I may or may not be understanding your concept though.     

 

I am completely understanding your frustration over this whole issue though, believe me!      

 

There is a freeware add-on module for FSX called Realtrim which facilitates trimming the elevator/stabilizer with conventional FSX aircraft without having to 'double trim' for both desired attitude AND the effect of the controller's self centering mechanism.    When you trim the 'normal' way with most FSX aircraft, you first must trim for attitude/airspeed, then again trim for the effect of releasing the controller back to it's neutral position.   In a real conventional aircraft of course, you simply trim off force and the yoke remains deflected in trimmed position by aerodynamic force.     The Realtrim module attempts to simulate the real-world trim experience in FSX by facilitating trim in one singular movement as you release the controller after your desired attitude or airspeed is achieved.   In other words, trim will be applied at the same time and in proportion to yoke movement in one single action.     I wonder how the Realtrim concept would work with PMDG FBW?    I'll test it today and report back.     

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Yesterday I did a full clean install of windows 7, still same issue.

 

Alex

Unbelievable......that is weird.

 

A real clean install?.........where you had to release the PMDG777 key via the CDU so you could use it again on your fresh install?

(If your fresh install did not ask for the 777key then it was not a fresh Win7 install. Not that a fresh Win7 install should be required, a reinstall of the 777 and SP1b should have been enough, but just saying)

 

Do you have an anti vir scanner running?

or

UAC still active

or

Windows defender active?

 

And, do you use Windows Generic game controller driver or a driver made by the manufacturer of your yoke/stick?

(my old CHpro yoke never worked right on the generic Win7 driver. Although I did not have SP1b installed correctly at that time......it might still have something to do with assymetric trim behavior).

Hi Rob,

 Are you referring to increasing yoke tension in order to have a stronger centering force?    

 

Yes

 

I can tell you from personal experience that control yokes like the CH Products models that are designed with a fluid centering mechanism (i.e. do not tightly center) are very difficult to use with the PMDG 777.     Tightly centering controllers on the other hand lend substantially more precision with 777 trimming.      I may or may not be understanding your concept though.

yes you got it right. Good to know that modding my yoke might help.

 

 

I am completely understanding your frustration over this whole issue though, believe me!      

 

I am really not as frustrated as it seems with the PMDG777.

 

More frustrated with the lack of community feedback.

Maybe we should open up a new thread, asking as much fellow simmers to do the overtrim/undertrim flight test?!

 

 

As I said, I can trim by feel now.

I can also fine trim it by feel allbeit with more difficulty than on the real thing.

After a few times of letting go at neutral I can trial and error my way to being in-trim and with the FBW trim ref speed displayed it is even easier.

 

A yoke mod is just something I think is fun to do and if it helps making trimmby feel easier than that would be nice......but even if not......now that my out of trim response is symmetrical...... I see no reason why I could not enjoy this 777.

 

 

There is a freeware add-on module for FSX called Realtrim which facilitates trimming the elevator/stabilizer with conventional FSX aircraft without having to 'double trim' for both desired attitude AND the effect of the controller's self centering mechanism.    When you trim the 'normal' way with most FSX aircraft, you first must trim for attitude/airspeed, then again trim for the effect of releasing the controller back to it's neutral position.

I have never noticed that. You sure about that? Can you give an example of that behavior.

 

If that is true then the PMDG777 behavior is inherrent to FSX......and not due to the two FBW modes the PMDG777 has been programmed with.


Rob Robson

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Unbelievable......that is weird.

 

A real clean install?.........where you had to release the PMDG777 key via the CDU so you could use it again on your fresh install?

(If your fresh install did not ask for the 777key then it was not a fresh Win7 install. Not that a fresh Win7 install should be required, a reinstall of the 777 and SP1b should have been enough, but just saying)

 

Do you have an anti vir scanner running?

or

UAC still active

or

Windows defender active?

 

And, do you use Windows Generic game controller driver or a driver made by the manufacturer of your yoke/stick?

(my old CHpro yoke never worked right on the generic Win7 driver. Although I did not have SP1b installed correctly at that time......it might still have something to do with assymetric trim behavior).

Yes

 

yes you got it right. Good to know that modding my yoke might help.

 

 

I am really not as frustrated as it seems with the PMDG777.

 

More frustrated with the lack of community feedback.

Maybe we should open up a new thread, asking as much fellow simmers to do the overtrim/undertrim flight test?!

 

 

As I said, I can trim by feel now.

I can also fine trim it by feel allbeit with more difficulty than on the real thing.

After a few times of letting go at neutral I can trial and error my way to being in-trim and with the FBW trim ref speed displayed it is even easier.

 

A yoke mod is just something I think is fun to do and if it helps making trimmby feel easier than that would be nice......but even if not......now that my out of trim response is symmetrical...... I see no reason why I could not enjoy this 777.

 

 

I have never noticed that. You sure about that? Can you give an example of that behavior.

 

If that is true then the PMDG777 behavior is inherrent to FSX......and not due to the two FBW modes the PMDG777 has been programmed with.

 

None of the above mate,

 

Full and complete fresh install, 

 

Alex


Alex Ridge

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I was thinking about the complexity of modeling the C*U Law without access to RW data / code, and

sometime ago when a 777 was released for X-Plane 10 I tried to tweak it's FDM to come closer to what I  understood

the Boeing FBW does...

 

The way it was done, but I left the project when I gave up on XP10, used a mix of XP's built in stability

augmentation system, and the fine tuning of some aircraft flight dynamics parameters.

 

Now, in MSFS / P3D, it is perfectly possible to design stable aircraft, and in particular speed stable.

Why not, for future work, consider an approach based on the fact that, as far as I understood from what 

I read in the many threads here at the PMDG forums, the C*U law creates a sensation of speed stability 

that is similar to your typical GA aircraft, deviating from it only when:

 

1) there are configuration changes, like flaps / slats and gear being operated

2) the aircraft enters a steady coordinated turn with bank not higher than 30º

 

Why not build the aircraft making it speed stable, although I don't know if it is possible to have info

on the short term and phugoid oscillations, and then implement auto-trimming only when in 1) we want to

matian the trimmed speed, and in 2) the pilot has to use just slight pressure ( back pressure ) on the column

to maintain the turn?

 

Auto trimming should use the standard MSFS pitch trim channel, even if graphically on outside views 

and in the EICAS STAT page the visuals might show the elevator moving first and then the stabilizer moving to

remove it's effort and deflection? Landing flare compensation and stall and overspeed protection could also

be modeled through the default MSFS elevator trim.

 

This way, the situation described by some of the users, that they have to play with joystick nullzone areas, and

or sensitivity, and even so the trimmed "forces" aren't always represented like in RW, might get solve?


Flight Simulation is the Virtual Materialization of a Dream...

 

 

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I think the only way to trim her is have the trim ref speed on the speed tape, I just don't think it's possible to trim by feel 

 

Yep, this is the only way I'm able to do it currently.

 

John


Boeing777_Banner_Pilot.jpg

 

- John Drago

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In a real conventional aircraft of course, you simply trim off force and the yoke remains deflected in trimmed position by aerodynamic force. The Realtrim module attempts to simulate the real-world trim experience in FSX by facilitating trim in one singular movement as you release the controller after your desired attitude or airspeed is achieved. In other words, trim will be applied at the same time and in proportion to yoke movement in one single action. I wonder how the Realtrim concept would work with PMDG FBW? I'll test it today and report back.

 

Hi Orlando!

Just want to thank you for your great inputs! Your explanations are really exciting to read, understandable and helpful!

Would be interesting to hear about the "Realtrim module" effects on the PMDG T7 FBW.

 

 

Why not, for future work, consider an approach based on the fact that, as far as I understood from what

I read in the many threads here at the PMDG forums, the C*U law creates a sensation of speed stability

that is similar to your typical GA aircraft, deviating from it only when:

 

1) there are configuration changes, like flaps / slats and gear being operated

2) the aircraft enters a steady coordinated turn with bank not higher than 30º

 

 

The presence of only two AUTOTRIM activation events (1= config changes + 2= std turns <=30° bank) are in fact (AFAIK) differentiating in essence the T7 FBW from the Airbus FBW.

While the "Bus" is based/computed on the "stable platform concept" ("flying carpet" I would call it), the Boeing FBW is most basically doing what FBW means: stearing the control surfaces alternatively in order to replace traditional steel wirings directly connected to the columns. And it does this in order to make it comparable to the Boeing family of A/Cs...

EDIT: it just came into my mind that one could probably compare the T7's FBW pitch/bank behaviour to the B737 CWS concept which is pitch and bank stable without really taking ALT, V/S or HDG into consideration. With A/T on (= constant speed and within limts like clean config close to 230kts) this B737 CWS pitch+bank stability leads to B777 FBW steering quality. (Just a thought.)

 

But this discussion of PMDG T7 FBW is somewhat "pre-SP1B", as PMDG has stated that they originally were mislead by an "unreliable" source of information about the FBW system's design. So PMDG originally went too much in the Airbus direction with its T7. They have changed it completely.

I did not fly the T7 prior to the SP1B too much. My experience in flying the T7-SP1B is fantastic though and steering it via a Madcatz V1 stick makes a lot of sense.

Because a real T7 yoke is not really affordable, a software like Orlando mentioned ("Realtrim module") could be a solution for different kinds of sticks and yokes out there...

As PMDG has put a lot of effort in "reloading" the FBW concept, there would be not much space in reprogramming it all over again. Probably they are already working on a module to adapt to different input devices?

Edited by vr-pilot

Claus KUEPPER

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Yep, this is the only way I'm able to do it currently.

 

John

Did you check that SP1b installed corrcetly amd that you have symmeyric trim behavior?

 

Here is the experiment again to test for that.

If you get results as I had during that test, then SP1b is not correctly installed!

 

 

Level in 5000ft or so.

 

1)

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. This is normal behavior as confirmed by PMDG.

 

2)

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

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 this extreme out of trim condition.

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!

 

So trim in the two out of conditions was not the same. I call this assymetric trim behavior.

 

This is a problem introduced by SP1 and should be fixed in SP1b (for me it is fixed).


Rob Robson

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I was thinking about the complexity of modeling the C*U Law without access to RW data / code, and

sometime ago when a 777 was released for X-Plane 10 I tried to tweak it's FDM to come closer to what I  understood

the Boeing FBW does...

 

The way it was done, but I left the project when I gave up on XP10, used a mix of XP's built in stability

augmentation system, and the fine tuning of some aircraft flight dynamics parameters.

 

Now, in MSFS / P3D, it is perfectly possible to design stable aircraft, and in particular speed stable.

Why not, for future work, consider an approach based on the fact that, as far as I understood from what 

I read in the many threads here at the PMDG forums, the C*U law creates a sensation of speed stability 

that is similar to your typical GA aircraft, deviating from it only when:

 

1) there are configuration changes, like flaps / slats and gear being operated

2) the aircraft enters a steady coordinated turn with bank not higher than 30º

 

Why not build the aircraft making it speed stable, although I don't know if it is possible to have info

on the short term and phugoid oscillations, and then implement auto-trimming only when in 1) we want to

matian the trimmed speed, and in 2) the pilot has to use just slight pressure ( back pressure ) on the column

to maintain the turn?

 

Auto trimming should use the standard MSFS pitch trim channel, even if graphically on outside views 

and in the EICAS STAT page the visuals might show the elevator moving first and then the stabilizer moving to

remove it's effort and deflection? Landing flare compensation and stall and overspeed protection could also

be modeled through the default MSFS elevator trim.

 

This way, the situation described by some of the users, that they have to play with joystick nullzone areas, and

or sensitivity, and even so the trimmed "forces" aren't always represented like in RW, might get solve?

You are I believe correct that PMDG has not designed this to work how the real C*U works. The end result is  good, but it has compromises which shouldn't be necessary. Reality is much simpler than the model PMDG have implemented. The Introduction Manual talks about the FBW being a simulation of a simulation. I've never read anything like that about FBW control systems anywhere else and my understanding of Boeing's C*U is that it is much less complicated than that.

 

As for designing basic speed stability, this is a red herring. The 777 aerodynamically is speed stable. If you installed conventional controls it would fly like a 747 does. Once you introduce FBW and autotrim the inherent speed stability goes away and has to be reintroduced back in the FBW system. So you are back where you started. Far better to do the FBW properly than make yet another complex solution.


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