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...

Airbus FBW is not a "magic carpet" at all. That makes it sound like a permanent autopilot with just some overall direction commands from the stick. Airbus and Boeing FBW are remarkably similar. Both control pitch as a mixture of g demand and constant attitude. Both control roll inputs as a roll rate demand. If you don't get anywhere near the flight envelope limits there is no other input modification, the pilots input drives the surface. The main difference is that the Boeing does not trim for speed changes and the envelope protection is done by increasing control feedback forces rather than limiting control input demands.

 

The 777 FBW does make it feel like a conventionally controlled airliner, but the Airbus system is just as pilot friendly to fly manually and you don't need to trim in normal law either.

 

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.)

Actually the 737 CWS is rather like a C* control system, more like the Airbus than the 777 as it trims all changes, including speed.

 

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?

BIB: This is the crux of things. Having put so much work into making the 777 FBW behave more or less like the real 777 I can't imagine PMDG wanting to go back to the RTM version and add C*U correctly to get it slightly closer. If that had been done in the first place there would not be the problem with trimming, there would be no need to reduce elevator effectiveness to increase the necessary stike/yoke inputs and so give us more "feel" to trim by.

 

In my opinion it's close enough for practical purposes. I'm enjoying flying it, especially the -300. I don't like the elevator effectiveness reduction, and there are other ways to achieve the same effect. But it's PMDGs product and their design decision. When flying it isn't an issue. It wouldn't be the first time users have to accept a compromise on system fidelity in FSX.

I have followed this thread with interest but have not posted before as fortunately I don't have problems trimming the PMDG 777. I have an Elite yolk which has a strong spring and this makes it easy to find and remain at the neutral point. I previously had a CH yolk with a far weaker spring and on changing to the Elite yolk I immediately found it a lot easier to trim all my simulated aircraft. 

 

 

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.

Therefore Rob I think your idea to mess about with springs etc could well be worth the effort. It would also be interesting to know what yolk Kevin and Martin use?

It is exactly for this mode switch over and the resulting pitch change that I want to modify my yoke.

Because if I increase the yoke force enough so that even when I am only a little out of trim I still feel considerable push/pull force, then I might not get into the CDU dead band untill actually IN-TRIM.

And then the strong pitch moment should never occur, right?

 

Does that make sence?"

Yes it does make sense, increasing control force versus deflection to more realistic levels will help considerably. But you could also reduce the dead band in the CDU to keep yourself in trimming mode for longer. Unless you are already at the minimum you can safely use.

 

For me the default 1% band is about right and I don't notice the switching in and out effect. I wonder if the problems Alex is suffering are related to adjusting this setting to suit his hardware better?

Airbus FBW is not a "magic carpet" at all. That makes it sound like a permanent autopilot with just some overall direction commands from the stick

 

Hi Kevin!

But this is what the A330 Instructor handbook tells the instructors to teach their students:

(quote)

Hence STICK FREE, the A/C maintains the flight path even in case of speed changes. Furthermore, STICK

FREE in case of Configuration changes, or thrust variations, etc… the pitching moment effects are reduced by

the feedbacks in the control law itself and compensated for by precommands. With STICK FREE in

turbulence, small deviations do occur on the flight path but with a tendancy of the A/C to regain a steady

condition.

, As a consequence the A/C is a STABLE PLATFORM and AUTOTRIMMED; it needs to be flown with minor

corrections from the pilot on the stick, when the A/C deviates from its intended flight path.

(unquote; remark: the capitals are the original format)

So IMO there is a "flying carpet" idea behind the Airbus FBW code which means a permanent autopilot which accepts some supervised overrides by the pilot.

(I know you don't like my opinion, but in this life you won't convince me of the opposite, sorry B)  )

 

 

Airbus and Boeing FBW are remarkably similar.

 

Sorry, but (exaggeratedly) I can not follow beyond the similarity of the three letters. Or let me tell it this way: Boeing's FBW will leave less question marks in case of doubt as it is by far more straight than Airbus' roundabout fashion programing:

you remember our side stick priority discussion. (Yes, it belongs to the FBW subject!) For me the "logic" behind these buttons is already "comedian style", but it's a matter of taste probably.

 

OFF-TOPIC:

Don't get me wrong. You are for sure a very knowledgeable person with insights/internals to Boeing and Airbus airline operations and training, which I don't have. I might be particularly wrong, and I once asked you if you are "married with Airbus" but your answer was no (as you might be married with your wife actually), BUT everytime we got into the discussion about Airbus' philosophy your arguments seem to come directly from their latest 4-color glossy brochure. You never accept even a touch of criticism concerning Airbus. :ph34r:

 

ON-TOPIC:

IMO Boeing has a lot of (good) reasons to differentiate from the Airbus philosophy.

So here at the FBW-crossroads of Boeing and Airbus it is clear that an FSX simulation using a "dead" Airbus sidestick would have been much easier than the "alive" Boeing columns...

Therefore Rob I think your idea to mess about with springs etc could well be worth the effort. It would also be interesting to know what yolk Kevin and Martin use?

A very old Microsoft sidewinder Pro joystick. :wink:

BUT everytime we got into the discussion about Airbus' philosophy your arguments seem to come directly from their latest 4-color glossy brochure. You never accept even a touch of criticism concerning Airbus. :ph34r:

Both Airbus and Boeing have very good safety records, so criticise Airbus if you like, subjectively disfavour the FBW philosophy, but it works, and safely too.

 

It should be mentioned of course, that older Boeing aircraft, like the 737, 727's and 747's had higher rates of fatal accidents. Airbus pilots love flying, that should tell us a lot.

 

Rob will tell us off for diverting the thread, so I better say no more. :smile:

None of the above mate,

 

Full and complete fresh install, 

 

Alex

You must have only browsed through my post because non of the above is not possible.

 

- you either had to enter a new key code or not.

If you did, then your install is really new and I suggest you contact PMDG to let them now that their SP1b installer is not correcting the assymetric problem that was introduced with SP1

If you did not have to enter a new key....then reinstall Win7 but use the option to format C.

 

- And you either use the generic Windows Game controller driver or you use your products own driver. But none is not possible.

 

I was going to suggest deleting your products driver and reinstalling it and then recalibrating your joke/joystick. (but on a really new/fresh Win7 install (after format C) this will not help ofcourse and all you can do then is contact PMDG.

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?

It is kind of up to PMDG how they code the FBW system isnt it?!

 

I think PMDG is pretty much done with the FBW system other than maybe fixing the SP1b installer if there is something wrong with it.

But we would need to offer a lot more proof of that before they will even look into it I am afraid.

 

Your suggestions might be good or not, I do not know because I am no programmer, but you would have to make those suggestions to PMDG directly.

Probably they are already working on a module to adapt to different input devices?

I do not think so......would be nice, but too much stuff out there......but I think that is why we have the deadzone thingy in the CDU.

I guess they read this forum Rob :-) so, while sharing my thoughts with you and other simmers, I guess I am also sharing them with PMDG :-)

 

I am also less than credited to discuss the results of SP1b here because I actually do not even have FSX installed, less the 777. 

 

The reason to think about it the way I expressed in my post has more to do with the experience I had with a 777 product that sometime ago became available  ( before the PMDG 777 ) to another simulation platform I used to share with FSX - X-Plane10.

 

That other product modeled practically nothing of what resembles the C*U law, yet, some airbus models for X-Plane 10 have been capable of approaching rather acceptably the C* law, so, I guess it could be easier to do it in X-Plane 10, but I am not sure...

 

One aspect is that X-Plane 10 includes it's own FBW / Augmented Stability system, which is directly incorporated into their "plane-maker" application. I used that with the 777 to try to somehow approach 1) and 2) in my post above, and while I didn't really get the ultimate results I wanted to, I confess I was not dissatisfied with the outcome. That 777 is designed to be speed stable, as a 747 or 767, 757 are, and then we can use the Stability Augmentation System to tweak some aspects of the ( natural ) stability ( static and dynamic ) pitch, roll, yaw and coupled responses to flight configuration changes or other induced perturbations.

 

What I think is that, if the solution you have found implies modification to the joystick deadzones, responses and even intervening with the hardware by making it stiffer, etc..., then it is going beyond what most simmers are willing to do, specially because it might affect their experience with other models / simulators.

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.

 

In my opinion the REAL difference between the two is that Boeing gives their pilot feedback in the way of moving controls and force feedback.

The need to trim for speed on Boieng is a difference too ofcourse, but not as major as feedback.

 

In Airbus you feel and see nothing as far as I know.

 

Otherwise the two are quite similar.

During manual flight they both try to maintain the pilot introduced flight path.

 

Both Airbus and Boeing will correct for or help with banking, config changes, turbulence wind gusts, auto rudder, assymetric thrust compensation (airbus?), yaw dampening, envelope protection, by correcting with flight controls and trim.

Airbus seems to correct more....as in more stiff or with less deviation..... than Boeing if I interpret Airbus stories correctly.

 

During landing flare I think Airbus is different again.

In my opinion it's close enough for practical purposes. I'm enjoying flying it, especially the -300. I don't like the elevator effectiveness reduction, and there are other ways to achieve the same effect. But it's PMDGs product and their design decision. When flying it isn't an issue. It wouldn't be the first time users have to accept a compromise on system fidelity in FSX.

Well said and I totally agree. Flies very very nice, final exact trim is a bit difficult on my yoke (cause it is too light build) but might be improvable with modding. If not, then displaying FBW trim speed is a great help.

I have followed this thread with interest but have not posted before as fortunately I don't have problems trimming the PMDG 777. I have an Elite yolk which has a strong spring and this makes it easy to find and remain at the neutral point. I previously had a CH yolk with a far weaker spring and on changing to the Elite yolk I immediately found it a lot easier to trim all my simulated aircraft. 

 

Therefore Rob I think your idea to mess about with springs etc could well be worth the effort. It would also be interesting to know what yolk Kevin and Martin use?

Thx for that feedback....guess I have an other project then (still working on my throttle also).

Yes it does make sense, increasing control force versus deflection to more realistic levels will help considerably. But you could also reduce the dead band in the CDU to keep yourself in trimming mode for longer. Unless you are already at the minimum you can safely use.

 

For me the default 1% band is about right and I don't notice the switching in and out effect. I wonder if the problems Alex is suffering are related to adjusting this setting to suit his hardware better?

And thanks Kevin as well. Appriciate your input a lot!

 

Interesting......I thought I would have to INCREASE the deadband.....

For me it seemed to work better between 5-10%

So the opposite.

 

To be honest the deadband zone was not as noticeble as I imagined.

1%-----5%------10% I could not see much difference......a little maybe but not much.

So little I might have made it up.....hard to tell

 

But theoretically I was thinking the following:

Having a large CDU deadband I figured that when you are out of trim.......and holding a certain pressure.......then you start trimming and simultanuously you have to start reducing yoke deflecting (push/or pull).........trim by feel right........at some point you are getting close to in-trim and if this situation is reached while still having a descent deflection (as is the case with a larger dead band zone I was reasoning) then the chance of feeling/noticing the small out of trim situation would increase....no?

 

And because of that I have left it at 10% for now.

Hence STICK FREE, the A/C maintains the flight path even in case of speed changes. Furthermore, STICK

FREE in case of Configuration changes, or thrust variations, etc… the pitching moment effects are reduced by

the feedbacks in the control law itself and compensated for by precommands. With STICK FREE in

turbulence, small deviations do occur on the flight path but with a tendancy of the A/C to regain a steady

condition.

, As a consequence the A/C is a STABLE PLATFORM and AUTOTRIMMED; it needs to be flown with minor

corrections from the pilot on the stick, when the A/C deviates from its intended flight path.

 

I see no difference from Boieng there........same same.

 

 

Well.....unless.....

 

If you set for example a 20 degrees banked turn while descending with 500ft/min and let go of the yoke the Boeing will try to smooth out outside disturbences (both pitch and roll) in order to maintain that.

But if the airplane IS disturbed enough to change to for example 15 degrees bank and 400ft/min then it does not go BACK to the initial path.

So it will try to prevent you getting of your patch......but it will not put you back ON it.

Which is why I allways describe it as a system that helps you, but you cant let go and expect things to stay constant.

 

Maybe that is where Airbus is different?

Maybe it rememers (desired path set in memory) those 20degrees and 500ft/min and corrects you right back to it even if you were momentarily at 15 bank and 400ft/min?

A very old Microsoft sidewinder Pro joystick. :wink:

Both Airbus and Boeing have very good safety records, so criticise Airbus if you like, subjectively disfavour the FBW philosophy, but it works, and safely too.It should be mentioned of course, that older Boeing aircraft, like the 737, 727's and 747's had higher rates of fatal accidents. Airbus pilots love flying, that should tell us a lot.Rob will tell us off for diverting the thread, so I better say no more. :smile:

Shoot.....you are right, got sucked right into that one ;-)

 

Well, as long as we dont start fighting over what plane is better.......

 

Hey Martin.....old joystick with original drivers or Windows generic driver?

IMO Boeing has a lot of (good) reasons to differentiate from the Airbus philosophy.

So here at the FBW-crossroads of Boeing and Airbus it is clear that an FSX simulation using a "dead" Airbus sidestick would have been much easier than the "alive" Boeing columns...

FSX simulation.....maybe, no idea, but real life not.

 

I have many colleges that recently changed from (years of) Airbus to the 777.

They all hate the yoke in cruise and miss their little table.

And they think it is silly to have to trim.

And they loved how stable the Airbus was.

 

And I understand all that and agree on some points, but if there is one thing they all admit, then it is that the 777 with its yoke handflies (much) better.

Specially during take of and landing in cross wind r other tricky situations!

Which I tend to find more important than all other things.

What I think is that, if the solution you have found implies modification to the joystick deadzones, responses and even intervening with the hardware by making it stiffer, etc..., then it is going beyond what most simmers are willing to do, specially because it might affect their experience with other models / simulators.

Absolutely agree with that. Rediculous ofcourse to have to mod your yoke!

 

Interesting stuff about Xplane.....I just can not relate to it though, sorry.

I installed Xplane9 once and deinstalled it again after two/three days of fighthing with the settings.

 

I might try Xplane64bit at some point though.

Hey Martin.....old joystick with original drivers or Windows generic driver?

It's so old that Microsoft stopped supporting it Rob, so no driver available from Microsoft. So yes, Windows generic.

 

Buttons assigned via FSX settings.

 

It's a bit slack these days, but still seems to do the trick.

It's so old that Microsoft stopped supporting it Rob, so no driver available from Microsoft. So yes, Windows generic.Buttons assigned via FSX settings.It's a bit slack these days, but still seems to do the trick.

Thx for the info.

 

The thing is that my previous yoke (untill two weeks ago) was also very old, analog (not usb) and not supported anymore......so also Win7 generic driver.

 

I now have the Saitek Cessna yoke and it came with drivers ofcourse.

 

 

I was thinking that maybe the problem is the Windows generic driver.

Maybe SP1b does not like it?

Both Airbus and Boeing have very good safety records, so criticise Airbus if you like, subjectively disfavour the FBW philosophy, but it works, and safely too.

 

Just a quick note:

I am not favouring the Boeing FBW because I would eventually think that the Airbus FBW is completely nonsense. Airbus did a lot to make Pilots' life easier by reducing the workload through automation, thus making the operation more safe than conventional aircraft/cockpit designs of the late 80s.

I also was 100% convinced of the "new concept's" superiority. But over the years my view on things changed, inter alia because when the automation technique fails, the explanations always end in "lousy pilots were unable to operate perfect flying machines".

The Airbus "man-machine-interface" is based on the thought that computers are better pilots. And as long as "computers make no mistakes" the blame game against pilots will not bring constructive results...

[...]

 

 

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!

[...]

 

 

Hi there,

 

My results on both tests. As soon as I put the trim ref speed above or below, I had to apply a lot of yoke, but my trim did not change at all during the stages of manual flight.

 

~Alex

Hi there,

My results on both tests. As soon as I put the trim ref speed above or below, I had to apply a lot of yoke

That is good......it means SP1b is working correctly as you have a symmetric (or identical) response in both situations.

but my trim did not change at all during the stages of manual flight.

 

Sorry, but I do not know what you mean by that :-(

That is good......it means SP1b is working correctly as you have a symmetric (or identical) response in both situations.

Sorry, but I do not know what you mean by that :-(

 

The trim on the FCTL page didn;t change going in manual flight (with a large difference in trim ref)