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aceridgey

Still Trim issues with Sp1b

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My hotas warthog has a very tiny spike issue where it fluctuate rapidly between 200 and 280 parameter in the pitch axis forward of center, and it disappears when the stick is dead center and reads 0. Setting the null zone in fsx solves it for me.

Good thing you solved the problem.

 

I just wanted to say FSUIPC has a spyke filtering option.

I have never tried it, but maybe that would help too.

 

Anybody know how this function effects PMDG aircraft (positive or negative)?

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Normal Mode Pitch Control

 

The PFCs automatically control pitch to

maintain a relatively constant flight path. This eliminates the need for the pilot to

make control column inputs to compensate for these factors. For turns up to 30°

of bank, the pilot does not need to add additional column back pressure to

maintain altitude. For turns of more than 30° of bank, the pilot does need to add

column back pressure.

 

 

Apparently, not even the Betas are aware of this.

I believe they were...

 

PMDG have said that during their Level D sim time, and after consultation, it was apparent that some back pressure is still required in a turn, regardless as to what the FCOM says.

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For those who test, fly, but do not read the manuals:

 

Reference FCOM, page 9.20.10 from Dec 13, 2010

 

Normal Mode Pitch Control

The PFCs also provide compensation for flap and speedbrake configuration

changes, and turns up to 30° of bank. The PFCs automatically control pitch to

maintain a relatively constant flight path. This eliminates the need for the pilot to

make control column inputs to compensate for these factors. For turns up to 30°

of bank, the pilot does not need to add additional column back pressure to

maintain altitude. For turns of more than 30° of bank, the pilot does need to add

column back pressure.

 

First, I do not see the need for unfriendlyness.

I think PMDG has been trying real hard to get things right and personlly I appriciate they listen to the community as much as they do.

So they desirve a thank you in my opinion....not a slappin.

 

Second, You cant just read a FCTM and say "ok, that is how the things flies.....that is how I will program it".

 

You have to feel it....and that is a problem because even a LEVEL-D sim is not the real thing. The real thing is still nicer and smoother to fly.....believe me.

 

If the FCTM sais "RELATIVE"!

Then that is correct.....the FBW system will hold a relative constant flight path.

Relative means much better than a B737 but not like an airbus in this case.

 

If the FCTM sais "elliminates" then that is not correct.

It does not elliminate the need for pilot input.

Pilot input, albeit small and only here and there, is still required.

What IS elliminated is the CONSTANT need to correct with elevator, during turns etc. You do not need to correct CONSTANTLY like in the 737, but you do need to correct here and there.

 

In the real 777 you do still have to correct here and there during turns.

The real 777 even balloons initially during flap extention believe it or not. (I dont recall what the LEVEL D does).

 

But all in all we are impressively close to the real thing :-)

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Apparently, not even the Betas are aware of this.

 

No.  We were aware of this, but we're also aware of the fact that, despite what the book may say, physics and the rules of the universe prevail.

 

How many days are in a year?  365, right?

Nope. 365.242.

 

Too abstract?  Go look at performance tables.  You think the plane comes off the ground precisely at the value indicated by the takeoff performance table?  Nope.  Why?  Physics.

 

But the manual says it's so!!!  It must be true!!!

 

Interestingly, and much to the chagrin of the group of people who have a distaste for me here, if the manual were always true, that would mean that I would always be right (part of my job is to be a tech writer, so I write and update manuals).

 

 

 

For someone who relies so heavily on written evidence, and who casts aspersions on those who apparently didn't read it, I find it funny that you didn't read the rule to sign your full, real name on the forum, by the way...

kermit-lipton-hed-2013.jpg

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I believe they were...

 

PMDG have said that during their Level D sim time, and after consultation, it was apparent that some back pressure is still required in a turn, regardless as to what the FCOM says.

As Rob says above in post #24, you need to be in good trim and it might need some assistance initially. The point is it shouldn't need continued back pressure in a steady turn up to 30 deg bank. I find if I do it carefully it doesn't. The FCOM is how the FBW is designed to work. As FBW is all software it's not like a mechanical system which might vary according to how it is rigged. It isn't going to fly on rails but it will do as the FCOM says in the right circumstances.

 

This is clearly shown in the ITVV Cathay Pacific 777 flight deck DVD. In that video the Cathay pilot demonstrates a few FBW features in the simulator, including turns. It holds vertical speed zero up to 30 deg bank with no back pressure.

 

 

No. We were aware of this, but we're also aware of the fact that, despite what the book may say, physics and the rules of the universe prevail.

In this case the FBW compensates for the rules of physics for moderate bank angles. That is what it is designed to do. And it does it in the PMDG 777 quite well. I can turn the 777 hands free (i.e. without maintaining back pressure). Can't you?

 

=====================================

 

Back on topic, I had a few problems with the OC and the patch process but SP1b itself is an improvement. Trimming is instinctive. The only problem I have is that short trim inputs don't always move the trim reference speed. You have to press and hold the trim switch before it starts to move. If you try and trim in short bursts nothing seems to happen (unless you are within 5 knots of trim). For normal flying this isn't a problem. If you change bug speed by 30 knots, press and hold the trim for about 3 seconds as you fly the speed change. When at bug speed, if it feels close to trim blip the trim switch to get it exact.

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But all in all we are impressively close to the real thing :-)

Great to read from a real 777 pilot. Do enjoy reading your posts on the 777.

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Can't you?

 

I wasn't the one complaining about the FBW, was I?  :wink:

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I love complex aircraft sims and I fly the 737 NGX all the time, but I'm really scared to purchase the 777 right now.     It just doesn't seem like FSX is truly capable of fully modeling FBW systems properly from what I'm reading in this thread.     If a real B777 pilot is still saying the FBW trim is not working completely right after all of this time, I just don't hold out any more hope.    

 

Maybe the 747v2 won't have to deal with these kinds of issues as it's a more conventional aircraft.      Think I'll hold out until that is released.    

 

 

Signed,

 

Arnold Bruce

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Arnold, I respect your caution but am compelled to say that, should you take a pass on the 777 as a result of this discussion, then you'll be missing out on a great simulation. It really does fly well, particularly after the latest service pack, and I interpret the comments here, all by folks who are actually flying this wonderful beast in FSX, as enthusiastic critiques from knowledgeable sorts who can't help themselves but delve into the finer points of the simulation.

 

But maybe I'm wrong...

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I wasn't the one complaining about the FBW, was I? :wink:

Of course not but you implied the FBW wasn't able to fly the 777 as per the FCOM when it clearly can. That's why I quoted you.

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I was backing up the performance of the sim. Rob's observations back it up as well. I was simply noting that the FCTM can't be used as an absolute. Just because it's in the manuals doesn't mean that it can escape the laws of actuality. That's not to say that the plane won't behave like the FCTM claims, but in the end, physics wins. There's a reason there's a difference between the EST and ACT columns on flight plans: no matter what the books, or the fancy flight planning software says, the real world is a highly variable place. Sure, the FBW might eliminate a lot of the back pressure required, but I wouldn't be surprised if you still have to hold in a little on the roll in (as is supported by the pilot in the thread).

Kyle, adjusting pitch initially, as Rob said, is one thing. Maintaining back pressure in the turn, which you suggested might be necessary is quite another. The latter is what people are expecting to see, more or less. And, more or less that is what the 777 is giving them. Just like Airbus FBW it isn't perfect and there are overshoots and wobbles. I suspect the problem here is some people are expecting it to be exact the entire time, and that isn't the case. Another problem is trying it with a joystick controller. It's not easy to separate pitch and roll inputs perfectly, unlike with a yoke.

 

Also, FBW is a closed loop system, just like an autopilot, and it can eliminate completely the pitch input required of the pilot in level coordinated turn. It's not like a mechanical system which might be misrigged. There is a pitch input of course, but it's provided by the FBW, the pilot doesn't feel it. If course if there's any turbulence, etc then it won't do this perfectly. That's why whenever I've checked this out I've selected "Clear Skies" theme.

 

Let me make this clear, I'm agreeing with you in the main. The only thing I disagree with you on is the idea that it isn't going to work as per the FCOM in practice for reasons of physics and the laws of the universe.

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I'm holiday for one day and the thread goes sour. Tut Tut gentlemen! :-P

 

Now, can people do an experiment for your OP.

 

Settle the aeroplane at a constant altitude and speed 240knots (use ap to stabilise under the above conditions if you want and then obviously disconnect).

 

Then add a small amount of back pressure and select trim nose down (increasing trim ref speed) heavily. Relax your joystick in neutral and wait one second, does the aircraft suddenly pitch?

 

Post your results please,

 

Cheers guys!

 

Alex

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I'm holiday for one day and the thread goes sour. Tut Tut gentlemen! :-P

 

Now, can people do an experiment for your OP.

 

Settle the aeroplane at a constant altitude and speed 240knots (use ap to stabilise under the above conditions if you want and then obviously disconnect).

 

Then add a small amount of back pressure and select trim nose down (increasing trim ref speed) heavily. Relax your joystick in neutral and wait one second, does the aircraft suddenly pitch?

 

Post your results please,

 

Cheers guys!

 

Alex

Hi Alex,

 

I tried your experiment a couple of times, but I didn't get any sudden pitch changes when I released the column, just a smooth pitch down. I was flying the -300ER but I don't think the airframe will make a difference.

 

Cheers

 

Kevin

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Hi Alex,

 

I tried your experiment a couple of times, but I didn't get any sudden pitch changes when I released the column, just a smooth pitch down. I was flying the -300ER but I don't think the airframe will make a difference.

 

Cheers

 

Kevin

 

Same experience here, Kevin, and I tried this with both the 777F and the 300ER.

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I am still getting this issue. 

 

Shall I make a video?

 

Alex

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I am still getting this issue.

 

Shall I make a video?

 

Alex

By all means. Videos and pics are the best way to make sure we are all talking about and looking at the same thing.

I'm holiday for one day and the thread goes sour. Tut Tut gentlemen! :-P

Now, can people do an experiment for your OP.

Settle the aeroplane at a constant altitude and speed 240knots (use ap to stabilise under the above conditions if you want and then obviously disconnect).

Then add a small amount of back pressure and select trim nose down (increasing trim ref speed) heavily. Relax your joystick in neutral and wait one second, does the aircraft suddenly pitch?

Post your results please,

Cheers guys!

Alex

Just one thing......

In your post above you wanted people to try pulling up and then trimming nose down.

But you can only trim in the same direction as you are moving the elevator (in the real 777).

This was simulated correctly in the first version of the PMDG777.

I have not checked in SP1b yet, but if trimming in the opposite direction is now possible then you discovered something that got broke in SP1b. You should also submit a ticket to PMDG in that case.

 

The info about opposite trimming not being possible is a little hidden, but I finally found something in the manuals. See the last paragraph under STABLIZER SHUTDOWN on page 9.20.13 of PMDG777_FCOMv2.pdf.

 

So if you make a video of the example you gave us......and if the PMDG777 is simulated correctly in SP1b, then we should see no STAB trimming taking place when you pull up but trim nose down.

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By all means. Videos and pics are the best way to make sure we are all talking about and looking at the same thing.

Just one thing......

In your post above you wanted people to try pulling up and then trimming nose down.

But you can only trim in the same direction as you are moving the elevator (in the real 777).

This was simulated correctly in the first version of the PMDG777.

I have not checked in SP1b yet, but if trimming in the opposite direction is now possible then you discovered something that got broke in SP1b. You should also submit a ticket to PMDG in that case.

 

The info about opposite trimming not being possible is a little hidden, but I finally found something in the manuals. See the last paragraph under STABLIZER SHUTDOWN on page 9.20.13 of PMDG777_FCOMv2.pdf.

 

So if you make a video of the example you gave us......and if the PMDG777 is simulated correctly in SP1b, then we should see no STAB trimming taking place when you pull up but trim nose down.

 

I'll look into it Rob, thank you so much for your time and effort, I'll get back to you

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The PMDG 777 pitch trim has never worked properly from the very beginning of the release of the RTM version, and at the current SP1b juncture it still does not behave like the real aircraft.      Aceridgey, I am seeing all of the same issues you are reporting;  you are far from alone with your experience.     Pitch trim is unpredictable, inconsistent, and hopelessly imprecise.   

 

PMDG need to be upfront and acknowledge this ongoing issue,  and also be completely honest about their ability to address it.     As it stands, using the 'cheat' trim reference speed indicator on the ADI is the only way to consistently achieve any kind of precise manual trim.    It should not be this way, and if PMDG cannot fix it, they need to state such.    

 

Signed,

 

Arnold Bruce

 

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Trim can't work the same way as the real 777, because you don't have force-feedback yokes that "feel" heavy (trying to pull the pitch axis of the yoke toward the trimmed position) that get 'lighter' the more you trim (trying to pull the pitch axis of the yoke toward the position it is already in).

The "Trimmed position" of a flightsim joystick or yoke is its "middle" position. So to trim out the forces you would either need a really expensive million dollar yoke system with biasies and hydraulics and springs and stuff.

 

Or you need to push the yoke back to its neutral position as you roll the trim.

 

In the real jet you hold the yoke (against the force trying to move it) in the position you need to maintain pitch, then trim the thing till the yoke stops trying to move on its own out of the position it is already in.

 

So if PMDG fix it so it works exactly like the real 777 works, then we will all need to trade in our Saiteks and get Boeing yokes worth more than the average house.

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Trim can't work the same way as the real 777, because you don't have force-feedback yokes that "feel" heavy (trying to pull the pitch axis of the yoke toward the trimmed position) that get 'lighter' the more you trim (trying to pull the pitch axis of the yoke toward the position it is already in).

 

The "Trimmed position" of a flightsim joystick or yoke is its "middle" position. So to trim out the forces you would either need a really expensive million dollar yoke system with biasies and hydraulics and springs and stuff.

 

Or you need to push the yoke back to its neutral position as you roll the trim.

 

In the real jet you hold the yoke (against the force trying to move it) in the position you need to maintain pitch, then trim the thing till the yoke stops trying to move on its own out of the position it is already in.

 

So if PMDG fix it so it works exactly like the real 777 works, then we will all need to trade in our Saiteks and get Boeing yokes worth more than the average house.

What you describe isn't unique to the 777. All aircraft are like this. Artificial feel forces in the real aircraft are not the problem. Most large airliners have such systems. Apart from it being able to trim opposite to column input I don't see much significantly wrong with the current 777 trim simulation in SP1b. Some users are clearly still having problems but I don't think that is to do with the simulation but with the hardware being used and set up inside and outside the 777.

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What the OP and myself are seeing is reference speed trim setting not taking effect until the yoke or joystick are released to neutral, trim reference speed not responding at all to trim switch input, and erratic/unpredictable trim reference speed response to input settings.     I'm sorry, but given PMDG's year-long struggle with the entire manual pitch trim issue, I cannot simply accept that we who are collectively experiencing the aforementioned problems are only plagued with specific individual hardware issues.   

 

I've personally tried using three different joysticks and two different control yokes made by both CH Products and Saitek, respectively.     Individual use of all of these various controllers result in the manual pitch trim anomalies I described in the above paragraph.     The same hardware works excellent with the PMDG 737NGX without any issues at all.

 

I suggest the problem lies in a remaining coding error on PMDG's part and that the issues being experienced are in fact universal among all 777 customers.     Apparently, there are relatively few PMDG 777 users who actually hand fly their simulations except for brief periods during takeoff and approach phases of their flights.    

 

I humbly suggest anyone who doubts my conclusions to try hand-flying their 777 sim from takeoff all the way to cruise altitude (i.e. no autopilot use whatsoever).    The initial pitch down at acceleration height right after takeoff should immediately manifest the trim issue in question.     It simply cannot be done consistently without using the 'cheat' on the ADI speedtape, and this is just not right.     The 777 should trim as effortlessly as the 737NGX, but it unfortunately never has.     

 

Signed,

 

Arnold Bruce

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Some users are clearly still having problems but I don't think that is to do with the simulation but with the hardware being used and set up inside and outside the 777.

Precisely. It's system specific.

 

Works great for me.

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Trimming works perfect for me and as expected if am honest... 

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