Jump to content

Sign in to follow this  
aceridgey

Still Trim issues with Sp1b

Recommended Posts

Yes animations has nothing to do with what the airplane is supposed to do.Logically they should be in sync.But just because animations are fine would not imply that the underlying logic is also fine.

 

Please wait guys, It not all just to do with animations. But if they are behaving as is suggested by the FBW manual, lets just trust that maybe, just maybe, PMG have that linked to the FDE, .air file etc; (which I for one would give then the benefit of the doubt on, given on how they go for fine details in so many aspects of this sim).

 

Just for starters trying to show that if that is what you are seeing on the ground, your control setups are fine.

 

Wait, the plot thickens. Now in the east its 10:30pm. I am bushed and I have a video to make to go with the second post. Sorry but tomorrow evening (EU, USA) is soonest I can do it.

 

Rob


Robin Harris
 

Share this post


Link to post
Share on other sites

Untill I get a response of how the system is supposed to work (in respect to elevator authority) by PMDG - nothing is cleared up.

 

As do going outside and looking at aircraft control surface - as far as I know animations have nothing to do with how the airplane acutally reacts.

 

I think you could make the animation of the elevator going up when you push on the yoke and still have the aircraft pitch down in flight.....but I could be wrong.

Correct. You could assign a 3D model of a brick and it would fly exactly the same.

 

Please wait guys, It not all just to do with animations. But if they are behaving as is suggested by the FBW manual, lets just trust that maybe, just maybe, PMG have that linked to the FDE, .air file etc; (which I for one would give then the benefit of the doubt on, given on how they go for fine details in so many aspects of this sim).

 

Just for starters trying to show that if that is what you are seeing on the ground, your control setups are fine.

 

Wait, the plot thickens. Now in the east its 10:30pm. I am bushed and I have a video to make to go with the second post. Sorry but tomorrow evening (EU, USA) is soonest I can do it.

 

Rob

I have no doubt that PMDG's external animations are following up on their simulation correctly. For example when you trim on the ground the stabiliser moves in 0.25 unit steps and this is clearly visible from the outside view. The doubt is whether the FBW trim model is working correctly in flight, not whether the surface animations are moving correctly in response.

 

Also, watching the stabiliser moving correctly on ground does not prove the user's hardware calibration set up is correct. The way the stab is controlled in flight is completely different and if the stab wasn't moving correctly on ground it would be immediately obvious as you prepared for takeoff.


ki9cAAb.jpg

Share this post


Link to post
Share on other sites

 

 


OK video is taking a while to upload. I will post now and make an edit with the link later.

 

Cannot edit my post #192;

 

Here is the link to the Youtube video to go with my post #192. Seems simple enough, but just laying the foundation here for a more complex examination.

 

http://www.youtube.com/watch?v=fJ8DMvDqNuk&feature=youtube_gdata_play


Robin Harris
 

Share this post


Link to post
Share on other sites

I seem to remember Kyle suggesting early on that you should fly the plane exactly like a cessna. Regardless of whether the 777 is programmed correctly or not, I cannot fly it like this.


captainhenrychen-1.jpg


Boeing777_Banner_Pilot.jpg


 


James Bennett

Share this post


Link to post
Share on other sites

Cannot edit my post #192;

 

Here is the link to the Youtube video to go with my post #192. Seems simple enough, but just laying the foundation here for a more complex examination.

 

http://www.youtube.com/watch?v=fJ8DMvDqNuk&feature=youtube_gdata_play

 

Yep Robin,

 

Our issues have nothing to do with behaviour on the ground, it's to do when the FBW trim is activating itself

 

Alex


Alex Ridge

Join Fswakevortex here! YOUTUBE and FACEBOOK

Share this post


Link to post
Share on other sites

Also, watching the stabiliser moving correctly on ground does not prove the user's hardware calibration set up is correct

 

Why not? Care to elaborate. To me it IS showing that hardware is giving the required inputs? If I am getting this on the ground that reflects how my controls are set up, and it follows then that what I experience in the air (a functioning FBW system) will, in all likelihood, follow (hardware being unable to sense grounded from airborne)

 

 

 

The way the stab is controlled in flight is completely different

 

Ah ha, oh Yes, Yes! Then you should be having no problem's with PMDG's implementation / modelling in the air. You should be totally happy with, and understand fully, why the stab trim is only kicking in with elevator in neutral (and the meaning / reason for PMDG's null zone "tweak"). If you are in this camp, then ignore my further postings in this thread, and enjoy the FBW experience!

 

I sense negativity to what I have only just started. Is that because some pilots and systems fundis know what is coming up, and do not want this information exposed? Have you just re-read the article I quoted and twigged on, had that ah-ha moment?

 

Common, lets approach this with an open mind! (But I expected flak - lots more to come)

 

Rob


Robin Harris
 

Share this post


Link to post
Share on other sites

I seem to remember Kyle suggesting early on that you should fly the plane exactly like a cessna. Regardless of whether the 777 is programmed correctly or not, I cannot fly it like this.

 

I've been suggesting this for quite some time, yes.  I can't, for the life of me, figure out how you can't trim this plane like you could with any other plane, though.  If people simply dispensed with the idea of "golly, this is a new system, and new things are scary," I can nearly guarantee that at least half of these threads wouldn't be here.


Kyle Rodgers

Share this post


Link to post
Share on other sites

If you chaps think it worthwhile to move things along I'll file a ticket as well.  James Bennett best describes my situation. Despite the sterling efforts of Rob Robson and co (and thank you hugely for going to such lengths to try and figure this all out guys) the technicalities of all this are a bit beyond me I'm afraid.  Suffice to say, I don't find this a particularly pleasant bird to hand fly, with or without the trim ref speed marker.  I have no difficulties trimming by feel in the NGX etc etc.

 

 

 


I too seem to have the issue of no trim being applied until controls are neutral input wise. This means when you trim you can't feel when you're in trim until you release the column to neutral, meaning you're guessing effectively.

I have severe difficulty on approach and landing, it seems I can't get her in trim for landing even when I'm at a constant speed, I have to maintain back pressure on the yoke otherwise the nose drops, and trim isn't applied until a few seconds after neutralising the controls and therefore I've dipped out of the glideslope by miles.

None of it feels intuitive like it should.

 

James, if you don't mind I'll file a ticket essentially paraphrasing what you've described here, if you have no objections?

 

Cheers


Richard Wells

 

Share this post


Link to post
Share on other sites

I dont know Kyle..i have been on the defending side .but i have been testing the 300 which works for me.able to trim by feel.but doing the same in 200 does not work..the trim gets applied or atleast makes an effect of control column is released to neutral..and my guess is people with less null zone are more prone to than people having bigger null zones.


Thanks,
Pankaj Dekate
 

Boeing777_Banner_Pilot.jpg

Share this post


Link to post
Share on other sites

Why not? Care to elaborate. To me it IS showing that hardware is giving the required inputs? If I am getting this on the ground that reflects how my controls are set up, and it follows then that what I experience in the air (a functioning FBW system) will, in all likelihood, follow (hardware being unable to sense grounded from airborne)

 

No one reporting problems with controlling the trim in flight is reporting problems with the trim behaviour on ground. On ground there is no connection via the FBW with elevator for a start and that is where column position comes in. So proving the inputs work on ground is not proof it will work in flight.

 

 

Ah ha, oh Yes, Yes! Then you should be having no problem's with PMDG's implementation / modelling in the air. You should be totally happy with, and understand fully, why the stab trim is only kicking in with elevator in neutral (and the meaning / reason for PMDG's null zone "tweak"). If you are in this camp, then ignore my further postings in this thread, and enjoy the FBW experience!

 

Hey, you talk about my supposed negativity then make this sarcastic comment. People in glass houses, etc.

 

The stab control is different in flight, in the real 777 and in the PMDG simulation. Me saying that does not make me completely satisfied with the current trim simulation far from it.

 

 

I sense negativity to what I have only just started. Is that because some pilots and systems fundis know what is coming up, and do not want this information exposed? Have you just re-read the article I quoted and twigged on, had that ah-ha moment?

 

 

 

Common, lets approach this with an open mind! (But I expected flak - lots more to come)

 

I tell you what Rob, why not read my other posts on the subject in this thread then tell me, in detail, why I don't know what I'm talking about. I'm not being negative, just pointing out the false assumption you made. I also keep an open mind, and don't judge people (unlike your judgement of me).


ki9cAAb.jpg

Share this post


Link to post
Share on other sites

I've been suggesting this for quite some time, yes.  I can't, for the life of me, figure out how you can't trim this plane like you could with any other plane, though.  If people simply dispensed with the idea of "golly, this is a new system, and new things are scary," I can nearly guarantee that at least half of these threads wouldn't be here.

  

 

I've been playing flight simulators for a decade now, I know what trimming is about and what it feels like/ how it works from a technical point of view. I have also flown real cessna aircraft several times and know what trim feels like on a real plane. Despite this flying the 777 it just doesn't feel right. Like I've said, if I trim on final approach, I have to maintain back pressure on the yoke and cannot feel the effect of trim until I release it. This is nothing like trimming in other FSX aircraft where you can feel trim feedback while you're applying pressure on the yoke. I feel like I'm guessing with this airplane, FBW trim ref indicator on or not.

 

You're saying you don't see how I can have am issue, have you ever considered that certain hardware might be specific to the issue such as certain yokes or drivers etc? You may not be experiencing what we are.

 

If you chaps think it worthwhile to move things along I'll file a ticket as well.  James Bennett best describes my situation. Despite the sterling efforts of Rob Robson and co (and thank you hugely for going to such lengths to try and figure this all out guys) the technicalities of all this are a bit beyond me I'm afraid.  Suffice to say, I don't find this a particularly pleasant bird to hand fly, with or without the trim ref speed marker.  I have no difficulties trimming by feel in the NGX etc etc.

 

 

 

James, if you don't mind I'll file a ticket essentially paraphrasing what you've described here, if you have no objections?

 

Cheers

I don't mind at all, that's effectively what I've said in my support ticket.

 

It's easy for people to see everyone who brings an issue up as a serial complainer due to one or two individuals making the same claim. I can assure everyone I'm not and I love the product, I'm just seeking to see whether this is behaviour I should be expecting or not. I actually had a very civilised and adult discussion via support ticket with Ryan who was very helpful and forthcoming.


captainhenrychen-1.jpg


Boeing777_Banner_Pilot.jpg


 


James Bennett

Share this post


Link to post
Share on other sites

PART TWO. FBW behaviour in the air; what should we expect?

 

OK, some seem to imply, based on my Part One post,  that I do not know the difference beteeen on the ground behaviour and in-flight behaviour of the FBW. I simply cannot wait to compile my video to show in-flight behaviour doing its thing, given this pre-judgement, so to heck with it, here goes. Video can wait!

Quote 2, Bartley, page 10 (Capitals for emphasis mine).

"While in flight, the pitch trim switches on the Captain’s and First Officer’s control wheels DO NOT
DIRECTLY CONTROL THE HORIZONTAL STABILISER
as they normally do on conventionally controlled airplanes."

So when in the air, will you see the stab trim change on the FCTL synoptic, or the stabilisers move in outside view?

NO (at least not not always)!

Try it. Get straight and level on AP, turn AP off, go to outside view and trim up / down. You will see ELEVATOR deflection, but the stabilisers do not move anything like they did on the ground, if at all! You may see a flick of the stabiliser (but see later when and why you would see this).

Correct, and by the book!

Quote 3, page 10 (Capitals for emphasis mine).

"When the trim switches are used in flight, the pilot is actually REQUESTING A NEW REFERENCED TRIM SPEED."

That is ALL one is doing with the trim switches in the air! Setting (asking for, requesting) a new referenced trim speed. So one ONLY trims for a speed change / when desiring to REQUEST a speed change.

Quote 4, page 10 (Capitals for emphasis mine)

"The airplane will pitch nose up or nose down, USING THE ELEVATOR SURFACES, in response to that reference airspeed change to achieve that new airspeed."

So all you will see on changing the trim in the air (requesting a new referenced trim speed) is ELEVATOR DEFLECTION, and a change in pitch.

If you trim UP (request a SLOWER referenced trim speed), the elevators will deflect ever so slightly UP (you are flying at some speed, these are big control surfaces, they do not require massive deflections)

The plane will pitch UP to SLOW DOWN to the lower referenced trim speed (and therefore climb, unless you counter with forward yoke force), until the trim reference speed is attained. As you get closer to the referenced trim speed you will "feel" the need to release force on the yoke, to hold a desired pitch.

If you trim DOWN (request a HIGHER referenced trim speed), the elevators will deflect ever so slightly DOWN.

The plane will pitch DOWN to SPEED UP to the referenced trim airspeed (and descend, unless you counter with backward yoke force), until the referenced trim speed is attained. As you get closer to the referenced trim speed you will "feel" the need to release down force on the yoke, to hold desired pitch.

Quote 5, page 10 (Capitals and underlining for emphasis, mine. Italics my insert)

"The STABILISER WILL AUTOMATICALLY TRIM WHEN NECESSARY, to OFFLOAD THE ELEVATOR SURFACE and ALLOW IT TO RETURN TO ITS NEUTRAL SURFACE (READ POSITION) WHEN the AIRPLANE IS IN A TRIMMED CONDITION."

Lets break this statement down a bit, particulatly in regards to the statement "WHEN the AIRPLANE IS IN A TRIMMED CONDITION."

As I interpret this (please offer your alternative interpretations), A TRIMMED CONDITION means;

When the aircaft is at referenced trim speed (TRIMMED CONDITION, part one),
AND IF control column forces are NEUTRAL (TRIMMED CONDITION, part two - if you are still yanking on the control collumn the aircaft is NOT in a TRIMMED CONDITION - it is changing pitch i.e. there is a pitch rate change - low speed, or load factor change - high speed  and therefore the C* function is not stable/constant, plus engines are adjusting power accordingly, and UNTIL THIS ALL NULLS OUT the plane is NOT IN A TRIMMED CONDITION!

THEN IF, AND ONLY IF THE AIRPLANE IS IN A TRIMMED CONDITION, will the stabiliser automatically trim to offload the elevator surface (align the stabiliser with the elevator).

What will you see!!??

 A "kick" in stab trim (on the synoptic), or in outside view a flick of the stabiliser, as it lines up with the elevator, WHEN the aircraft senses an in-trim condition (at referenced trim speed AND yoke  forces are neutral!)

That is EXACTLY what one gets and sees in the PMDG FBW model, and this explains why you sometimes ("erratically") see that trim "is only coming in" when you release the yoke to neutral! The "sometimes" refers to the fact that stab trim only kicks in only when you hit a referenced trim speed and yoke is neutral, at the same time.

It also explains why PMDG have catered for a null zone setting in the FMC setup options. Aware of different hardware  specs, and age (pots aging, sensitivity, feeling etc,) they have allowed the user to set a band within which the software FBW can "sense" a neutral force on the controls, and decide (in code) " Ah ha, I am at FBW reference trim speed AND zero control force is being applied to controls, so now allow auto-stabiliser trim to offload elevator. You then see a kick in stabiliser trim.

OK, I may be wrong in my interpretation of what Bartley meant by "IN A TRIMMED CONDITION"

So now is the time for someone from PMDG to pipe up and say "Rob H, you've nailed it" or " you've got it totally wrong" . Preferrably Capt. Robert Randazzo, an experienced 777 pilot, who I am confident tested the FBW for many hours to ensure he was happy. He delays release of software and SPs, (to my and others exasperation at times, and huge expectations), which I perfectly understand, because he "wants it to be right". I, for one, simply have to trust his judgement - I am, after all, not a 777 pilot (now there is a quick out for many of you who want to discount what I am posting here, right here, right now).

 

Tell the truth, if I had the bucks right now I'd rather try to find a Level-D 777 sim in Bangkok and check these observations out for myself. Must be one around.

Going by the only Boeing Systems 'authority" I can access for now, FBW is supposed to behave like that in flight, and PMDG have programmed this behaviour of the FBW system absolutely correctly. That is honestly as I see it acting in practise, and this is very clear in outside view.

Video to follow!

 

Rob


 

 


Hey, you talk about my supposed negativity then make this sarcastic comment. People in glass houses, etc.



The stab control is different in flight, in the real 777 and in the PMDG simulation

 

Kevin

 

Apologies. I was actually, and honestly, not being sarcastic, I know you as one off the positive contributors here. I was actually suggesting that you were one "in the know" and therefore more aware than some in this thread, that the FBW implementation is not totally wrong! Maybe needs some tweaking, but it is not "trash" and is not unflyable as some have implied.

 

Maybe went overboard in my expressing my thoughts, Chastisement accepted.

 

Rob


Robin Harris
 

Share this post


Link to post
Share on other sites

I sense negativity to what I have only just started. Is that because some pilots and systems fundis know what is coming up, and do not want this information exposed? Have you just re-read the article I quoted and twigged on, had that ah-ha moment?

 

Common, lets approach this with an open mind! (But I expected flak - lots more to come)

 

Rob

Common now. Nowbody is against you making videos.

Anything that helps us unraffle this mystery is highly welcome.

 

I just wanted to save you the trouble and all the work of making a video about the wrong thing or with the wrong understanding of things.

EDIT: I mean as far as FSX concerned......not the FBW system!

 

IF you make a video it should be a GOOD video no?

 

Everybody else here also just wants to find out what is going on.

 

Please go ahead and post videos all we can.......when we/I have time we will look at them and we can then still let you know if the video addresses the problem we have or not.

 

 

Ps....Just to confirm.....the behavior of the FBW system IS totally different on ground versus in flight when in NORMAL flight control mode. Both in the PMDG amd in the real thing.

 

EDIT: your post above was posted while I was typing so I had not seen that as I posted this.


Rob Robson

Share this post


Link to post
Share on other sites

 

 


Our issues have nothing to do with behaviour on the ground, it's to do when the FBW trim is activating itself

 

Alex

 

I am aware of that, and have been trying to find some info on when and how the switch from "ground-type" stab trim behaviour, to "flight mode" stab trim behaviour takes place (fbw activating itself as you term it).

 

In doing this I am specifically trying to find out why, and thinking about why, you are seeing what you see on take off.

 

So far drawn a blank, but maybe it is all to do with being in that exact "in trim condition" I harp on about in post #207, or not, on take off. So, lets say you are excactly at fbw ref trim speed, and yoke is laready nuetral at the moment the fbw kicks in (about 400ft agl?), then you do not get a pitch blip (already perfectly in trim). But say you are at ref trim speed, and happened to pitch with the yoke ever so slightly and then relax pressure so that elevators hit the neutral zone exactly when fbw becomes active, stabtrim kicks in just then, and you see a resultant pitch kick. May explain why some see it, some do not. Just a suggestion, OK.

 

So I am only trying to get some thinking going here, based on the lines of what the fbw is supposed to be doing in flight (elevator and stab actions) according to documented specs  (my part two post #207, not the post you quote from).

 

Another observation I can offer is that if I take off totally in manual mode (no VNAV or other vertical mode armed), I have complete control of pitch and can do as I wish, point the plane where I want it to go. Then I do not see what you are seeing at all (300ER). I really do not think the 200 would be any different as the base code for systems is the same ( is that not why we waited for SP1 for the 200 to come out before the 300 could be released?).

 

Rob


Robin Harris
 

Share this post


Link to post
Share on other sites

I am not qualified enough to suggest PMDG implementation of FBW and trim is wrong nor have I ever flown anything bigger than a Glider, a Cessna 182 or a 30 min ride in a C310 a decade ago. However, I do understand the theory and have "felt" (as subjective as that may be) the effect of using elevator trim and the joy of flying a properly trimmed aircraft.

 

In my case, out of the last three flights in the 77W and F, two have been using (to quote "The Matrix") a "there is no spoon" attitude towards the trim indicator (bubble) cheat in the PFD and mostly concentrating on treating the aircraft as a Cessna indeed. My (again subjective) opinion is that it felt somewhat "unnatural" (specially in the approach phase) and I can't say I enjoyed hand flying the aircraft the way I enjoy doing so in the Leonardo Maddog or the NGX.

 

In my last session (a quick hop between LFPG and EDDF with a very light GW that allowed me to climb to FL400) I hand flew the entire flight (with A/T on) using the bubble trim indicator and just pre-setting it to the airspeed I wanted to maintain. This provided a more "enjoyable" experience even tho I experienced very small struggles during the approach phase due to the deceleration of the 77F and the fluctuation of the trim bubble cheat. 

 

I love this aircraft and find PMDG's rendition of it nothing short of amazing, but I hate to admit that the constant monitoring of available VAS after reaching T/D and the need to "worry" about the trim bubble can undermine the experience and joy of flying the 777.

 

cheers

-E

 

EDIT & disclaimer: my comparison between the 777X and the NGX/Maddog in my post was done from a personal and absolutely subjective opinion as I believe these two are a joy to hand-fly. It is not my intention to drift the conversation or engage in stupid comparisons between great products that contribute nothing and lead nowhere. 


Enrique Vaamonde

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    21%
    $5,490.00 of $25,000.00 Donate Now
×
×
  • Create New...