trim on final approach

[scandinavian13]

 

 

I can not look at your setup Kyle, so I dont know how well things are working on your end.

 

There may be some quirks, but my bet is that they're just from not reconfiguring my hardware settings.

 

My main point was that I think most of this is coming from people overthinking it as if they need to learn something new.  They hear "FBW" and think that it's a new system like the FMS that they'll have to wrap their head around.  This is not the case.  If you approach it as you'd approach a conventional airplane, you've already understood most of it.

 

Basically, it looks like a lot of people are approaching the FBW with the "I'm going to have to re-learn how to fly," when that's not really the case.  Thus the "making it more complicated than it really is."

[3-2-1-Now]

I can not look at your setup Kyle, so I dont know how well things are working on your end.

 

On my end though, this 777 trims NOTHING like a Cessna or 737!

 

So either you dont know how a real airplane flies (which I dont think is the case).

or

You think the 777 is now behaving as it should (as a conventional airplane) where it really is not

or

You are not having the issues I /others are having.

 

But I am sure we shall get to the bottom of this!

 

+1

 

I seem to have greater success if I set the null zone to 10%. I think calling it a null zone is a misnomer as the stick still functions in this region and the aircraft still responds to stick inputs.

 

That said, the aircraft pitch reaction whilst trimming is still very low vs. center (it's still not possible to trim it out by feel - it is trial and error), the FBW still "catches up" with the trim at center, but it has meant that I just flew the best fully manual ILS approach yet in the T7, and all with the FBW symbol hidden.

 

Maybe it hints at the cause?

 

I have a TM Warthog, configured directly in FSX.

 

I also re-flew a late go-around, and it handled very well. I need to fly a few more to be sure.

 

Best regards,

Robin.

[eurowing]

Robin, are you talking about the null zone in FSX or the one in the PMDG options?

[vesalius]

Reading this, only one thing comes to my mind: Ground Effect kicking in

 

http://en.wikipedia.org/wiki/Ground_effect_(aircraft)

 

But I highly doubt this is simulated... :blush:

[maukro_1990]

This is something i don´t really understand, too!!! If i am on final at about 600ft over ground with AP and AT on, Flaps 25 and a Vref of 150kts, the airplane is trimed out, right? I mean the trim reference speed is 150kts because i don´t change anything. But after i turn off the AP, the nose starts to raise. 

 

If i am completely configured for the final/ touchdown, i don´t really have to touch the trim, right? I don´t even changing the speed or something, so i would thinking that the aircraft is trimed out for my vref speed. ... hmmm. 

[3-2-1-Now]

Reading this, only one thing comes to my mind: Ground Effect kicking in

 

http://en.wikipedia.org/wiki/Ground_effect_(aircraft)

 

But I highly doubt this is simulated... :blush:

 

Ground effect only applies within half a wingspan of the ground (so for the 777, that would be in the last 80 ft or so), and simply results in reduced vertical speed. It doesn't really take effect at 200 ft in such a way that it would cause the nose to sometimes pitch up the way we see.

 

Best regards,

Robin.

[rsrandazzo]

Gerard-

 

I am intrigued by your description because this isn't something we have seen, nor is it something we are hearing much about at tech support.

 

A couple of things to be blunt about:  This is not ground effect- and the airplane shouldn't be pitching level on you at 200' AGL...  there really isn't any reason it would do that.

 

So that leaves you and I asking the same question:  What is causing what you are seeing?

 

A couple of questions for you:

 

1) Are you seeing this on EVERY flight?

 

2) If you disconnect the A/T after getting fully configured- does it still happen?

 

3) do you have any trim or pitch commands mapped to hardware?

 

4) Do you have FSUIPC installed?  If so- would you mind uninstalling it and running the same test again?  (Sometimes FSUIPC does things that users do not expect because they don't fully understand some of the settings- and in our experience the only way to rule that out is to eliminate it temporarily...)

 

5) In the same keeping as #4, do you have a weather engine running?  Can you please set the weather manually in FSX to "Clear" and no wind and try again so that we can positively eliminate any causal factors in weather?

 

Thanks, sir- I appreciate the feedback.  We will sort this out one way or another!

[AlanB77L]

Hello,

 

I wanted to add to this thread because I have an issue where the aircraft pitches up on final approach following autopilot disconnect.

 

To answer the questions above:

 

1) Are you seeing this on EVERY flight? Yes

 

2) If you disconnect the A/T after getting fully configured- does it still happen? Yes

 

3) do you have any trim or pitch commands mapped to hardware? Elevator trim mapped to keys on yoke, Saitek yoke for pitch control. Hardware disconnected for experimentation.

 

4) Do you have FSUIPC installed?  If so- would you mind uninstalling it and running the same test again?  (Sometimes FSUIPC does things that users do not expect because they don't fully understand some of the settings- and in our experience the only way to rule that out is to eliminate it temporarily...) Removed for experimentation.

 

5) In the same keeping as #4, do you have a weather engine running?  Can you please set the weather manually in FSX to "Clear" and no wind and try again so that we can positively eliminate any causal factors in weather? ASN not loaded, clear weather theme in FSX.

 

I set up an ILS, stabilised and configured for landing by 2000'. I then opened the lower EICAS FCTL page and noted trim had stablised at 4.5 units at Vref + 5. I waited until 500' AGL before disconnecting the autopilot and noticed that the elevators deflected upwards, then returned to centre. At this stage of the approach, the end result was quite pronounced and immediate correction was required to continue the approach.

 

I took off again and joined a downwind leg while watching the FCTL page continuously. While intercepting the selected altitude, I noticed the elevator making small corrections up and down, oscillating around centre while the trim fine tuned itself. Eventually the elevator was centred and the trim value stable. I disconnected the A/P and again the elevators deflected upwards, then centred again within about a second. At this stage of flight, the slight pitch up corrected itself and the aircraft continued hands off.

 

I believe this little deflection could cause an issue on short final. Fighting it immediately could exacerbate the situation and ignoring it could leave the aircraft slightly high but "re-stabilised".

 

Is anyone else noticing this upward deflection on A/P disconnect?

[Tristan Marchent]

Hello,

 

I wanted to add to this thread because I have an issue where the aircraft pitches up on final approach following autopilot disconnect.

 

To answer the questions above:

 

1) Are you seeing this on EVERY flight? Yes

 

2) If you disconnect the A/T after getting fully configured- does it still happen? Yes

 

3) do you have any trim or pitch commands mapped to hardware? Elevator trim mapped to keys on yoke, Saitek yoke for pitch control. Hardware disconnected for experimentation.

 

4) Do you have FSUIPC installed?  If so- would you mind uninstalling it and running the same test again?  (Sometimes FSUIPC does things that users do not expect because they don't fully understand some of the settings- and in our experience the only way to rule that out is to eliminate it temporarily...) Removed for experimentation.

 

5) In the same keeping as #4, do you have a weather engine running?  Can you please set the weather manually in FSX to "Clear" and no wind and try again so that we can positively eliminate any causal factors in weather? ASN not loaded, clear weather theme in FSX.

 

I set up an ILS, stabilised and configured for landing by 2000'. I then opened the lower EICAS FCTL page and noted trim had stablised at 4.5 units at Vref + 5. I waited until 500' AGL before disconnecting the autopilot and noticed that the elevators deflected upwards, then returned to centre. At this stage of the approach, the end result was quite pronounced and immediate correction was required to continue the approach.

 

I took off again and joined a downwind leg while watching the FCTL page continuously. While intercepting the selected altitude, I noticed the elevator making small corrections up and down, oscillating around centre while the trim fine tuned itself. Eventually the elevator was centred and the trim value stable. I disconnected the A/P and again the elevators deflected upwards, then centred again within about a second. At this stage of flight, the slight pitch up corrected itself and the aircraft continued hands off.

 

I believe this little deflection could cause an issue on short final. Fighting it immediately could exacerbate the situation and ignoring it could leave the aircraft slightly high but "re-stabilised".

 

Is anyone else noticing this upward deflection on A/P disconnect?

 

Chad,

 

I took the 77W up for a spin over Zurich today doing two approaches both on the ILS 16. Regardless of the airport and approach from today, I too HAVE Noticed the pitch up on A/P Disconnect.

 

When I am hand-flying the approach and fully take my hands off the controls or put controls back to centre when I've trimmed it all out and it's stable, it will pitch down. Is this due to the Trim Reference Speed at all??

 

Definitely following this topic...

 

Thanks for bringing this up

[rsrandazzo]

Gents-

 

We got some feedback from a few of the posters in this thread- and we think we are on to something...

 

We found that in a specific set of circumstances the airplane would adjust pitch when it was not intended or supposed to do so shortly after A/P disconnect.

 

We should have a fix in the update we are planning for Friday- so please give us your feedback after you get that update.

 

Thanks, gents!

[willywonka]

Thanks for getting on top on it, Robert!

 

 

 

We found that in a specific set of circumstances the airplane would adjust pitch when it was not intended or supposed to do so shortly after A/P disconnect.

 

Would you mind sharing what these circumstances are, for our education?

[doog79]

I am one of those experiencing an non commanded pitch up at AP soft disconnect and also right before landing. 

 

On the landing phase it feels like its trying to autoland but to early even although I`m flying manual and have been stable from FAF.  It takes quite a push on the stick to counter this upward pitch of the aircraft and does not feel normal at all.

 

I have about 15 landings in the 77W this week and experience it every time.

 

The only controls I have mapped through FSUIPC and sent to FSX are the brake axis.

 

I came on looking to see if anyone else had the issue and it seems I`m not alone.  Also looks like you guys have a fix in the works Robert so I`ll see what happens with that.

 

Douglas Reid

[RobbSpeed]

We found that in a specific set of circumstances the airplane would adjust pitch when it was not intended or supposed to do so shortly after A/P disconnect.

 

Thanks so much for confirming this. Looking forward to the update.

[ger]

hi Robert ,

 

Tonight when the kids are in bed i shall try what you asked me too .

 

1 i can confirm this is happening on every flight  , i really have to push the controls hard forward to lower the nose so i get it on the runway  , even when pusing the controls i land half way the runway

 

even if i disconnect the A/T (what i do most of the time , it gives me reverse while my nose gear is not on te ground yet , only  main gear is on the ground wich i can;t get done with A/T on , than i have revers whe the nose gear is on the ground )

it is the same.,and i have to pull back the thrust before it reduces the height  wich in that case i get a huge rate of descent onto the runway .

 

my trim commands are mapped on my joystick but tried the keys within fsx but the same.

 

4 5   i shall uninstall fsuipc and don't run it with ASN.

Settings in ASN are default except cloud drawing 90miles , turbulence 50% and cloud layer max 3

 

This moment i m between EHAM and KIAH , when i land i shall look carefully for the trim and when it piches up and then  i set up a new flight without fsuipc and ASN

 

Thanks in advance

 

Gérard

Edited July 24, 2014 by ger

[senci82]

Just making sure that we know it's happening on the 200 & 300