Just watched the video, it is clear now, thanks a lot for the link

 

but there is something that I don't understand ?

 

When he trim up or down, the plane remain level, How is that possible ??? He was barely giving input just like in a a320 where the FBW can't maintain perfectly the flight path while decelerating especially 300kts to 220 kts  ????

 

 

When he trim up or down, the plane remain level, How is that possible ??? 

 

Because while trimming, he's applying pressure at column as long as it resists. You do not feel the force at your home yoke so it can never be so perfect.

Because while trimming, he's applying pressure at column as long as it resists. You do not feel the force at your home yoke so it can never be so perfect.

 

yes but he was barely appying pressure, on a A320 the VS would have dropped to -500 to -600 fts/min

I found an issue with the FBW and trim. I'm going to try and bullet point this to make it as clear to understand as possible.

 

* Aircraft is OUT OF TRIM, and "nose heavy".

* I pull back on the control column to counter the out of trim condition

* Once I stabilized the pitch, I start trimming nose up, and returning the control column to center at the same time (same as on the NGX).

 

PROBLEM: the trim reference speed changes, but the trim is NOT applied until I return the control column to dead center, at which point ALL the trim change I made is applied at once, and if I got the trim wrong, the aircraft would then aggressively pitch relative to that out of trim condition.

 

The result is that I can't trim the aircraft by feel. If I don't have the trim reference speed displayed, it is virtually impossible to trim.

 

Seperately, the trim often either doesn't move, or even moves in the opposite direction to that selected.

 

Anyone else see this?

 

Best regards,

Robin.

yes but he was barely appying pressure, on a A320 the VS would have dropped to -500 to -600 fts/min

Never tried to fly airbus, but at some videos I watched, that stick is really sluggish.

Don't forget that the Airbus pitch mode in Normal Law is a g demand law. It blends to a pitch rate demand law at low altitude/on the ground.

 

Best regards,

Robin.

Don't forget that the Airbus pitch mode in Normal Law is a g demand law. It blends to a pitch rate demand law at low altitude/on the ground.

 

Best regards,

Robin.

it's more a pitch rate demand at low speed < 240 kias, on the ground pitch mode is in direct law

 

 

Regards

 

CMB

Probably the best you can do is watching the video on this other thread:

 

https://www.youtube.com/watch?v=kae_wDCGex0

 

Besides this, I must say that, now that I understand it, I really don't find the Boeing C*U very wise.... I will probably be smashed by saying this, but, give me the good "old" Airbus C* law and I'll be just fine... 

 

In trying to do it more intuitive, I think Boeing has turned it into something awkward.

 

Thanks for that video! That helped a lot.

Thanks for that video! That helped a lot.

Here's the whole playlist if you want to see more: https://www.youtube.com/playlist?list=PL5caETAZRBN6mPhNASIlMg2bkWH2DbtIz

I found an issue with the FBW and trim. I'm going to try and bullet point this to make it as clear to understand as possible.

 

* Aircraft is OUT OF TRIM, and "nose heavy".

* I pull back on the control column to counter the out of trim condition

* Once I stabilized the pitch, I start trimming nose up, and returning the control column to center at the same time (same as on the NGX).

 

PROBLEM: the trim reference speed changes, but the trim is NOT applied until I return the control column to dead center, at which point ALL the trim change I made is applied at once, and if I got the trim wrong, the aircraft would then aggressively pitch relative to that out of trim condition.

 

The result is that I can't trim the aircraft by feel. If I don't have the trim reference speed displayed, it is virtually impossible to trim.

 

Seperately, the trim often either doesn't move, or even moves in the opposite direction to that selected.

 

Anyone else see this?

 

Best regards,

Robin.

Yep... I've noticed the trim going the wrong direction too Robin, Try to trim say up, and it suddenly reverses and goes down.

 

Not sure about the other points you mention, will have to test.

 

 

 

 

I think many of you are over thinking trim.

 

As confirmed by a real world 777 pilot on the forum, just trim the way you do with any aircraft, it shouldn't feel any different to trimming a 757 or 737.

I found an issue with the FBW and trim. I'm going to try and bullet point this to make it as clear to understand as possible.

 

* Aircraft is OUT OF TRIM, and "nose heavy".

* I pull back on the control column to counter the out of trim condition

* Once I stabilized the pitch, I start trimming nose up, and returning the control column to center at the same time (same as on the NGX).

 

PROBLEM: the trim reference speed changes, but the trim is NOT applied until I return the control column to dead center, at which point ALL the trim change I made is applied at once, and if I got the trim wrong, the aircraft would then aggressively pitch relative to that out of trim condition.

 

The result is that I can't trim the aircraft by feel. If I don't have the trim reference speed displayed, it is virtually impossible to trim.

 

Seperately, the trim often either doesn't move, or even moves in the opposite direction to that selected.

 

Anyone else see this?

 

Best regards,

Robin.

You might be on to something there......I think that is what causing me to have difficulty trimming and keep over/under trimming in an endless trimming effort!

 

I can only get it right when trim ref speed is displayed!

 

Too bad I am not at home to test your findings.

Gonna try it later and report

 

Hope Rob will give us input when he finds a time to test as well.

Trim it like a Cessna.

 

Done.

 

That is not fair....those are my words exactly, lol :-)

 

Only one problem with that.....

I can trim the default FSX Cessna with zero problems.

I can trim the PMDG737 (which trims like a Cessna) with zero problems.

But I am having a darn hard time trimming the PMDG777 (which should trim like the Cessna and the 737).

 

So something is not right!

S***. Last time Rob have said "something is not right! " we waited almost a full year for fix   

I found an issue with the FBW and trim. I'm going to try and bullet point this to make it as clear to understand as possible.

 

* Aircraft is OUT OF TRIM, and "nose heavy".

* I pull back on the control column to counter the out of trim condition

* Once I stabilized the pitch, I start trimming nose up, and returning the control column to center at the same time (same as on the NGX).

 

PROBLEM: the trim reference speed changes, but the trim is NOT applied until I return the control column to dead center, at which point ALL the trim change I made is applied at once, and if I got the trim wrong, the aircraft would then aggressively pitch relative to that out of trim condition.

 

The result is that I can't trim the aircraft by feel. If I don't have the trim reference speed displayed, it is virtually impossible to trim.

 

Seperately, the trim often either doesn't move, or even moves in the opposite direction to that selected.

 

Anyone else see this?

 

Best regards,

Robin.

I cannot reproduce this. Can you give more informations. What exactly are you doing? What speed, what trim reference speed? AT on or off?

 

I found when I fly 250kts and trim reference speed is at 329 (maximum nose heavy), I need only about 5mm of joystick aft input to keep aircraft straight and level. Press trim down button and slowly release joystick pressure > aircraft stays in level flight.