A telling statement in the FCTM reveals why the system is designed this way, it states "The pilot still needs to trim for speed changes. Column forces increase when out of trim to provide the conventional speed error cue." The dumbed down FBW is a safety feature which helps pilots be aware they are speeding up or slowing down by feel even if they haven't noticed it by sight!

How cool is that,

Cheers,

K

Yeah very cool.....except the PMDG does not fly ike that......so not so cool

 

Which is why I asked you TWICE to do an experiment!

And you still have not done so.

Or you have done it but refuse to inform us of your findings for some reason.

 

You can stop explaining how the FBW system works to me, because I know how the thing flies first hand!

 

Just do the test K, and see that in the PMDG 777 you do NOT have to trim for speed!

 

Ciao.

Last response 777 simmer because your tone is getting increasingly less polite for some reason. I've done " your experiment" and yes the aircraft stays pretty much in trim, the reason which I explained in my last response. It is meant to stay in trim because you are applying a force on the yoke, the FBW is sending a signal to the flight control surfaces that you wish to maintain this attitude and they are responding to minimize forces required to do so, when you reach the new speed you release the yoke, and magically the aircraft is in trim, correct? Yes it is, and no further trimming required because at that moment you are not changing speed, or making an input of the control column. If you were to make a speed change WITHOUT an input to the yoke the aircraft will not trim, understood? That is how the system functions in the real aircraft period. How this proves to you that the FBW is not simulated properly comes from your misunderstanding of how the system functions, I will not post another reply to you, and sorry you're dissapointed with PMDG's simulation of this I AM NOT and think they have modelled th FBW very well considering this a product for FSX.

I am used to the PMDG NGX and before that the 747X.

 

And I get some very strange behavior on approach. it's like I loose the G/S when flying by the FLT DIR, I nearly had almost 3 Asiana type crashes, the plane seemed very very hard to maneuver, and flying with the auto throttle on would leave my plane starting to flare around 100 AGL.

 

I think I need to hand fly it in circuits a bit, but I still would like to hear if you have any advice? The auto pilot flares so nicely, I want to be able to beat this computer brain.

Please lets not get each other worked up about this, please... 

Last response 777 simmer because your tone is getting increasingly less polite for some reason. I've done " your experiment" and yes the aircraft stays pretty much in trim, the reason which I explained in my last response. It is meant to stay in trim because you are applying a force on the yoke, the FBW is sending a signal to the flight control surfaces that you wish to maintain this attitude and they are responding to minimize forces required to do so, when you reach the new speed you release the yoke, and magically the aircraft is in trim, correct? Yes it is, and no further trimming required because at that moment you are not changing speed, or making an input of the control column. If you were to make a speed change WITHOUT an input to the yoke the aircraft will not trim, understood? That is how the system functions in the real aircraft period. How this proves to you that the FBW is not simulated properly comes from your misunderstanding of how the system functions, I will not post another reply to you, and sorry you're dissapointed with PMDG's simulation of this I AM NOT and think they have modelled th FBW very well considering this a product for FSX.

Ok, now that you have finally responded to my question I can revert to being friendly again.

Of course you are free to decide wether or not you reply to me.

My tone was getting inpolite for a reason.

This topic needs an answere to my question/experiment so we can get rid of contradicting information and stop confusement.

And you were not giving that answere.

 

No that you have, we can move on.

Into what seems an even more complicated or maybe uncomfortable scenario where two real life 777 pilots have a different opinion.

 

1)

"yes the aircraft stays pretty much in trim, the reason which I explained in my last response. It is meant to stay in trim because you are applying a force on the yoke"

 

I a totally disagree with that. The aircraft does not autotrim any forces away that are related to being away from the trim reference speed.

 

However, I have mentioned before in this thread that I have not tried what happens if you dont trim for speed changes.

I instinctively trim away the forces I feel when accelerate/decellerate.

Maybe if you keep that yoke force on there long enough...maybe after some time it will take away some of that force...I will try on my next flight.

But I have never heard of this feature, nor experienced it.

 

 

2)

when you reach the new speed you release the yoke, and magically the aircraft is in trim, correct? Yes it is, and no further trimming required because at that moment you are not changing speed, or making an input of the control column

 

I disagree again. yes the PMDG is in trim but not the real aircraft (is my opinion).

 

How does this by the way sync with your earlier statement:

 

"Cowl the FBW system on the 777 does not trim for speed changes only for configuration changes. This was an intentional design concieved to give the pilot a feedback response from the aircraft to changing the flight path of the aircraft."

 

3)

If you were to make a speed change WITHOUT an input to the yoke the aircraft will not trim, understood? That is how the system functions in the real aircraft period.

 

?? we are still talking manual flight here right?

 

I disagree again.

It is not even possible to make a speed change without touching the yoke!

Add thrust and the airplane will climb at the same trim reference speed (unless you push on the yoke)

Pitch up or down to change speed....how do you do that without touching the yoke?

 

4)

sorry you're dissapointed with PMDG's simulation of this I AM NOT and think they have modelled th FBW very well considering this a product for FSX.

 

Finally we agree on something here..

They did a wonderfull job on the 777, I love how well all systems are modelled and how they work.

I could write a 1000 pages with compliments to PMDG.

But the trim function is wrong (in my opinion)

 

 

So, there you have it.

 

Like I mentioned earlier on in this topic, I will do some testing on my next flight (if conditions permit) which will be wednesday.

 

I will do the following:

a)

Not trimming during acceleration after take off

Does it get heavier and heavier to keep the nose down.....or do you get autotrim help at some point?

 

b )

Accelerating from 250kt to 300kt without trimming.

Does the nose shoot up when you let go or does it stay where it is(increase maybe a little bit) and keeps 300kt?

 

c)

Does reducing thrust drop the nose?

Does it maintain its altitude while reducing thrust.

I say that initially it will correct for this nose down moment, but then as speed decreases it should start a descend at the in trim speed (same speed)

 

Any Other Requests Anybody?

 

Either I will have to come back here next week and take everything back, applogize, feel utterly embarassed and we then know why Captains are Captains and FO's are not!

 

Or,... you are going to have to admit that Captains can be wrong!

I have tested this: Maintain altitude and reduce speed, the nose go down. If you maintain altitude and increase speed the nose comes up. The plane hold only the bank.

 

But in approach mode with activated App mode in ILS, I need only reduce or increase thrust. The Trim is working and goes up and down and my nose goes up and down, too. That confuse me a little bit.

 

Can somebody tell me the page number of FCTM with the explaining sentence?

 

Thanks.

From 777 FCTM :

 

chapter 1. general Information

page 70 : Electronic Flight control System:

"the system MINIMIZES the  airplane PITCH response to thrust changes, configuration changes, turbulence and turns.  Thrust changes no longer need to be countered with a column input.

...

The pilot still needs to trim for speed changes."

 

Chapter 7 Maneuvers

page 277  Acceleration to and Deceleration from VMO

"Begin the maneuver at existing cruise speed with the autothrottle connected and the autopilot disengaged. Set command speed to VMO. As speed increases observe:

• nose DOWN TRIM REQUIRED to keep airplane in trim and maintain level flight

...

When the overspeed warning occurs reduce thrust levers to idle, set command speed to 250 knots, and decelerate to command speed.

As airspeed decreases observe that nose UP TRIM is REQUIRED to keep airplane in trim and maintain level flight."

 

So what ?  :smile:

 

Guy

From 777 FCTM :

 

chapter 1. general Information

page 70 : Electronic Flight control System:

"the system MINIMIZES the airplane PITCH response to thrust changes, configuration changes, turbulence and turns. Thrust changes no longer need to be countered with a column input.

...

The pilot still needs to trim for speed changes."

 

Chapter 7 Maneuvers

page 277 Acceleration to and Deceleration from VMO

"Begin the maneuver at existing cruise speed with the autothrottle connected and the autopilot disengaged. Set command speed to VMO. As speed increases observe:

• nose DOWN TRIM REQUIRED to keep airplane in trim and maintain level flight

...

 

When the overspeed warning occurs reduce thrust levers to idle, set command speed to 250 knots, and decelerate to command speed.

 

As airspeed decreases observe that nose UP TRIM is REQUIRED to keep airplane in trim and maintain level flight."

 

So what ? :smile:

 

Guy

Thank you, good find, that is what I have been saying the whole time.

 

I have not looked at that chapter for a while, forgot that exercise was in there.

Guy, thanks for your input! Page 71 is interesting, too.

 

So that's how it works in flight. Who works this in approach phase... Sorry if I ask to many questions, but I will understand that completely.

 

Thanks for your sympathy. ;-)

On APPROACH, you need not trim for configuration changes, but again you must TRIM for Speed.

(on MANUAL only as on autopilot trimming is automatic)

 

See 777 FCTM Chapter 5 Approach and Missed Approach

page 220 VISUAL APPROACH 

Downwind and base leg:

"Extend landing flaps before turning final. Allow the speed to decrease to the proper final approach speed and TRIM the airplane"

Visual approach - general:

"Once the final approach is established, the airplane configuration remains fixed and only small adjustments to the glide path, approach speed, and TRIM are necessary"

 

Happy landings ! :smile:

 

Guy

Guy save the world. ;-)

 

Thanks I will take a look on it.

No word from PMDG about this yet. They're probably looking into it, but they could at least answer out Support Tickets saying so, would be nice.

Strange things happens if you have very rough weather.... The trims drive me crazy then. Its a hard fight.

Any Other Requests Anybody?

 

Either I will have to come back here next week and take everything back, applogize, feel utterly embarassed and we then know why Captains are Captains and FO's are not!

 

Or,... you are going to have to admit that Captains can be wrong!

 

Hi Rob.

 

I'll be expecting to what you have to say after you've done the experiments.

 

Nevertheless, to me, the fact of watching two full blown real world 777 pilots contradicting each other about this issue has me utterly confused. I wish I could put my hands on a RW 777 and test-fly myself...

 

And I don't have to admit it.....I can assure you (and you know, just like me), there are a lot of captains who are very very wrong too many many times.... ;)

 

 

See ya...

 

EDIT: I'm not talking about anyone...I meant "in general"...Don't anybody take me wrong! :lol:  

Hi Rob.

 

I'll be expecting to what you have to say after you've done the experiments.

 

Nevertheless, to me, the fact of watching two full blown real world 777 pilots contradicting each other about this issue has me utterly confused. I wish I could put my hands on a RW 777 and test-fly myself...

 

And I don't have to admit it.....I can assure you (and you know, just like me), there are a lot of captains who are very very wrong too many many times.... ;)

 

 

See ya...

 

EDIT: I'm not talking about anyone...I meant "in general"...Don't anybody take me wrong! :lol:  

Yep, we are still human....I mean flying gods ofcourse....but also human, lol

Yep, we are still human....I mean flying gods ofcourse....but also human, lol

 

LOL

 

PMDG did respond to my ticket. 

 

 

We have submitted several FBW issues to the team to look into including this but please keep in mind that the FBW model was built with direct interaction with Boeing so any changes will only be made with there approval.

 

 

Paul Gollnick

Technical Support

PMDG Simulations, LLC