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cmbaviator

PMDG B777 FBW and Auto trim ( issue ? )

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Hi all

 

Fisrt of all I'm quite new to Boeing, as I'm a real Airbus enthusiastic :), but due to the lack of A320 hardcore addon, I decided to give it a go on the pmdg b777 which for me the B777 is the  Boeing Aircraft I can fly ( philosophy much closer to an airbus ). this B777 from PMDG is just ...... there is no word to describe it. I hope one day PMDG will do an A320 :).

 

I started to read the B777 FCOM and the FBW is close to the Airbus A320 one, except the fact that you need to trim manually in speed changes ( speed stability). But I noticed that the B777 autotrim and keep the flight path perfectly even if the speed was decreasing, shouldn't the vesrtical speed decrease when the speed is decreasing as you need to manually trim the aircraft ? But sometimes it doesn't autotrim in speed changes which is the correct behaviour, but how does the priority work ??: I mean even if i trim the aircraft in speed changes, then the auto trim " takes the control " resulting with some " little oscillation", so in speed chnages does the pilot have fully control of the THS ?? becasue it seems that the FBW always change the trim value in speed changes, So i don't know if PMDG have correctly simulated this behaviour with all due respects.

 

Last thing, at take off, the auto trim is frozen until approx 1000 Fts AGL, i have to always keep back pressure in order to maintain the flight path, this is not explain in the FCOM, so it don't know if it's the correct behaviour.

 

 

If somebody can explain me how the B777' FBW works,i'd appreciate :)

 

Thank you

 

 

regards

 

CMB


Camille MOUCHEL-BLAISOT ( CMB )

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This was a much debated topic, and the FBW is being addressed in the SP.


Kyle Rodgers

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Pmdg is reviewing the fbw behavior and it will be corrected in the SP. There is a lengthy discussion here in the forum about how it works in the real plane.


Bryan Richards

 

"People depend so much on automation that they forget how to get the automation to work." B.W.

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http://forum.avsim.net/topic/429900-fbw-trim-issue-fixed-for-sp1-or-not/?hl=+fbw +issues

 

here is one link , as its been beaten  to death already. as Kyle has mention above its going to be fixed in the sp1   when its finally released.

 

Since your new to the forum to get quicker results  instead of waiting , you can use the search option  in the top of the page just type in what you looking for etc

 

Also you need to add you name  to your signature block otherwise you might your post might get deleted due to forum rules


I7-800k,Corsair h1101 cooler ,Asus Strix Gaming Intel Z370 S11 motherboard, Corsair 32gb ramDD4,    2  ssd 500gb 970 drive, gtx 1080ti Card,  RM850 power supply

 

Peter kelberg

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Hi all

 

Fisrt of all I'm quite new to Boeing, as I'm a real Airbus enthusiastic :), but due to the lack of A320 hardcore addon, I decided to give it a go on the pmdg b777 which for me the B777 is the  Boeing Aircraft I can fly ( philosophy much closer to an airbus ). this B777 from PMDG is just ...... there is no word to describe it. I hope one day PMDG will do an A320 :).

 

I started to read the B777 FCOM and the FBW is close to the Airbus A320 one, except the fact that you need to trim manually in speed changes ( speed stability). But I noticed that the B777 autotrim and keep the flight path perfectly even if the speed was decreasing, shouldn't the vesrtical speed decrease when the speed is decreasing as you need to manually trim the aircraft ? But sometimes it doesn't autotrim in speed changes which is the correct behaviour, but how does the priority work ??: I mean even if i trim the aircraft in speed changes, then the auto trim " takes the control " resulting with some " little oscillation", so in speed chnages does the pilot have fully control of the THS ?? becasue it seems that the FBW always change the trim value in speed changes, So i don't know if PMDG have correctly simulated this behaviour with all due respects.

 

Last thing, at take off, the auto trim is frozen until approx 1000 Fts AGL, i have to always keep back pressure in order to maintain the flight path, this is not explain in the FCOM, so it don't know if it's the correct behaviour.

 

 

If somebody can explain me how the B777' FBW works,i'd appreciate :)

 

Thank you

 

 

regards

 

CMB

 

 

The current PMDG 777 FBW is completely borked in terms of speed stably and pitch trim, yes, and this is not at all how the real 777 behaves in flight.      The best workaround I've found is to go into the FMC menu and purposely fail the PFCs into Secondary Mode.     This should make the pitch trim behave realistically as it should.    

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