Tech Log The very best in practical technical discussion on the web

FM/FG A320

Old 15th Aug 2019, 20:45
  #1 (permalink)  
Thread Starter
Join Date: Oct 2001
Location: hot tub
Posts: 293
FM/FG A320

Hello everyone,

Is it possible to lose the flight management portion of the FMGS without the flight guidance portion?
In other words, FCU/AP/FD/AT still working but Flight management portion inop..
I am quite certain this is possible as when one activates nav backup on one MCDU, the other side can remain coupled with the same side AP.
So my question is: what has to go wrong in the FMGS for the flight management portion to be lost whereas the FG portion still works?
Thanks a lot in advance.
saviboy is offline  
Old 15th Aug 2019, 22:09
  #2 (permalink)  
Thread Starter
Join Date: Oct 2001
Location: hot tub
Posts: 293
Ok I sort of answered some of my questions but still have a few.

in case of dual latch, we are directed to Select the NAV B/UP prompt on both MCDU DATA pages.
(Refer to DSC-22_20-60-130 General HOW TO USE, concerning navigation backup

During Dual latch: -22_20-90-10
1) Both FMGCs are inoperative. FM and FG capability are lost.
2) AP/FD, A/THR are lost

When referring to 22-2-60-130, one can see this caution note :The MCDU NAV B/UP is to be used only in case of FM 1 + 2 failure. It can be selected temporarily in case of FM1 or 2 only failure, in order to ensure that the function is available on the failed side.
When in MCDU NAV B/UP on both sides, one FG at least must be available to engage AP and A/THR.

So, section -22_20-90-10 tells us that both FMGC's are lost including FG.
Yet, 22-2-60-130 tells us at least one FG must be available to engage AP and AT
I am confused.
saviboy is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.