A320 FAC/MCDU Speeds
Joined: Jan 2008
Posts: 2,173
Likes: 51
From: Blighty (Nth. Downs)
Hi butcher,
I don't know how old your A320s are, but have you read the previous posts, in particular from #6 onwards? Until I saw that, my understanding was similar to yours and I was not aware that the system architecture may be different in newer aircraft.
http://www.pprune.org/tech-log/59331...ml#post9735039
I don't know how old your A320s are, but have you read the previous posts, in particular from #6 onwards? Until I saw that, my understanding was similar to yours and I was not aware that the system architecture may be different in newer aircraft.
http://www.pprune.org/tech-log/59331...ml#post9735039
Joined: May 2013
Posts: 3
Likes: 0
From: Turkey
Initial calculation
Hello Chris,
My company's MSNs are in between 3000 and 5000ish.
At the beginning of the flight FAC uses crew entered data on MCDU but it changes to FAC's own calculation after switching to aerodynamic calculation model. (#6 says a bit different) At least that's what I know. I found an article as an answer from Airbus on old WISE which states that.
I think this is an important subject and FCOM should be more detailed on matters like this one.
My company's MSNs are in between 3000 and 5000ish.
At the beginning of the flight FAC uses crew entered data on MCDU but it changes to FAC's own calculation after switching to aerodynamic calculation model. (#6 says a bit different) At least that's what I know. I found an article as an answer from Airbus on old WISE which states that.
I think this is an important subject and FCOM should be more detailed on matters like this one.
Joined: Feb 2010
Posts: 112
Likes: 3
From: At home
For older aircrafts FCOM says:
The characteristic speeds displayed on the PFD are computed by the Flight Augmentation Computer (FAC), according to aerodynamic data.
For newer:
The characteristic speeds displayed on the PFD are computed by the Flight Augmentation Computer (FAC), according to the FMS weight data (for PFD/MCDU display consistency and accuracy purposes), and aerodynamic data as a backup.
The characteristic speeds displayed on the PFD are computed by the Flight Augmentation Computer (FAC), according to aerodynamic data.
For newer:
The characteristic speeds displayed on the PFD are computed by the Flight Augmentation Computer (FAC), according to the FMS weight data (for PFD/MCDU display consistency and accuracy purposes), and aerodynamic data as a backup.
Joined: Jul 2006
Posts: 1,100
Likes: 111
From: Somewhere over the rainbow
I noticed even on the newest models that the PFD speed gap between VLS and VAPP is not always 5kts difference ... Like for example sometimes VLS on PFD is 135kt but VAPP is only 138 when it should be 140kt. How do you guys explain we don’t see a 5kt difference between VLS and VAPP?
