FMC and FMS

[slip-stream 5]

Hi there, I have been a way a while and have always been wanting to ask this question. I am happy computing the 737ng's FMC thanks to the tutorials, and was wondering if the up-coming queen of the skies uses the same FMC, or is it completely different? Also, what is an FMS?Many thanks. Keith

[Guest]

FMS stands for Flight Management System.FMC stands for Flight Management Computer.An FMC is a specific type of FMS.

[marcom 139]

"An FMC is a specific type of FMS."Not entirely correct.While correct that the FM(S) and FM© stand for system / computer, the FMS incorporates both the FMC and the (M)CDU. Confused?The FMC is a box located in the avionics compartment and has no (pilot) interface. (ie no buttons for the crew to push)The thing you use on the flight deck to access the FMC is a CDU (or in more complex aircraft a MCDU). While a CDU will only access one computer (the FMC) a MCDU can access a lot of things such as maintenance computers or ACARS.So, in a nutshell, FMS = FMC + (M)CDU

[slip-stream 5]

Thankyou very much for clearing that up for me. So, I assume that both systems are more or less the same in the 737 and the 747.

[Guest]

Ah, so I got it the other way around :)Often I hear the CDU referred to as FMC as well (and yes, I know the brains are located elsewhere ;) ).

[marcom 139]

well except that the thing actually works in the 744 ;-)Forget the 737's VNAV "capability" - it works like a charm in the 744.Also, its much more advanced in the 744 and has more options.

[Guest tmetzinger]

>well except that the thing actually works in the 744 ;-)>Forget the 737's VNAV "capability" - it works like a charm in>the 744.>Also, its much more advanced in the 744 and has more options.While much of the functionality is similar in the 37 and 47 FMS', they are different.The 747 uses the same CDU as the 777, I believe, and is covered in Bill Bulfer's "Big Boeing" guide. I think (don't have the references with me) that the CDU is common among all Boeings except the 737.

[marcom 139]

Tim,the older B757/767 CDUs are similar to the 737's (in that they offer the three different VNAV pages and no FMC COMM or ATC buttons).Later versions (pegasus version) are similar to the B744/777 concept.Regards,Mark

[Qavion 19]

>and yes, I know the brains are located elsewhereTo be accurate, the later CDU's have half a brain ("ALTN NAV").Or is it a quarter... I forget? :-hah Cheers.Ian.

[ps1flyer 9]

> While much of the functionality is similar in the 37 and 47> FMS', they are different.this is certainly true. In particular, the 747-400 FMC is manufactured by Honeywell (like the FMCs of 777, 757/767, MD-11 and most Airbusses) while the 737 FMC is manufactured by Smith Avionics.A lot of functionality is indeed similar but there are many subtle differences when looking at the details.Markus

[chiswick72 145]

hmmmm,A big shot in the dark....but do I smell a centralised PMDG server connecting with the PMDG 747 FMS directly ....? :(Shooting madly in the dark for facts !!! ;)Armen at EGLLwww.veryquiet.com