What's the difference between FMS (Flight management System), and FMC (Flight management computer)?

Can the flight management computer be thought of as what's manipulating the input information from the performance/navigation databases, and the FMS as being what actually provides the information?

I understand the information that's involved with the system, I'm just trying to define the difference based off an analogy of sorts.


1 Answer 1



Its definition is that the FMC is part of the FMS:

An FMS comprises four main components:

  • The Flight Management Computer (FMC)
  • The Automatic Flight Control or Automatic Flight Guidance System (AFCS or AFGS)
  • The Aircraft Navigation System
  • An Electronic Flight Instrument System (EFIS) or equivalent electromechanical instrumentation.

The FMC is a computer system that uses a large data base to allow routes to be pre-programmed and fed into the system by means of a data loader [...]

Putting that as a diagram plus the typical inputs and outputs:

diagram 1
— Own work


Since the inception of the FMS, it's been the same:

diagram 2
— CREEDON, J. "Flight management systems-What are they and why are they being developed?." Guidance and Control Conference. 1973.

  • 1
    $\begingroup$ Typically, the CDU's (or MCDU's) are considered part of the FMS as well. $\endgroup$
    – Ralph J
    May 23, 2019 at 22:12
  • $\begingroup$ @ymb1 I know this was a long long time ago but I need the info from the second picture (the NASA one) for a scientific work. Do you have any access to the conference paper that includes this picture? I tried finding the whole document (in PDF form) on the internet but couldn't... I just need the page that the picture is on. It would really mean a lot to me if you could help me with that matter. Kind regards, Niels $\endgroup$
    – My Tree
    Jan 2 at 15:43
  • $\begingroup$ Hi @MyTree: The NASA download seems unavailable, but since that "paper is declared a work of the U.S. Government and therefore is in the public domain" (says so on the paper), you can try Sci-Hub or similar if you can access them, if not, there is a paywalled version that is easy to google for. If you want just that page, then here it is. $\endgroup$
    – user14897
    Jan 3 at 14:07

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