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.



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 '19 at 22:12

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