This glossary is written for virtual airline and flight simulation use within Virtual Air Canada Airline. It is not intended as a real-world aviation reference.
FMC/FMGC
Flight Management Computer / Flight Management Guidance Computer
The Flight Management Computer (FMC) is Boeing’s term for the central processor within the FMS that handles navigation database management, performance calculations, route sequencing, and predictions. It takes inputs from GPS, VORs, DMEs, and inertial reference systems, then computes the most accurate position estimate and guides the aircraft along the programmed route. Pilots interact with the FMC through CDUs (Control Display Units) mounted on the center pedestal. The Airbus equivalent is the FMGC - the Flight Management and Guidance Computer - which performs the same core functions but additionally integrates autopilot guidance commands directly, combining FMC and flight director functions into a single unit.
On Airbus aircraft, two FMGCs operate simultaneously in an active/monitoring arrangement. If one fails, the other takes over seamlessly. The FMGC manages the lateral and vertical navigation profiles (LNAV and VNAV), computes top-of-climb and top-of-descent points, predicts fuel burn and arrival time, and generates speed targets for each phase of flight. Pilots program the FMGC through the MCDU (Multipurpose Control and Display Unit). The distinction between FMC and FMGC matters because on Airbus aircraft, disconnecting the autopilot does not disconnect the FMGC - the flight director continues to provide guidance derived from the same computer.