What does FMC stand for in aviation and flight simulators?
FMC stands for Flight Management Computer. In aviation and flight simulators, it is the onboard computer that uses route, performance and navigation data to calculate and manage a flight plan. Pilots usually interact with it through a CDU or MCDU, while the wider Flight Management System includes more than the computer alone.
What does an FMC do?
An FMC combines aircraft position, navigation-database entries and crew inputs to create a flyable lateral and vertical plan. Depending on the aircraft, its functions can include:
- Storing the route, waypoints, airways and instrument procedures.
- Calculating track, distance, estimated arrival times and fuel predictions.
- Managing speed and altitude constraints for climb, cruise and descent.
- Calculating take-off, climb and approach performance when the aircraft supports it.
- Supplying guidance targets to the flight director, autopilot and autothrottle systems.
The exact capability depends on the aircraft and its avionics. A modern airliner FMC is considerably more capable than a simplified unit fitted to an older aircraft or simulated by a basic cockpit panel.
What is the difference between FMC, FMS, CDU and MCDU?
The FMC is the computer doing the calculations; the other terms describe the wider system or the interface used to control it.
| Term | Meaning | Role |
|---|---|---|
| FMC | Flight Management Computer | Runs route, navigation and performance calculations. |
| FMS | Flight Management System | The complete flight-management function, including computers, databases, sensors and interfaces with other aircraft systems. |
| CDU | Control Display Unit | The keypad and screen through which pilots enter data and view FMC pages. |
| MCDU | Multipurpose Control and Display Unit | An interface used on many Airbus aircraft to access flight management and other systems. |
| FMGC | Flight Management and Guidance Computer | The computer name used in common Airbus architectures, combining flight-management and guidance functions. |
Simmers often call the cockpit keypad and screen “the FMC”. That is understood conversationally, but the screen is technically a CDU or MCDU. On many Boeing aircraft, CDUs provide access to one or more FMCs; on Airbus types, the MCDU commonly provides access to the Flight Management and Guidance System.
How do you program an FMC in a flight simulator?
You normally initialise the aircraft position, enter the route and procedures, add performance data, then check and activate the resulting flight plan. The page names and required entries differ significantly between Boeing, Airbus and other avionics.
- Initialise the flight. Enter or confirm the aircraft position, origin, destination and any required reference data.
- Build the route. Add waypoints and airways, or import a route if that aircraft supports compatible flight-plan files.
- Select procedures. Choose the departure runway, SID, arrival, STAR and approach, including the correct transitions.
- Enter performance data. Supply weights, reserves, cruise altitude, speeds and other required values.
- Inspect the route. Check waypoint order, altitude constraints and any discontinuities on the LEGS or F-PLN pages.
- Activate the plan. Execute or insert the temporary changes as appropriate, then select the required lateral and vertical guidance modes.
For aircraft-specific procedures, use our step-by-step Boeing 737 FMC programming guide or the corresponding Airbus A320 MCDU and FMS setup guide. Users of older simulator panels can also follow this practical FS2004 FMC tutorial, although individual page layouts will vary.
Why does an FMC route not work in a flight simulator?
Most failed FMC routes result from an incomplete entry, an unresolved route break or the wrong autoflight mode rather than a defective computer.
- The route was not activated. Entering waypoints does not always make the route active. Confirm the execute or insert prompt after checking the changes.
- A route discontinuity remains. Join the appropriate legs, but do not automatically delete every discontinuity: vectors and some manual procedure segments are intentionally open.
- The aircraft position is invalid. Complete position initialisation and, where simulated, allow the inertial reference system to align.
- Navigation databases do not match. A route created with a different data cycle may contain missing waypoints, renamed procedures or changed runway transitions. Rebuild the affected section using entries available in the aircraft.
- Performance data is incomplete. Missing weight, cruise altitude, cost index or speed data can prevent valid vertical-navigation predictions.
- The wrong mode is selected. An active FMC route does not guarantee that the autopilot is following it. Check the flight-mode annunciator rather than relying only on illuminated buttons.
Does the FMC fly the aircraft automatically?
No. The FMC calculates guidance, but the flight director and automatic-flight systems turn that guidance into pitch, roll and thrust commands. Pilots must activate the appropriate modes, monitor the flight-mode annunciator and intervene if the aircraft does not follow the intended path.
This distinction explains a common simulator problem: the route is displayed correctly on the navigation display, yet the aircraft flies straight ahead. The flight plan may be valid while lateral navigation has not been armed or captured.
Does every simulator aircraft have an FMC?
No. The simulated aircraft must be equipped with a flight-management system and the developer must model it. Light aircraft usually use conventional radio navigation or a GPS navigator, while airliner simulations range from simplified route-following units to detailed FMC implementations.
A route loaded through a simulator's world map also may not populate a particular aircraft's FMC. Import support depends on the aircraft, its accepted format and its integration with the simulator, so manual entry is sometimes required.