Using the FMS

How do I program the FMC (flight management computer)?

This description was provided by Cormac Shaw. I've added the illustrations and updated the description to version 8.60.

Here's the entire FMS panel, showing a fix that's been programmed in:


The buttons are laid out immediately below the FMS instrument's display screen thus:


Initialise: Clear out all previously entered information, set your current location as the first flight plan waypoint and display a blank waypoint 2 for you to enter.

Previous: Display the previous waypoint on the instrument's display screen.

Next: Display the next waypoint on the instrument's display screen.

Clear: Delete the data for the currently displayed segment.

Select: Set the currently displayed segment as the active segment.

Select an airport for the waypoint.

Select a VOR for the waypoint.

Select an NDB for the waypoint.

Select a fix for the waypoint.

Select any location by latitude and longitude.

Toggle + or - to specify north/south and east/west coordinates.

Load a flight plan from a file.

Save the current flight plan to a file.

The remaining keys on the keypad are used to enter waypoint identification and altitude. Remember it's a "virtual keypad". You enter data by clicking with the mouse on the keys, not by typing on the keyboard.

Here's how you enter a flight plan:

  1. At the start of your flight, while on the runway, click the INIT button. You will see the top of the display change from "Plan Segment 01" to "Plan Segment 02". (What has happened - the FMC has entered the airport you are currently at as the initial waypoint and moved the flightplan on to the next entry for you to enter it. Press the PREV button  to change the view to "Plan Segment 01" and you will see the first waypoint listed. Click NEXT to return to the blank "Plan Segment 02").

  2. To enter the second and subsequent waypoints, first click the appropriate button for the type of waypoint, AIRP, VOR, NDB or FIX. Then type in the code for the navaid (2-3 characters) / airfield (4 characters) / fix (5 characters) by clicking on the instrument's keypad (not typing on your keyboard!). After entering the code, you need to enter an altitude at which you will fly towards the waypoint. To do this, move to the altitude line of the waypoint's details by clicking on the button to the left of the "FLY AT" line on the screen. Then type in the required altitude. Press NEXT to move to the next waypoint to enter its details in the same manner.

  3. To delete any waypoint, move to it by using the NEXT or PREV button and then click on the CLR button.

  4. For the last waypoint, you will presumably enter an airport code. Note that if you enter 00000 feet for this waypoint, you may fly into the ground before you get there! If the penultimate waypoint is relatively near your destination airport, then its best to enter the pattern/approach altitude for the final waypoint. If the last leg is going to be fairly long, then enter an appropriate cruise altitude.

That's the flight plan programmed. You can save/load flight plans to/from discreet files at any time using the LD and SA buttons on the bottom-left of the instrument itself.

Following a programmed flightplan: 

You can of course, fly your flightplan manually. Routes from one waypoint to the next are shown as bright red lines on the EFIS Moving map (the heading bug is a dark red line). Most aircraft that have an FMC will also have a moving map. Also, HSI instruments can have their sources switched to GPS/FMC mode to show the direction to the current waypoint. EFIS should also have a DME-to-waypoint display.

To fly a flightplan by autopilot, first take off! Once you've climbed out you can activate the flightplan. The second waypoint should activate automatically as soon as you take off. You can make sure by using the PREV key to get to the second waypoint ("Plan segment 02") and pressing the "->" button (to the right of the CLR button). Engage HDG mode in your autopilot and set your heading to intercept the FMS course, which runs from your initial position to the second waypoint. (Usually your runway heading will initially take you off course; you must intercept the FMS course to make the autopilot lock on.)

Now set your HSI/autopilot source selector to GPS and press the LOC autopilot mode button to arm FMS course capture. As you approach the course, the autopilot will lock on and turn toward the waypoint. Press the autopilot VNAV button to select the waypoint's 'Fly at' altitude for the autopilot. NB: if you want the autopilot to control throttle, you must set the desired speed and activate the autopilot's ATHR mode manually.

Warning! The VNAV implementation in X-Plane 8.60 causes extremely violent and abrupt response to altitude changes programmed in the FMC. You are usually better off not using the 8.60 VNAV feature and managing your altitude using the autopilot's VS or FLCH modes.

When the aircraft reaches the waypoint, the FMC's active waypoint will automatically switch to the next Plan Segment and any altitude change will be passed to the autopilot. The GPS receiver will always indicate which waypoint is currently active. You do nothing unless you want to change the speed or rate-of-climb / descent settings on the autopilot.

If for some reason, the FMC fails to switch to the next waypoint automatically, you can force it to step forward by using the NEXT button to display the desired waypoint and then the "->." button to activate it. You can also use this technique to skip waypoints if you so wish.

As you approach your destination you can take the autopilot off the FMC by deactivating the GPS mode on the autopilot. Fly your approach to the destination as normal, manually or using the autopilot's other modes.

You can't auto-land the plane with the FMC, because it doesn't have airport runways programmed into it. If you want to make your flight entirely under autopilot control and know what runway you're going to land on, you can program in a couple of fixes that line up your flight path with the runway. During the last leg, set up the ILS in the Nav receiver, and as you cross the last fix, switch your autopilot source to the Nav receiver and press the glideslope button to arm glideslope capture.

How do I save and load flight plans with the FMS?

Thanks again to Cormac:

You can use the FMS itself to create and save flight plans and use them  again and again. Enter the flight plan data and then use the "SA"  button at the bottom left of the FMS panel to save it to a text file.  Give the filename a '.fms' ending and press the Return key on your  keyboard to save it. You can load saved .fms files to the FMS using the  "LD" key on the FMS panel.

'.fms' files are just text files so you can create them using any text  editor too. To understand the format required, make a complex one with  the FMS instrument using all possible waypoint types and then save it  and open it in your text editor and study carefully. [Editor's note: Make sure you get the format of the .fms file exactly right! X-Plane tends to be very unforgiving of errors in its data files. - Andy]

How do I create routes to use in the FMS?

You have a couple of options:
  1. You can work them out yourself and toggle them into the FMC, as described above.
  2. You can use the Goodway flight planning tool, sold separately. Goodway creates complete flight plans, ready to load into the FMC.
  3. You can use the Route Finder web page, described on the FAQ page on flying real airline routes.


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