Boeing FMC Preflight

In the Aerofly FS Flight Simulator the Boeing 747, 777 and 787 Control Display Units (CDUs) are simulated realistically and in great detail. This device can be used to create a new flight plan, tune navigation radios, set and adjust the performance of the aircraft and a whole lot more.

The CDU has many pages of which a lot are simulated. You can access the most relevant pages directly by clicking one of the page buttons under the CDU screen or screen area. Some sub-pages can then be accessed through clicking line select keys, e.g. then an arrow on the screen is pointing at the line select key.

Data entry is accomplished by typing a value into the CDU scratchpad first. Then the value can be inserted into a field on the displayed CDU page with the line select key next to it. We’re now demonstrating the necessary steps to create a flight plan for the Flight Management Computer (FMC) using the CDU available in the Boeing 787 on the MFD screens. Per default those pages are selected on the lower MFDs.

Note - If you select the “before engine start”, “ready for taxi”, takeoff or landing states these steps will all be taken care of for you. And you can always go back to the navigation menu to change the navigation route, too.



After powering up the aircraft the CDUs normally display the IDENT page. We can also access this page manually.

  • Push the INIT REF button
  • Select the lower left option INDEX
  • On the INIT/REF INDEX page select the option IDENT

On this page pilots would have to verify the navigation data cycle, the engine and model information.

Position Initialization

At the beginning of the flight the aircraft does not yet know its current position. The Inertial Reference System (IRS) needs to have a position so that it can align its position.

  • Type in the ICAO airport identifier where you are currently at and enter it into the REF AIRPORT field on the left. The airport reference position is then displayed on the right side.
  • Verify that the currently displayed GPS POS latitude/longitude is near the airport reference position
  • Click the GPS POS field to copy its text to the scratchpad
  • Insert the scratchpad field into the SET IRS POS field to tell the IRS that this is your correct position

Route Initialization

Next we’re going to create a new route. As an example we’re using Frankfurt to San Francisco.

  • Type the ICAO identifier of your origin airport into the scratchpad and select the ORIGIN field to insert it, for us it’s “EDDF”
  • Type the ICAO identifier of the destination airport and insert it into the DEST field, for us “KSFO”
  • If you already know what will be your departure runway you can insert it into the RUNWAY field on the left side, we’re using “25C”
  • Push the ACTIVATE field to make this your active flight route
  • Press EXEC to execute this change.

Route Editing


Now we want to select a Standard Instrument Departure (SID).

we go to the on the left hand side in the first row.

  • Push the DEP/ARR button
  • On the DEP/ARR INDEX page that is now displayed select DEP for departures next to the ICAO identifier of the origin
  • If we already inserted the departure runway earlier it may already be selected, then you can skip the next step.
  • On the right hand side select your departure runway, we’re using 25C
  • On the left hand side select your SID, we’re using the RID3Q departure in this example


To enter an approach (APPR) and a Standard Arrival Route (STAR) for our destination we can do that via the DEP/ARR index page as well.

  • Push the DEP/ARR button
  • On the DEP/ARR INDEX page select the ARR option next to your destination airport (not the origin)
  • Select your desired approach on the right side, e.g. the ILS28R
  • If there are approach transitions available you may select one from the list if desired
  • Select the STAR on the left
  • If arrival transitions are listed you may pick one if desired


After inserting a departure and arrival the flight management system does not yet know how to connect them. We can now insert new waypoints or just connect the end of the departure to the beginning of the arrival directly.

  • Press the LEGS page to display the list of waypoints
  • Step through the legs page either by using the STEP button in the lower right or using the NEXT PAGE and PREV PAGE buttons
  • If you see an empty field with white boxes with the “NEXT” and or “DISCONTINUITY” then you have found a discontinuity in the route which should be closed so that the autopilot can follow the route properly
  • Go to the next waypoint in the list and select it with the line select key on the left side next to it. This copies the waypoint name into the scratchpad
  • Insert that waypoint name into the NEXT field to close the gap. This removes the discontinuity.

Takeoff Performance

Performance Initialization

Next we need to tell the FMS some parameters of the aircraft so that it can start computing the estimated speeds, altitudes, time and fuel burn for each waypoint correctly.

  • Push the INIT REF button. If the PERF INIT page is not already displayed then select INDEX in the lower left and select PERF INIT from the list
  • Insert the gross weight (GR WT) or zero fuel weight (ZFW). If you don’t know that it is you can cheat and click the field with an empty scratchpad and the correct value is then copied to your scratchpad.
  • Insert the reserve fuel mass (RESERVES) and COST INDEX
  • Insert your planned cruise altitude (CRZ ALT), we’re using 38000ft in our example
  • Insert the cruise center of gravity (CRZ CG)
  • The EXEC button should now illuminate, press it to execute these changes

Thrust Limit

From the PERF INIT page select the THRUST LIM button in the lower right corner, or go to the INDEX and select THRUST LIM from there. On this page we have the option to select a reduced takeoff thrust. If runway length permits we can use less than maximum available takeoff thrust to reduce engine wear and noise during takeoff.

  • Insert an assumed temperature to reduce the takeoff thrust limit or
  • Select TO, TO 1 or TO 2 on the left side to select that rating for takeoff
  • On the right hand side you arm a climb thrust rating (CLB, CLB 1 or CLB 2) which will activate after the takeoff thrust acceleration height is passed.

Takeoff Reference

From the THRUST LIM page select the TAKEOFF option in the lower right. On this TAKEOFF REF page we can set the planned takeoff flaps, acceleration and thrust reduction height as well as enter our v-speeds.

Note - If you don’t know the correct values for a field just click it with an empty scratchpad and it automatically suggests a value for you. This is a cheat that the real aircraft does not have.

  • Type in a a valid flaps setting for takeoff into the scratchpad, e.g. 5, 10, 15, 17, 18 or 20 for the 787 - 10 or 20 for the 747 and 5, 10 or 15 for the B777.
  • Insert that value into the FLAP/ACCEL HT field on the top left
  • To enter an acceleration height type in a slash and then the altitude (e.g. “/1000”) and insert it to the acceleration FLAP/ACCEL HT field
  • Check the thrust reduction height (THR REDUCTION) and change it if needed
  • On the right hand side insert the V1, VR and V2 speeds, e.g. 150, 155 and 160 respectively
  • Enter the takeoff CG position
  • Execute these changes with the EXEC button

Radio and Navigation Aids

Navigation Radio Tuning

We’ve not completed the necessary FMC preflight steps. Now we can optionally tune some VORs or ILS frequency for additional guidance during departure.

Note - If you are inserting manual frequencies it prohibits the FMS auto-tuning functionality. So after the departure, if you no longer need your manually selected NAV-aids, you should remove them to allow the auto-tuning to resume normal operation.

  • Press the NAV RAD button to display the NAV RADIO page
  • You can save a frequency for later by typing it into the scratchpad and selecting the PRESELCT left or right fields.
  • You can also copy a frequency into your scratchpad by selecting the VOR L or VOR R or one of the PRESELECT fields with an empty scratchpad.
  • Type in a VOR frequency into the scratchpad or use the copy method described above and then insert that frequency into the VOR L or VOR R field.

To enter an ILS frequency you need to type in the ILS frequency AND the course value, e.g. 111.55/250 for the EDDF 25C departure runway localizer.

Waypoint Fix Info

Using the CDU we can draw guidance lines onto the navigation display. These help us judge distances or inbound radials towards navigation fixes. We’re now adding the extended centerline for our departure runway and a 10NM range ring. You can also add multiple fixes using the next pages.

  • Open the FIX page by pressing the button labeled FIX
  • Type in the identifier of a waypoint, VOR, NDB, airport or runway (e.g. EDDF25C)
  • Insert it into the FIX field on the top left

You can add a bearing and distance or just one of them:

  • Type in the bearing on its own and insert it (e.g. “250”)
  • Type in the bearing slash distance for both (e.g. “250/10”) or
  • Type in slash + distance (e.g. “/15”)

On the navigation display you can now see green helper lines or circles. To remove the fix info later:

  • Go to the FIX page and scroll to the page that has the FIX that you want to delete
  • Press the DELETE button to enter DELETE into the scratchpad
  • Click the FIX field to delete it

VNAV and Progress

Vertical Navigation

During flight you can change the planned cruising altitude on the VNAV pages.

  • Press the VNAV button to access the VNAV pages.
  • Use NEXT and PREV PAGE buttons to step through the VNAV pages
  • Type in a new cruise altitude, e.g. 40000 to set FL400 and insert it into the CRZ ALT field
  • You can modify the speed restriction, e.g. type 250/10000 to allow the aircraft to fly 250kt below 10000ft
  • Or you can delete the speed restriction: press the DEL key to insert a DELETE command into the scratchpad, then select the SPD RESTR field to remove the speed restriction all together
  • You can also change the transition altitude and transition level (TRANS ALT or LVL)

Approach Reference

To be set for an immediate return or during the descent preparations you should enter your planned gross weight for landing and can then compute the approach reference speeds.

  • Overwrite the GROSS WT value if you are expecting a different weight value for the approach
  • You can copy one of the suggested flap speeds into the scratchpad by pressing the button on the right side next to it.
  • The flap and speed pair can then be inserted into the FLAP SPEED field on the right so set the approach V-REF speed. You can also manually type in a valid flap setting and speed in knots, e.g. 30/150 and insert it into the field.