Learn the PMDG 737 FMC workflow in MSFS 2020: position setup, route entry, SID/STAR selection, performance data and LNAV/VNAV fixes.
In Microsoft Flight Simulator 2020, use the PMDG 737’s CDU to initialise position, enter or import the route, choose the runway and procedures, clear unintended discontinuities, and complete performance and take-off data. Activate and execute the route, then verify every leg before arming LNAV or VNAV.
The FMC is the computer; the CDU is the keypad and display used to control it. The six keys down each side are line-select keys, while typed entries appear in the scratchpad at the bottom of the screen.
PMDG 737 FMC setup from cold and dark
- Prepare the aircraft and IRS. Set the required fuel and payload before entering performance figures, because changing the load later can invalidate the take-off data. Place both IRS selectors to NAV and allow alignment to begin.
- Initialise the position. Open the IDENT page, confirm the aircraft model and navigation database, then select POS INIT. Enter the reference airport and copy a displayed GPS position into SET IRS POS. The reference airport alone does not align the IRS.
- Enter the route. On the RTE page, enter the departure airport under ORIGIN and the arrival airport under DEST. A flight number is optional. On subsequent route pages, place an airway in the VIA column and its exit waypoint in the TO column; enter direct fixes in the TO column without an airway.
- Select the departure and arrival. Open DEP/ARR, choose the runway, SID and transition for departure, then the STAR, transition and approach for arrival. Use procedures that match the clearance or intended flight plan rather than selecting the first available options.
- Activate and execute the route. Select ACTIVATE on the RTE page and press the illuminated EXEC key. An illuminated EXEC key means a modification is still pending; it does not mean the change has already been accepted.
- Inspect the LEGS page. Check waypoint order, altitude and speed constraints, duplicate fixes and route discontinuities. A mistake we see constantly is pressing EXEC without checking what the modified route will actually do.
- Complete PERF INIT. Enter zero-fuel weight, reserves, cost index and cruise altitude. Where the CDU offers a calculated weight beside a line-select key, selecting it is safer than retyping the figure. Cruise altitude must be realistic for the aircraft’s loaded weight.
- Set thrust and take-off data. Review N1 LIMIT, then enter the take-off flap setting and centre of gravity on TAKEOFF REF. Select or confirm V1, VR and V2, note the indicated stabiliser trim, and set that trim physically. Use assumed-temperature or derated thrust only when supported by valid planning data.
- Cross-check the MCP. Set the cleared initial altitude, runway heading or assigned heading, and an appropriate speed. The FMC does not remove the need to configure the Mode Control Panel.
Waypoint names and airways must exist in the PMDG navigation database. If a planned airway or fix is rejected, our guide to finding valid PMDG FMC airways and waypoints explains how to recognise spelling, database and AIRAC mismatches.
How do I check the FMC route before take-off?
Check the route in PLAN mode on the navigation display and step through every LEGS-page waypoint before departure. Look for unexpected turns, doubled waypoints, route gaps, the wrong runway and an arrival connected to the wrong transition.
The ND route line is more useful than simply seeing an EXEC light go out. Our explanation of the PMDG 737 EFIS controls and PLAN mode covers the display settings used to inspect each leg.
How should I clear a route discontinuity?
To connect two intended legs, select the waypoint immediately below ROUTE DISCONTINUITY, place it over the discontinuity, and press EXEC. Do not automatically remove every gap: a VECTORS leg usually represents an expected radar vector and may need to remain until ATC sends the aircraft towards the next fix.
After closing a gap, inspect the resulting track. Connecting the wrong duplicate waypoint can create a turn across the route or send the aircraft hundreds of miles away.
Can the MSFS World Map load the PMDG 737 FMC?
Do not rely on the MSFS 2020 World Map to produce a complete, ready-to-fly PMDG route. The PMDG 737 uses its own FMC logic, so manual entry or a supported route import is more dependable.
An imported route also does not finish the setup. Confirm the runway, SID, STAR and approach, then enter weights, reserves, cruise altitude, thrust settings and V-speeds manually. Never assume a route is active until it appears correctly on RTE, LEGS and the navigation display.
Why will LNAV or VNAV not work?
LNAV and VNAV depend on a valid active route, complete performance data and sensible MCP settings. The FMC creates the guidance, but the autopilot and flight director modes must still be selected and monitored correctly.
- LNAV will not arm: Confirm that the route is activated and executed, the IRS is aligned, and there is a valid active leg. If the aircraft cannot intercept that leg from its present position or heading, use HDG SEL to establish an intercept or select an appropriate direct-to waypoint.
- VNAV will not arm: Complete PERF INIT and TAKEOFF REF, including cruise altitude, weights and take-off speeds. Missing or contradictory performance entries commonly block VNAV.
- The aircraft ignores an altitude: Check the MCP altitude. VNAV cannot climb or descend through the selected MCP limit simply because the FMC route contains another altitude.
- The aeroplane follows the wrong mode: Read the flight-mode annunciations at the top of the primary flight display. The FMA, not an illuminated MCP button by itself, shows which mode is active.
- Controls change unexpectedly: Disable any MSFS piloting assistance or AI control that is interfering with the PMDG systems.
For the MCP sequence, engagement conditions and FMA checks, use our PMDG 737 autopilot and LNAV/VNAV guide.
Common PMDG FMC messages and fixes
| Message or symptom | Likely cause | What to do |
|---|---|---|
NOT IN DATABASE | The fix, airway or procedure is absent, misspelt or from a different AIRAC cycle. | Check the identifier and use route data matching the PMDG navigation database. |
INVALID ENTRY | The value has the wrong format or is not valid for that field. | Clear the scratchpad, check the expected units or format, and enter it again. |
ROUTE DISCONTINUITY | Two route segments are not connected. | Join the legs only if the flight plan requires a continuous path; retain intentional vector segments. |
UNABLE CRZ ALT | The planned cruise altitude is unsuitable for the loaded weight or route. | Check weight entries and use a lower initial cruise altitude if required. |
| V-speeds are unavailable | Runway, flap, weight or centre-of-gravity data is incomplete. | Finish the load and take-off setup, then return to TAKEOFF REF. |
| New entries do not affect the route | The modification has not been executed. | Review the modified legs and press EXEC. |
How do I change the FMC route after departure?
Use the LEGS page for shortcuts, waypoint changes and revised restrictions, then inspect and execute each modification. For an ATC shortcut, follow the dedicated PMDG 737 direct-to procedure rather than deleting route legs at random.
Before descent, confirm the arrival runway and approach, review all altitude constraints, add forecast winds when available, and select an appropriate VREF on APPROACH REF. Changing the approach can rewrite several legs, so repeat the PLAN-mode check after every runway, STAR or transition change.