Fix GPS PRIMARY LOST in the FlyByWire A32NX by checking GPS status, alignment, failures and installation, plus safe in-flight fallback steps.
In Microsoft Flight Simulator, “GPS PRIMARY LOST” means the A32NX FMGS no longer trusts GPS as its primary position source. Check the MCDU GPS MONITOR and PROG pages, let a cold-start aircraft finish powering and aligning, remove any GPS failures, then update or cleanly reinstall the A32NX if both receivers remain unavailable.
What does GPS PRIMARY LOST mean in the A32NX?
GPS PRIMARY LOST means the FMGS has stopped accepting GPS as its primary position input; it does not necessarily mean that all navigation has failed. The aircraft may continue calculating its position from the inertial reference systems and available radio-navigation updates.
The warning is not caused simply by a flight-plan discontinuity, an old route or a lost internet connection. Microsoft Flight Simulator supplies simulated GPS data internally. Our explanation of Airbus GPS-primary logic and its fallback position sources covers what the message represents behind the scenes.
Pressing CLR on the MCDU only acknowledges the scratchpad message. It does not restore the receivers or correct the underlying condition.
How do I clear GPS PRIMARY LOST?
Use the receiver status and navigation-accuracy indications to identify the cause before resetting anything.
- Check the MCDU GPS status. Open
DATAand selectGPS MONITOR. Inspect GPS 1 and GPS 2 to see whether either receiver is supplying valid data. Page wording can differ slightly between A32NX builds. - Check navigation accuracy. Open the
PROGpage and look forNAV ACCUR HIGHorNAV ACCUR LOW. Cross-check the displayed aircraft position against the runway, airport or a known radio-navigation aid. - Finish the cold-start sequence. Supply stable electrical power, place all three IR mode selectors in
NAV, initialise the aircraft position correctly when required and allow alignment and GPS acquisition to finish. Do not move the aircraft during a full alignment. - Remove injected failures. Check the A32NX flyPad/EFB and Microsoft Flight Simulator failure controls for GPS, receiver or electrical failures. Clear only failures that were introduced for the simulation.
- Investigate electrical indications. If the warning appears with ECAM electrical messages, blank displays or several failed systems, GPS loss may be a consequence rather than the original fault. Our guide to A320 electrical sources and buses explains what to check.
- Rule out an installation conflict. Quit the simulator, make sure only one A32NX package is installed, remove incompatible aircraft or avionics modifications, and update the aircraft. If necessary, uninstall it before installing a fresh copy rather than merging files over an older build; our A32NX package and compatibility reference provides the relevant installation context.
There is no normal cockpit switch for turning the A32NX GPS receivers back on. Repeatedly cycling the ADIRS is not a GPS fix and can leave the aircraft with less navigation capability, especially in flight.
Which symptom points to which fix?
The point at which the warning appears usually identifies the most likely cause.
| Symptom | Likely cause | Best action |
|---|---|---|
| Message appears just after a cold start | Power-up, GPS acquisition or IRS alignment is incomplete | Keep stable power connected, verify the IR selectors and wait for initialisation |
| Both GPS receivers are unavailable after using failures | An injected receiver or electrical failure remains active | Remove the failure and reset the aircraft state on the ground |
| Warning appears with electrical or display faults | Loss of power to avionics or a wider aircraft-system failure | Address the electrical fault and use the remaining navigation sources |
| Warning began after changing or updating add-ons | Duplicate, outdated or conflicting package | Test with other aircraft-related add-ons removed, then perform a clean reinstall |
| GPS appears valid but NAV ACCUR is low | Position disagreement or degraded navigation accuracy | Cross-check raw data and do not rely solely on managed navigation |
Can I keep flying after GPS PRIMARY is lost?
Yes, provided the displayed position remains credible and the FMGS reports adequate navigation accuracy for the phase of flight. The autopilot does not always disconnect because the FMGS can fall back to inertial and radio-updated positioning.
Monitor the ND, raw radio-navigation data and the Flight Mode Annunciator. Our guide to interpreting the A320 PFD and FMA helps confirm what guidance the aircraft is actually following.
- If position and navigation accuracy remain sensible, continue cautiously while monitoring for drift.
- If
NAV ACCUR LOWappears or the map position is visibly displaced, use selected heading or track guidance and reliable radio aids. - Do not continue an approach that specifically requires GNSS unless the required integrity and accuracy have returned. Use a suitable ILS or other supported procedure, or go around.
- Do not switch the IR selectors off in flight in an attempt to restore GPS.
Does changing the route or navdata fix the warning?
No; route and navdata problems normally affect waypoint availability or lateral guidance, not whether the GPS receivers provide a trusted position. Repair discontinuities and database mismatches separately.
If GPS 1 and GPS 2 both show valid data, NAV ACCUR HIGH is displayed and the warning repeatedly returns, suspect a stuck aircraft state, an add-on conflict or an A32NX installation problem. Reproduce the flight with other aircraft modifications removed, then reload or reinstall the A32NX on the ground.