NAV vs GPS explained: choose the right source and autopilot mode for flight plans, VORs, ILS approaches, LNAV, HDG/TRK and MSFS.
Use GPS/FMS as the navigation source for a programmed route or GPS approach, and VLOC/NAV for a VOR, localiser or ILS. NAV is usually the autopilot mode that captures and tracks whichever lateral source is selected; use HDG/TRK to steer or establish an intercept first, and APP/APR for approach guidance.
NAV vs GPS: are they separate autopilot modes?
Usually, GPS is a guidance source, while NAV is an autopilot tracking mode. In our Aviation & Real-World Flying guidance, this distinction is the key to understanding most general-aviation autopilots and their simulator equivalents.
A GPS/NAV, CDI or source selector determines what drives the CDI or HSI. Selecting GPS does not necessarily tell the autopilot to follow it; after selecting the source, you normally engage NAV, LNAV or another appropriate lateral mode. Our explanation of what the GPS/NAV source switch changes covers the panel arrangements where these controls are easily confused.
There is no universal autopilot mode called GPS mode. Some panels display GPS as the selected source, while others provide GPSS roll steering or use an integrated FMS. The flight-mode annunciator and the aircraft’s own documentation take precedence over a generic rule.
Which NAV, GPS, HDG or APP setting should I choose?
Choose the source that generates the path you intend to fly, then engage the mode designed to capture that path.
| What you want to fly | Source or target | Typical lateral mode |
|---|---|---|
| Programmed GPS or FMS route | GPS/FMS with an active leg | NAV on many GA aircraft; LNAV or managed NAV on airliners |
| VOR radial or radio airway | VLOC, NAV1 or NAV2 with the correct station and course | NAV or VOR/LOC, depending on the installation |
| ILS localiser and glideslope | Correct ILS receiver or automatically tuned radio source | APP/APR; LOC or VOR/LOC provides lateral capture only |
| RNAV GPS approach | GPS/FMS with the procedure active | NAV/LNAV for lateral guidance; APP/APR or an aircraft-specific approach mode for supported vertical guidance |
| ATC vector or manual course intercept | Selected heading or ground track | HDG/TRK initially, then NAV, LNAV or APP when positioned to capture |
Do not choose GPS merely because a flight plan is displayed on the moving map. The active CDI source, active leg and autopilot coupling determine what the aircraft will actually follow.
How do I fly GPS with the autopilot?
To fly GPS successfully, activate the required route leg, select GPS/FMS as the source, establish a reasonable intercept and then engage NAV or LNAV.
- Load and check the route. Look for incorrect waypoints, route discontinuities and a first leg that points behind the aircraft.
- Activate the intended leg. Loading a route or approach does not always activate it. Use the appropriate direct-to, leg activation or procedure function when required.
- Select GPS or FMS. Confirm the source label beside the CDI or HSI. Do not rely only on needle colour, because displays and add-ons differ.
- Use HDG or TRK to intercept. Approach the active leg at a moderate angle rather than expecting NAV to recover from a distant, parallel or badly offset position.
- Arm NAV or LNAV. Watch the flight-mode annunciator to see whether the mode is merely armed or has become active.
- Monitor the capture. The deviation should reduce and the commanded bank should turn towards the active path. If it does not, disconnect or select HDG and correct the setup.
For navigator-specific preparation, including route activation and approach sequencing, see our practical guide to flying a GPS route in a simulator.
HDG vs NAV: when should I select HDG/TRK first?
Use HDG or TRK first when receiving vectors, avoiding weather, resolving an invalid route or positioning the aircraft for NAV or approach capture.
HDG follows the selected magnetic heading and therefore allows the wind to move the aircraft sideways. TRK follows a selected ground track where the avionics support it, automatically commanding a wind-corrected heading. NAV follows a defined path such as an active GPS leg, VOR course or localiser.
Selecting HDG/TRK first is especially useful when the aircraft is too far from the route, approaching it at an excessive angle or flying towards the wrong leg. Once the deviation begins moving towards centre and the correct mode is armed, NAV should capture without a sudden reversal or full-scale intercept.
What does SELECT HDG/TRK FIRST mean in the Fenix A320?
In the Fenix A320, SELECT HDG/TRK FIRST means the flight-guidance system requires a selected heading or track target; it is not asking you to change from GPS to a NAV receiver.
Set the required value in the FCU heading/track window and pull the HDG/TRK selector to request selected mode. Confirm HDG or TRK on the flight-mode annunciator. After correcting the route, discontinuity or intercept geometry, push the selector to request managed NAV again and verify that NAV arms or engages.
The exact trigger depends on the aircraft state being modelled. If managed guidance is unavailable, repeatedly pushing the knob will not repair an inactive flight-plan leg or an unsuitable intercept.
How do LNAV and NAV differ in the A320 and B737?
On airliners, LNAV or managed NAV normally follows the FMS route, while selected heading and radio-approach modes handle vectors and localiser capture.
In an A320, NAV is the managed lateral mode associated with the FMGS flight plan; pulling the HDG/TRK selector requests a selected target, while pushing it requests managed guidance. In many B737 simulations, LNAV follows the active FMC route, HDG SEL follows the MCP heading, VOR/LOC captures radio lateral guidance, and APP arms the ILS localiser and glideslope.
There is no standard cockpit function called an LNAV log. Check the FMC LEGS and route-progress pages for active-leg information, and the flight-mode annunciator for the mode actually controlling the aircraft. Exact capture logic varies among B737 generations and simulator add-ons.
What is approach mode in MSFS?
Approach mode in MSFS arms the compatible lateral and vertical guidance needed for an approach; it does not automatically configure, slow or land the aircraft.
In both MSFS 2020 and MSFS 2024, the result depends on the simulated aircraft and avionics. For an ILS, APP or APR normally arms localiser and glideslope capture. Tune and identify the correct ILS where manual tuning is required, set or verify the inbound course, intercept the localiser and approach the glideslope from below.
For an RNAV GPS approach, keep GPS/FMS selected and activate the procedure. APP/APR may capture a GPS glidepath if the navigator, approach and autopilot support it; otherwise NAV or LNAV may provide lateral guidance only. An approach with only lateral guidance does not gain a valid glidepath merely because APP was pressed.
Some airliners manage radio tuning and source changes automatically. On A320-style panels, the LS button displays landing-system information but does not itself arm the approach; the APPR button requests approach capture. On a B737-style panel, VOR/LOC normally captures only the localiser, while APP also arms the glideslope.
For the complete ILS sequence, including when GPS should give way to radio guidance, follow our source and mode checks for flying an ILS.
Why does NAV mode ignore my GPS route?
NAV mode most often ignores a GPS route because the wrong source is selected, no valid leg is active or NAV has armed without reaching its capture conditions.
- Wrong source: the CDI still shows VLOC, NAV1 or NAV2 instead of GPS/FMS.
- No active leg: the plan is loaded but inactive, a discontinuity remains, or the navigator is in OBS or SUSP mode.
- HDG remains active: NAV or LNAV was never armed, or the aircraft has not entered its capture area.
- Bad intercept: the aircraft is too far away, almost parallel to the course or approaching a leg that lies behind it.
- Wrong receiver: the autopilot or flight director is coupled to a different side or NAV receiver from the one being displayed.
- Invalid radio guidance: a VOR or localiser is mistuned, out of range or not providing the expected signal.
- Installation-specific GPSS: some retrofit systems feed GPS roll steering through HDG mode rather than conventional NAV mode.
- Conflicting simulator bindings: duplicate controller assignments can immediately cancel or replace the selected autopilot mode.
On common FSX panels, the GPS/NAV switch selects the signal and the NAV button commands the autopilot to track it. If that arrangement still fails, work through these FSX GPS and NAV coupling checks.
Always diagnose the annunciator rather than the illuminated button. An illuminated NAV or APP button may mean the mode is armed and waiting, not that it is controlling the aircraft.
Can radio navigation act as backup NAV if GPS fails?
Radio navigation can provide backup guidance where the aircraft has a working receiver and suitable VOR, DME, localiser or ILS coverage, but NAV mode does not switch to that backup automatically.
Select the appropriate radio source, tune and identify the station, set the required course, establish an intercept and then arm NAV, VOR/LOC or APP. If the panel has no independent radio receiver, or the available ground aid does not support the intended route, selecting NAV will not create backup guidance.
Airliners may retain FMS guidance through inertial or radio-position updating after losing GPS, depending on their equipment and failure state. That is different from manually selecting raw VOR or localiser data. In every case, confirm the displayed source, deviation indication and active flight mode before relying on the autopilot.