Make autopilot follow a GPS flight plan by selecting the correct nav source and active leg, then using a proper intercept and NAV or LNAV mode.
In a flight simulator, load or enter the GPS flight plan, activate the correct leg, set the CDI/navigation source to GPS or FMS, then engage the flight director and autopilot and select NAV or LNAV while close to an intercept course. Altitude, speed and descent require separate modes.
Which autopilot mode follows a GPS flight plan?
Use NAV in most general-aviation aircraft and LNAV or managed navigation in an airliner fitted with an FMS. The exact label changes between aircraft, but the selected navigation source must match the system containing the route.
| Aircraft setup | Navigation source | Lateral mode |
|---|---|---|
| Conventional panel GPS and autopilot | GPS | NAV |
| G1000-style glass cockpit | GPS shown on the PFD | NAV |
| Airliner FMS | FMS or active managed route | LNAV or managed NAV |
| VOR or ILS tracking | NAV1, NAV2 or VLOC | NAV or APR |
Seeing the route on a moving map does not prove that the autopilot is coupled to it. The source annunciation on the primary flight display or course indicator is what matters.
How to couple the autopilot to a GPS route
The reliable sequence is route, active leg, GPS source, intercept and then NAV capture.
- Load the route into the cockpit avionics. Confirm that the GPS or FMS itself displays the waypoints. A route drawn on the simulator's planning map may not automatically reach a third-party aircraft's avionics. If needed, follow our guide to building and loading a simulator flight plan.
- Activate the route and correct leg. Check for an active magenta leg from your present position towards the next intended waypoint. Remove route discontinuities, and use the unit's leg-activation or direct-to function if it is trying to return to a waypoint behind the aircraft.
- Select GPS or FMS as the navigation source. On many GA panels, a CDI or source control changes between GPS and VLOC/NAV1. If VLOC or NAV1 is displayed, NAV mode will track a radio course rather than the GPS route.
- Create a sensible intercept. After take-off and once the aircraft is stable, use HDG mode to approach the active leg. An intercept of roughly 20–30 degrees is a sound starting point; capture may fail if the aircraft is far abeam, parallel to the route or flying away from it.
- Arm NAV or LNAV. Engage the flight director and autopilot as required by the aircraft, then select the lateral navigation mode. Watch the flight-mode annunciator: NAV or LNAV normally appears armed first and active after capture. The annunciator, not merely an illuminated panel button, tells you what the autopilot is doing.
- Select the vertical modes separately. Set the required altitude and use ALT, vertical speed, flight-level change or VNAV as appropriate. Our explanation of autopilot modes and their correct sequence covers those controls without assuming one particular aircraft.
Why is NAV armed but not capturing the GPS route?
NAV usually remains armed because the autopilot has no valid course to capture, the wrong source is selected or the aircraft has not reached the active leg.
- Wrong navigation source: change VLOC, NAV1 or NAV2 to GPS/FMS for route tracking.
- Wrong active waypoint: activate the intended leg or use direct-to for the next waypoint rather than allowing the system to turn back.
- Poor intercept geometry: use HDG mode to cross the course at a shallow angle. NAV capture is not guaranteed from any position or heading.
- OBS or SUSP is active: cancel OBS or sequencing suspension when appropriate. These modes prevent normal automatic waypoint sequencing.
- Route discontinuity: connect or clear the break in an FMS route and activate or execute the amended route if required.
- HDG remains active: NAV may only be armed. Wait for capture rather than repeatedly pressing the NAV button, which can disarm it on many panels.
- No GPS coupling: some older or simplified autopilots can follow VOR and localiser signals but are not connected to the installed GPS.
Simulator-specific implementations add their own traps. FSX users can work through our FSX GPS source and NAV-capture checks, while the X-Plane G1000 route-tracking checklist covers incorrect legs, CDI selection and OBS/SUSP behaviour.
Does GPS NAV mode control altitude?
No; NAV or LNAV normally follows the route laterally but does not control altitude by itself. Use ALT, vertical speed or flight-level change, or arm VNAV when the aircraft supports it and the route contains valid vertical constraints.
In some GA avionics, VNAV information is advisory rather than coupled to the autopilot. In more advanced systems, the selected altitude can act as a limit, so the aircraft may refuse to descend until a lower altitude has been set and the appropriate vertical mode is active.
When should I switch from GPS to VLOC?
Switch from GPS/FMS to VLOC or NAV1 when tracking a ground-based VOR, localiser or ILS, not when flying an RNAV/GPS approach.
For an ILS, tune and identify the frequency, set the inbound course where required, select the radio source early enough to intercept the localiser, and arm APR. Integrated airliners may tune or change sources automatically, so confirm the displayed source and captured modes.
For an RNAV/GPS approach, keep GPS selected, load and activate the approach, then arm APR if the avionics support glidepath capture. An approach offering lateral guidance only still requires manual descent management or another suitable vertical mode.
Can every simulator autopilot follow GPS?
No; the aircraft must have a GPS or FMS connected to an autopilot capable of GPS steering. If NAV follows VOR signals correctly but ignores GPS despite the correct source and active leg, the simulated installation may not support GPS coupling.
In that case, use HDG mode and adjust the heading bug to follow the route manually, or select an aircraft equipped with compatible GPS and autopilot systems. A magenta route on the simulator map alone does not add that capability.