ILS vs RNAV: what is the difference in flight simulation?

ILS and RNAV guide an aircraft to a runway in different ways. In a general flight simulator, ILS uses ground-based localiser and glideslope radio signals, while RNAV uses the aircraft’s GPS/FMS position and a coded procedure. ILS provides lateral and vertical guidance; RNAV guidance depends on the approach minima and aircraft.

ILS vs RNAV at a glance

An ILS beam becomes progressively more sensitive as the aircraft approaches the runway. RNAV follows a calculated path instead; LPV guidance behaves similarly to an angular localiser and glidepath, but it is not an ILS signal.

How does the cockpit setup differ?

Setting up an ILS approach

1. Select the published procedure. Check the runway, ILS frequency, inbound course, intercept altitude and minima against the approach chart.
2. Tune and identify the ILS. Some airliners do this automatically. Otherwise, tune the correct NAV radio and confirm the identifier where the simulator models it.
3. Select the radio guidance source. A mistake we see constantly is leaving the display on GPS/FMS guidance while expecting the autopilot to capture the localiser.
4. Intercept from a sensible position. Join the localiser at a moderate angle and normally capture the glideslope from below.
5. Arm approach mode. Confirm LOC and GS capture on the flight-mode annunciator rather than trusting the button light alone.

For the aircraft-specific mode sequence, our MSFS 2024 ILS setup and capture guide covers tuning, source selection and approach-mode use.

Setting up an RNAV approach

1. Load the exact approach and transition. Verify every waypoint, altitude constraint and the runway suffix; similarly named procedures can follow very different paths.
2. Check for route discontinuities. Remove only those that should be removed. A deliberate vector leg is not always an error.
3. Select GPS/FMS guidance. The aircraft cannot follow an RNAV path while the course display is using a NAV radio.
4. Establish the aircraft on the coded path. Avoid using direct-to near the final approach fix unless you understand how that avionics unit handles approach sequencing.
5. Arm the supported modes. Some aircraft use APP/APR for an RNAV glidepath; others require lateral navigation and VNAV modes separately. The flight-mode annunciator is decisive.

Our practical GPS/RNAV approach workflow explains procedure loading, activation, LNAV versus LPV guidance and missed captures in Microsoft Flight Simulator.

Does RNAV always provide vertical guidance?

No. RNAV describes area navigation, not a guarantee of a glidepath. The minima line on the chart and the aircraft’s installed capability determine what guidance can be used.

• LNAV: lateral guidance only. Descend using published step-down fixes and the minimum descent altitude.
• LNAV/VNAV: lateral guidance plus a vertical path, provided the aircraft and simulated avionics support it.
• LPV: precise lateral and vertical guidance with a decision altitude, normally displayed as a glidepath rather than an ILS glideslope.

A magenta vertical path does not automatically authorise LPV or LNAV/VNAV minima. Some default or older simulator avionics display advisory VNAV even though they do not fully model the published approach capability. Fly the minima matching the approach indication actually shown by the avionics.

Which approach should you choose?

Choose the procedure supported by the runway, weather, chart and simulated aircraft—not whichever technology sounds more advanced.

• Choose ILS when the runway has a working ILS and the aircraft can receive it. It offers a familiar, stable final approach but still requires correct tuning and interception.
• Choose RNAV when it provides a useful procedure to a runway without ILS, a better arrival path, or appropriate minima for the aircraft’s capability.
• Use another procedure if the simulator’s navigation database, aircraft implementation or scenery does not reproduce the selected approach correctly.

Neither approach is automatically easier or more realistic. ILS setup is straightforward once the radio source is correct; RNAV reduces manual tuning but demands careful procedure verification and waypoint management.

Why will the autopilot not capture the approach?

Most failed captures come from the wrong navigation source, an invalid intercept or an approach mode that was armed without meeting its capture conditions.

• ILS stays on GPS guidance: select the NAV receiver carrying the ILS and verify the correct frequency and identifier.
• Localiser captures but glideslope does not: intercept from below, check the published altitude and confirm that GS is armed.
• RNAV turns away from final: inspect the loaded transition, active waypoint, discontinuities and any direct-to command.
• No RNAV glidepath appears: check that the selected minima provide vertical guidance and that the aircraft supports that approach type.
• The aircraft passes through the path: reduce speed, use a shallower intercept and establish earlier. Autopilots have capture limits.
• The indications disagree with the runway: the simulator’s scenery and navigation data may be from different revisions. Follow the instruments only after confirming that the procedure matches the installed runway.

Is RNP the same as RNAV?

RNP is a form of RNAV that adds defined navigation-performance requirements plus onboard monitoring and alerting. The terms are therefore related but not interchangeable; our RNP approach explanation and workflow covers those extra requirements and the avionics checks they introduce.