ILS vs RNAV approach: what is the difference?

In aviation and real-world flying, an ILS approach uses runway-based radio transmitters to provide localiser and glideslope guidance. An RNAV approach uses the aircraft’s navigation system, usually GNSS/GPS and an FMS, to follow coded waypoints. ILS provides a vertical path; RNAV may provide lateral guidance alone or both lateral and vertical guidance.

The fundamental difference is where the guidance comes from. ILS indications respond to signals transmitted near the runway, while RNAV guidance is calculated aboard the aircraft from its position and a database procedure. RNAV is therefore a family of navigation capabilities rather than one fixed approach type.

ILS vs RNAV approach at a glance

The decisive differences are the selected cockpit source, availability of vertical guidance and the equipment on which each procedure depends.

How does the cockpit setup differ?

An ILS requires the correct radio signal and intercept geometry, whereas RNAV requires the exact database procedure, correct waypoint sequencing and GPS/FMS guidance. In both cases, the approach chart controls the procedure; our guide to reading the restrictions, guidance and minima on an instrument approach chart explains what to verify before loading or tuning anything.

Setting up an ILS approach

For an ILS, tune or verify the runway’s ILS and make sure the aircraft is displaying radio guidance before attempting to capture it.

1. Check the published procedure. Confirm the runway, frequency, inbound course, intercept altitude and minima.
2. Tune and identify the ILS. Some aircraft tune it automatically; otherwise, use the correct NAV radio and confirm the identifier where the simulator models it.
3. Select the radio source. Set or verify the front course and select VLOC, NAV or the equivalent source instead of GPS/FMS.
4. Establish a suitable intercept. Join the localiser at a moderate angle and normally capture the glideslope from below. Intercepting from above can prevent capture and may expose the receiver to false glideslope lobes.
5. Arm and verify approach mode. The button only arms the modes; the flight-mode annunciator must show actual LOC and GS capture.

The ILS beam becomes increasingly sensitive near the runway, so late, fast or steep intercepts can exceed an autopilot’s capture limits. Our practical MSFS 2024 sequence for tuning and capturing an ILS shows how these stages appear in the simulator cockpit.

Setting up an RNAV approach

For RNAV, load the exact procedure and keep the navigation display on GPS/FMS guidance throughout the approach.

1. Load the approach and cleared transition. Check every waypoint, altitude constraint and runway suffix because similarly named procedures can follow different paths.
2. Inspect the flight plan. Remove only discontinuities that should be removed; a vector leg may be intentional rather than a database error.
3. Select GPS/FMS guidance. The aircraft cannot follow the coded RNAV path while the course display is using a NAV radio.
4. Join the coded path correctly. Avoid an improvised direct-to near the final approach fix unless you know how that avionics unit will sequence the remaining legs.
5. Arm the supported modes. Some installations use APP or APR for an RNAV glidepath, while others require lateral navigation and VNAV separately. Trust the flight-mode annunciator, not the button light.

The loading and source-selection details are covered in our step-by-step method for flying RNAV approaches in Microsoft Flight Simulator.

Does RNAV always provide vertical guidance?

No; RNAV describes area navigation, not a guaranteed glidepath. The minima line and installed aircraft capability determine the guidance that may be used.

• LNAV: Lateral guidance only. Observe the published step-down restrictions and normally descend to an MDA.
• LNAV/VNAV: Approved lateral and vertical guidance, normally flown to a DA. The path may use barometric VNAV or satellite-based augmentation; temperature restrictions can apply to baro-VNAV.
• LPV: Satellite-based augmentation supplies increasingly sensitive lateral guidance and an approved glidepath to a DA. The receiver, aircraft and augmentation service must support it.
• LP: Satellite-based lateral guidance with localiser-like sensitivity but no approved vertical guidance.

A magenta vertical path does not prove that LNAV/VNAV or LPV minima are available. Some simulator avionics show advisory VNAV during an LNAV approach without fully modelling an approved vertical capability. Use the minima matching the approach indication actually annunciated by the avionics.

Is RNAV the same as GPS?

RNAV is the broader navigation concept; GPS is one possible position source. Most RNAV approaches encountered by general-aviation pilots and simmers are GNSS-based, and a procedure labelled RNAV (GPS) specifically requires suitable GPS capability. Other RNAV operations may combine GNSS, DME/DME and inertial sensors, subject to the procedure and aircraft approval.

Is RNP the same as RNAV?

RNP is a form of RNAV that adds defined navigation-performance requirements plus onboard performance monitoring and alerting. Ordinary RNP approaches should not be confused with RNP AR procedures, which require specific aircraft capability, crew approval and operational authorisation.

Is an LPV approach the same as an ILS?

No. LPV can look and feel similar because it provides angular lateral guidance and a glidepath, but it uses augmented GNSS rather than localiser and glideslope transmitters. It remains an RNAV procedure and must be flown using the GPS or FMS source.

ILS is conventionally classified as a precision approach. LPV provides precision-like guidance, but its formal classification and approval basis differ. Use the published equipment requirements and minima rather than treating LPV as an interchangeable ILS.

Which approach should a pilot choose?

Use the approach that is cleared or authorised, available for the runway, supported by the aircraft and suitable for the weather. Neither ILS nor RNAV is automatically more accurate, realistic or easier.

• Compare the minima: An ILS often has low minima at a well-equipped airport, but LPV may be comparable. The chart decides, not the approach label.
• Check aircraft capability: An ILS receiver cannot fly LPV, while a basic GPS installation may support LNAV but not LNAV/VNAV or LPV.
• Check serviceability: ILS can be affected by transmitter maintenance or protected-area restrictions. RNAV can be affected by integrity warnings, augmentation outages or invalid procedure data.
• Consider the arrival geometry: RNAV may offer useful waypoint transitions where an ILS would require vectors, but the loaded transition must match the clearance.
• Plan the missed approach: Confirm that the aircraft and its simulated avionics can sequence and fly the published missed procedure.

Use another procedure if the simulator’s aircraft implementation, navigation database or scenery does not reproduce the selected approach correctly.

Why will an ILS or RNAV approach not capture?

Most failed captures come from the wrong navigation source, unsuitable intercept geometry, incorrect flight-plan sequencing or unsupported minima rather than a broken autopilot.

A mistake we see constantly is pressing approach mode without checking the flight-mode annunciator. Confirm VLOC with LOC/GS for ILS, or GPS/FMS with the appropriate lateral and vertical modes for RNAV. If a real-world chart and navigation database disagree, use matching valid data and never improvise an instrument procedure.