ILS vs localizer explained: compare lateral and vertical guidance, approach minima, cockpit modes, glideslope failures and simulator use.
An ILS provides both lateral guidance from its localizer and vertical guidance from its glideslope, guiding an aircraft towards the runway in two dimensions. A localizer by itself provides lateral course guidance only. Consequently, a localizer-only approach normally has higher minima and is flown as a non-precision approach.
In real-world aviation and flight simulators, “localizer” can mean either the radio signal itself or a published localizer-only approach. That distinction explains why an ILS and a LOC procedure may use the same frequency yet have different instructions and minima.
ILS versus localizer at a glance
The decisive difference is vertical guidance: an ILS has it, while a localizer-only approach does not.
| Feature | ILS approach | Localizer-only approach |
|---|---|---|
| Guidance | Lateral localizer plus vertical glideslope | Lateral localizer only |
| Conventional classification | Precision approach | Non-precision approach |
| Vertical profile | Follow the electronic glideslope | Follow published altitudes, step-down fixes or an approved continuous descent technique |
| Typical minimum | Decision altitude or decision height | Minimum descent altitude or height |
| Typical autopilot mode | APP or APPR | LOC, VOR/LOC or the aircraft's equivalent |
| Landing minima | Usually lower | Usually higher |
The published approach chart always governs. Terrain, obstacles, equipment and local procedures can produce exceptions to the usual minima pattern.
Is the localizer part of an ILS?
Yes. The localizer is the lateral-guidance component of an Instrument Landing System.
Its ground transmitter is normally aligned with the runway centreline and tells the pilot whether the aircraft is left or right of the final approach course. The separate glideslope transmitter indicates whether the aircraft is above or below the intended descent path. Selecting an ILS localizer frequency normally pairs the corresponding glideslope frequency automatically in the receiver.
A localizer-only procedure can use the same transmitter and frequency as the ILS for that runway. The approach chart may therefore contain separate ILS and LOC minima, but the LOC procedure does not rely on the glideslope even if a glideslope indication happens to appear. Our practical guide to localizer and glideslope indications shows how the two signals work together in Microsoft Flight Simulator.
A published localizer back-course approach is also lateral-only. It must not use the reverse side of the glideslope, and some avionics require a dedicated back-course mode to prevent reversed steering commands.
Can you fly a localizer approach if the glideslope fails?
You may use localizer-only minima only when a LOC procedure or LOC minima are published and the applicable operational rules permit it.
Do not simply continue an ILS after receiving a glideslope warning flag or losing vertical guidance. You must rebrief the localizer altitude restrictions, minimum descent altitude and missed-approach point. If the failure occurs too late to make that transition safely, fly the missed approach.
A calculated GPS or VNAV descent path may help with a continuous descent, but it does not turn a LOC procedure into an ILS. It also does not replace compliance with every published altitude constraint unless the procedure and approved avionics explicitly provide otherwise.
How are ILS and LOC modes used in a flight simulator?
The aircraft's flight-mode annunciator is the best evidence of what the autopilot has actually captured; selecting an approach mode is not enough by itself.
- Load and verify the procedure. Confirm whether the chart says ILS, LOC or a combined ILS-or-LOC procedure, then check the final approach course, frequency and minima.
- Tune and identify the localizer. Some aircraft do this automatically through the flight-management system; others require manual radio tuning and course selection.
- Choose the correct intercept. For an ILS, establish on the localizer and intercept the glideslope from below. For a localizer-only approach, maintain the charted altitudes and do not wait for vertical capture.
- Arm the appropriate mode. Approach mode normally arms both localizer and glideslope capture. LOC or VOR/LOC mode commands lateral tracking only, although labels differ between aircraft.
- Check capture and fly the correct minima. Look for active rather than merely armed modes. On a LOC approach, observe the minimum descent altitude and published missed-approach point instead of descending on an unverified glide indication.
For a worked example, our MSFS 2024 ILS procedure explains the setup, intercept and mode changes without treating localizer capture as full ILS capture.
Why does the localizer capture but not the glideslope?
Localizer capture without glideslope capture usually means the aircraft is not correctly positioned or only lateral mode has been armed.
- The aircraft approached the glideslope from above rather than below.
LOCor navigation mode was selected instead of approach mode.- The published procedure is localizer-only or the glideslope is unavailable.
- The aircraft has not reached a valid glideslope interception area.
- The simulator's navigation data, selected runway or scenery installation does not match the procedure being flown.
FSX users can work through our focused glideslope-capture troubleshooting checks. The same basic checks—correct procedure, intercept from below and confirmation on the mode annunciator—apply to many other simulators.
Does an ILS automatically land the aircraft?
No. An ILS supplies approach guidance; it does not by itself provide an automatic landing.
Autoland requires a suitably equipped and certified aircraft, an appropriate ILS installation, valid operating conditions and the correct crew procedures. A localizer-only approach cannot support an ILS autoland because it lacks approved vertical guidance. In a simulator, pressing APP may track an ILS, but that does not guarantee automatic flare, touchdown or rollout.