Find why an FSX ILS localizer guides off-centre and fix NAV1 setup, GPS/NAV mode, wrong runway ends, offset beams and scenery conflicts.
FSX and FSX: Steam Edition ILS localizers can guide you off-centre because of a wrong runway end, GPS rather than NAV guidance, reception from behind, an offset beam, or scenery with mismatched runway and navaid positions. If the CDI is centred but the runway is displaced, suspect an offset approach or scenery mismatch.
What does an off-centre localizer look like in FSX?
The position of the CDI and the aircraft’s ground track usually reveal whether the fault is in the radio setup, autopilot or airport data.
| What you see | Most likely cause | Next check |
|---|---|---|
| CDI centred, but the runway stays on one side | Intentional offset or mismatched scenery and navaid data | Compare the localizer course with the runway heading, then test the stock airport |
| CDI reacts, but the aircraft follows the magenta flight-plan line | GPS selected instead of NAV or VLOC | NAV/GPS switch, GPS CDI mode and active receiver |
| Guidance appears reversed or leads away from the runway | Wrong runway-end localizer or reception from behind | Runway number, identifier, frequency and approach direction |
| Aircraft captures, overshoots and crosses repeatedly | Excessive speed or intercept angle | Use a stable 20–30 degree intercept rather than a close, steep cut |
| Nose points sideways while the CDI remains centred | Normal crosswind crab | Judge the ground track, not just the aircraft heading |
How do I correct an FSX localizer that guides off-centre?
Rebuild the approach setup from the runway end backwards before changing scenery or aircraft files.
- Confirm the exact runway end. Runway 09 and runway 27 are separate approach directions. The reciprocal end may have a different localizer frequency, use a back course or have no localizer approach at all.
- Use the data installed in FSX. Check the simulator’s airport information, map or flight-planning data. Stock FSX navigation data does not follow later real-world runway renumbering, frequency changes or airport reconstruction, while an add-on may supply different information.
- Tune and identify NAV1. Place the localizer frequency in the active side of
NAV1and enable its audio identifier if the panel provides that control. Most default FSX aircraft use NAV1 for autopilot localizer tracking; tuning NAV2 may move another indicator without giving the autopilot the required signal. - Select NAV or VLOC. Set the panel’s NAV/GPS selector to NAV, or change a GPS-driven CDI source from GPS to VLOC. Otherwise the localizer receiver can be working while the autopilot continues along the flight-plan route.
- Set the inbound front course. Use the published localizer course rather than simply converting the runway number into a heading. The course selector does not physically move the FSX localizer beam, but the correct setting prevents a misleading HSI presentation and is required by some add-on avionics.
- Intercept from the approach side. Join the front course at a shallow angle, at a controlled speed and preferably below the glideslope. Receiving the signal from behind the antenna can produce reverse or confusing lateral guidance.
- Arm approach mode on a stable intercept. Use heading mode to establish the intercept, then arm APP before reaching the centreline. Do not expect the default autopilot to recover cleanly from a fast, close-in intercept.
- Watch the raw CDI. If the needle centres but the autopilot flies elsewhere, the problem is the selected guidance source or aircraft avionics. If the needle remains centred on a path beside the runway, investigate the airport and localizer geometry.
Our full FSX ILS tuning and capture procedure shows the correct order for NAV1, front-course and approach-mode setup. If the indication never becomes alive or the autopilot will not capture it at all, use the checks for diagnosing a localizer that will not capture.
Can an ILS localizer be intentionally offset from the runway?
A localizer approach can deliberately follow a course that is not exactly aligned with the runway centreline.
Compare the stated localizer inbound course with the runway’s actual magnetic heading. Do not use the runway number alone: runway designations round the magnetic direction to the nearest ten degrees, so a small difference is normal. FSX’s older magnetic and airport data can also differ from a later chart.
A clear angular difference, combined with a stable centred CDI, indicates that the aircraft may be tracking the beam correctly. Follow the published course to the specified visual transition or minimums, then align visually as the approach requires. Do not force the aircraft towards the runway while still treating the offset beam as centreline guidance. Our guide to recognising and flying an offset localizer explains that distinction in more detail.
Why is the CDI centred when the runway is not?
A centred CDI beside the runway usually means the localizer coordinates and visible airport scenery do not match.
This often happens when replacement scenery moves or rotates a runway but leaves FSX using localizer data from another airport facility file. Two active airport packages can cause the same fault: one supplies the runway while a higher-priority or duplicate file supplies the navaid. A nearly parallel beam displaced consistently to one side is a strong clue.
- Disable the add-on airport temporarily. Restart or reload FSX and fly the same approach using the stock airport.
- Compare the result. If the stock runway and localizer align, the add-on package or its interaction with another scenery layer is responsible.
- Check for duplicate airport files. Keep only the intended package active unless its instructions explicitly require supporting airport files. Do not delete unfamiliar BGL files without making a backup.
- Correct the facility data, not the cockpit course. A course knob or heading bug cannot relocate a geographically misplaced beam. The runway and localizer must be defined by compatible airport data.
Experienced scenery users can place a corrected facility in a separate, higher-priority scenery layer rather than modifying stock files directly; our instructions for creating or correcting a custom FSX ILS cover the required runway association and beam alignment.
Why does the autopilot turn away from a valid localizer?
The autopilot is usually following the wrong navigation source, the wrong receiver or a signal received from the rear.
Default FSX panels generally expect NAV1 and the NAV position of the NAV/GPS switch. More complex add-on aircraft may instead use an avionics source selector, flight-management system or dedicated approach mode. Confirm which source is displayed on the primary instrument rather than assuming that an active NAV1 frequency controls the autopilot.
The selected course cannot repair reverse reception. Verify that the aircraft is approaching the localizer from the front-course side and that the tuned identifier belongs to the intended runway end. If the same behaviour occurs at every airport, test a default aircraft at a stock airport in calm conditions; that separates aircraft configuration and controller drift from airport-specific data.
Is the aircraft off-centre, or only pointing sideways?
An aircraft can point noticeably to one side while tracking the localizer centreline correctly in a crosswind.
Use the CDI and ground track as the test. If the needle remains centred and the aircraft travels along the runway centreline, the offset nose angle is a normal crab into wind. The fault is genuine only when the flight path itself remains beside or diverges from the localizer course.