Learn how to intercept and track an ILS localizer, choose the right intercept angle, correct for wind, and fix common capture problems.
In real-world aviation and flight simulation, intercept an ILS localizer by tuning and identifying the correct ILS, selecting NAV/VLOC, setting the published front course and approaching it on a cleared or published heading that gives a shallow intercept angle. As the deviation bar centres, turn inbound, then use small wind-correction changes to hold it.
What should I set before intercepting the localizer?
Before intercepting, confirm the approach, receiver, navigation source, front course and joining geometry.
- Approach: Verify the runway, ILS identifier, localizer frequency, inbound course and assigned or published intercept altitude.
- Receiver: Tune the correct navigation receiver and identify the facility by its displayed or audible identifier where modelled. A valid frequency alone does not prove that the correct ILS is selected.
- Navigation source: Select NAV, VLOC or the equivalent radio-navigation source. A common simulator mistake is leaving the CDI or PFD coupled to GPS/FMS guidance.
- Front course: Set the published inbound course. Although the course knob does not alter raw localizer sensing on some traditional indicators, it keeps the HSI, flight director and autopilot presentation meaningful.
- Aircraft state: Establish a manageable speed, stable altitude and sensible configuration before the needle becomes active. For a complete ILS, join the localizer below the glideslope unless the published procedure says otherwise.
If the cockpit indications are unfamiliar, our guide to how the NAV receiver, CDI or HSI and source selector work together explains the required equipment. The localizer provides lateral guidance only; see our explanation of localizer guidance versus the complete ILS for the vertical-guidance distinction.
How do I intercept an ILS localizer correctly?
- Join from authorised geometry. Follow the published transition or ATC vector. An intercept angle of roughly 20–30 degrees is a practical norm, but the chart or clearance takes precedence. Avoid attempting capture from behind the antenna, at a large angle or far outside the published sector.
- Hold the intercept heading and altitude. Do not turn towards every early needle movement. Wait for a positive, steady indication while maintaining the assigned altitude.
- Watch the closure rate. The faster the needle moves towards centre, the earlier the turn must begin. Airspeed, intercept angle and wind all affect this rate, so there is no universal CDI-dot turn cue.
- Lead the turn. Start turning towards the inbound course before the bar reaches the centre. Waiting until it is centred usually produces an overshoot, especially with a steep intercept angle.
- Roll out with wind correction. Aim initially for the inbound course plus an estimated crab angle. If the bar remains centred, hold that heading; if it drifts, adjust in small increments.
Localizer deflection is angular and becomes increasingly sensitive as the aircraft approaches the runway. Corrections that work several miles out can produce an S-turn close to the threshold.
How should LOC or APP autopilot mode be used?
Arm LOC or APP while the aircraft is established on a sensible intercept heading, then verify capture on the flight-mode annunciator rather than assuming the button press worked.
LOC normally captures lateral guidance only, while APP usually arms both localizer and glideslope capture. Exact mode logic differs between aircraft. Armed and captured are separate states; if the aeroplane crosses the course without capture, use heading mode to establish another intercept rather than repeatedly pressing APP. Airliner users can follow our 737-specific LOC, APP and flight-mode annunciator sequence.
How do I track the localizer without chasing the needle?
Track the localizer by bracketing a stable wind-correction heading, not by continuously steering towards the moving deviation bar.
With a correctly configured front-course display, a needle displaced left means the localizer course lies to the left. Turn left by a small amount, observe the trend, then remove most of that correction before the needle reaches centre. The resulting heading becomes the new wind-corrected heading.
If the needle drifts again, repeat with a smaller change. Close to the runway, one or two degrees may be enough in smooth conditions. The published inbound course is the ground track, so the aircraft heading may legitimately differ from it because of crosswind.
A mistake we see constantly in simulators is holding the corrective turn until the needle centres. That guarantees an overshoot: the aircraft still has lateral momentum when the bar reaches the middle. Reduce the correction as soon as the needle develops a clear trend towards centre.
Why will the localizer not capture or remain centred?
| Symptom | Likely cause | What to check |
|---|---|---|
| No needle or a warning flag | Wrong frequency, unavailable facility or aircraft outside usable coverage | Confirm the approach, frequency, identifier and receiver status. |
| GPS route remains displayed | GPS/FMS is still the selected navigation source | Select NAV/VLOC or verify that the aircraft's automatic source change occurred. |
| Needle moves in an unexpected direction | Wrong runway, back-course geometry or incorrect course presentation | Confirm the front-course approach and set the published inbound course. Do not improvise a back-course approach. |
| Autopilot flies through the course | LOC/APP was not armed, the intercept was too steep or capture limits were exceeded | Return to heading mode, create a shallow re-intercept and re-arm the correct mode according to the aircraft procedure. |
| Aircraft repeatedly S-turns | Late corrections, excess speed or needle chasing | Reduce correction size, anticipate the centre and establish a steady crab heading. |
| Needle is centred but heading differs from the chart | Normal crosswind correction | Hold the heading that maintains the course; do not force the nose onto the published course number. |
Chart and simulator navigation databases can also disagree, particularly when an older aircraft database is paired with newer procedure information. If the frequency, identifier or course does not match, stop the approach setup and resolve the discrepancy rather than forcing a capture.
Does localizer capture mean I can descend?
No. Localizer capture establishes lateral guidance; it does not by itself authorise or command descent.
On a full ILS, remain at the cleared or published altitude until valid glideslope capture and follow the charted altitude restrictions. A localizer-only approach instead uses its published step-down fixes and minimum descent altitude. In real-world flying, the approach chart, ATC clearance, aircraft manual and operator procedures always override generic technique.