How do I tune the correct ILS frequency for an approach?

In real-world aviation and flight simulation, tune the correct ILS frequency by selecting the exact published approach for the airport and runway, entering its localiser frequency in the active NAV receiver, setting the published inbound course and verifying the localiser identifier. The glideslope frequency is paired automatically and is not normally tuned separately.

How do you tune an ILS frequency correctly?

The safest sequence is to copy the localiser frequency, identifier and inbound course from the same published approach, then verify all three in the cockpit.

1. Select the exact approach. Match the airport, runway designator and procedure name, including left, right or centre runways and any Y or Z suffix. Do not assume every approach to the same runway uses an identical setup.
2. Read the published ILS data. Find the localiser frequency, identifier and final approach course on the chart or in the aircraft's navigation database. Our explanation of finding runway-specific ILS data and matching it to the procedure shows where these values normally appear.
3. Enter the frequency in the correct receiver. On a conventional radio, place it in the active NAV1 position, not the COM radio or standby window. In an airliner, enter or confirm it on the radio-navigation page or dedicated ILS field. Only recognised localiser channels within the valid ILS frequency range will be accepted.
4. Set the published inbound course. Use the charted final approach course rather than estimating it from the runway number. Depending on the avionics, this may be labelled CRS, COURSE or OBS.
5. Select the localiser navigation source. A glass cockpit normally needs VLOC, LOC1 or an equivalent source instead of GPS. Loading an ILS into the flight plan does not guarantee that every aircraft will tune the radio or switch the source automatically.
6. Verify the identifier. Compare the decoded identifier on the display, or listen to its audio identification where modelled, against the chart. An unexpected identifier can mean that the wrong facility is being received, even when the frequency looks plausible.
7. Intercept before capture. Approach the localiser from a sensible angle and at the published glideslope intercept altitude. If using the autopilot, follow the correct timing for arming ILS approach mode rather than pressing it after passing through the beam.

Where should the ILS frequency come from?

The correct source is the chart or navigation data for the specific cleared approach, not the runway number, an old flight plan or a frequency remembered from an earlier flight.

For real flying, use an approved, current source and check whether the localiser or glideslope is reported unavailable. For simulation, chart data, the aircraft database and the simulator's radio-navigation data can occasionally use different update cycles. If they disagree, compare the procedure identifier and course as well as the frequency; updating only one source can create a mismatch.

Some aircraft auto-tune the ILS after the approach is selected or activated. Treat that as assistance, not proof: confirm the displayed frequency and identifier. A previous manual entry may also prevent automatic tuning until it is cleared.

Do you tune the glideslope frequency separately?

No, normal ILS equipment pairs the glideslope channel automatically with the selected localiser frequency.

If the localiser works but there is no glideslope indication, check that the published procedure is a full ILS rather than a localiser-only approach. The glideslope may also be unavailable, the aircraft may be outside its usable reception area, or the simulator may have mismatched navigation data.

Can you use the runway number as the ILS course?

No, the runway number is only a rounded indication of magnetic direction; set the exact inbound course printed for the procedure.

For example, a runway numbered 27 does not guarantee a published course of exactly 270 degrees. The selected course does not move or retune the localiser beam, but it affects the HSI presentation and can matter to autopilot logic. A published localiser back-course procedure also requires its own charted setup and must not be improvised by simply entering a reciprocal heading.

How can you tell that the correct ILS is tuned?

A correct setup has the expected frequency, the published identifier, the correct inbound course and a localiser indication appearing from the expected side of the approach.

• The frequency is active in the receiver used by the flight instruments and autopilot.
• The displayed or audible identifier matches the chart.
• The navigation source shows VLOC, LOC or the aircraft's equivalent, not GPS.
• The localiser deviation responds as the aircraft approaches the final approach path.
• The glideslope becomes usable near the published intercept point on a full ILS.

In some simulators the audio identifier is not modelled reliably. In that case, use the decoded cockpit identifier where available and cross-check the frequency, course, airport and runway rather than relying on needle movement alone.

Why is the ILS not working after tuning?

Most ILS failures after tuning come from an inactive frequency, the wrong navigation source, an incorrect procedure or poor intercept geometry rather than a faulty radio.