Learn how COM and NAV radios work in a flight simulator, including active and standby frequencies, audio panels, CDI sources and common fixes.
In a flight simulator, COM radios handle two-way voice communications with ATC, while NAV radios receive navigation signals from VORs, localisers and ILS glideslopes. You enter a frequency in standby, swap it to active, select the correct radio or display source, then identify and use the signal.
What is the difference between COM and NAV radios?
COM radios are for communications; NAV radios provide guidance from ground-based navigation aids.
| Equipment | Purpose | What the pilot selects |
|---|---|---|
| COM1 and COM2 | Transmit and receive ATC or air-to-air communications | Active frequency, transmit radio and monitored receivers |
| NAV1 and NAV2 | Receive VOR, localiser and compatible glideslope signals | Frequency, CDI or HSI source, and course where required |
| ADF | Points towards an NDB | ADF frequency and bearing display |
| GPS or FMS | Provides database-based route guidance | Flight plan and GPS/FMS navigation source rather than a NAV frequency |
COM1 and COM2 are independent radios. You can normally listen to both through the audio panel, but only one is selected for transmission at a time unless the aircraft models a specialised split mode.
NAV1 and NAV2 are also independent, but their indications depend on the aircraft's wiring and avionics. NAV1 might drive the main HSI and autopilot while NAV2 feeds a second CDI or bearing pointer; glass cockpits often let you change those assignments.
Most radio stacks have active and standby frequency windows. The active frequency is being used, while standby is only a convenient place to prepare the next one. Pressing the transfer or swap button exchanges them. Older radios may tune the active frequency directly, and some glass cockpits can auto-tune frequencies through the flight-management system.
How do I tune and use COM and NAV radios?
To use either radio, power the avionics, tune the correct frequency, make it active and route that radio to the appropriate audio or flight instrument.
- Find the frequency. Obtain the ATC channel, VOR frequency or runway-specific ILS frequency from the simulator's ATC interface, map or compatible chart data. An ILS frequency belongs to a particular approach, not merely to the airport.
- Power the equipment. Check the battery, alternator or generator, avionics master and relevant radio controls. Some simulated aircraft model separate electrical buses and circuit breakers.
- Tune and transfer. Enter the frequency in the standby field and swap it to active. Confirm that it went into COM1, COM2, NAV1 or NAV2 as intended.
- Route the radio. For COM, select the required transmitter and enable its receiver on the audio panel. For NAV, set the CDI or HSI source to NAV1, NAV2 or VLOC rather than GPS.
- Configure the indication. For a VOR, set the desired radial or course with the OBS control. For a localiser, set the published front course so the HSI and course guidance are presented sensibly; the OBS setting does not move the localiser beam.
- Identify the station. Listen for the Morse identifier or check the decoded identifier where the aircraft models it. A frequency alone is not proof that the intended station has been received.
- Use the signal. Transmit through the simulator's ATC menu, push-to-talk system or connected voice client. For navigation, intercept and follow the CDI or HSI indication rather than flying directly towards the station in every situation.
A mistake we see constantly is tuning COM2 while the audio panel still transmits on COM1, or tuning NAV1 while the CDI remains set to GPS. The displayed frequency can be correct and still control nothing useful.
Microsoft Flight Simulator users can follow our explanation of using COM radios with the simulator's built-in ATC. For radials, station passage and the difference between VOR and NDB equipment, see our practical VOR and NDB tuning guide.
Does tuning a NAV radio make the autopilot follow it?
No: tuning the frequency only makes the signal available; the correct flight-instrument source and autopilot mode must also be selected.
For a VOR, select NAV or VLOC as the CDI source, intercept the chosen course and engage the appropriate lateral navigation mode. For an ILS, the approach mode normally captures the localiser laterally and the glideslope vertically, provided the aircraft is suitably positioned and both signals are valid.
Do not expect approach mode to rescue a poor intercept from the wrong side of the airport or far above the glideslope. Use heading mode or hand-fly to establish a sensible intercept, verify that the localiser indication is alive, then arm the mode specified for that aircraft. Our explanation of how the ILS glideslope is received and displayed covers the vertical signal in more detail.
Why is my COM or NAV radio not working?
Most simulated radio failures come from an incorrect selection, missing electrical power, poor signal geometry or conflicting navigation data rather than a defective radio.
- The frequency is still in standby: transfer it to the active field and confirm the digits after the swap.
- The wrong radio is selected: match COM1 or COM2 to the audio-panel transmitter, and NAV1 or NAV2 to the CDI, HSI or bearing-pointer source.
- The audio path is muted: turn up the radio and intercom volumes, select the receiver on the audio panel and check the simulator's communications audio settings.
- The signal is out of range: VOR and ILS reception is largely line-of-sight. Low altitude, terrain, distance and being outside the directional localiser or glideslope coverage can prevent a usable indication.
- The frequency data do not match: an old chart, updated aircraft database or scenery package can disagree with the simulator's navigation database. Compare the identifier and runway, not only the frequency.
- GPS is still the active source: change the CDI from GPS or FMS guidance to NAV or VLOC before expecting the radio signal to move the course deviation indicator.
- A control binding is changing the radio: hardware panels, rotary encoders and duplicate keyboard assignments can immediately overwrite a frequency or source selection.
- The communications method is different: offline ATC may use menu responses and synthetic speech, so a microphone is unnecessary. Online voice operation requires the external client, push-to-talk input and selected COM radio to agree.
For a quick diagnosis, read four items directly from the panel: the active frequency, radio number, selected COM transmitter and CDI source. Those checks expose the most common cases where a correctly tuned radio is connected to the wrong system.