Radio and Navigation Equipment Operation
This domain tests practical knowledge of the radios and navigation receivers you will use: frequencies, controls, transponder and emergency equipment, and what to do when something fails.
Core rules
- VHF communications use 118.000–136.975 MHz, with 8.33 kHz or 25 kHz channel spacing; reception is essentially line-of-sight, so range falls with altitude and terrain.
- 121.5 MHz is the international aeronautical emergency frequency and is guarded; 243 MHz is the military counterpart. Do not use either for routine calls.
- The transponder codes are 7700 (emergency), 7600 (radio failure) and 7500 (unlawful interference). Select ALT (Mode C/S) when airborne unless instructed otherwise; use IDENT only when asked.
- An ELT transmits on 121.5 and/or 406 MHz; know how to arm, test and activate it.
- Navigation receivers: VOR gives radial or bearing, ILS has localizer and glideslope, DME is usually paired with VOR or ILS, ADF uses NDB, and GNSS provides RNAV. Check audio, volume, squelch and the audio panel before blaming the radio.
Worked example
You lose contact with approach. Check the audio panel, volume and squelch, confirm the frequency and try the second radio. If still no contact, squawk 7600, follow the published lost-communication procedure and land; report the failure after landing. Reasoning: most “radio failures” are panel or frequency errors; 7600 alerts ATC while you continue safely.
Traps
Using 121.5 for a chat; forgetting to select ALT; not knowing that 8.33 kHz channels have distinct displays; assuming VHF works behind terrain; and transmitting on a stuck PTT without checking.