Microlight » Flight Radio » Loss of Comms - Aircraft Equipment

Checks that should be followed when becoming aware of an aircraft communication system failure, including a check of:

(a) radio power source;

• master switch is on
• avionics switch is on
• circuit breakers/fuses are not popped or blown

(b) function settings (frequency, squelch and similar);

• correct frequency is selected
• squelch function and level is set correctly
• volume is not turned down too low
• correct comms box is selected

(c) microphone or headset.

• microphone and leads are correctly plugged in
• volume on the headset is up

Carrier Wave Only

One fault a transmitter can have is an unmodulated carrier wave (carrier wave with no message on it).

If you hear this, it will sound like a silent radio transmission.

The station with the problem will still be able to receive messages but will not be able to send any and will not realise they have a problem.

You could advise the station of the problem by transmitting the message "Station calling, Carrier Wave Only".

Speechless technique using unmodulated transmissions

​​​​​​AIP ENR 1.15-11 (Pink pages)