Duplication of equipment makes complete loss of communication an extremely rare event.
Sleeping receiver. Pilot realises that he/she has heard no communication from ATC or from other aircraft for some time. Pilot transmits successfully to ATC and finds that ATC have been trying unsuccessfully to make contact for some time. Post-flight investigations reveal no identifiable fault in the radio equipment.
Airborne Equipment. Pilot selects a new frequency but equipment does not respond to change, so pilot is unable to transmit or receive on this frequency.
Stuck Microphone. Microphone remains live after pressure on the transmit switch used has been released, blocking other transmissions on this frequency.
Flight crew should always record occurrences as defects in the Aircraft Technical Log after flight. This will provide usable data and ensure that a technical asessment/response is made, recorded and signed for.
Pilots and ATCOs report any equipment malfunction, including suspected sleeping receiver, using the national occurrence reporting system, to enable trends to be detected.
Operators and ATCUs report equipment malfunctions to the manufacturer to allow improvements to be made to equipment.
National authorities continue to investigate sleeping receivers in order to develop solutions.