Description

Sound communications rely on reliable and efficient communication equipment. This article deals with technical problems involving communication equipment.

Types of Equipment Problems

The problems which contribute most commonly to communication breakdown are:

• Airborne radio equipment malfunction;
• Ground equipment malfunction; and,
• Stuck microphone selector.

Effects

Impairment of communication, or complete or partial loss of communication.

Defences

Duplication of equipment makes complete loss of communication an extremely rare event.

Typical Scenarios

• 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.

Solutions

• 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.
• The CPDLC UM157 "CHECK STUCK MICROPHONE [frequency]" may be used to alert the pilot that their radio is blocking the frequency.

Further Reading

• ALLCLEAR? Toolkit

AGC Safety Letters:

• AGC Safety Letter December 2004;
• AGC Safety Letter August 2005;
• AGC Safety Letter April 2006;

EUROCONTROL Action Plan for Air-Ground Communications Safety, including:

• AGC Briefing Note 3 - Loss of Communication;

OGHFA Briefing Notes:

• Pilot-Controller Communications (OGHFA BN);

EUROCONTROL Reports:

• Investigation into Loss of Communication;
• AGC Safety Study - Causes and Recommendations;
• AGC Safety Study - An Analysis of Pilot-Controller Occurrences;