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|Category:||Air Ground Communication|
Until data link communication comes into widespread use, air traffic control will depend primarily upon voice communications, which are affected by various factors. Any breakdown in communication between pilot and ATCO can result in the pilot not fully understanding and therefore not following his/her clearance correctly. Equally, it may not be possible for the pilot to pass a message to the ATCO. Such hazardous situations have been significant direct or indirect factors in a number of aircraft accidents and incidents.
Types of Communication Breakdown
Communication breakdown may result from:
- Failure to hear or to respond to a message because of:
- Communication equipment problems, including prolonged loss of communication; or,
- Radio Interference, which makes the message difficult or impossible to read; or,
- Blocked Transmissions / Undetected Simultaneous Transmissions (USiT); or,
- Call-sign Confusion - the message was wrongly addressed or was taken by another aircraft;
- A breakdown in radio discipline resulting in the pilot receiving and acting on an incorrect version of the message passed, due for example to:
Communication breakdown may result in:
- The pilot not flying the required vertical profile (level bust), or not following the required horizontal profile:
- Either situation can lead to loss of separation from other aircraft, which may result in collision. This is especially likely when RVSM procedures are in force;
- Either situation may cause the aircraft to enter protected airspace (airspace infringement);
- Level bust may also lead to collision with an obstacle or the ground (Controlled Flight Into Terrain (CFIT));
- Injury, especially to cabin crew or passengers, may be occasioned by violent manoeuvres to avoid collision with other aircraft or the ground, or from wake vortex turbulence encounter;
- The pilot changing to an incorrect frequency or not implementing a frequency change, leading to:
- Situational Awareness;
- Inability to respond to further clearance or to emergency instructions, e.g. avoiding action.
Defence against the effects of communication breakdown include the following:
- Onboard aircraft equipment designed to warn of potential collision with other aircraft (ACAS/TCAS).
- Ground-based equipment designed to warn of potential collision with other aircraft: Short Term Conflict Alert (STCA), potential collision with the ground, Minimum Safe Altitude Warning (MSAW), or airspace infringement Area Proximity Warning (APW).
- The pilot or ATCO does not use Standard Phraseology resulting in the message being misunderstood.
- Part of the message is lost due to radio interference, or because of Blocked Transmissions / Undetected Simultaneous Transmissions (USiT).
- The pilot mishears all or part of a clearance, the pilot does not read back the clearance and the ATCO does not challenge the absence of a read-back (read-back/hear-back).
- The pilot reads back all or part of the clearance incorrectly but the ATCO does not note the error and does not correct the pilot’s read-back (read-back/hear-back).
- The pilot accepts a clearance intended for another aircraft (call-sign confusion).
- Pilot workload.
- ATCO workload;
- Inadequate language proficiency;
- Frequency Congestion;
- Non-standard phraseology;
- Radio Interference;
- Distractions or interruptions;
- Emergency Communications.
- Improved pilot and ATCO training to ensure that pilots and ATCOs understand and follow SOPs, particularly with regard to:
- Recognise and understand respective pilot and ATCO working environments and constraints.
- Listen to party-line communications as a function of the flight phase.
- Action by the flight crew to improve Crew Resource Management in order to ensure that:
- The flight clearance is understood. This includes checking to ensure that both pilots agree and understand the flight clearance;
- The aircraft follows the flight clearance and does not unintentionally deviate from it. This includes checking the settings made to technical equipment and monitoring the performance of that equipment and the aircraft in order to detect any error or malfunction.
- Action within ATM to improve Team Resource Management, thereby ensuring that:
- The flight crew understand the flight clearance;
- Deviation from an essential element of the clearance is detected and corrected at an early point.
- Improved technical equipment.
EUROCONTROL Action Plan for Air-Ground Communications Safety
The Action Plan for Air-Ground Communications Safety may be viewed as a whole. Alternatively, the Briefing Notes may be viewed separately as follows:
- AGC Briefing Note 1 - General;
- AGC Briefing Note 2 – Call Sign Confusion;
- AGC Briefing Note 3 – Loss of Communication;
- AGC Briefing Note 4 – Blocked Transmissions;
- AGC Briefing Note 5 – Radio Discipline.
- HS2 Getting the Message Across;
- HS2 Analysis of an AIRPROX in Japan.
- HS4 Loss of Separation - A Lesson for the Instructor;
- Effective Communication in the Aviation Environment;
AGC Safety Letters
- Investigation into Loss of Communication;
- AGC Safety Study – Causes and Recommendations;
- AGC Safety Study - An Analysis of Pilot-Controller Occurrences;
- AGC Top 10 Tips;
- All Clear Phraseology Manual.
For further information refer to the EUROCONTROL "All Clear" web-site: http://www.allclear.aero.