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ATC Team Coordination
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|Category:||Loss of Separation|
This article describes the specifics of coordination procedures within an ATC unit.
The article does not cover the coordination procedures:
- within a planner-executive team;
- between different ATC units (described in ATC Unit Coordination);
- between ground and tower operating at the same airfield (described in GND-TWR Co-ordination).
Coordination procedures within the same ATC unit are defined in local instructions (e.g. Manual of Operations). Unlike the coordination with neighboring units, these are not subject to a letter of agreement. In general, however, coordination procedures within the unit are similar to those with the adjacent units because both are based on ICAO SARPS and the same (or similar) methods and tools are used - verbal (phone) and non-verbal (electronic).
Coordination with controllers of the same unit is usually smoother (but not necessarily better) due to:
- Improved system support. It is much easier (and therefore more widespread) to have more and better functions to support electronic coordination between sectors of the same ATC unit. While OLDI generally offers a broad range of messages, it is very often the case that only basic features are used. This is mainly because different ATC units are at a different stage of their ATM system development/deployment. For a new inter-unit feature to work, both sides need to implement it at the same time (otherwise the first unit to implement a new capability will have to wait and depend on someone else to be able to use it). By contrast, within a single ATC unit the new features are:
- Radily available. There is no need to wait or negotiate the use of a new function with another party. This makes implementation of new features more cost-efficient.
- Customizable. Sometimes different units have different needs (e.g. some would appreciate the possibility to coordinate weather avoidance electronically while other would not use the feature and prefer verbal communication).
- Enhanced communitaction features. The voice communication system (VCS) is usually tailored to the needs of the ATC unit and offers some advantages for internal users. For example, most modern VCSes have a priority feature which is used by the caller to indicate higher importance.
- Sharing the same picture. Using the same ATM system generally means that all controllers see more or less the same picture. While in most cases this is true for inter-unit interaction, there are specific situations where being in the same unit gives an advantage, e.g.:
- Primary radar targets are usually assigned unique system numbers. Different systems, however, assign different values. Therefore, in an inter-unit coordination it is impractical to refer to such a target by its system name.
- Map features. The focus is generally on the unit's airspace and while usually there is a possibility to show those of a neighboring unit, it is often neither ergonomic nor as user friendly as with the own airspace. This often restricts references to the common boundary points.
- Correlation. All flights of interest to the ATC unit are supposed to be correlated. Therefore the controllers have extended information about flights that are flying in proximity to their boundary but are not supposed to enter their sector. This improves the situational awareness and is especially useful during weather avoidance. Also, some ATS system functions are only available for correlated flights which may potentially improve coordination within the unit.
- Better understanding of the other party's tasks. Often controller within the same unit are qualified to work on a number of sectors and are therefore well acquainted with the specifics of the next sector (i.e. landmarks, hotspots, etc.). This usually helps to achieve better coordination. Sometimes however this can be abused to the point where a controller "extends" their area of responsibility in the neighbouring airspace while not having the necessary level of situational awareness (due to e.g. the colours used in the aircraft labels).
- Language. In most cases controllers are not native English speakers. While it is possible to have verbal inter-unit coordinations in the mother tongue (e.g. between two ACCs or an ACC with an APP or TWR unit in the same country) it is more common to use English for inter-unit interactions and the national language within the unit. Therefore, coordination within the unit is somewhat easier, especially in complex situations where Standard Phraseology cannot be used.
- Inter-personal relations. People wrorking together inevitably develop some sorts of relationships. This sometimes facilitates better coordination but may also lead to non-operational conversations.
- Face-to-face communication. It is possible for controllers within the same unit to make direct verbal coordinations without using any equipment. This may increase efficiency (and also safety in some cases) due to the zero delay of message delivery. The downside is that such communication can easily distract other, non-involved sectors. Also, if there is no ambience recording, it is not possible to objectively establish the facts during an investigation. Therefore, face-to-face coordination is generally not favoured by prevailing operational procedures.
The best practices for inter-sector coordinations are mostly the same as those used between different ATC units (described in detail in the dedicated article). In summary:
- Identification of situations that are subject to coordination is critical.
- A coordination done twice is usually better than no coordination. Verify instead of assuming.
- Coordination is all about two controllers agreeing to and being comfortable with the same plan.
- Coordinations should be timely.
- A simpler plan is less ambiguius, easier to coordinate, implement and monitor and generally safer.
- Electronic coordinations should be used whenever possible.
- Controllers should try to stick to the standard procedures and reduce coordinations, except if:
- safety concerns arise.
- the workload is low.
- the coordination would reduce traffic complexity.
- Rejection should only be used with good reason.
- A "block" coordination applicable for a defined period of time and portion of the air traffic may sometimes be used to significantly reduce the workload.
In addition to the above, some specific aspects of inter-sector coordination are:
- Refrain from making non-operational conversations or calls.
- Use the enhanced coordinations tools. They often provide richer options compared to those for external coordinations.
- Use system support to draw attention. Marking an aircraft before initiating a coordination may help the other party distinguish the aircraft within the bunch by its e.g. blinking label or special colour.
- Fixing aircraft trajectories in line with the clearances given allows the ATS system to correctly represent the aircraft to the neighbouring sectors.
Accidents and Incidents
- A310 / C421, en-route, northeast of Montréal Canada, 2018 (On 16 May 2018, an Airbus A310 and a Cessna 421 being positioned for ILS approaches to adjacent parallel runways at Montréal by different controllers lost separation. One controller incorrectly believed that he had transferred control of the Cessna to the other when the shift supervisor re-opened a sector which had been temporarily combined with his. The Investigation attributed the conflict to multiple deviations from standard procedures, memory lapses relating to controller information exchange of information and a loss of full situational awareness compounded by the shift supervisor also acting as an instructor whilst being distracted by his other duties.)
- A320 / B738, en-route, north northwest of Sofia Bulgaria, 2016 (On 4 June 2016, a Boeing 737-800 instructed to climb from FL340 to FL380 by the controller of one sector in Bulgarian upper airspace came into sufficiently close proximity to an Airbus A320 under the control of a different sector controller to trigger co-ordinated TCAS RAs. Separation was eventually restored after the 737 followed its RA despite the A320, which had already deviated from its clearance on the basis of a prior TCAS TA without informing ATC, ignoring their RA. The Investigation found that the root cause of the conflict had been inadequate coordination between two vertically separated ATC sectors.)
- A320 / E145, vicinity Barcelona Spain, 2019 (On 27 September 2019, an Airbus A320 and an Embraer 145 both inbound to Barcelona and being positioned for the same Transition for runway 25R lost separation and received and followed coordinated TCAS RAs after which the closest point of approach was 0.8nm laterally when 200 feet vertically apart. The Investigation found that the experienced controller involved had initially created the conflict whilst seeking to resolve another potential conflict between one of the aircraft and a third aircraft inbound for the same Transition and having identified it had then implemented a faulty recovery plan and executed it improperly.)
- AT75 / B739, Medan Indonesia, 2017 (On 3 August 2017, a Boeing 737-900ER landing at Medan was in wing-to-wing collision as it touched down with an ATR 72-500 which had entered the same runway to depart at an intermediate point. Substantial damage was caused but both aircraft could be taxied clear. The Investigation concluded that the ATR 72 had entered the runway at an opposite direction without clearance after its incomplete readback had gone unchallenged by ATC. Controllers appeared not to have realized that a collision had occurred despite warnings of runway debris and the runway was not closed until other aircraft also reported debris.)