Human Factor Considerations on “New Working Methods”

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Human Factor Considerations on “New Working Methods”

58TH ANNUAL CONFERENCE, Conchal, Costa Rica, 20-24 May 2019

Agenda Item: C.6.2 – WP No. 155

Human Factor Considerations on
“New Working Methods”

Presented by PLC


New technologies, tools and the possibilities to have ATM data available not only in one physical location but wherever requested are introducing new ATM concepts and working methods. The main aim of these implementations is to reduce costs through the reduction of personnel employed on each sector/position and through the efficiency of the remaining personnel.
This paper will discuss the Human Factor consequences of these implementations, especially those commonly related to interactions between operators (Communication and Teamwork). It will also provide a revision of some TPM’s policy statements to consolidate their use in future scenarios.


1.1. Tools and technologies have been developed to assist ATM personnel to improve the safety and efficiency of operations. In recent years, efficiency has become ever more important to such a degree, that now the cost reduction is achieved primarily through the replacement of the human component with technological devices.

1.2. Exploiting the possibility of having ATM data available in different locations, new ATM concepts and new working methods have been developed. These range from centralizing several Remote Towers into a Remote Tower Centre to splitting the control of two adjacent terminal sectors into two controllers seated in different centres.

1.3. These new approaches have a noticeable impact on Human Factors aspects, especially on Teamwork and Communication, and the compliance of some of IFATCA’s basic principles need consequently to be evaluated (i.e.: Four Eyes Principle (4EP)).

1.4. This paper will provide some examples of these new methods and a general analysis of the Human Factors involved. It will also provide a revision of some TPM’s policy statements to consolidate their use in future scenarios.


2.1. ATM world is changing

2.1.1. The constant pressure from National Authorities and Airspace Users, in a tough competitive environment, to decrease costs and airspace congestion while increasing its limited capacity have pushed ANSPs to introduce ever more technology to cope with these requests. The result of these implementations leads to an increase in efficiency of the ATM system’s personnel in terms of quantity (number of flights managed) but also to change the pillars of consolidated working methods (teamwork, communication).

2.1.2. Another important secondary effect of this process is a constant trend to not use a team but only one person to manage a sector or, even worse, the entire unit: ATCOs/FISOs can take advantage of the guarantees given by the Four Eyes Principle (4EP, Situation where an executive controller is assisted by another appropriately qualified controller monitoring the same area of responsibility as the executive controller. (IFATCA TPM 2018, page 182)) that are not applicable neither for the Two Eyes Principle (2EP, Operations where an ATC unit provides service with one ATCO per sector, but with at least one more equally qualified ATCO on duty and available to assist or provide breaks. (IFATCA TPM 2018, page 182)) nor for Single Person Operations/Lone Person Operations (SPO, Operations where an operational ATC unit is providing service with only one appropriately qualified ATCO on duty. (IFATCA TPM 2018 pag. 182))(LPO, Operations where an ATCO is providing a service with no other person available on the unit, ATCO or otherwise. (IFATCA TPM 2018 pag. 182))

2.1.3. In past years IFATCA has developed strong policy statements on this and recognize the 4EP as the basic principle to ensure the adequate safety level both for ATM personnel and for the entire system (IFATCA TPM 2018 pag 182 WC 8.1.6 Single/Lone Person Operations, IFATCA TPM pag 183 WC 8.1.7 Four Eyes Principle). But now these policy statements have to be updated to avoid a possible undesired extensive interpretation on the new working methods.

2.2. Examples

2.2.1. New working methods and tools are continuously developed by research programs (SESAR JU, NextGen and others) and the following examples provide an overview on some of these ongoing processes.

2.2.2. New Zealand Currently in New Zealand, Airways NZ operates a single ACC. In order to increase resiliency, there are plans to open a second ACC where some sectors will be duplicated. Airways plan to reorganise the country’s two busiest, most complex, geographically remote and very different TMAs (Wellington and Auckland) into one roster so that all controllers are qualified on all positions. Additionally, the roster will then be split with half operating from each ACC. This reorganisation involves controllers from both rosters moving from a shared airspace model, where aircraft in the same airspace can be under the control of different controllers. (i.e. departures with a departures controller, arrivals with an arrivals or approach controller) to a geographic based model where each controller has a defined lateral boundary and is responsible for all aircraft within that area, irrespective of whether they are arrivals, departures or overflights. Controllers from each sector will be trained on the other and be expected to perform duties on both sectors within the same shift. Apart from this spatial reorganisation, the main changes of the new model are:

  1. Removal of all planning positions and the introduction of a new tool; Time Based Flow Management (TBFM) to support the executive controllers.
  2. The new combined sectors will be duplicated in the two ACC and operated simultaneously by personnel in both ACCs.
  3. Requirement for staff to switch between operating each TMA several times within one shift.
  4. Siloed operating positions, where the controller with whom they are sharing approach duties to an aerodrome, maybe located in a different ACC.

2.2.3. SESAR PJ.10 PROSA “Controller Tools and Team Organisation for the Provision of Separation in Air Traffic Management” The SESAR 2020-project PROSA focuses on separation management. It aims at providing the air traffic controller with more automated tools, thus freeing capacity for situations where human intervention is crucial (tactical level). The project also addresses new ways of working together, changing the traditional setup to multi-planner setup, sectorless airspace and seamless cross-border operations. Below are reported some working packages’ insights.

2.2.4. S-ATM (Sectorless ATM)(The sectorless ATM Concept: Flight-centred ATC”, DLR Deutsches Zentrum für Luft- und Raumfahrt) Deriving from SESAR PJ 10.01b “Flight Centered ATC”, DFS is planning for the end of 6 2020 to finish the first phase of the program Robusto, Sectorless ATM at Karlsrhue ACC. S-ATM represents a paradigm shift from the spatial responsibility of air traffic controllers to aircraft-centred responsibility: a controller is no longer in charge of managing the entire traffic within a given sector but only for a certain number of aircraft throughout their entire flights within a given airspace. One controller will be assigned several aircraft using one radar display (or a portion of it) for each aircraft under control to track the path of its aircraft and the surrounding traffic. Various functionalities support the conflict analysis and a medium-term conflict detection tool will indicate the predicted conflict.

2.2.5. SESAR PJ10.06 “ANY CONTROLLER, ANY AIRSPACE” The purpose of this concept is to investigate the possibility of removing the current operating method whereby the controller relies on detailed knowledge of a sector, to a more flexible approach where knowledge of the environment is supported by systems and procedures to allow the controller to perform their task based on a sector type, rather than a geographical area. Within a Centre or between ANSP’s centres, controllers may work a variety of sectors that have been grouped by type. The solution also creates the possibility for controllers from one ANSP to manage the airspace of another, thereby potentially increasing resilience. In other words, this solution looks at flexible delegation of airspace from one unit to another. Sectors both within units as well as more generically across borders can be controlled from another geographical location, as the ATCO validation is not on the geographic and specific local knowledge but on the systems and the sector type. This is the operational part, complementing the virtual centre’s technical solution.

2.3. Human Factors

2.3.1. The aim of human factors in ATM is to match the specifications of the working environment and of the working station design with human capabilities and limitations. The approach supported by IFATCA corresponds to the concept of a so-called Joint Human-Machine System (JHMS)(“Optimising ATM staff working stations in the Joint Human-Machine System” EGHD Position Paper 2018) which considers the user and the system as one: the achievement of the expected benefits of working station design requires the successful matching of humans and systems.

2.3.2. For controllers, the Controller Working Position (CWP) is both their working environment and the tool trough which they exercise their professional skills. The correct design of a CWP, as well as the correct environment where the CWP is inserted, are incorporated into the term “ergonomic” and the respect of these parameters is essential to allow controllers’ best performances (IFATCA TPM 2018 page 188 WC 8.2.3 “Working environment” and WC 8.2.4 “ATC systems”).

2.3.3. All three Human Factors domains (Physical, Cognitive and Organisational)(“Human Factor consideration when operation multiple operational positions/sectors”, IFATCA WP No.162 Accra 2018) are influenced by new working methods, but studies carried out by the organisations involved have not clearly defined the severity of this influence yet. Analysing this research, the most noticeable differences are detectable on teamwork and communication.

2.3.4. A common thread from the examples above is the reduction of the direct interactions between controllers. On the one hand, as contributions from the planner controller is missing and/or controllers are located in different units, this reduces distractions and workload derived from coordination tasks. But, on the other hand, this does not encourage the development of “shared mental models” (Shared mental models, associated with what Weick and Roberts (1993) call the collective mind, represent the “knowledge structures held by members of a team that enable them to form accurate explanations and expectations for the task, and, in turn, to coordinate their actions and adapt their behaviour to demands of the task and other team members” (Cannon-Bowers et al., 1993)). that can improve the teams’ ability to coordinate efforts, adapt to requests for change and anticipate the requirements of task and colleagues.

2.3.5. Teamwork Teamwork represents an activity aimed at achieving a goal, accomplished through carrying out a task, and organised through specific times, methods, resources and systems of communication. It refers to the ability to work in a team by promoting the support of others, conflict resolution, information exchange and co-ordination of activities. One element that distinguishes group work is the establishment of “shared mental models” that foster the perception and anticipation of alterations in the present situation. Within a team, a shared mental model makes constructive relationships possible between subjects who have understood the dynamics of key processes in a similar way. The teamwork between controllers of the same unit/sector (intra-sectorial teamwork) is hardly comparable with the teamwork associated with other units’ interactions (inter-sectoral and inter-organisational teamwork)(“The profession of Air Traffic Controller: operating safely and efficiently in a context of high reliability”, ANACNA 2015). These two teamwork’s levels are affected by different culture and the absence of close personal relations doesn’t allow the creation of the organisational culture that facilitates work practices. Inter-sectoral teamwork could be seen as a “strong collaboration” but it cannot reach the level of synergy associated to the intra-sectoral level. To describe this, the word “teamwork” can be rephrased in “teams that work” indicating a not perfect blend of team members. If the team members are located in different units, how are they able to pick-up verbal and non-verbal signals of extremes in workload of team members if they are not in the same place? Workload may become clearly apparent to other team members when verbal communication is used, i.e. one team member can say to the other “please wait, I’m too busy right now”. But there are also a large number of non-verbal signals, that team members use, as indications of each other’s workload (for example going tense)(“Team co-ordination study”, EUROCONTROL 2009).

Distance, in addition to a non-common organisational culture and poor personal relationship, can reduce the possibility to catch these signals, especially non-verbal ones.

2.3.6 Communication Communication permeates all air traffic management activities and its effectiveness helps to maintain high levels of reliability. To ensure the required standard of safety is achieved in carrying out work, it is necessary to monitor the ways in which the passage of the various kinds of information occurs, trying to limit forgetfulness and loss of data. Communication between controllers of different units is purely verbal. As controllers of different units do not see each other, and do not necessarily know each other, this communication is intermediate between controllers’ intra-unit communication and communication with pilots. It is a one-to-one communication, but no visual feedback is provided (except through radar screen, where, for example, the a/c squawk is a common reference). Also on communication’s scope, different local or national cultures and infrastructures influence working styles and the reliability of communications. Such attitudes are rather resistant to change; they really operate as stereotypes, and each unit is globally convinced to behave better than the others (“Proceedings of the Second EUROCONTROL Human Factors Workshop: Teamwork in Air Traffic Services”, European Air Traffic Control Harmonisation and Integration Programme (EATCHIP) Reference Material). Distance and/or no visual contact between team members places a great limitation on indications that an ATCO is available/approachable for communication. An information exchange when the receiver is not ready, is a waste of time and resources and can cause confusion with other active processes. Another example is the commonly known “finger pointing”: this useful practice to timely and quickly highlight a specific situation requires the possibility for a direct interaction.

2.3.7. Situational awareness (SA) and Handover-Takeover (HOTO) When an ATCO/FISO starts to work on its operational position, it assumes the responsibility for the provision of the Air Traffic Services and SA must be acquired through the correct HOTO procedure. There are already safety issues related to HOTO procedures. If the HOTO is being carried out between two different units, then this creates new safety issues. As an example, the fact that there are personnel of two different units involved in the procedure, raises the issue of the means of communication. Only telephone (or similar) communications are available between the two ATCOs/FISOs and this could cause an increase in workload and the possibility of distractions. In fact, information has to be transferred without the support of the non-verbal communication (with a consequent lengthening of the HOTO’s duration, which may impact directly to the personnel’s efficiency) and also the application of common HOTO’s safety practices is almost impossible (i.e. overlap period between the taking-over and the relived controller to ensure all information have been transferred properly, team members’ rotation). Difficulties arise further if the same operator changes sectors frequently (i.e. change in vertical or lateral limits, different airspace classification).

2.4. 4EP and Virtual Centres

2.4.1. IFACTCA supports and recommends the Four Eyes Principles (4EP),

Four Eyes Principle (4EP)

Situation where an executive controller is assisted by another appropriately qualified controller monitoring the same area of responsibility as the executive controller.

(IFATCA. (2018). TPM, 2018 Ed., page 182, WC 8.1.6 Single/Lone Person Operations; Definitions)

2.4.2. The principle was defined (definition and policy statements) for the first time by IFATCA at the 44th Annual Conference in Melbourne (2005) and revised in 2013. The discussion focused on positive aspects deriving from two controllers managing the same sector (i.e. redundancy, reduction of fatigue and stress levels). These positive attitudes are still valid, but nowadays another important concept that wasn’t present in the past, needs to be added to the discussion: virtual centres.

2.4.3. The 4EP is nowadays requiring only two controllers to manage the same sector: in this context, the same sector could theoretically be managed by two controllers (planner controller and executive controller) seated in two different centers: this introduces a possible extensive interpretation of the current 4EP.

2.4.4. Following the considerations on teamwork and communications, this interpretation does not ensure the same levels of safety and reliability that have pushed IFATCA to recognize the 4EP as one of the basic safety principles.

2.4.5. To ensure the correct and coherent application of the 4EP, an integration of the policy statements is necessary.


3.1. The impact of the new working methods on the consolidated practices is significant. The direction in which ANSPs and other stakeholders are pushing, is to delegate to technology as much as possible (i.e. planning tasks, conflict detection). Controllers will act only tactically.

3.2. New working methods, with the purpose of increasing the efficiency of the personnel, are pushing towards a sector compartmentation, reducing to a minimum the direct interaction between controllers. This cause difficulties on the establishment of a shared mental model that is essential for a correct and valuable teamworking, a pillar of the current ATM system.

3.3. Technology must improve and enhance the data exchange for controllers and support ATCOs in the execution of their duties. Reaffirming that the controller is the key element of the ATC system, IFATCA support the 4EP as a “Human Safety Net”.

3.4. Due to the possibilities introduced by virtual centres (same sector managed by controllers of different centres), in addition to the known requirement, the 4EP is correctly applied if the two controllers involved are seated one next to each other.

3.5. The rate with which the experiments on the new systems and working methods follow one another suggests that polices included in the IFATCA TPM will need to be adapted in the near future. To facilitate such update, MAs are encouraged to evaluate the experimentation activities in which their members are involved or of which they are aware and report to the Federation (IFATCA TPM 2018, page 18) those that, in their opinion, may introduce new operating concepts or may highlight the inadequacy of actual policies.


4.1. As a direct consequence of the discussion above, to safeguard the correct and coherent applicability of IFATCA’s policy statements to future scenarios:

4.2. It is recommended that the definitions of Single Person Operation (SPO), Lone person Operation (LPO), Two Eyes Principle (2EP) and Four Eyes Principle (4EP), reported on WC 8.1.6 “Single/Lone Person Operations (SPO)”, shall be included in TPM Part 2 “Acronyms and Terms”.

4.3. The following TPM policy:

Existing knowledge of human factors should be incorporated in design for new operational rooms and new ATC working positions and in modernisation of existing facilities.

has been reviewed and it is recommended to consider it still valid (TPM 2018 page 188, WC 8.2.3 and 8.2.4).

4.4. it is recommended that IFATCA policy:

WC 8.1.7

Implementation of 4EP shall be strongly encouraged by MAs, both through their ANSP(s) and their regulator(s).

An ATCO shall not be held liable for incidents or accidents resulting solely or in part from the non-implementation of the 4EP safety net.

is replaced by:

IFATCA recognizes the 4EP as a “Human Safety Net” and therefore its implementation shall be recommended by MAs, both through their ANSP(s) and their regulator(s).

An ATCO shall not be held liable for incidents or accidents resulting solely or in part from the non-implementation of the 4EP safety net.

To ensure the highest level of safety, teamwork and communication, the 4EP has as its basic requirement two ATCOs working physically next to each other.

and is included in the IFATCA Technical and Professional Manual.



“The profession of Air Traffic Controller: operating safely and efficiently in a context of high reliability”, ANACNA 2015

“Team co-ordination study”, EUROCONTROL 2009.

“Optimising ATM staff working stations in the Joint Human-Machine System” EGHD Position Paper 2018.

Last Update: October 2, 2020  

November 19, 2019   650   Jean-Francois Lepage    2019    

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