Towards a new task distribution between controller and flight crew to

To appear in The Controller, IFATCA, July 2002 Volume 41, N°2.

Towards a new task distribution between controller and flight crew to manage aircraft spacing Isabelle Grimaud, Eric Hoffman, Laurence Rognin, Karim Zeghal EUROCONTROL Experimental Centre, BP 15, 91222 Bretigny, France

Background Depending on the type of flight and class of airspace, the controller is responsible to provide separation in order to prevent collisions (ICAO Annex 11, section 3.3). In this context, the task distribution between the controller and the flight crew follows a fixed scheme: the controller is in charge of conflict detection, identification of solutions, and implementation through manoeuvring instructions, while the flight crew has to execute these instructions. There is one exception to this task distribution however: the visual separation in which the controller delegates to the flight crew the implementation of a solution with respect to a designated traffic. The flight crew can thus be tasked to report when the traffic is passed, or manoeuvre according to it. This procedure aims at optimising the trajectory, but also at alleviating the controller of some of his/her tasks. The procedure requires however flight crew to keep the other traffic insight, which restricts its use to daily operations under full visibility, and for aircraft close to each other. How to overcome this constraint of visual contact? Is it possible to transpose this procedure to situations in which the other traffic would be visible on a display onboard the aircraft? What are the technical means required? What could be the impact on controller and flight crew activity? What would be the benefits and what issues arise? The study introduced here aims at providing initial elements to address these issues.

Principles The key driver of the study presented here is to increase controller availability through a reorganisation of tasks between controller and flight crew. The motivation is neither to “transfer problems” nor to “give more freedom” to flight crew, but really to identify a more effective task distribution beneficial to all parties. It is expected that the increased controller availability could lead to improved safety, which in turn could enable better efficiency and/or, depending on airspace constraint, more capacity. In addition, it is expected that flight crew would gain in awareness and anticipation by taking an active part in the management of his/her situation with respect to the concerned aircraft. Starting with the analogy of visual separation, the proposed task distribution relies on the delegation of spacing tasks in which the flight deck is tasked to implement a solution defined by the controller. Restricting the delegation to implementation tasks (as opposed to decision making tasks) is expected to preserve controller authority and understanding of the situation (“mental picture”). The delegation of spacing is at controller initiative, who can decide to end it at any time. The flight crew however can only abort it in case of problem onboard such as a technical failure. The delegation applies to pairwise situations: one aircraft is “delegated”, the other being “target”. In terms of responsibility, as opposed to visual separation which implies a transfer of separation responsibility, the delegation of spacing can be seen as the use of a new instruction [3]. Thus, the controller is responsible to issue the appropriate instruction to guarantee the spacing (and the separation), and the flight crew is responsible to follow it. The full responsibility issue (as discussed in [8]) goes beyond the scope of the study and would eventually be addressed at a regulatory level. A first formal framework for delegation was proposed in 1995 at the ICAO/SICASP [9]. Within ICAO, work is continuing as shown in [1][10][11]. Recently, the ATM Concept Panel during its first meeting also provided a new perspective on the notion of separation provision [2]. Both IFATCA and IFALPA have issued position statements on this concept [4][5].

Illustration Similarly to visual separation, two classes of operation are envisaged: crossing for en-route airspace, and sequencing for terminal areas. For illustration purposes, let us consider the situation of two arrival aircraft converging to a point, then following the same route to the airport. Today, the controller must ensure that the spacing is maintained, and therefore has to continuously monitor the situation and if necessary issue heading and/or speed instructions. With delegation, the maintaining of the spacing (distance or time) through speed adjustments is transferred to the flight

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To appear in The Controller, IFATCA, July 2002 Volume 41, N°2. deck (Example 1 and Figure 1). However, applicability conditions of the delegation shall be respected. In this example, prior to delegating, the controller must ensure that aircraft speeds are compatible, and the spacing at the converging point is not lower than the desired spacing. Whereas the “land after” clearance can generally be given in final approach only (visual contact/traffic insight required), the delegation of spacing can start earlier, typically before descending, and whatever the meteorological conditions, thanks to the display of the target aircraft onboard. Sequencing of converging aircraft: XYZ, select target 1234.

Selecting target 1234, XYZ.

The designation of the target aircraft is done through a unique identifier (here the mode A code). After selection and identification on the screen, the pilot replies: XYZ, target 1234 identified. The controller can then issue the delegation instruction: XYZ, behind target, merge to WPT to be 8 miles behind.

Merging to WPT to be 8 miles behind target, XYZ.

The pilot has to adjust his/her speed to maintain the spacing at the converging point and after the point. The delegation will be ended by the controller when appropriate: XYZ, cancel delegation, reduce speed 220 knots.

Cancelling delegation, reducing speed 220 knots, XYZ.

Example 1. A typical exchange between controller (left) and pilot (right). Target

Future positions

WPT 8NM

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Delegated 280 - 46

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Figure 1. Converging situation. The delegated aircraft has to adjust its speed to maintain the spacing with the target aircraft at the converging point.

Technical means The delegation of spacing requires the display of the target aircraft onboard the delegated aircraft. The Automatic Dependant Surveillance – Broadcast (ADS-B) [6] is a surveillance mean in a pre-operational state in which equipped aircraft transmit spontaneously their position and velocity (and eventually their trajectory). The Traffic Information Service – Broadcast (TIS-B) is an additional mean to be used when some aircraft are not ADS-B equipped: position and velocity are transmitted via a ground station to equipped aircraft. The traffic data received through ADS-B or TIS-B is displayed on a screen in the cockpit. This capability is denoted Cockpit Display of Traffic Information (CDTI) [7]. In addition to the display of the target aircraft, assistance to maintain spacing is required, typically through graphical cues (Figure 2). This capability is usually denoted Airborne Separation

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To appear in The Controller, IFATCA, July 2002 Volume 41, N°2. Assistance System1 (ASAS). Despite the similarity between terms, it should be noted that ASAS is completely distinct from the collision avoidance system ACAS/TCAS which is a last resort system. On the controller side, the only modification required to the current working environment is the knowledge of ASAS equipages, for example through a field of the flight plan. In addition, graphical “marking” capabilities on the controller screen would be useful as a reminder of on-going delegations as well as a support of co-ordination when transferring delegations to next sector.

Figure 2. Navigation display with the representation of the target aircraft (same converging situation as in Figure 1). The target aircraft is represented by the white chevron. The merging configuration is highlighted by a double dashed line linking target and delegated (own-ship) via the converging point. The arc of circle in magenta indicates represents the position on the trajectory where the spacing will be the required position, and the symbol acquired. In order to limit the clutter of the screen and also to avoid request from pilots, it is suggested to display only the target aircraft.

Experimental results In the scope of assessing the acceptance from controllers and measuring the impact on their activity, four human-inthe-loop experiments were carried out (June 1999, June 2000, November 2000 and December 2001). A total of 23 controllers from different European countries participated over a total duration of 9 weeks2. For the last simulation, the airspace comprised four en-route sectors from Paris ACC handling south-east arrivals to Orly (LFPO) and Charles-De-Gaulle (LFPG) airports and the two associated initial approach sectors. The traffic simulated was derived from a real traffic. Two levels of traffic were simulated: medium and high with respectively 27 and 31 arrivals per hour, plus over-flying traffic. To allow for comparison, each exercise was played twice: with and without delegation. The feedback from the controllers3 was positive: the delegation is perceived as useful and potentially leading to more anticipation and to an overall workload reduction. 1

This term was introduced in 1995 [9] at a time where the distinction between separation and spacing was not identified.

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Three flight deck experiments were also conducted (June 1999, November 2000 and May 2002). A total of 15 airline and test pilots participated over a total duration of 10 days. 3

Some words about the pilot feedback: despite a new task in the cockpit which requires appropriate assistance to contain workload, pilots stress the positive aspects of getting in the loop, understanding their situation (through goal-oriented instructions), and gaining anticipation.

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To appear in The Controller, IFATCA, July 2002 Volume 41, N°2. To assess the impact of delegation of sequencing operations on the control activity, a "geographical based" analysis of instructions was performed. It consisted in mapping the manoeuvring instructions over the considered area, and more specifically in analysing their distribution as a function of their distance to the exit point (Initial Approach Fix). The results suggest that delegation leads to anticipate the building of the sequences (earlier use of heading instructions), and to relieve the controller of maintaining these sequences (reduction of speed instructions by 60%) (Figure 3 and 4). An overall reduction of manoeuvring instructions (about 26%) was also observed. 25

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Figure 3. Distribution of instructions as a function of distance to IAF. Without delegation (left) and with delegation (right), medium traffic, LFPG south-east arrivals. 25

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Figure 4. Distribution of instructions as a function of distance to IAF. Without delegation (left) and with delegation (right), high traffic, LFPG south-east arrivals. To have more insight into the impact on the monitoring activity, a similar geographical mapping of eye fixations was performed4. In medium traffic, the global monitoring was similar without and with delegation: more fixations occurred around the converging point (located approximately at 120Nm from exit point). In high traffic, curves are opposite: with delegation, most of the fixations are concentrated over the converging point, while without delegation, they are concentrated after, near the exit point. This suggests that with delegation in high traffic, controllers can still concentrate where the sequences need to be built, whereas without delegation, the building of sequences could not be anticipated. Controllers were thus more in a reactive position. To summarise, with delegation, the reduction of time spent actively monitoring the sequence maintaining (from 100Nm to transfer) seems to increase controller availability. One question arises: is the reduced monitoring not detrimental to safety? In 4

This was obtained through the use of eye-tracker devices, which allow to record the eye-gaze position on the screen and the duration of each fixation.

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To appear in The Controller, IFATCA, July 2002 Volume 41, N°2. other words, are the delegated aircraft still monitored?5 As an attempt to answer this question, a "contextual" analysis of monitoring has been performed. It consists in analysing the frequency of the monitoring of each aircraft, i.e. the interval between two consecutive fixations on a same aircraft. Initial results suggest that the frequency remains similar with or without delegation. 25

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Figure 1. Distribution of fixation duration as a function of distance to IAF, medium traffic (left) and high traffic (right).

Conclusion A first insight into the impact of delegation on the controller activity has been obtained though human-in-the-loop simulations, suggesting potential benefits. However some issues remain: what is the capability of the controller to detect and managed degraded situations with delegated aircraft? To which type of airspace the delegation could apply? In particular, could delegation be applied in approach? Beyond the controller perspective, what is the impact on the flight deck activity, and what level of assistance is needed onboard? In order to progressively address these questions, additional human-in-the-loop experiments are planned on both controller and pilot sides.

Acknowledgements We would like to recognise here the controllers and pilots, either seconded by their respective organisations, or on their own time, that have accepted over the years to discuss with us and to take part in our experiments, allowing us to gradually build an understanding of how limited delegation of separation tasks may be used to improve the ATM system. Their willingness to make progress, their patience and their constructive criticisms were and are very much appreciated.

References [1] ADSP5/WP61 - Report on Agenda Item 4 – Appendix B – Information relevant to the use of a system to increase traffic situational awareness and provide airborne separation assurance, October 1999. [2] ATMCP/1-WP/30, Report on Agenda item 2, Appendix A, ATM Operational Concept Document, October 2002. [3] EUROCONTROL / FAA cooperative R&D, "Principles of operations for the use of airborne separation assurance systems", Edition 7.1, 2001. [4] IFALPA, " The responsibility for separation", Press release, 3rd November 2000, www.ifalpa.org/Press%20Release/01PRL007_Separation_Nov00.pdf [5] IFATCA, "Transfer of Control Functions to the Cockpit", Press release, 16th October 2001, www.ifatca.org/press/161001.htm. [6] RTCA SC-186, Minimum Aviation System Performance Standards for Automatic Dependent Surveillance Broadcast (ADSB), DO-242. [7] RTCA SC-186, Guidance for Initial Implementation of Cockpit Display of Traffic Information, DO-243, 1998. [8] Schubert, F., "Pilots or Controllers: Who’s Liable in the Free Flight Environment", www.aviationtoday.com/reports/avionics/previous/0202/0202legal.htm.

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It should be reminded that the controller is still responsible for separation provision.

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To appear in The Controller, IFATCA, July 2002 Volume 41, N°2. [9] SICASP/WG2/WP489 – Airborne Separation Assistance System – The ASAS Concept, Sydney, March 1995. [10] SICASP6/WP44 – Report on Agenda Item 6 - The ASAS Concept, February 1997. [11] SICASP7/WP27 - Report on Agenda Item 6 – Appendix A - ASAS Circular, September 2000.

Biographies of authors Isabelle Grimaud has been working for the past 25 years as an air traffic controller at Aix / Marseille ACC. She took part in the design and evaluation phase of new controller working positions and tools, and now is involved in the definition and evaluation of the delegation concept. Eric Hoffman leads, at the Eurocontrol Experimental Centre, the Air Ground Integration project structure investigating in particular the concepts and benefits of ASAS applications in the context of several collaborative European projects. Laurence Rognin is a human factors specialist (seconded from Pacte Novation). She is involved in the evaluation of the impact of ASAS applications on pilot and controller activity. Karim Zeghal is involved in the definition of the delegation concepts and leads the human-in-the-loop experiments on ASAS applications, with both controller and pilot perspectives.

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