Karim Zeghal

A comparison of different approaches based on force fields for coordination among multiple mobiles

This paper addresses the issue of real-time coordination among multiple mobiles, using the force fields approach. Firstly, a brief overview of different formulations of force fields is presented along with two techniques for handling multiple mobiles. Secondly, a new straight forward formulation of force fields is proposed based on the concept of closest point of approach, and following the principle of increasing the minimum distance. Finally, some comparative results along with typical simulations are presented.

Assessing the impact of a new air traffic control instruction on flight crew activity

A new allocation of tasks between controller and flight crew is envisaged as one possible option to improve air traffic management and in particular the sequencing of arrival flows. It relies on a set of new spacing instructions where the flight crew can be tasked by the controller to maintain a given spacing with respect to a designated aircraft. In order to assess the benefits and limits of airborne spacing, two streams of air and ground experiments were conducted. The latest air experiment aimed at assessing the feasibility of time-based spacing in final approach and its impact on flight crew activity. Flight crews were tasked to maintain a spacing behind a target aircraft, through adjustments of the selected speed. Their feedback on feasibility was generally positive despite an increase of mental effort which remained acceptable. Every crew successfully achieved the spacing task: the deviation was maintained within the tolerances. The impact on flight crews’ activity was assessed through the speed actions needed to perform the spacing task. The average number of speed actions was less than 1 per minute, and most were small adjustments comprised between -15kt and +5kt. The effect of various reactions of preceding aircraft under airborne spacing will be investigated in further experiments, as well as monitoring load and scanning pattern.

The Point Merge Arrival Flow Integration Technique: Towards More Complex Environments and Advanced Continuous Descent

This paper reports on a recent series of simulation s on Point Merge, a new method for merging arrival flows with existing technology. The paper shows how Point Merge can be adapted to typical terminal area configurations wit h benefits in terms of staffing (standardisation of working methods), predictability (extensive use of lateral flight management system guidance) and environment (advanced continuous descent), even under high traffic load. These investigations contributed to demonstrate the intrinsic flexibility and scalability properties of Point Merge. They paved t he way to the implementation in the short term to three real environments. The paper shows also how Point Merge can be seen as a “building block” for queue management, and a sound basis towards 4D trajectory management.

Effect of aircraft self-merging in sequence on an airborne collision avoidance system

This air traffic management research study analysed the interaction between a potential future airborne spacing application and an existing Airborne Collision Avoidance System (ACAS). The time-based airborne spacing application ‘merge behind’ was simulated in fasttime for a range of merge angles (45°, 90°, 135° and 180°), target spacing times (60 and 90 s) and altitudes (6,000 and 11,000 feet) under turbulent wind and extreme entry conditions. Trajectory pairs were analysed for potential collision alerting conditions using an ACAS simulator based on Traffic Alert and Collision Avoidance System (TCAS) II version 7 logic. Results show how, with realistic turn anticipation, the TCAS estimated time to go to Closest Point of Approach (CPA) decreased as merge angle was increased and as target spacing was reduced, but still remained above the Traffic Advisory (TA) and Resolution Advisory (RA) thresholds for the duration of all trials.

Airborne Spacing: Flight Deck View of Compatibility with Continuous Descent Approach (CDA)

This paper reports on an experiment conducted with airline pilots on a full flight simulator. The objective was a) to confirm the feas ibility of airborne spacing with speed and lateral managed modes and b) to assess the compatibility of airborne spacing and continuous descent approach (CDA). The overall feedback was globally positive and consistent with previous experiments. All pilots found airborne spa cing feasible from cruise until 2000ft, although more sensitive during the approach phase than in initial descent. The speed and lateral managed mode were well accepted. The pilots agreed that performing a CDA while maintaining spacing was feasible. The spacing was w ell maintained within the tolerance of 5s in initial descent (95% containment within ±2.1s). However, a cross-track error in approach led to larger deviation (95% containment within ±5s) and extreme values outside the tolerance. The cost induced was in the order of 115kt additional speed changes for the complete descent phase. In the terminal area, the r oute structure and altitudes were already optimised to allow a continuous descent from FL100.

Towards Performance Requirements for Airborne Spacing - a Sensitivity Analysis of Spacing Accuracy

The objective of this air traffic management study was to analyse the trade-off between time spacing accuracy and corresponding control effort in a potential future application of airborne separation assistance systems (ASAS). The ASAS application airborne spacing sequencing and merging was simulated in fast-time. Lead aircraft speed profiles were generated using complete descent profiles from real-time experiments. For validation purposes, three metrics were derived from real-time experiments: time spacing error (accuracy), frequency of speed adjustments (control activity), and cumulative airspeed variations (control cost). Four experimental parameters were varied: automatic and manual speed control, spacing dead-zone, guidance law dynamics time constant and initial time spacing error. A trade-off between the metrics was found for a sequence of two aircraft by comparing their variation with the experimental parameters. Corresponding ‘minimum’ performance requirements for the metrics are proposed: (i) time spacing error - mean less than 1.5s with 0.5 to 85% of the values between -4 and +4s (automatic mode), and mean less than 2.5s with 0.5 to 85% of the values between -6 and +6s (manual mode), (ii) frequency of speed adjustments - mean less than 1 action per minute (manual mode) and (iii) cumulative airspeed variations - mean less than 10 knots (automatic and manual modes). These requirements form a basis for investigating sequences longer than two aircraft where chain propagation effects may lead to additional constraints.

Introducing a New Spacing Instruction. Impact of Spacing Tolerance on Flight Crew Activity

To assess the benefits and limits of a new spacing instruction from flight crew perspectives, a pilot-in-the-loop experiment was conducted. Beyond assessing interface usability and overall feasibility, the experiments aimed at analysing the impact of various tolerance margins on flight crew activity and efficiency. Flight crew feedback was generally positive. Despite a new task in the cockpit, which requires appropriate assistance to contain workload, pilots highlighted the positive aspects of getting in the loop, understanding their situation (through goal-oriented instructions), and gaining anticipation. Results showed that even though the smallest tolerance margin (0.25NM) led to increased workload, the spacing deviation was usually below 0.5NM.

Impact of ADS-B Link Characteristics on the Performances of In-Trail Following Aircraft

In the general context of the delegation of some controller tasks to the flight deck, the pilots could be instructed to adjust its aircraft speed so as to maintain a prescribed longitudinal spacing with respect to the aircraft flying ahead. ADS-B (Automatic Dependent Surveillance – Broadcast) technology is one of the potential key enabler to support the implementation of such application. In this paper, the relationship between the ADS-B surveillance data characteristics (information exchanged, update rate, latency, accuracy) and the performance of the in-trail following aircraft application (stability of the in-trail aircraft, expected accuracy of in-trail aircraft time or distance spacing) is investigated based on a mathematical model of the in-trail aircraft.

Combining Sequencing Tool and Spacing Instructions to Enhance the Management of Arrival Flows of Aircraft

This paper reports on an experiment conducted with air traffic controllers to investigate the joint use of a sequencing tool and spacing instructions to enhance the management of arrival flows. The experiment simulated two en-route and one approach sectors (total of seven positions). It was shown that sequencing tool and spacing instructions can be jointly used in en-route and in the terminal area, with high benefits particularly in the terminal area. Main benefits are: a positive impact on controller activity (earlier flow integration and relief from late vectoring) and on control effectiveness (more regular inter-aircraft spacing on final approach, a slight increase of throughput and straighter trajectories with no dispersion below 4000ft).

Design of cockpit displays for limited delegation of separation assurance

The Evolutionary Air-ground Co-operative ATM Concepts (EACAC) study of the FREER-FLIGHT project investigates the delegation, by the controller to the pilot, of some tasks related to separation assurance. Starting from the analogy of visual clearances, EACAC investigates the possibility of giving electronic clearances in managed airspace. One of the issues of the study deals with the appropriate assistance scheme to be provided to the pilot, considering the proposed concept of limited delegation. An initial design work has been done, leading to the definition of key elements for cockpit displays: three different levels of assistance are identified, with different representations. All these options will be evaluated by pilots, first through a cockpit environment in a stand-alone mode (end 1999), and then using a cockpit simulator in a real-time simulation with controllers (mid 2000).