FACES: Free-Flight Autonomous Conflict Enhanced Solver


La page de présentation de FACES est aussi disponible en français.



FACES is an autonomous and coordinated embarked (on board) conflict solver for Free Flight airspace. It solves conflict by computing simple manoeuvres that guarantee conflict free trajectories for the next 5 minutes. Coordination is ensured by giving sequential manoeuvres to aircraft with a token allocation strategy in order to solve the priority problem encountered in the Eurocontrol FREER-1 project.

FACES can be implemented with the current positioning, broadcasting and flight management technology. Moreover, it is robust to communication or system failure for time up to two minutes.

This is a very simple example of a resolution of a 3 aircraft conflict. Aircraft 808, 989 et 338 are in conflict, and 338 turns right to avoid collision with 989 and overtake 808 (figures close to each planes are the callsign, the heading, the flight level and the speed).

One of the other objectives of this project was a comparison of the centralized and distributed strategies for solving conflicts (see also projects ERCOS and SAGES ). One of the most interesting results of FACES was to show that the centralized approach was more capacitive than the autonomous one.

FACES was implemented as a module of the CATS simulator, and tested on real traffic data.

FACES is thoroughly described in the publications available at the end of this page.


FACES is not in the public domain.

Useful links

Main publications

Scheduling heuristics for on board sequential air conflict solving Nicolas Archambault, Nicolas Durand 23rd DASC (2004/10/24)

Heuristiques d'ordonnancement pour une résolution embarquée de conflits aériens par une méthode séquentielle Nicolas Archambault, Géraud Granger, Nicolas Durand RIVF'04 (2004/02/02)

Token allocation strategy for free-flight conflict solving Geraud Granger, Nicolas Durand, Jean-Marc Alliot IJCAI'01 (2001/08/01)

FACES: a Free flight Autonomous and Coordinated Embarked Solver Nicolas Durand, Jean-Marc Alliot, Geraud Granger ATC Quarterly (2000/2/1)

Détection et résolution de conflits aériens: modélisations et analyse Géraud Granger Thèse doctorat informatique de l'Ecole Polytechnique (2002/12/01)

Résolution de conflits embarquée dans les espaces de faible densité Géraud Granger Rapport de DEA IFP (1998/09/29)

Peut-on supprimer le contrôle au sol Nicolas Durand, Jean-Marc Alliot La Recherche (1999/04/01)

Méthode d'optimisation pour l'évitement aérien: systèmes centralisés, systèmes embarqués Frédéric Médioni Thèse doctorat informatique de l'Ecole Polytechnique (1998/10/8)

All the publications of the log are available here.

Short bibliography

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