Modelling Lateral Spacing and Separation for Airborne Separation Assurance Using Petri Nets

Abstract

Airborne separation assurance is seen as a promising option for the future air traffic management concept to provide an increase in capacity and flight efficiency while maintaining flight safety. So-far, studies or expectations are largely based on assumptions about the achievable spacing and separation criteria. These assumptions range from optimistic to reserved, when comparing these separation criteria to currently used radar surveillance-based values. In any case, there is a clear knowledge gap on this subject. Thus, it is important to assess the relationship between spacing and separation distances on one hand and safety on the other hand. This relationship directly affects the effectiveness of airborne separation assurance. The aim of this paper is to address this issue by conducting an accident risk assessment, including a bias and uncertainty assessment and an assessment of risk sensitivity to spacing and separation values. Each stage in the methodology used is illustrated by examples. It is shown that the methodology provides valuable feedback on both the airborne separation assurance operation and the accident risk assessment.

A probabilistic measure of air traffic complexity in 3‐D airspace

“…Approaches to evaluating the probability of conflict involve predicting aircraft trajectories into the future and computing the probability that two aircraft get closer than a minimum required distance based on these trajectories [19][20][21][22]. A Petri net model combined with a Sequential Monte Carlo approach was used in [23][24][25] to estimate the criticality of a free flight operational concept. A Monte Carlo approach for conflict resolution in the presence of uncertainty in aircraft dynamics is given in [26].…”

Free Flight Collision Risk Estimation by Sequential MC Simulation

“…The large increase in handling complexity of multiple aircraft encounter situations is a major improvement over what was feasible before for two aircraft flying in a parallel route structure [4], [29]. Inherent to the IPS way of simulation, the dynamic memory of the computers used appeared to pose the main limitation on the full exploitation of the novel sequential MC simulation approach.…”

“…The results obtained show that the novel simulation model specification and collision risk estimation method allow to speed up the Monte Carlo simulations for much more complex air traffic encounter situations than what was possible before, e.g., [4], [29]. Moreover, for the simulation model of the free flight operational concept considered, behaviour has been made visible that was expected by free flight concept designers, but could not be observed in straightforward Monte Carlo simulations of free flight concepts (e.g., Hoekstra [37]): the rare chance of clogging multiple conflicts at far higher traffic density levels than where the particular concept has been designed for.…”

“…The civil aviation community also has established some approximate models to estimate (an upper-bound of) the risk of collision between aircraft flying within a given parallel route structure [32], [38], [40]. Additional methods have been exploited to develop some valuable extensions of this approach, e.g., using fault trees see [22] and using stochastic analysis and Monte Carlo (MC) simulation [3], [4], [29]. Andrews et al [1] have shown how statistical data in combination with a fault tree of the functionalities of the advanced operation can serve to predict how reliability of free flight supported systems impact contributions to collision risk of an advanced operation [24], neglecting other contributions to collision risk.…”

A causal model to explore the ACAS induced collisions

“…Short-term CD&R (STCD&R) 3 requires particular attention because it works at the operational level to attempt to avoid imminent crashes by the implementation of alert mechanisms for controllers, such as the short-term conflict alert (STCA), 4 and alert mechanisms for pilots, such as the traffic alert and collision avoidance system (TCAS), which provides some degree of collision threat alerting and orients its function to a broad spectrum of aircraft types. Until now, TCAS I and its improved version, TCAS II, have been defined and approved by International Civil Aviation Organization (ICAO), differing primarily by the alerting capability.…”