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    User Evaluation by Remote Pilots of Two Types of Detect-and-Avoid Systems: Remain Well Clear Bands Versus Route Guidance
    (MDPI, 2026) Stroeve, S.H. ; Tanevska, A. ; Kroon, M. ; Castellano, G.
    The remain well clear (RWC) function of a detect-and-avoid (DAA) system provides guidance to a remote pilot (RP) of a remotely piloted aircraft to prevent a conflict from developing into a collision hazard. The ACAS Xu standard is a decision support system that uses RWC bands to advise a RP which headings to avoid. A recent A* DAA system is a resolution support system that advises a RP which route to take. The objective of this study is to achieve structured feedback by professional RPs on the horizontal RWC guidance of both systems. Nine RPs participated in on-line experiments, where they were shown videos of DAA displays of encounter scenarios between two aircraft. At various stages the RPs were asked for their opinion about transparency, pilot manoeuvring, situation awareness, display orientation, risk perception, competence, trust, and overall system preference. The results show that the scores for competence, trust and pilot manoeuvring were significantly higher, and the score for perceived risk was significant lower for the RWCroute guidance. Overall, 89% of the RPs preferred the RWC route guidance, while one RP had no preference. An implication of the uncertainty in pilot behaviour is that ACASXumodel-based optimisation may provide suboptimal RWC guidance strategies, while the A* DAA optimisation can be managed effectively.
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    Systematic Identification of Stakeholder Needs for the Design of Sustainable Long-Range Aircraft of 2050
    (MDPI, 2026) Markatos, D. ; Psihoyos, H. ; Peerlings, B. ; Paletti, L. ; Boggero, L. ; Pantelas, P. ; Scheers, E. ; Söffing, L.A. ; Page, J. ; Pantelakis, S. ; Pasqualone, A. ; Filippatos, A.
    Designing long-range aircraft for 2050 is a complex, multi-disciplinary challenge requiring integration of technical performance with sustainability objectives, including environmental responsibility, economic viability, circularity, and social acceptance. Existing studies on stakeholder needs in aviation are limited, focusing on specific groups, technical requirements, or individual aircraft concepts, resulting in a fragmented understanding of sustainability-driven needs. This study addresses this gap by systematically identifying stakeholders who influence long-range aircraft development and deriving 191 stakeholder needs, organized into coherent categories spanning manufacturers, operators, passengers, regulators, communities, and energy suppliers. Needs were classified across technical, environmental, economic, circular, and social dimensions, based on a comprehensive review of academic and grey literature, regulatory documents, and industry sources. The resulting framework provides a structured, reproducible approach to support conceptual aircraft design and requirement definition within the European EXAELIA project. By integrating multi-dimensional stakeholder expectations early in the design process, this approach facilitates aircraft development that is technically robust, environmentally sustainable, economically viable, circular, and socially inclusive, demonstrating the value of a stakeholder-driven method for sustainable systems engineering.
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    The critical impact of remote pilot modelling in evaluation of detect-and-avoid systems explained for ACAS Xu
    (TU Delft Open, 2024) Stroeve, S.H. ; Villanueva-Cañizares, C.J. ; Dean, G.
    Detect-and-avoid (DAA) systems for remotely piloted aircraft systems (RPAS) can provide remain well clear (RWC) guidance as well as shorter term resolution advisories (RAs) for collision avoidance, which are both provided in the vertical and horizontal planes. Simulation-based studies for large sets of encounter scenarios are used in the development and evaluation of DAA systems, which encompass safety and operational acceptability of the DAA supported operations. Given the key role of the remote pilot (RP) in responding to RWC guidance and RAs, a RP model is an essential element in such simulations. This paper describes the development of a RP model for evaluation of encounter scenarios involving the ACAS Xu DAA system. The model describes RP situation awareness (perception, comprehension, projection) as basis for decision-making, modes for responding to RAs and/or RWC guidance, response delays, response strengths, and the flight control actions. The RP model includes deterministic and stochastic settings. It is integrated in a simulation environment for encounters of manned and/or unmanned aircraft, the involved DAA and airborne collision avoidance systems, the surveillance and communication systems, and the human operators. Simulation results are provided for a set of encounters between pairs of RPAS both having ACAS Xu for various configurations of the RP model, and for cases with and without sensor errors. The results show that there can be large differences between the results of deterministic and Monte Carlo simulations, indicating that limited sensor errors can have a large impact on the nonlinear system dynamics. Furthermore it is shown that deadlock conditions can exist where the RPAS show oscillatory behaviour and do not manage to effectively pass each other, dependent on the encounter geometry and RP model settings. It is advised to perform a broad sensitively study for RP performance and to study extending the scope of DAA systems to include guidance for efficiently returning to mission without triggering new conflicts.
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    Assessing and Advancing Safety Management in Aviation
    (MDPI, 2022) Stroeve, S.H. ; Smeltink, J.W. ; Kirwan, B.
    A safety management system (SMS) is the overall set of procedures, documentation, and knowledge systems as well as the processes using them, which are employed within an organisation to control and improve its safety performance. Safety management systems are often observed as being bureaucratic, distinct from actual operations, and being too much focused on the prevention of deviations from procedures rather than on the effective support of safety in the real operational context. The soft parts of advancing safety in organisations, such as the multitude of interrelations and the informal aspects in an organisation that influence safety, are often only considered to a limited extent. As a way forward, this paper presents two coupled approaches. Firstly, a generic tool for assessing the maturity of safety management of aviation organisations is presented, which accounts for recent insights in effectively incorporating human factors. This assessment tool provides insight into the strong and weak topics of an organisation’s SMS. Secondly, an overview is given of a range of approaches that aim to improve the safety of aviation organisations by strengthening relevant organisational processes and structures, with a focus on human factors. The relations of these approaches with SMS are discussed, and the links with topics of the SMS maturity assessment tool are highlighted.
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    Including intent in detect-and-avoid systems for remotely piloted aircraft systems
    (EUROCONTROL, 2025) Stroeve, S.H. ; Kroon, M.
    Current standards for detect-and-avoid (DAA) systems of remotely piloted aircraft systems (RPAS) use state data like (relative) position and speed for the provision of guidance to remain well clear (RWC) with air traffic. They do not use intent data for planned route towards a destination. This paper proposes an intent-based DAA system that uses an A* path planning approach. The performance of this A* DAA system is compared with the ACAS Xu standard for a set of horizontal encounters between RPAS pairs. This comparison is done for deterministic and stochastic encounter-scenarios, which account for sensor errors and variation in remote pilot performance. The results show that in the ACAS Xu scenarios the aircraft can attain livelock conditions that prevent them from reaching their destination. Also, in these encounter-scenarios often loss of DAA well clear (LDWC) conditions occur, and they are sensitive for sensor errors and closed-loop delays. The simulation results of the A* DAA encounter-scenarios are without livelock or LDWC conditions and the variations due to sensor errors and closed-loop delays are limited. They show that the intent-based A* DAA system is a promising approach for more effective DAA.