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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.
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    Dutch Ministry of Infrastructure and Water Management as part of grant M240045 and commissioned to the National Institute for Public Health and the Environment
    (Elsevier, 2023) Voogt, M. ; Zandveld, P. ; Erbrink, H. ; Dinther, D. van ; Bulk, P. van den ; Kos, G. ; Blom, M. ; Jonge, D. de ; Helmink, H. ; Meydam, J. ; Visser, J. ; Middel, J. ; Hoek, G. ; Ratingen, S. van ; Wesseling, J. ; Jansen, N.A.H.
    Background and objectives In recent years it has been shown that aircraft emissions are a dominant source of ultrafine particles in the surroundings of airports. However, health effects of long-term (monthly to yearly) exposure to these particles are unknown. As part of an integrated research program into the health risks of ultrafine particles around Schiphol Airport, the applicability of the dispersion model STACKS+ to assess long-term exposure to ultrafine particles from aviation was assessed. Methodology A detailed comparison between modelled and measured particle number concentrations (PNC) due to aircraft emissions was carried out at ten locations in the surroundings of Schiphol Airport during two six-month periods in 2017 and 2018. In order to deduce the contribution of aviation to measured PNC, we applied a fitting method of the sum of the modelled contributions from aviation, the modelled contributions from traffic on main roads and the contributions from outside the study area estimated from the measurements, to the measured total PNC. The analysis yielded scaling factors and uncertainty estimates for each of the main contributions. We then subtracted the estimated background and modelled contributions of road traffic from the total measured PNC and took the remainder as an approximation of the measured contribution from aviation to PNC. We compared it to the modelled contribution from aviation, based on the averaged values for the six-month periods. Results Both six-month averaged modelled and measured PNC due to aircraft emissions (i.e., adjusted for background) showed a large range at the monitoring locations representative for population exposure (from close to zero to 10 000 particles/cm3). Spearman and Pearson correlation coefficients between model and measurement results were high (>0.83). Conclusions The applied approach enabled us to obtain a robust estimate of the contribution of aviation to the measured PNC. The dispersion model is able to determine the spatially varying average concentrations due to aircraft emissions in residential areas over periods of 6 months, allowing for application in epidemiological studies into long-term exposure.
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    Corrosion protective performance evaluation of structural aircraft coatings in cyclic salt spray, outdoor and In-Service environments
    (Elsevier, 2025) Cornet, A.J. ; Homborg, A.M. ; Hoen - Velterop, L. 't ; Mol, J.M.C.
    Eliminating hexavalent chromium-based corrosion inhibitors from structural aircraft coatings remains a significant challenge, primarily due to the lack of reliable accelerated test methods. This study evaluates the performance of various structural aircraft coatings under different exposure conditions, i.e. outdoor exposure, cyclic salt spray testing and in-service conditions, supplemented by environmental sensors. Quarterly inspections and scanning electron microscopy were used to evaluate corrosion damage. The findings highlight a lack of correlation between accelerated testing and outdoor exposure testing, likely driven by disparities in salt deposition, UV-radiation, time of wetness and temperature cycling. Additionally, galvanic couples between skin and fasteners remain difficult to protect, with chromate-based systems offering limited inhibition and alternative systems struggling to protect such complex assemblies. However, in lap-joints, alternative coatings outperformed chromate-based counterparts, likely due to their polymer matrices providing improved barrier properties, hence limiting access of electrolyte to the coating-aluminium alloy interface.