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    Post-service analysis of the degradation and protective mechanisms of chromate-based structural aircraft coatings
    (Elsevier, 2024) Cornet, A.J. ; Homborg, A.M. ; Hoen - Velterop, L. 't ; Mol, J.M.C.
    The substitution of chromate-containing structural coating systems in aviation with alternatives complying with nowadays strict environmental, health and safety regulations remains a formidable challenge. This complexity is partly due to the absence of a standardized from-test-to-market methodology, including a performance comparison between chromate-containing and alternative coating systems. To address this gap, the present study delves into the identification of crucial degradation factors that merit inclusion in such a methodology. Concurrently, it investigates the protective mechanisms inherent in chromate-containing coating systems and proposes improvements that can be applied to alternative coating systems. This study entails a comprehensive post-service examination of the degradation of paint applied to an aircraft component with over 35 years of service, employing electrochemical, microscopic and spectroscopic techniques. The findings underscore the role of thermo-oxidation as a significant degradation factor in the aging process of such coatings. Furthermore, the investigation elucidates a notable phenomenon in which aluminium ions within the coating pores form an aluminium hydroxide gel onto which chromate adsorbs. This process contributes to an increase in pore resistance upon exposure to electrolyte, leading to a self-healing barrier effect within the coating. Remarkably, this self-healing mechanism continues to offer long-term protection even when the coating matrix is sub-optimally cured due to application errors. Furthermore, this study reveals that the significant changes in capacitance during immersion testing result primarily from inhibitor leaching, emphasizing the effectiveness of combining Electrochemical Impedance Spectroscopy (EIS) with Scanning Electron Microscopy (SEM) analysis for studying coating degradation.
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    Unravelling corrosion degradation of aged aircraft components protected by chromate-based coatings
    (Elsevier, 2024) Cornet, A.J. ; Homborg, A.M. ; Anusuyadevi, P.R. ; Hoen - Velterop, L. 't ; Mol, J.M.C.
    Despite extensive research, eliminating hexavalent chromium-based inhibitors from aerospace coatings remains challenging due to a lack of understanding of coating degradation during aircraft service. This study addresses the issue by investigating the protective mechanisms and aging processes of chromate-containing coatings on aircraft components after service for over 35 years. Four aircraft parts underwent visual inspection, disassembly, and analysis using scanning electron microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). While most coating areas remained intact after extended use, three distinct degradation modes were identified: tip erosion, corrosion around rivets, and corrosion around fasteners at the leading edge. These findings reveal the complexity of corrosion protection, emphasizing that hexavalent chromium-containing coatings may not offer comprehensive protection at local design heterogeneities. The study also highlights the need to revisit traditional laboratory analysis protocols based on accelerated corrosion testing of oversimplified sample configurations, given the revealed end-of-service failure mechanisms.
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    Integrating a virtual simulator in a large-scale live exercise : Lessons learned regarding training and operations aspects
    (Clarion Defense & Security, 2024) Petermeijer, S.M. ; Thijssen, D. ; Lubsen, Z.A. ; Lemmers, A.J.J.
    LVC training for fighter pilots has been argued to reduce training cost, enrich training scenarios and to be flexible and scalable. An LVC environment with a high level of interoperability requires a dedicated datalink to exchange training data with a high throughput and low latency. Research and development regarding the standardization of such links and technology is ongoing, but it is unlikely an highly interoperable LVC environment will become prevalent in the coming years. Fortunately, a highly interoperable LVC environment is not required to enhance the relatively small-scale training scenarios which are typically used during day-to-day training. Using existing technologies and operational datalinks effective LVC training can be facilitated, albeit with a reduced level of interoperability and limited set of possible interaction between the entities. Training experts agree that even a slight enhancement of the live day-to-day training might provide relatively large training benefits. The goal of this research is to investigate how day-to-day training can be facilitated without major changes to the training organisation and investment and to what extend such a set-up can offer in terms of training benefits. In October 2023 a synthetic environment – consisting of a virtual fighter and several constructive entities – was integrated into a large-scale international live flying exercise. The synthetic and live entities were able to exchange data through an operational Link-16 datalink. The virtual simulator joined the training scenario as a two-ship and supported the live players in their Offensive and Defensive Counter Air missions. After the training exercises the perceived added training value, for the live pilots as well as the pilot in the simulator, was evaluated through questionnaires and interviews. A detailed analysis of the results and a synthesis of the lessons learned is currently being performed. Preliminary results show that the virtual simulator and constructive entities add to the perceived training value of the live pilots. Moreover, the pilots of the virtual simulator also experienced training value in the simulator, albeit of a reduced magnitude. The preparation and operation of the LVC environment required too much technical support to offer a realistic option for day-to-day training in the current setup, but these are foreseen to be surmountable without excessive effort. Finally, the paper describes the design of a LVC environment in more detail, the training value such a setup is foreseen to offer, and the operational requirements in order to be effectively integrated in day-to-day training.
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    Navigating the Skies : Enhancing Military Helicopter Pilot Training through Learning Analytics
    ( 2024) Thijssen, D. ; Marez Oyens, P.M.W. de ; Pal, J. van der
    Ensuring safety and proficiency in aviation requires effective training and maintenance of pilot skills. Pilots must maintain currency, implying regular flight, though some critical elements (e.g. emergency procedures) are rarely prac-ticed in-flight. Simulator sessions are employed for safe practice and training. Simulators provide more opportunities for pilots to experience sophisticated training without safety risks and dependencies on for example weather and logis-tics. While human assessors currently evaluate pilot performance, a simulator can provide rich data for assessments, utilizing learning analytics for individual in-sights. Simulator data (and potentially aircraft data) is not regularly used yet in training to gain insights in performance. Furthermore, current training planning lacks consideration for individual needs, relying on fixed intervals and syllabi. This study aims to investigate how simulator data can be used to assess perfor-mance and if it provides valid statements about pilot performance. Thereafter, the data is used to develop a skill retention model accommodating personal differ-ences. The research involves Chinook helicopter pilots from the Royal Nether-lands Air Force, using simulator data to create tailored performance metrics for maneuvers. The ongoing study investigates the integration of simulator data into training assessments and aims to contribute valuable insights into pilot perfor-mance and skill retention. This paper presents the preliminary findings in the de-velopment of learning analytics within this context.
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    Using eXtended Reality as Digital Twin for Training and Collaboration: the FLEX-XR case study
    (National Training & Simulation Association, 2022) Thijssen, D. ; Petermeijer, S.M. ; Nabben, A.C.
    More than fifty years ago man first set foot on the moon, followed by six more successful crewed missions to the lunar surface. The last crewed mission dates back to 1972, after which interest in moon exploration diminished. Renewed interest in lunar exploration and colonization sparked the development of the Lunar analogue facilities (LUNA) at the ESA’s Astronaut Centre (EAC) in Cologne. Part of LUNA is the Future Lunar Exploration Habitat (FLEXHab), which will serve as a simulation habitat to train for future lunar missions. In order to maximize efficiency and flexibility in the use of FLEXHab, the user should be able to familiarize themselves with the simulation before entering or during the utilisation of the facility. Extended Reality (XR) is expected to provide these benefits with a low-cost solution. The FLEX-XR project goal is to showcase possibilities of Virtual Reality for user familiarisation with the FLEXHab facilities, as well as support them in their experiment design process, by creating a digital twin of the facility and some of the intended experiments. This digital twin will consist of a Virtual Reality (VR) application allowing users to prepare for their experiments (e.g. laboratory lay-out, required instruments and wiring) and to train as a group, with a focus on familiarizing these users with the facility. At a later stage, an Augmented Reality (AR) application will also be developed to offer just-in-time and just-in-place information, procedures and data streams, while working in the real FLEXHab. Cooperation with ground support can also be facilitated by this AR application. FLEX-XR aims to demonstrate the added value of VR- and AR-applications for future lunar missions.