Search Results (203)

The aviation industry aims to reduce environmental impact by adopting alternative propulsion systems, including hydrogen-based, hybrid-electric, and all-electric architectures, requiring a new Thermal Management System (TMS). In addition, new design methods are needed for the TMS, at the system and component levels, to handle various fluids and varying fluid properties. Within the TMS, heat exchangers are critical components that may require significant space and must be considered early in the design process. This paper presents a parametric sizing methodology for heat exchangers suitable for early design phases within a Multidisciplinary Design Analysis and Optimization (MDAO) framework, specifically for cryogenic heat transfer. The method combines physical equations with validated empirical relationships, using iterative solver algorithms for sizing. To address multi-variable design challenges, the methodology integrates discretization schemes for fluid properties, temperature, and energy calculations, and constraint-based optimization with a weighted-sum approach for solution selection. The methodology is validated with a commercial heat exchanger, and cross-validated with a cryogenic Heat Exchanger (HX). A case study for an all-electric hydrogen fuel cell aircraft architecture with a 7.6 MW propulsion system is presented to demonstrate the effectiveness of the methodology. The presented heat exchanger performance can be predicted across multiple conditions quickly enough to enable large design space exploration. Overall, the presented model is a crucial element for the design of a TMS for future aircraft with hydrogen-based propulsion systems. Full article

In this paper, we examine the existing artificial intelligence policy documents in aviation for the following three regions: the United States, the European Union, and China. These global economic leaders were selected for their dominance in economic activity; as a result, their influence on aviation policy direction is a logical assumption. Historically, the aviation industry has always been a first mover in adopting technological advancements. This early adoption offers valuable insights because of its stringent regulations and safety-critical procedures. Consequently, the aviation industry provides an optimal platform to address AI vulnerabilities through its stringent regulations, standardized processes, and certification of new technologies. Our research aims to compare AI regulations across these regions to guide other sectors in shaping effective policies. The findings of our comparative analysis show that there are vastly differing approaches to the application of AI regulations in the aviation sector, thus weakening desired prospects for global cooperation and worsening existing geopolitical tensions. Therefore, we propose a hybrid model approach as a way forward. Under this model, regions maintain their distinctive AI policies but collaborate on high-risk aviation applications through joint working groups, shared safety intelligence, or mutual recognition agreements. This would preserve incentives for innovation but also reduce regulatory friction. Full article

Three-dimensional printing is the most commonly used method for producing customized or mock-up products for industrial applications. In particular, aviation devices for drones usually require a high spatial resolution to satisfy the small size requirement. In practical applications of drones, the two main tasks are inspection and detection. However, the working environment is often filled with flammable gases, such as natural gas or petroleum gas. Thus, the parts of drones that can easily produce an electrical spark, such as electronic connectors, should be specially protected. In this study, atmosphere control was applied to enhance the printing performance and manufacture of anti-explosion devices. The results demonstrate that atmosphere control can efficiently improve the print quality and that the print resolution of a commercial 3D printer can be enhanced to reach the mm scale. In the anti-pressure testing via a high-pressure smoke experiment, the manufactured anti-explosion devices for drones showed an appropriate intrinsic safety level, suggesting that they can be used in drones used for daily inspections of pipelines in petrochemical plants. The two main contributions of this study are the development of a practical method for improving FDM 3D printers and an anti-explosion device for drones. Full article

Despite substantial advances in turbofan engineering, a crucial gap persists: there remains the need for an all-inclusive comparative analysis that includes real-world operational data and evaluates the performance of modern turbofans used in aviation. Specifically, systematic investigations that examine the exergy and efficiency of turbofan engines for takeoff and cruise remain scarce. Further, the current literature needs to address rigorous performance assessments that include simultaneous consideration of the combined effects of ambient conditions (e.g., temperature, density, relative humidity), Mach number, and turbine inlet temperature on high-bypass turbofan engines used in modern, commercial aircraft. Energetic and exergetic analyses were conducted on five commercial high-bypass turbofan engines with different configurations for both takeoff and cruise flight modes. The computational thermodynamic models developed showed strong correlation with manufacturers’ specifications. Performance evaluations included variations in ambient conditions, altitude, Mach number, and turbine inlet temperature. Results demonstrate that three-spool engine architecture exhibits 70–71% reduction in exergy destruction between flight phases compared to 62.5% for two-spool designs, indicating greater operational adaptability. The combustion chamber emerged as the dominant contributor to irreversibilities, representing approximately 55–58% of overall exergy destruction during takeoff operations. Results demonstrate that increased ambient temperature and/or humidity increase both degraded exergetic efficiency and thrust-specific fuel consumption, and that Mach number and altitude influenced efficiency metrics through ram compression and density effects, while higher turbine inlet temperatures enhanced exhaust kinetic energy via increased thermal input. We show that cruise operations demonstrated superior exergetic efficiency (68–74%) compared with takeoff (47–60%) across all engine configurations. Our results confirm the fundamental trade-off in turbofan design: for long-range applications, high-bypass engines prioritize propulsive efficiency, while for power-intensive operations, moderate-bypass configurations deliver higher specific thrust. Full article

This study critically examines the technological feasibility, regulatory challenges, and societal acceptance of Pilotless Passenger Aircraft (PPAs) in commercial aviation. A mixed-methods design integrated quantitative passenger surveys (n = 312) and qualitative pilot interviews (n = 15), analyzed using SPSS and NVivo to capture both statistical and thematic perspectives. Results show moderate public awareness (58%) but limited willingness to fly (23%), driven by safety (72%), cybersecurity (64%), and human judgement (60%) concerns. Among pilots, 93% agreed automation improves safety, yet 80% opposed removing human pilots entirely, underscoring reliance on human adaptability in emergencies. Both groups identified regulatory assurance, demonstrable reliability, and human oversight as prerequisites for acceptance. Technologically, this paper synthesizes advances in AI-driven flight management, multi-sensor navigation, and high-integrity control systems, including Airbus’s ATTOL and NASA’s ICAROUS, demonstrating that pilotless flight is technically viable but has yet to achieve the airline-grade reliability target of 10⁻⁹ failures per flight hour. Regulatory analysis of FAA, EASA, and ICAO frameworks reveals maturing but fragmented approaches to certifying learning-enabled systems. Ethical and economic evaluations indicate unresolved accountability, job displacement, and liability issues, with potential 10–15% operational cost savings offset by certification, cybersecurity, and infrastructure expenditures. Integrated findings confirm that PPAs represent a socio-technical challenge rather than a purely engineering problem. This study recommends a phased implementation roadmap: (1) initial deployment in cargo and low-risk missions to accumulate safety data; (2) hybrid human–AI flight models combining automation with continuous human supervision; and (3) harmonized international certification standards enabling eventual passenger operations. Policy implications emphasize explainable-AI integration, workforce reskilling, and transparent public engagement to bridge the trust gap. This study concludes that pilotless aviation will not eliminate the human element but redefine it, achieving autonomy through partnership between human judgement and machine precision to sustain aviation’s uncompromising safety culture. Full article

This study analyzes the injection behavior of fossil and sustainable aviation fuel blends, in comparison with conventional diesel fuel, using a common-rail injection system applied to reciprocating engines. Neat commercial diesel and Jet A1 were tested as fossil fuels. A neat Fischer–Tropsch Synthetic Paraffinic Kerosene was tested and blended with Jet A1. Another alternative fuel, Hydrotreated Vegetable Oil, was also blended with Jet A1. The blending proportion was established to meet 51 as the derived cetane number, as required for fuels used in diesel reciprocating engines. Experimental tests were carried out under an energizing time of 2 ms at injection pressures between 50 and 110 MPa, with a fuel temperature ranging from 293 to 313 K, and a constant back pressure of 5 MPa, using a 130 µm single-hole injector. The results show that kerosene fuel exhibits slightly lower injection rates and total injected mass than diesel fuel, mainly due to their lower density. Under low-pressure conditions, an increase in hydraulic injection delay with diesel fuel is observed, mainly at the highest tested temperature. Mass flow rate, hydraulic injection delay, injection duration, total mass injected, and nozzle discharge coefficient do not show significant variations within the tested temperatures. Fossil kerosene fuel and its blend with Synthetic Paraffinic Kerosene show slightly higher injection rates. Overall, the results indicate that both neat kerosene and the studied blends may achieve injection characteristics comparable to diesel fuel, supporting their technical feasibility in reciprocating engines within the framework of the Single Fuel Concept. Full article

The aviation sector is one of the largest sources of greenhouse gas emissions, and the European Union (EU) is calling for a rapid transition to sustainable aviation fuels (SAFs). This study aims to assess market dynamics and regulatory challenges of sustainable aviation fuels (SAFs) in the European Union, with emphasis on economic feasibility and the role of policy frameworks. Using econometric methods: Autoregressive Integrated Moving Average (ARIMA) and Vector Autoregression (VAR) models, forecasts of SAF infrastructure development trajectories were produced, while regression analysis was applied to assess the relationship between national GDP and the scale of SAF deployment. The results revealed a statistically significant positive link between higher economic development and faster expansion of SAF infrastructure, highlighting the policy-driven nature of market dynamics. Germany and France demonstrate the greatest growth potential, while countries such as Italy and Denmark show slower progress. The findings confirm that clear regulatory frameworks and targeted economic incentives are essential to stimulate SAF uptake; however, additional investment and stronger policy harmonization across Member States are required to achieve large-scale commercialization and long-term sustainability. The empirical analysis utilizes data from 2015 to 2023 to estimate SAF infrastructure trajectories and policy effects, ensuring sufficient temporal coverage for robust econometric modeling and forecasting. Full article

At the moment, there are no available data or studies exploring the production of naphtha boiling range hydrocarbons via hydroprocessing of pretreated residual lipids. To that aim, this study targets the production of naphtha, jet and diesel boiling range hydrocarbons via hydroprocessing of refined waste cooking oils utilizing solar hydrogen. The technology was first optimized in a TRL-3 plant. A heteroatom removal catalyst and a saturation catalyst were combined with an isomerization and hydrocracking catalyst to upgrade lipids. The results show that the severity of the process plays an important role in the yields of the fuels. Higher naphtha yields were observed at 663 K, 13.78 MPa and a liquid hourly space velocity of 0.33 h⁻¹, leading to the production of a fuel consisting of 34 wt% naphtha, 23 wt% jet and 42 wt% diesel boiling range hydrocarbons. Subsequently, the technology was validated and demonstrated in an industrially relevant unit (TRL-5). The results from the fuel characterization show that the diesel fraction can be used as a high-quality road transport drop-in fuel, as it is characterized by a high cetane index (~96) and a high flash point (414 K). Although jet and naphtha meet most commercial fuel specifications, further optimization of the process is necessary to meet fuel standards. In conclusion, the current work provides novel data relevant to industrial applications for road, aviation and maritime fuel production via hydroprocessing of refined waste cooking oil. Full article

In commercial aviation, accurate estimation of the remaining track miles (RTM) during descent is essential for energy-efficient trajectory management. Currently, pilots often rely on heuristics and experience due to the lack of consistent RTM information, which can result in suboptimal decisions. This study investigates the accuracy of RTM estimations made by commercial pilots through a structured survey involving scenario-based assessments across seven European airports. Results show a consistent underestimation bias, with a root mean square error (RMSE) of 9.69 NM. To quantify the potential of data-driven alternatives, a machine learning model based on gradient boosting was developed using ADS-B surveillance and weather data. The model achieved significantly lower prediction errors, with an RMSE of 5.43 NM, particularly outperforming pilots in early descent segments. Feature importance analysis revealed that spatial and trajectory-related variables were key to accurate predictions. The findings suggest that integrating predictive models into flight management systems or pilot decision support tools could improve descent planning and operational efficiency. This study provides an empirical comparison between human and AI-based RTM estimations, highlighting the potential for machine learning to complement pilot expertise in future air traffic operations. Full article

The transition to sustainable aviation fuel (SAF) is critical for reducing the carbon footprint of the aviation sector while ensuring compatibility with current engines and infrastructure. Regulatory constraints, such as ASTM D7566, currently limit SAF blending to 50% in commercial flights, emphasizing the need for accurate evaluation of SAF properties to enable broader adoption. This review presents an updated overview of fuel studies evaluating key thermophysical and transport properties of hydrocarbon-based SAFs—including density, viscosity, specific energy, flash point, and thermal stability—with particular emphasis on molecular dynamics (MD) simulations. Among the MD simulations, the OPLS-AA force field demonstrates high accuracy in modeling liquid-phase hydrocarbons and shows strong agreement with experimental data. Coupled with MD engines like LAMMPS and GROMACS, it enables scalable and efficient simulations of SAF blends. Emerging research trends highlight integrative approaches that combine classical MD and machine learning (ML) in fuel property prediction, and force-field optimization to improve predictive capability. Future research in fuel is moving toward multi-force-field coupling using reactive frameworks such as ReaxFF for studying pyrolysis and oxidation, and data-driven experiments with in situ simulation feedback loops to accelerate SAF design and facilitate wider implementation in aviation. Full article

Aircraft maintenance delays (AMD) remain a significant challenge in commercial aviation, adversely affecting operational efficiency, flight punctuality, and passenger satisfaction. Despite advancements in maintenance strategies, recurring disruptions continue to generate financial losses and reputational risks. This study proposes an integrated five-step framework that combines failure mode and effects analysis (FMEA) with the Define–Measure–Analysis–Improve–Control (DMAIC) methodology to systematically address and reduce AMD. The framework involves the definition of problems, the identification of contributing factors and failure modes, the assessment of risk and root cause analysis, the mitigation of risk, and continuous monitoring. The main contribution of this study lies in the integration of FMEA and DMAIC into a unified data-driven system that proactively reduces maintenance delays, offering a novel approach to continuous process improvement in aviation operations. Its practical applicability is demonstrated through a case study of the AFRIQIYAH Airways Airbus A320 fleet, which represents the majority of the airline’s operations. High-risk landing gear failure modes were identified, evaluated and addressed through targeted improvement projects, including predictive maintenance, supplier diversification, inventory optimization, and improved quality assurance for critical spare parts. Implementing these initiatives is expected to reduce the overall Risk Priority Number (RPN) by approximately 59%, highlighting the effectiveness and potential to minimize AMD. Full article

The angular momentum flowmeter addresses critical challenges in aviation fuel flow measurement during commercial flight operations. This study designed a visualization platform to observe the dynamic responses of internal components under varying flow conditions. By employing the sliding mesh method coupled with an angular momentum algorithm, it enabled the dynamic rotation simulation of the upstream straight-bladed rotor and provided calculation of the deflection angle in the downstream straight-bladed rotor of an angular momentum flowmeter. Experimental results categorize the flow process into three distinct regimes based on flat and spiral spring response states: pre-spring, single-spring, and dual-spring regimes. Under a flow condition of 0.091 kg/s, the upstream straight-bladed rotor maintained stable rotation at a speed of 1.1 rad/s. At a flow rate of 0.20 kg/s, the flat spring initiated outward expansion, and with further increase in flow rate, the rotational speed of the upstream straight-bladed rotor remained within the range of 25.34–26.21 rad/s. Mathematical analysis demonstrates that the flat spring configuration extends the lower measurement limit and promotes dissipation of the secondary vortex through dominant kinetic energy of the primary vortex during dual-spring operation, thereby improving high-pressure zone stability. This work elucidates the operational mechanism of angular momentum flowmeters and provides a theoretical basis for structural optimization. Full article

India’s aviation sector, crucial for connectivity, economic growth, and national integration, faces sustainability measurement challenges focused solely on carbon emissions. This study proposes the Aviation Sustainability Performance Index (ASPI-India), spanning four pillars: Environmental Stewardship, Social Responsibility, Governance Maturity, and Economic Resilience. Measurable indicators are derived from regulatory filings, commercial flight databases, geospatial tracking, and targeted surveys. Data sources include DGCA safety audits, AAI operational statistics, ADS-B flight path data, and passenger satisfaction surveys from 2010 to 2024. Fixed-effects panel models link ASPI-India to operational and financial outcomes like load factor stability, CASK, and credit rating resilience. Quasi-experimental designs exploit policy shocks through difference-in-differences estimation. Factor analysis validates the four-pillar structure, and robustness checks compare entropy, PCA, and equal weighting. Results show that a one-standard-deviation increase in ASPI-India improves load factor stability, ancillary revenue share, and credit terms, especially for carriers with diversified route networks. The framework provides actionable insights for airlines, regulators, and investors to embed sustainability in aviation management. Full article

Hydrogen propulsion technologies are emerging as a key enabler for decarbonizing the aviation sector, especially for regional commercial aircraft. The evolution of aircraft propulsion technologies in recent years raises the question of the feasibility of a hydrogen propulsion system for beyond regional aircraft. This paper presents a comprehensive review of hydrogen propulsion technologies, highlighting key advancements in component-level performance metrics. It further explores the technological transitions necessary to enable hydrogen-powered aircraft beyond the regional category. The feasibility assessment is based on key performance parameters, including power density, efficiency, emissions, and integration challenges, aligned with the targets set for 2035 and 2050. The adoption of hydrogen-electric powertrains for the efficient transition from KW to MW powertrains depends on transitions in fuel cell type, thermal management systems (TMS), lightweight electric machines and power electronics, and integrated cryogenic cooling architectures. While hydrogen combustion can leverage existing gas turbine architectures with relatively fewer integration challenges, it presents its technical hurdles, especially related to combustion dynamics, NOx emissions, and contrail formation. Advanced combustor designs, such as micromix, staged, and lean premixed systems, are being explored to mitigate these challenges. Finally, the integration of waste heat recovery technologies in the hydrogen propulsion system is discussed, demonstrating the potential to improve specific fuel consumption by up to 13%. Full article

Background: Aviation is one of the most demanding professions, exposing pilots to persistent stressors such as fatigue, irregular schedules, and high safety responsibility. These conditions heighten vulnerability to depression, anxiety, and stress (DAS), yet the protective mechanisms mitigating such effects remain less well understood. Objective: This study examined the roles of resilience, coping strategies, and fatigue in predicting DAS among commercial airline pilots. Method: A sample of 200 pilots completed validated self-report measures: the Connor–Davidson Resilience Scale (CD-RISC), the Coping Inventory for Stressful Situations (CISS), the Fatigue Severity Scale (FSS), and the Depression Anxiety Stress Scale (DASS-21). Data were analyzed using bivariate correlations, hierarchical multiple regression, and mediation/moderation analyses via the PROCESS macro. Results: Resilience was negatively correlated with total DAS scores (r = −0.46, p < 0.001), while fatigue (r = 0.42, p < 0.001) and avoidance coping (r = 0.38, p < 0.001) were positively correlated. The regression model accounted for 46% of the variance in DAS (R² = 0.46). Task-focused coping predicted lower stress levels, whereas avoidance coping predicted higher anxiety and depression. Resilience moderated the relationship between stress and depression, buffering the impact of stress on mood outcomes. Mediation analyses indicated that coping styles partially explained the protective effect of resilience. ANOVA results confirmed that pilots with high resilience reported significantly lower depression scores than those with medium or low resilience, F(2, 197) = 6.72, p < 0.01. Conclusions: Resilience emerged as both a direct and indirect buffer against psychological strain in aviation. These findings underscore the importance of promoting adaptive coping and resilience training, alongside effective fatigue management, to enhance pilot well-being and maintain safety in aviation systems. Full article