Search Results (1,574)

There is growing interest in the design of maneuvering high-speed aircraft to fly within or at the edge of the atmosphere. We identify and develop novel quasi-static vehicle screening methodologies, suitable for use during preliminary design, to better predict an incipient loss of control due to the dynamic effects of feedback. We validate these metrics by reverse-engineering Neil Armstrong’s 1962 loss of control and inadvertent atmospheric skip while piloting the X-15. In 1962, then-extant flight dynamics screening methods did not forecast likely troubles. We assemble and refine a collection of predictive metrics which operate upon basic quasi-static aerodynamic data and predict the confluence of lateral/directional stability and controllability issues which plagued the flown mission. These tools, which leverage McRuer’s “equivalent stability derivative” approach, enable future engineers to make proactive design changes which can avoid lateral/directional instabilities developing at high speeds. Full article

Unmanned tilt-rotor electric Vertical Take-Off and Landing (eVTOL) aircraft face significant control challenges during the transition from hover to forward flight, particularly when using open-source autopilot systems that rely on open-loop tilt control and static control gains. After the transition, the Total Energy Control System (TECS) becomes active in fixed-wing mode, but its default static gains often fail to correct energy imbalances, resulting in substantial altitude loss. This paper presents the Steepest Descent-based Total Energy Control System (SD-TECS), a real-time adaptive TECS framework that dynamically tunes gains using the steepest descent method to enhance post-transition altitude and airspeed regulation in unmanned tilt-rotor eVTOLs. The proposed method integrates gain adaptation directly into the TECS loop, optimizing control actions based on instantaneous flight states such as altitude and energy-rate errors. This enables improved responsiveness to nonlinear dynamics during the critical post-transition phase. Simulation results demonstrate that the SD-TECS approach significantly improves control performance compared to the default PX4 TECS, achieving a 35.5% reduction in the altitude settling time, a 57.3% improvement in the airspeed settling time, and a 66.1% decrease in the integrated altitude error. These improvements highlight the effectiveness of SD-TECS in enhancing the stability and reliability of unmanned tilt-rotor eVTOLs operating under autonomous control. Full article

The variable camber wing (VCW) is a morphing wing design anticipated to enhance unmanned aerial vehicles’ (UAVs’) performance in flight through continuously changing shape. The performance of VCWs has been proven, but techniques for their integration, including aerodynamic analysis, mechanism synthesis, and structural tests, still lag in development at the conceptual design stage. Therefore, this research focuses on designing a variable camber wing, a key area for the advancement of morphing aircraft. Inspired by the high-lift capabilities of traditional aircraft devices but aiming for smoother airflow through continuous shape alteration, this research proposes a novel three-step design for a structurally integrated VCW. This approach begins with a critical aerodynamic analysis to determine wing shape adaptations across various flight conditions, followed by a mechanism synthesis phase to design a four-bar linkage that accurately approximates the desired trailing edge deflections by utilizing a variant of teaching–learning-based optimization. The objective is to minimize error between the intended and actual coupler link while adhering to design constraints for proper integration in the wing structure. Finally, structural analysis evaluates the skin’s ability to withstand operational loads and ensure the integrity of the VCW system. The design result demonstrates the success of this three-step approach to synthesizing a VCW mechanism that meets the defined aerodynamic (actual deflection of 9.1764°) and structural targets (maximum Von Mises stress of 81.5 MPa and maximum deflection of 0.073 m), paving the way for enhanced aircraft performance. Full article

Urban Air Mobility (UAM) has high potential as an ecofriendly transportation mode that can alleviate traffic congestion on the ground and reduce travel times by utilizing three-dimensional airspace. However, efficient vertiport operational plans are needed for UAM to become an accessible transportation mode for the public. In this study, the numerical analysis program MATLAB (R2023a) and the traffic simulation software VISSIM (PTV VISSIM 2024) were used to model vertiport operations and analyze the on-ground traffic environment, including vertiport capacity and UAM aircraft delays. Additionally, on-time performance was considered by applying uncertainties to the intervals between consecutive generations and the turnaround time to simulate situations where UAM aircraft cannot adhere to their scheduled arrival and departure times. Operational scenarios were developed by varying the interval time between UAM aircraft generated in the simulation (3–10 min) in two cases: (1) without considering the on-time performance and (2) considering the on-time performance. This study aimed to maximize vertiport capacity and minimize UAM aircraft delay times. In addition, the reduction of delay times and improvement of turnaround efficiency directly contribute to sustainable urban airspace management by lowering ground energy use and environmental impact. In Case 1, the vertiport was most efficient at an interval time of 7 min. In Case 2, capacity was maximized at an interval time of 6–7 min while delay times were minimized at an interval time of 8–10 min. The simulation results provide valuable insights for developing not only efficient but also environmentally responsible vertiport operational plans, contributing to the successful and sustainable implementation and scalability of UAM systems. Full article

When Typhoon Kong-rey hit Taiwan in October 2024, an aircraft attempting to land at Taoyuan International Airport undertook a missed approach and landed successfully on the second attempt. The possible meteorological factors causing this missed approach are studied in this study based on a methodology specifically adopted for Hong Kong International Airport; namely, studying crosswind as derived from aircraft and airport meteorological observations, as well as the low-level turbulence derived from data on the aircraft’s vertical acceleration and high-resolution numerical weather prediction model results. A significant crosswind component and a gusting crosswind are the major reasons for the missed approach. The low-level turbulence appears to have been secondary/minor, as shown by the successful landings of aircraft before and after the event. It is concluded that the methodology supporting airport operations in Hong Kong may be used to explain missed approach cases at other airports under the influence of tropical cyclones. Full article

Aviation has become an essential part of the modern world’s ability to grow personal, market and international connections. To enable continued benefits while reducing emissions, future aircraft will need radical redesign and novel, complementary technologies. Hydrogen aircraft are potentially the means to emissions reduction. As part of the European Union’s (EU’s) Clean Aviation Joint Undertaking (CAJU), it is aimed to have hydrogen aircraft entering into service by 2035. To realise this, it would require the certification of these aircraft in a relatively short timeline, which the CONCERTO project aims to help enable. Given the lack of mature experimental designs and pending certification processes, this endeavour is ambitious. To accelerate this, dedicated preparation for the certification through regulatory analysis should be complete, requiring initial options for technologies and aircraft operations to be defined. The technologies and operations were defined, analysed and weighted in CONCERTO, upon which a Generic Concept was made, outlined in this paper, with Level 1 on the Certification Readiness Level Scale. The aircraft systems which are likely to experience the largest changes; Fuel Storage, Fuel Distribution, Propulsion, Auxiliary Power Unit (APU), Heat Exchange (HEX) System and Sensing and Monitoring for Hydrogen (H2), will be outlined in this paper with respect to their components and integration challenges, and the subsequent changes to operations to enable this. Full article

Various sectors focus on transitioning to clean and renewable energy sources, particularly airport microgrids (AMGs), which offer the potential for highly reliable and resilient operations. As airports increasingly integrate renewable energy sources, ensuring stable and efficient power becomes a critical challenge. In this context, maintaining proper frequency is essential for the reliable operation of AMGs, which helps maintain grid stability and reliable operation. This paper proposes a new hybrid disturbance observer-based controller with a fractional-order controller (DOBC/FOC) for operating AMGs with high levels of renewable energy integration and advanced frequency regulation (FR) capabilities. The proposed controller utilizes DOBC coupled with a non-integer FOC for load frequency control (LFC), optimized for peak performance under varying operational conditions. In addition, a decentralized control strategy is introduced to manage the participation of electric vehicles and lithium-ion battery systems within the airport’s energy ecosystem, enabling effective demand response and energy storage utilization. Furthermore, the parameters of these controllers are optimized simultaneously to ensure optimal performance in both transient and steady-state conditions. The proposed DOBC/FOC controller demonstrates strong performance and reliability according to simulation outcomes, showcasing its superior performance in maintaining frequency stability, reducing fluctuations, and ensuring continuous power supply in diverse operating scenarios, such as 55.5% and 76.5% in step load perturbations when compared to the utilization of electric vehicles (EVs) and electric aircraft (EAC), respectively. These results underline the potential of this approach in enhancing the resilience and sustainability of AMG and contributing to more intelligent and eco-friendly airport infrastructure. Full article

Soil pollution at airports is a critical environmental issue that affects not only the local ecology but also the health of people living near these infrastructures. The main causes of pollution include the use of chemical products such as de-icing agents, fuels, and lubricants, as well as waste from aircraft and ground vehicles. These substances often seep into the soil, leading to the accumulation of toxic elements. However, due to security reasons, there is a great scarcity of real data on the impact of airport operations on ecosystems and the role trees could play in pollutant limitation. Thus, the aim of this study was to determine whether airport operations have toxic effects on soils within and around Macedonia Airport, Thessaloniki, Northern Greece, by determining the concentrations of potentially toxic elements (Cu, Ni, Pb, Mn, Fe, Co, Cr, Cd, and Zn) in soil samples taken within the airport and near the airport. Furthermore, this study aimed to investigate the effect of the canopies of forest species on the accumulation of toxic metals in the soil inside the airport and in the peripheral zone. The results show that, overall, no important pollution was detected in the soil of the Thessaloniki Airport, Northern Greece, both inside and outside the airport area. Some differences were observed in the content of toxic metals studied between the samples taken inside and outside the airport, and some effects of tree canopy were noted. However, all values were lower than the defined permissible limits according to international standards (except for iron). It is important, however, to perform regular re-checking of soil quality with new samples in order to prevent soil contamination and mitigate any contamination found. Full article

Flight delays represent a significant challenge for airlines, airports, and passengers, impacting operational costs and customer satisfaction. Traditional prediction methods often rely on complex statistical analysis and mathematical models that may not be easily implementable. This study proposes scorecards as an innovative and simplified approach to forecast flight delays. Historical flight data from the United States were used, incorporating variables such as departure and arrival times, flight routes, aircraft types, and other factors related to delay. Exploratory data analysis identified key variables influencing delays, and scorecards were constructed by assigning weights, normalizing, and scaling variables to improve interpretability. The model was validated using test datasets, and predictive performance was evaluated by comparing forecast delays with actual results. The results indicate that scorecards provide accurate and interpretable predictions of flight delays. This method facilitates the identification of critical factors that contribute to delays and allows for an estimation of their likelihood and duration. Scorecards offer a practical tool for airlines and airport operators, potentially enhancing decision-making processes, reducing delay-related costs, and improving service quality. Future research should explore the integration of scorecards into operational systems and the inclusion of additional variables to increase model robustness and generalizability. Full article

Strict sustainability objectives have been established for the upcoming generation of aircraft. A promising innovative airframe concept is the ultra-high-aspect-ratio Strut-Braced-Wing Aircraft (SBWA). Hydrogen-powered concepts are strong candidates for sustainable propulsion. The study investigates the influence of Liquid Hydrogen (LH2) propulsion on the optimal wing geometry of medium-range SBWA for minimum-cost and minimum-emission objectives. Multiobjective optimizations are performed in two optimization frameworks of differing fidelity for both kerosene- and LH2-propelled SBWA concepts. Furthermore, a range of Pareto-optimal designs show the changes in the optimized planform for variable weighting of the two objectives. The results show that the differences in the optimal wing geometry between the kerosene- and LH2-powered results for each respective objective function are small. For both aircraft, the minimum-emission objective optimizes for lower fuel burns and hence lower emissions, albeit at an increase in wing structural mass. The minimum-cost objective balances the reductions in structural and fuel masses, resulting in a lighter design at lower aspect ratios. Other wing-shape parameters only have minor contributions. Although the wing aspect ratios for both objectives differ by ca. 50%, the actual changes are only 2.5% in fuel and 1.5% in Direct Operating Cost (DOC). Due to a larger set of design variables used in the higher-fidelity optimizations, further parasite and wave drag reduction opportunities result in increased optimal aspect ratios. Full article

The water environment is a dynamic domain critical to global transportation and commerce, where seaplanes operate during take-offs, landings, and ground operations, often near maritime traffic. Canada’s vast remote regions and unique geography increase reliance on seaplanes, especially for private and recreational purposes. This article examines the intersection of aviation and maritime operations through a mixed-methods approach, analyzing seaplane safety on waterways using quantitative and qualitative methods. First, data from 1005 General Aviation (GA) seaplane accidents in Canada (1990–2022) are analyzed, revealing 179 fatalities, 401 injuries, and 118 destroyed aircraft—significant given that seaplanes comprise under 5% of GA aircraft. Of these, 50.35% occurred while the seaplane was not airborne. Second, insights from interviews, focus groups, and questionnaires involving 136 participants are explored through thematic and content analysis. These capture pilot concerns that are not evident in accident data, such as hazards from jet ski interactions and disruptive boat wakes. The findings highlight risks like limited visibility and maneuverability during waterborne take-offs, worsened by seaplanes’ lack of priority over maritime vessels in shared spaces. This article concludes with recommendations for both the seaplane and maritime communities, including increasing awareness among boaters about the presence and operations of seaplanes, as well as regulatory adjustments, particularly considering the right of way. Full article

This study investigates the degradation of aircraft paint and its impact on aerodynamic performance, using the PZL M-20 “Mewa” aircraft as a case study. Paint samples were collected from both damaged and intact areas of the airframe and analyzed using electron paramagnetic resonance (EPR) spectroscopy, scanning electron microscopy (SEM), and aerodynamic testing. One of the major challenges addressed in this work was the non-destructive identification of chemical aging effects in operational paint coatings and their correlation with aerodynamic behavior. The application of EPR spectroscopy in conjunction with real-world aerodynamic testing on naturally degraded surfaces represents an innovative approach that offers both scientific insight and practical guidance for maintenance practices. The results indicate significant deterioration in aerodynamic characteristics—such as increased drag and reduced lift—due to coating damage, particularly around riveted and bolted joints. EPR spectra revealed a notable increase in the density of unpaired electron spins in aged coatings, confirming ongoing oxidative degradation processes. While this study was limited to a single aircraft, the findings highlight the critical importance of regular inspection and maintenance of paint coatings to ensure flight safety and operational efficiency. Full article

The construction of concrete airfield pavements aims to ensure sufficient load-bearing capacity for the safe operation of aircraft. In order to reduce the pavement thickness and the associated costs, materials with improved properties compared to conventional concrete mixtures are generally used. This measure also aims to reduce the use of cement raw materials as part of a more sustainable strategy. On this basis, various fibers can be added to conventional concrete to improve the compressive and flexural strength of the concrete. Against this background, the present study aims to quantify the effect of polypropylene and steel fibers on the thickness of airfield concrete pavements. For this reason, international experience on this topic is first summarized in order to select suitable weighted values of concrete flexural strength for further analysis. Subsequently, an airfield concrete pavement for the edge of an airport runway is designed according to the Unified Facility Criteria (UFC) of the US Department of Defense. Comparisons are made between the pavement thicknesses determined using the above method and conclusions are drawn on the effects of using steel and polypropylene fibers on the design of airfield pavements. The analysis showed that the use of steel fibers can lead to a 25% reduction in concrete layer thickness, while the use of polypropylene fibers reduces the concrete layer thickness by 8–16%. Full article

In this paper, we propose and prove an innovative radar antenna concept suitable for collision avoidance (CA) systems installed onboard small, unmanned aircraft (UA). The proposed architecture provides 360° monopulse coverage around the host platform, enabling the detection and accurate position estimation of airborne, non-cooperative intruders using lightweight, low-profile antennas. These antennas can be manufactured using low-cost 3D printing techniques and are easily integrated into the UA airframe without compromising airworthiness. We present a Detect and Avoid (DAA) concept of operations (ConOps) aligned with the SESAR U-space ConOps, Edition 4. In this ConOps, the Remain Well Clear (RWC) and CA functions are treated separately: RWC is the responsibility of ground-based U-space services, while CA is implemented as an airborne safety net using onboard equipment. Based on this framework, we derive operation-centric design requirements and propose an antenna architecture based on a fixed circular array of sector waveguides. This solution overcomes key limitations of existing radar antennas for UAS CA systems by providing a wider field of view, higher power handling, and reduced mechanical complexity and cost. We prove the proposed concept through a combination of simulations and measurements conducted in an anechoic chamber using a 24 GHz prototype. Full article

Every year, airlines invest considerable resources in recovering from irregular operations caused by delays and disruptions to aircraft and crew. Consequently, the need to reschedule aircraft and crew to better address these problems has become pressing. The airline scheduling problem comprises two stages—that is, the Aircraft-Routing Problem (ARP) and the Crew-Pairing Problem (CPP). While the ARP and CPP have traditionally been solved sequentially, such an approach fails to capture their interdependencies, often compromising the robustness of aircraft and crew schedules in the face of disruptions. However, existing integrated ARP and CPP models often apply static rules for buffer time allocation, which may result in excessive and ineffective long-buffer connections. To bridge these gaps, we propose a robust integrated ARP and CPP model with two key innovations: (1) the definition of new critical connections (NCCs), which combine structural feasibility with data-driven delay risk; and (2) a spatiotemporal delay-prediction module that quantifies connection vulnerability. The problem is formulated as a sequential decision-making process and solved via a novel multi-agent reinforcement learning algorithm. Numerical results demonstrate that the novel method outperforms prior methods in the literature in terms of solving speed and can also enhance planning robustness. This, in turn, can enhance both operational profitability and passenger satisfaction. Full article