Search Results (52)

Aviation is widely recognised to have global-scale climate impacts through the formation of ozone (O₃) in the upper troposphere and lower stratosphere (UTLS), driven by emissions of nitrogen oxides (NO_X). Ozone is known to be one of the most potent greenhouse gases formed from the interaction of aircraft emission plumes with atmospheric species. This paper follows up on previous research, where a Photochemical Trajectory Model was shown to be a robust measure of ozone formation along flight trajectories post-flight. We use a combination of a global Lagrangian chemistry-transport model and a box model to quantify the impacts of aircraft NO_X on UTLS ozone over a five-day timescale. This work expands on the spatial and temporal range, as well as the chemical accuracy reported previously, with a greater range of NO_X chemistry relevant chemical species. Based on these models, route optimisation has been investigated, through the use of network theory and algorithms. This is to show the potential inclusion of an understanding of climate-sensitive regions of the atmosphere on route planning can have on aviation’s impact on Earth’s Thermal Radiation balance with existing resources and technology. Optimised flight trajectories indicated reductions in O₃ formation per unit NO_X are in the range 1–40% depending on the spatial aspect of the flight. Temporally, local winter times and equatorial regions are generally found to have the most significant O₃ formation per unit NO_X; moreover, hotspots were found over the Pacific and Indian Ocean. Full article

The aviation industry significantly contributes to global greenhouse gas (GHG) emissions, accounting for approximately 2–3% of total annual CO₂ emissions, with high-altitude operations amplifying radiative forcing effects. This study quantitatively examines aviation’s contributions to global pollution compared to other transportation sectors, such as road and maritime, highlighting the substantial challenges in mitigating its environmental footprint. We focus on emissions of organic compounds, including polycyclic aromatic compounds and dioxins, and analyze key pollutants such as CO₂, NO_X, and ultrafine particles alongside the sector’s indirect effects. Our estimation indicates that dioxin emissions from commercial flights are negligible, at only 0.76 g annually; however, the sector’s broader impact on climate and air quality is significant. The analysis also evaluates current mitigation strategies, including the adoption of sustainable aviation fuels (SAFs), international initiatives like CORSIA, and advancements in aircraft technologies and operational efficiency. Despite these efforts, the projected growth in air traffic, estimated to increase annually by 5% over the next decade, underscores the urgent need for accelerated innovation and robust policy frameworks to achieve sustainable aviation. These findings emphasize the necessity of addressing aviation’s unique environmental challenges through international cooperation, technological advancements, and targeted climate actions. Full article

The taxiing stage of an aircraft is characterized by its long duration, low operating thrust, and low combustion efficiency, resulting in substantial emissions of CO, CO₂, and VOCs, which adversely affect air quality near airports. This study has developed an open-path Fourier transform infrared spectroscopy (OP-FTIR) monitor with second-level time resolution to enable the optical remote monitoring of pollutants during taxiing. Measurements of CO, CO₂, and VOCs were conducted over one month at Hefei Xinqiao International Airport (HXIA). The generalized additive model (GAM) is used for data analysis to reveal complex nonlinear relationships between aircraft emission concentrations and meteorological factors, aircraft models, and their corresponding registration numbers. The GAM analysis shows that among meteorological factors, humidity, and atmospheric pressure have the most significant impact on aircraft exhaust monitoring, with a relative average contribution value as high as approximately six. The explanatory power of aircraft models for emissions is low (R² < 0.18), whereas that of registration numbers is high (R² > 0.6), suggesting that individual differences between aircrafts play a crucial role in emission concentration variations. Furthermore, a noticeable correlation was found between the CO/CO₂ ratio and volatile organic compound (VOC) concentrations (R² > 0.63), indicating that combustion efficiency significantly affects VOC emissions. This study not only advances the real-time remote sensing monitoring of pollutants during aircraft taxiing but also underscores the crucial role of the GAM in identifying the key drivers of emissions, providing a scientific basis for precise environmental protection management and policy-making. Full article

A composite strategy is proposed to address the optimal power management for a hybrid powered compound-wing aircraft, which integrates bang–bang regulation with optimal demand chasing regulation. The electro-gasoline hybrid power system enhances the overall flight endurance of vertical take-off and landing compound-wing aircraft. The power consumption in level flight appears to be much lower than that in hovering, enabling the hybrid power system to simultaneously energize and charge the battery pack. In order to minimize fuel consumption and battery pack degradation during level cruise flight, a power management strategy that serves for both battery charging and thrust energizing is worthy of careful consideration. To obtain the desired features and design the regularity strategy of the power system, linear and nonlinear models are established based on the configuration of an electro-gasoline series hybrid power system installed in the proposed aircraft, with mathematical modelling of key components and units. A notable feature of semi-fixing for battery voltage and engine rotational speed has been qualitatively identified and subsequently quantitatively validated on the testbench. After conducting simulations and comparing with other strategies, the composite strategy demonstrates appropriate fuel consumption and battery degradation, effectively achieving cost minimization. Testbench evaluation confirms the effectiveness of this proposed power management strategy. Furthermore, the practicality of the hybrid power system and its associated level flight composite power management strategy are validated by tests conducted on a 30 kg aircraft prototype, thereby showcasing the potential to enhance flight performance. Full article

This systematic literature review (SLR) focuses on indoor environmental quality (IEQ) in passenger transport vehicles within tropical and subtropical regions. It specifically examines indoor air quality (IAQ), thermal comfort (TC), acoustic comfort (AC), and visual comfort (VC) of passenger vehicle cabins (PVCs) in auto rickshaws, sedans, trucks, bus rapid transits (BRTs), buses, trains, trams, metro systems, aircraft and ferries of tropical and subtropical regions. The SLR used the PRISMA approach to identify and review scientific studies between 2000 and 2024 on the IEQ of PVCs in the tropics. Studies reviewed were found in SCOPUS, Web of Science, Science Direct, and EBSCO databases including relevant citation references. Findings reveal a significant geographical imbalance in research, with most studies concentrated in tropical Asia (78.2%), while sub-Saharan Africa (8.2%), South America (11.8%), and Oceania (1.8%) are considerably underrepresented. In 113 studies, most addressed IAQ and TC but limited attention to AC and VC. Moreover, fewer studies have jointly addressed all the IEQ parameters, highlighting the need for a more comprehensive approach to IEQ for tropical PVCs. Several studies alluded to in-cabin commuter risk linked to PM_2.5, PM₁₀, carbon monoxide (CO), and volatile organic compounds (VOCs). These risks are exacerbated by traffic hotspots, poor ventilation, ambient pollution, overcrowding, and poor vehicle conditions. Additionally, thermal discomfort is compounded by extreme heat loads, inefficient HVAC systems, and high vehicle occupancy. Common gaps include a paucity of IEQ studies and inadequate IEQ regulations or adapted standards in developing tropics. Infrastructural and regulatory deficiencies have been identified, along with strategies for mitigation. Recommendations are for more holistic IEQ studies in the tropics, including exposure studies for emerging gaps in new indoor pollutants, integration of AI and IoT for sustainable ventilation strategies, and development of effective regulatory frameworks considering region-specific conditions. Finally, Policymakers are encouraged to establish localized IEQ standards, enforce regulations, and prioritize upgrades to transport infrastructure. The SLR findings emphasize the urgent need for targeted interventions in developing tropical regions to address disparities in IEQ, ensuring healthier and more sustainable transport environments that could be replicated across transport systems worldwide. Full article

The article reviews autogiros, concentrating on their flight history, development, application, flight principle, components, and advantages over other aircraft. Firstly, the history of autogiros is presented, focusing on breakthrough inventions and clarifying their significance for overall rotorcraft development. Then, contemporary scientific research on the autogiro is reviewed in detail, and the available research gap is determined. The flight principle and technical fundamentals of autogiros are also briefly discussed, and a comparison between autogiros, helicopters, and fixed-wing aircraft is performed. Autogiros’ applications for civil, military, and mixed purposes are pointed out and schematically presented. The main part of the article comprises an overview of the different components and systems in the structure of the reviewed aircraft, including the main rotor, propeller, engine, cockpit, and others. Additionally, a comprehensive classification mostly concerning contemporary and homologated autogiros is described and schematically presented. Experimental and compound gyroplane designs are also examined and marked in the classification. The aircraft are categorized depending on the main structure type, mast availability, number of seats, number of rotors and rotor blades, rotor and mast position, propeller and tail type and position, pre-rotator type, and power source. The idea of different autogiro variants presented in the classification is enhanced with visual examples. This work is an addition to the efforts of promoting autogiros and research on them. It offers complete information regarding the aircraft and could serve as a kind of starting point for engineers in the design process of such types of flying machines. Full article

With the development of the low-altitude economy, the demand for low-altitude flight missions has steadily increased. However, such flights often encounter special circumstances requiring emergency landings. To address this, a forced landing guidance law is designed in this paper, using a small compound-wing aircraft as the research object and based on proportional guidance principles. The guidance law calculates lateral and longitudinal acceleration commands using azimuth and elevation angles provided by a seeker, which are then input into the inner-loop control law to generate control surface commands. These commands guide the aircraft toward a nearby landing point. Hardware-in-the-loop simulations demonstrate the effectiveness and robustness of the proposed guidance law, and flight tests further validate its practical applicability. Full article

The popularity of ultralight planes in non-commercial aviation is on the rise; however, non-compliance with regulations and the use of faulty equipment poses significant risks. This study explores the consequences of such lapses in adherence to safety standards by thoroughly examining the conditions leading to an ultralight plane crash, focusing on data related to causative factors. The accident involved an unregistered ultralight aircraft, lacking proper inspection and the required license. The pilot’s error during takeoff led to a stall, resulting in a fatal crash. Upon impact with the ground, the pilot’s shoulder and lap belts were torn off, leading to immediate death. This case underscores the critical importance of compliance with safety regulations in ultralight aviation. The findings illuminate the dire consequences of non-compliance with safety regulations and the utilization of unregistered, uninspected ultralight aircraft in private aviation. The tragic accident analyzed herein underscores the pivotal role of adherence to safety standards in mitigating the risks associated with ultralight planes. The pilot’s fatal error during takeoff, compounded by the absence of proper inspection and licensing, serves as a stark reminder of the potential dangers inherent in neglecting established safety protocols. Full article

The civil aircraft cabin is enclosed and highly occupied, making it susceptible to a decline in indoor environmental quality. The environmental quality of civil aircraft cabins not only depends on objective factors such as temperature, relative humidity, and the presence of air pollutants such as carbon dioxide (CO₂), carbon monoxide (CO), ozone (O₃), particle matter (PM), and volatile organic compounds (VOCs) but also the subjective factors pertaining to the perceptions and health symptoms of passengers and crew. However, few studies have thoroughly examined the air quality and thermal comfort parameters that are measured during in-flight testing in airplane cabins, as well as the passengers’ subjective perceptions. In order to evaluate the in-flight thermal comfort and air quality status, this study conducted a review of the recent literature to compile data on primary categories, standard limits, and distribution ranges of in-flight environmental factors within civil aircraft cabins. Following a search procedure outlined in this paper, 54 papers were selected for inclusion. Utilizing the Monte Carlo method, the Predicted Mean Vote (PMV) distributions under different exercise intensities and clothing thermal resistance were measured with the in-cabin temperature and humidity from in-flight tests. Recommendations based on first-hand data were made to maintain the relative humidity in the cabin below 40%, ensure wind speed remains within the range of 0–1 m/s, and regulate the temperature between 25–27 °C (for summer) and 22–27 °C (for winter). The current estimated cabin air supply rate generally complies with the requirements of international standards. Additionally, potential carcinogenic and non-carcinogenic risks associated with formaldehyde, benzene, tetrachloroethylene, and naphthalene were calculated. The sorted data of in-flight tests and the evaluation of the subjective perception of the occupants provide an evaluation of current cabin thermal comfort and air quality status, which can serve as a reference for optimizing indoor environmental quality in future generations of civil aircraft cabins. Full article

Interactions between urban and wildfire pollution emissions are active areas of research, with numerous aircraft field campaigns and satellite analyses of wildfire pollution being conducted in recent years. Several studies have found that elevated ozone and particulate pollution levels are both generally associated with wildfire smoke in urban areas. We measured pollutant concentrations at two Utah Division of Air Quality regulatory air quality observation sites and a local hot spot (a COVID-19 testing site) within a 48 h period of increasing wildfire smoke impacts that occurred in Salt Lake City, UT (USA) between 20 and 22 August 2020. The wildfire plume, which passed through the study area during an elevated ozone period during the summer, resulted in increased criteria pollutant and greenhouse gas concentrations. Methane (CH₄) and fine particulate matter (PM_2.5) increased at comparable rates, and increased NO_x led to more ozone. The nitrogen oxide/ozone (NO_x/O₃) cycle was clearly demonstrated throughout the study period, with NO_x titration reducing nighttime ozone. These findings help to illustrate how the compounding effects of urban emissions and exceptional pollution events, such as wildfires, may pose substantial health risks. This preliminary case study supports conducting an expanded, longer-term study on the interactions of variable intensity wildfire smoke plumes on urban air pollution exposure, in addition to the subsequent need to inform health and risk policy in these complex systems. Full article

Titanium alloys face challenges of high temperature oxidation during the service period when used as aircraft engine components. In this paper, the effect of Y₂O₃ addition on the oxidation behavior and the microstructural change of the Ti6Al4V alloy fabricated by selective laser melting (SLM) was comprehensively studied. The results show that the surface of the Ti6Al4V alloy is a dense oxide layer composed of TiO₂ and Al₂O₃ compounds. The thickness of the oxide layer of the Ti6Al4V increased from 59.55 μm to 139.15 μm. In contrast, with the addition of Y₂O₃, the thickness of the oxide layer increased from 35.73 μm to 80.34 μm. This indicates that the thickness of the oxide layer formation was a diffusion-controlled process and, therefore, the thickness of the oxide layer increased with an increase in temperature. The Ti6Al4V-1.0 wt.% Y₂O₃ alloy exhibits excellent oxidation resistance, and the thickness is significantly lower than that of the Ti6Al4V alloy. The oxidation kinetics of the Ti6Al4V and Ti6Al4V-1.0 wt.% Y₂O₃ alloys at 600 °C and 800 °C follows a parabolic rule, whereas the oxidation of the Ti6Al4V and Ti6Al4V-1.0 wt.% Y₂O₃ alloys at 1000 °C follows the linear law. The average microhardness values of Ti6Al4V samples after oxidation increased to 818.9 ± 20 HV_0.5 with increasing temperature, and the average microhardness values of the Ti6Al4V-1.0 wt.% Y₂O₃ alloy increases until 800 °C and then decreases at 1000 °C. The addition of Y₂O₃ shows a significant improvement in the microhardness during the different temperatures after oxidation. Full article

In recent years, commercial air transport has increased considerably. However, the compositions and source profiles of volatile organic compounds (VOCs) emitted from aircraft are still not clear. In this study, the characteristics of VOCs (including oxygenated VOCs (OVOCs)) emitted from airport sources were measured at Shenzhen Bao’an International Airport. The results showed that the compositions and proportions of VOC species showed significant differences as the aircraft operating state changed. OVOCs were the dominant species and accounted for 63.17%, 58.44%, and 51.60% of the total VOC mass concentration during the taxiing, approach, and take-off stages. Propionaldehyde and acetone were the main OVOCs, and dichloromethane and 1,2-dichloroethane were the main halohydrocarbons. Propane had the highest proportion among all alkanes, while toluene and benzene were the predominant aromatic hydrocarbons. Compared with the source profiles of VOCs from construction machinery, the proportions of halogenated hydrocarbons and alkanes emitted from aircraft were significantly higher, as were those of propionaldehyde and acetone. OVOCs were still the dominant VOC species in aircraft emissions, and their calculated ozone formation potential (OFP) was much higher than that of other VOC species at all stages of aircraft operations. Acetone, propionaldehyde, formaldehyde, acetaldehyde, and ethylene were the greatest contributors to ozone production. This study comprehensively measured the distribution characteristics of VOCs, and its results will aid in the construction of a source profile inventory of VOCs emitted from aircraft sources in real atmospheric environments. Full article

The issue of fatigue in modern hydraulic pipelines is increasingly severe, and there remains a lack of effective prediction methods for pipeline fatigue life. In practical engineering, hydraulic pipelines are primarily subjected to random excitation and fluid excitation, representing a typical composite excitation. Most current research relies on solutions considering only single excitations, which leads to inaccuracies. To accurately calculate the fatigue life under composite excitation, this study incorporates resonance excitation and pulsation excitation into the optimal transport meshless method (OTM) within a strong fluid–structure coupling computational framework. Subsequently, by utilizing the hazard point method based on obtained stress data, an estimation of the service life for engine hydraulic lines can be determined. This work provides both practical guidance and theoretical insights for designing hydraulic lines in modern aircraft. Full article

Magnesium alloy is extensively used in aircraft, automobiles, and electronic industries due to its low density, high specific strength, and enhanced machinability. However, low hardness and poor corrosion resistance limit its application. In this work, an Al-TiC metal matrix composite (MMC) was prepared on AZ31B magnesium alloy via laser cladding. The effects of laser power and TiC content on the microstructure, hardness, and corrosion resistance of the MMC were investigated. The results showed that the MMC with 10% TiC had a hardness of 184 HV_0.1, which was 3.5 times higher than 52 HV_0.1 of the substrate. The current density of MMC with 10% TiC was 3.90 × 10⁻⁷ A/cm², which was three orders of magnitude lower than 5.45 × 10⁻⁴ A/cm² of the substrate. Due to more intermetallic compounds (IMCs) and TiC particles, the MMC with 30% TiC had higher hardness. The increased laser power would not change the phase composition, but it contributed to the formation of a concave crescent shape, promoted the diffusion of Mg, and induced the formation of a thicker Al₃Mg₂ transition layer. Modifications in the TiC concentration markedly influenced the coating’s microstructural characteristics. Full article

This paper proposes a soft switching mode for electric vertical takeoff and landing (eVTOL) compound-wing unmanned aerial vehicles (UAVs) to achieve a smooth transition between modes. The proposed mode pre-compensates the lift loss with the rotary wing during the deceleration stage before UAV landing. The control law adopted in this paper consists of implicit nonlinear dynamic inversion (NDI) and incremental nonlinear dynamic inversion (INDI). The outer loop (attitude angle loop) control law is based on implicit NDI, while the inner loop (attitude angle rate loop) controller is based on INDI. An extended state observer (ESO) is employed to estimate the angular acceleration. This paper innovates by proposing a soft switching strategy that improves the robustness, safety, and smoothness of the transition for the compound-wing UAV, and applying advanced control law to mode transition design. For the future application of eVTOL aircraft in UAM scenarios, this paper evaluates the smoothness of transition and passenger comfort using normal overload as a physical quantity. The Monte Carlo (MC) simulation results demonstrate that the proposed mode can reduce the peak normal overload by about 89%. Full article