Search Results (50)

Accurate quantification of aircraft emissions and their uncertainties is essential for well-informed policy-making, air quality management, and the development of sustainable airport strategies. This study addresses uncertainties in aircraft emission estimates implemented for local air pollutants with hourly resolution at six European airports. Publicly available flight-tracking data were used to determine aircraft movements and types, but they typically lack detailed information on aircraft engine models, thus contributing to uncertainties in emission factors. Times-in-mode for take-off, climb-out, and approach modes followed International Civil Aviation Organization (ICAO) recommendations, while taxi times, known to vary between airports, were modeled using statistical distributions derived from Eurocontrol, and the contribution of taxi time to overall uncertainty in emission estimates was investigated. Monte Carlo simulation combined with Sobol sensitivity analysis identified the relative contribution of each uncertainty source. On average, the results indicate an uncertainty of 23% for CO, 34% for HC, 7% for NO_x, and 21% for PM across the airports analyzed. Overall, the proposed methodology introduces a novel framework utilizing publicly available, hourly resolved flight-tracking data with robust uncertainty analysis to estimate airport-level emissions with enhanced reliability, providing crucial information for local air quality assessment and policy development. Full article

The impact of the aviation sector on the Earth’s atmosphere and climate is not limited to the effects of CO₂ emissions generated by the combustion of hydrocarbon-based fuel in an aircraft engine. It is complemented by other combustion products and non-CO₂ emissions, such as CO, NO_x, unburnt hydrocarbons (UHCs), and soot, as well as the formation of condensation trails (contrails) as a result of emitted H₂O and condensation nuclei. To evaluate the overall atmospheric impact of an aircraft mission, it is necessary to model the aero engine and the combustion chamber in context with the atmospheric conditions over the course of the flight trajectory. Following that rationale, this paper presents the novel multidisciplinary ‘Modeling and System analysis of Aero Engines’ (MSAE) platform, aiming to evaluate the emission products over the flight trajectory with realistic atmospheric and operative boundary conditions. MSAE comprises an ambient condition model, an aircraft operating model, an aero engine performance model, and a combustion chamber model. The functionality of the individual models as well as their interconnections are demonstrated using the example of an Airbus A320 powered by an International Aero Engines V2500-A1 turbofan engine. Non-CO₂ emissions, including CO, NO_x, UHC, and soot emission indices, can be predicted at a selected operating point. Furthermore, an evaluation of contrail formation for both annually averaged and intraday ambient conditions is conducted, showing the benefit of considering ambient conditions in a finer temporal resolution. The results show the functionality of the presented MSAE platform and the necessity of performance and emission analysis under realistic conditions. Full article

The present work adopts a cooled cooling air (CCA) technology based on the integrated aircraft/engine thermal management concept, by coupling an air-kerosene heat exchanger with a high-temperature combustor. Using the heat exchanger, kerosene is preheated to near-critical and supercritical conditions, and the combustion characteristics of kerosene at ambient, near-critical, and supercritical states were investigated. The combustion performance tests were carried out in a model combustor under varying fuel-to-air ratios (FARs) and different kerosene injection conditions. The experimental results show that when the combustor’s FAR is increased to 0.055, the supercritical kerosene exhibits significant advantages over kerosene of the ambient state. The comparison of the combustion performance parameters shows that the combustor outlet temperature distribution factor (OTDF) and radial temperature distribution factor (RTDF) decrease by 52.26% and 51.07%, respectively; in terms of the pollutant emissions, the CO emission index (EI_CO) and unburned hydrocarbon emission index (EI_UHC) are reduced by 66.63% and 68.33%, respectively, while the NOx emission index (EI_NOx) increases by 76.26%, and the combustion efficiency improves by 2.0%. It is noteworthy that once the kerosene reaches the supercritical state, the threshold for the optimal FAR in the combustor rises to 0.055, which carries the significant engineering value for enhancing an aero-engine combustor’s operability across variable conditions and its low-emission combustion performance. 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

This review synthesizes recent research on alternative fuels for piston-engine aircraft and related propulsion technologies. Biofuels show substantial promise but face technological, economic, and regulatory barriers to widespread adoption. Among liquid options, biodiesel offers a high cetane number and strong lubricity yet suffers from poor low-temperature flow and reduced combustion efficiency. Alcohol fuels (bioethanol, biomethanol) provide high octane numbers suited to high-compression engines but are limited by hygroscopicity and phase-separation risks. Higher-alcohols (biobutanol, biopropanol) combine favorable heating values with stable combustion and emerge as particularly promising candidates. Biokerosene closely matches conventional aviation kerosene and can function as a drop-in fuel with minimal engine modifications. Emissions outcomes are mixed across studies: certain biofuels reduce NO_x or CO, while others elevate CO₂ and HC, underscoring the need to optimize combustion and advance second- to fourth-generation biofuel production pathways. Beyond biofuels, hydrogen engines and hybrid-electric systems offer compelling routes to lower emissions and improved efficiency, though they require new infrastructure, certification frameworks, and cost reductions. Demonstrated test flights with biofuels, synthetic fuels, and hydrogen confirm technical feasibility. Overall, no single option fully replaces aviation gasoline today; instead, a combined trajectory—biofuels alongside hydrogen and hybrid-electric propulsion—defines a pragmatic medium- to long-term pathway for decarbonizing general aviation. Full article

Airport operations significantly contribute to air pollution in their vicinity through various sources, including aircraft activities—particularly taxiing and take-off—as well as ground support equipment, service vehicles, and maintenance work. Since emissions from aircraft engines represent the primary pollution source at airports, it is essential to reduce emissions at every phase of the LTO (landing and take-off) cycle to improve local air quality and promote environmental sustainability. Given the research gap in emission analysis, a comprehensive LCA framework for airport pushback and taxi operations is proposed, integrating tow truck propulsion, a taxiing strategy, and fleet management. Given the complexity of the issue, the authors first decided to investigate emissions from taxiing operations using tow trucks with different powertrains. The analyses performed were considered preliminary and a starting point for exploring emissions during taxiing operations at airports. Typically, aircraft are pushed back from the apron and then taxi under their own power using both engines at approximately 7% of maximum thrust. To substantially reduce exhaust emissions, external towing vehicles can be employed to move aircrafts from the apron to the runway. This study evaluates the potential for emission reductions in CO₂ and other harmful compounds such as CO, HC, NO_x, and PM by using electric towing vehicles (ETVs). It also compares emissions from different taxiing methods: full-engine taxiing, single-engine taxiing, ETV-assisted taxiing, and taxiing using diesel and petrol-powered tow vehicles. The analysis was conducted for Warsaw and Poznań airports. Three aircraft types—the most commonly operating at these airports—were selected to assess emissions under various taxiing scenarios. The results show that using electric towing vehicles can reduce CO and NO_x emissions to nearly zero compared to other methods. Interestingly, CO emissions from full-engine taxiing were lower than those from petrol-powered towing, although the Embraer 195 showed the highest CO emissions among the selected aircrafts. HC emissions were lowest for the A321neo and also relatively low for the diesel towing vehicle. The use of electric tow trucks significantly reduces CO₂ emissions: only 2.8–4.4 kg compared to 380–450 kg when taxiing with engines. This research highlights the critical role of sustainable ground operations in reducing harmful emissions and underscores the importance of integrating sustainability into airport taxiing practices. Full article

This study examines scientific and technical solutions designed to enhance thermodynamic processes in modern aircraft turbine engines by utilizing heat exchangers. A comprehensive literature review informed the development of a conceptual design for a turbofan engine incorporating both an intercooler and a recuperator. The research included an original parametric and constrained optimization analysis conducted for two engine configurations as follows: one intended for narrow-body and the other for wide-body aircraft. The study focused on achieving the required thrust while enhancing efficiency. Results indicate that integrating heat exchangers can significantly reduce specific fuel consumption (SFC) and/or increase engine power or thrust. Moreover, the recovery of residual heat from exhaust gases through recuperation contributes to improved overall energy efficiency. The study also explores a novel cryogenic design that utilizes liquid hydrogen for cooling the intercooler, recuperator, and turbine. Although not modeled directly, this concept demonstrates the potential to increase the bypass ratio, further reduce SFC, and lower NO_x emissions. These findings highlight the promise of combined intercooling and recuperation strategies for improving both economic and environmental performance, with optimal system parameters dependent on aircraft class. The research aligns with ongoing efforts in mechanical engineering and aviation to enhance turbine engine efficiency through innovative thermal management solutions. Full article

The sustained growth of air traffic over the past decades has increased the aviation’s contribution to anthropogenic radiative forcing through both ${CO}_2$ and non-${CO}_2$ emissions. Although the industry has committed to achieving net-zero emissions by 2050, this goal appears unrealistic without curbing, or at least stopping, the continued rise in traffic. To assess the potential of alternative travel options and quantify their environmental benefits, simple and flexible emission models are needed. In this work, we present a set of analytical models for estimating fuel consumption and associated emissions, including ${CO}_2$, SO_x, water vapour, and other key non-${CO}_2$ emissions such as NO_x and carbon monoxide. We also examine the emissions of non-volatile particulate matter. These models require only flight distance and aircraft seat numbers, enabling broad applicability across traffic scenarios. The models are openly available via a GitHub repository, and their practical use is demonstrated through a case study of a representative day of Spanish air traffic. Full article

Emissions from civil aviation not only degrade the environmental quality around airports but also have the significant effects on climate change. According to the flight schedules, aircraft/engine combination information and revised emission factors from the International Civil Aviation Organization (ICAO) Aircraft Engine Emission Databank (EEDB) based on meteorological data, the emissions of climate forcers (CFs: BC, CH₄, CO₂, H₂O, and N₂O), conventional air pollutants (CAPs: CO, HC, NO_X, OC, PM_2.5, and SO₂), and hazardous heavy metals (HMs: As, Cu, Ni, Se, Cr, Cd, Hg, Pb, and Zn) from flights of civil aviation of eight airports in Shandong in 2018 and 2020 are estimated in this study. Moreover, the study quantifies the impact of COVID-19 on civil aviation emissions (CFs, CAPs, and HMs) in Shandong, revealing reductions of 47.45%, 48.03%, and 47.45% in 2020 compared to 2018 due to flight cuts. By 2020, total emissions reach 9075.44 kt (CFs), 35.57 kt (CAPs), and 0.51 t (HMs), with top contributors being Qingdao Liuting International Airport (ZSQD) (39.60–40.37%), Shandong Airlines (26.56–28.92%), and B738 aircraft (42.98–46.70%). As byproducts of incomplete fuel combustion, the shares of CO (52.40%) and HC (47.76%) emissions during taxi/ground idle mode are significant. In contrast, emissions during cruise phase are the dominant contributor of other species with a share of 74.67–95.61% of the associated total emissions. The findings highlight the disproportionate role of specific airlines, aircraft, and operational phases in regional aviation pollution. By bridging gaps in localized emission inventories and flight-phase analyses, this research supports targeted mitigation strategies, such as fleet modernization and ground operation optimization, to improve air quality in Shandong. The study highlights how sudden shifts in demand, such as those caused by pandemics, can significantly alter emission profiles, providing insights for sustainable aviation planning. Full article

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

Clean Sky 2 (CS2) was established to reduce the environmental impact of air transport by the introduction of new advanced aeronautical technologies, to improve mobility and to demonstrate reduction potentials for CO₂, NO_x, and noise emissions of from 20% to 30% as compared to state-of-the-art aircraft in 2014. A wide range of new technologies has been integrated into vehicle performance models for a set of concept aircraft, and the Clean Sky 2 Technology Evaluator (TE) has performed assessments with three major pillars: Vehicle- or mission-level reference aircraft, reflecting 2014 technologies, are compared with new Clean Sky 2 concept aircraft with a focus on CO₂ and NO_x emission and noise reduction potentials. At the airport level, environmental impact assessments for different traffic and fleet mixes are carried out, namely, noise on the ground and population impacted by certain noise levels and emissions (CO₂ and NO_x). At the level of the global air transport system (ATS), those new concept aircraft are embedded in fleet projections until 2050 and compared to a projection without new Clean Sky 2 aircraft to understand the emission reduction potentials of future global fleets and the long-term aviation footprint. This paper gives a conceptual overview of the work carried out in Clean Sky 2. Full article

As a consequence of measures imposed during the COVID-19 pandemic, anthropogenic emissions worldwide decreased markedly in impacted sectors, including the aviation industry. The aim of this study is to investigate the effects of the pandemic on aircraft emissions below the mixing height (3000 feet above ground) at Václav Havel Airport Prague during 2020. For this purpose, real aircraft emissions during 2020 were computed using provided surveillance data, while business-as-usual aircraft emissions that could have been expected at the airport that year under normal circumstances were estimated using traffic data from previous years and derived emission factors. We found that the median real emissions at the airport in 2020 were 220.859 t of NO_X, 101.364 t of CO, 15.025 t of HC, 44,039.468 t of CO₂, 17,201.825 t of H₂O and 11.748 t of SO₂. The median estimated reduction in emissions due to the pandemic in 2020 was −476.317 t of NO_X, −203.998 t of CO, −28.388 t of HC, −95,957.278 t of CO₂, −37,476.400 t of H₂O and −25.595 t of SO₂. Absolute differences between the real and business-as-usual emissions peaked in June 2020, while the relative differences peaked in April/May at −89.4% to −92.0%. Full article

Retrofitting regional turboprop aircraft with hydrogen (H₂)-electric powertrains, using fuel cell systems (FCSs), has gained interest in the last decade. This type of powertrain eliminates CO₂, NOx, and fine particle emissions during flight, as FCSs only emit water. In this context, the “Hydrogen Aircraft Powertrain and Storage Systems” (HAPSS) project targets the development of a H₂-electric propulsion system for retrofitting Dash 8-300 series aircraft. The purpose of the study described in this paper is to analyze the performance of the retrofitted H₂-electric aircraft during critical operating conditions. Takeoff, as well as climb, cruise and go-around performances are addressed. The NLR in-house tool MASS (Mission, Aircraft and Systems Simulation) was used for the performance analyses. The results show that the retrofitted H₂-electric aircraft has a slightly increased takeoff distance compared to the Dash 8-300 and it requires a maximum rated shaft power of 1.9 MW per propeller. A total rated FCS output power of 3.1 MW is sufficient to satisfy the takeoff requirements, at the cost of lower cruise altitude and reduced cruise speed as compared to the Dash 8-300. Furthermore, a higher-rated FCS is required to achieve the climb performance required for the typical climb profile of the Dash 8-300. Full article

To address the technical challenges of implementing Continuous Descent Operations (CDO) in high-traffic-density terminal control areas, we propose a cooperative low-carbon trajectory planning method for multiple arriving aircraft. Firstly, this study analyzes the CDO phases of aircraft in the terminal area, establishes a multi-phase optimal control model for the vertical profile, and introduces a novel vertical profile optimization method for CDO based on a genetic algorithm. Secondly, to tackle the challenges of CDO in busy terminal areas, a T-shaped arrival route structure is designed to provide alternative paths and to generate a set of four-dimensional (4D) alternative trajectories. A Mixed Integer Programming (MIP) model is constructed for the 4D trajectory planning of multiple aircraft, aiming to maximize the efficiency of arrival traffic flow while considering conflict constraints. The complex constrained MIP problem is transformed into an unconstrained problem using a penalty function method. Finally, experiments were conducted to evaluate the implementation of CDO in busy terminal areas. The results show that, compared to actual operations, the proposed optimization model significantly reduces the total aircraft operating time, fuel consumption, CO₂ emissions, SO₂ emissions, and NO_x emissions. Specifically, with the optimization objective of minimizing total cost, the proposed method reduces the total operation time by 22.4%; fuel consumption, CO₂ emissions, SO₂ emissions by 22.9%, and NO_x emissions by 23.7%. The method proposed in this paper not only produces efficient aircraft sequencing results, but also provides a feasible low-carbon trajectory for achieving optimal sequencing. Full article