With the aviation industry ever growing the climate impact of the aviation industry grows too. Although most innovations focus on reducing the CO2 emissions, non-CO2 emissions play a large role in shaping the climate impact of flying. Contrail formation due to aviation is the primary non-CO2 factor, but there is a large amount of uncertainty in determining the impact of contrails. Currently most contrail formation theory is based on using the Schmidt-Appleman criteria (SAC), but the underlying thermodynamic assumptions are being increasingly challenged by new turbofan engines with ever higher and higher bypass ratio’s. This thesis aims to evaluate the impact of the bypass ratio on the mixing physics and contrail formation in the near field, and see if a relation between bypass ratio and contrail occurrence can be found. To evaluate the relation between bypass ratio and contrail formation, 4 different modern and future turbofan engines were simulated in the Fluent CFD solver, all with a thrust rating of about 120kN and designed for short-to-medium range aircraft such as the A320. 2D Axisymmetrical meshes were made in ICEM of around 300.000 cells for each of the engines. Grid independence was evaluated using the Grid Convergence Index method and the results were proven to be independent of the grid. To evaluate which turbulence model to use two experimental cases were used from which the κ − ω − SST-model was chosen as the most accurate one. A validation case for the CFM56-3 based on research by Cantin et al. was used to check the validity of the flow field results obtained using Fluent. Contrail modeling was performed based on thresholds for Gibbs free energy, temperature and relative humidity over ice. These thresholds were used to determine the area of possible contrail formation, and again checked against the same case from Cantin et al. . The contrail analysis model presented here showed good agreement with the verification case, although it does overestimate the contrail a bit The contrail analysis model showed that there was a relation between bypass ratio and contrail formation, with higher bypass ratio engines having a higher absolute plume intensity. The presence and intensity of a shock in the nozzle seems to correlate better with the possible contrail formation volume and plume intensity. The SAC diagrams showed that the SAC underestimated the slope of the mixing lines as calculated from the flow field. Since the plume did not return to ambient conditions at the end of the domain, no statement could be made on the persistency of the contrail. The impact of H2 was also researched, as well as the impact of relative humidity on contrail characteristics.

This document describes the development and outcomes of a comprehensive analysis to quantify the climate impact reduction of Sustainable Aviation Fuels (SAFs). Firstly, it is shown that existing Life Cycle Analyses (LCAs) exclude or do not properly model pump-to-wake (PtW) non-𝐶𝑂2 effects resulting from 𝑁𝑂𝑥 & 𝐻2𝑂 emissions and contrail formation, of both Conventional Jet Fuel (CJF) as well as SAF. To this end, a method is developed with which these PtW emissions are thoroughly quantified and incorporated into an existing LCA.

The method is designed to answer the following research question: ”What is the potential climate impact reduction of SAF in aviation?” and is divided into a well-to-pump (WtP) and a pump-towake (PtW) analysis. The WtP values are taken from literature (the CORSIA default values [3]) and indicate how much 𝐶𝑂2-equivalent (𝐶𝑂2𝑒) emissions are made for the production & transport of 1 𝑀𝐽 (unit of energy) of CJF and SAF, in gram: [𝑔𝐶𝑂2𝑒/𝑀𝐽]. For the PtW values, the 𝐶𝑂2 emissions released during the combustion of 1 𝑀𝐽 of SAF or CJF of 70.2 & 73.3 [𝑔𝐶𝑂2 /𝑀𝐽] respectively, are multiplied with a 𝐶𝑂2𝑒 factor for both SAF as well as CJF. This 𝐶𝑂2𝑒 factor is a ratio that evaluates the climate impact caused by all aviation emissions & effects (𝐶𝑂2, 𝑁𝑂𝑥, 𝐻2𝑂 & contrails) relative to that of 𝐶𝑂2. The climate impact is quantified using the Global Warming Potential (GWP) and Average Temperature Response (ATR) climate metrics over a given time horizon (20, 50 & 100 years), which analyze a radiative forcing (RF) and a temperature change (Δ𝑇) response respectively. The RF & Δ𝑇 responses are generated for a baseline CJF scenario as well as a SAF scenario using the non-linear climate chemistry model AirClim. All important aspects of SAF relative to CJF are accounted for: the dissimilar energy density and thus fuel flows, the different 𝐸𝐼𝐻2𝑂 & 𝐸𝐼𝐶𝑂2 , the different 𝐸𝐼𝑠𝑜𝑜𝑡 and thus contrail characteristics, and the similar 𝐸𝐼𝑁𝑂𝑥 . Finally, the WtP part is added to the PtW part to be able to quantify SAF’s well-to-wake (WtW) climate impact reduction potential. The results of this new analysis indicate that:
• Uponinclusion of PtW non-𝐶𝑂2 effects into the CORSIA SAF LCA from Prussi et al. (2021), the lifecycle 𝐶𝑂2𝑒 emissions per 𝑀𝐽 of CJF increase from 89 to 257.2 [192.3-334.9] 𝑔𝐶𝑂2𝑒/𝑀𝐽. Similarly, for all paraffinic CORSIA eligible SAFs [3], the 𝐶𝑂2𝑒 emissions per 𝑀𝐽 increase by 147.7 [88.4-223.3] 𝑔𝐶𝑂2𝑒/𝑀𝐽. The values in the brackets indicate a 5%-95% confidence interval range based on a Monte Carlo uncertainty analysis with 1000 simulations.
• As aresult of the previous point, a hypothetical SAF that is able to reduce lifecycle GHG emissions by 100% (with 0 WtP emissions), only has a climate impact reduction of 42.5% [33.5%-54.1%] when using ATR100, and58%[53.3%-66.7%]when using GWP100 as the climate metric. Nevertheless, the absolute WtW reduction in climate impact increases from 89 𝑔𝐶𝑂2𝑒/𝑀𝐽 to 109.5 [99.2-118.3] 𝑔𝐶𝑂2𝑒/𝑀𝐽 (using ATR100), meaning that SAF’s climate impact reduction potential actually increases when PtW non-𝐶𝑂2 effects are included. This is explained by the fact that SAF not only reduces 𝐶𝑂2 emissions, but also contrail climate impact, which strongly outweighs the increase in SAF’s 𝐻2𝑂 climate impact.
• When adding the CORSIA default WtP values [3] to the PtW values derived in this analysis, SAF’s climate impact reduction potential ranges from 3% or 8.9 𝑔𝐶𝑂2𝑒/𝑀𝐽 (for corn grain EtJ) to 47% or 121.1 𝑔𝐶𝑂2𝑒/𝑀𝐽 (for Herbaceous Energy Crops-FT)- depending on the exact feedstock and conversion process used.

A sensitivity analysis has been carried out for the PtW analysis from which it was concluded that the PtW climate impact of both SAF & CJF strongly varied. However, the absolute WtW climate impact reduction potential stayed very similar: the lifecycle 𝐶𝑂2 climate impact reduction remained unaffected, and the PtW non-𝐶𝑂2 climate impact reduction potential varied from 11.75-24.4 𝑔𝐶𝑂2𝑒/𝑀𝐽. Lastly, by allocating SAF to longer flights with higher average flight altitudes, SAF’s non-𝐶𝑂2 climate impact reduction potential is substantially increased from 4.06 to 25.6 𝑔𝐶𝑂2𝑒/𝑀𝐽.

The demand for commercial aviation is growing at an annual rate of 4%, posing significant environmental challenges. Large-capacity aircraft designed for long ranges are often used on short-to-medium range routes, leading to inefficient fuel consumption and higher emissions. With a future market need for aircraft seating 211 to 300 passengers, there is a clear gap for such a passenger airliner. This report examines the feasibility of the X-300 EcoFlyer, a proposed short-to-medium range aircraft with reduced environmental impact. Designed to carry 300 passengers over 3000 km, the X-300 aims to achieve 25% lower CO2 emissions, 50% lower NOx emissions, and 20% lower noise emissions compared to the Airbus A320neo. The study covers aircraft functions, system design, performance analysis, manufacturing, sustainability, operations, logistics, business viability, and technical risks. The findings confirm the X-300 EcoFlyer's potential to meet future demands with lower environmental impact. Innovations include a noise-shielding fuselage, a water-injected turbofan engine, in-wheel electrical taxing, and an electrical environmental control system. Overall, the X-300 EcoFlyer represents a promising solution to the challenges facing the future of high-capacity air transport.

The escalating concerns surrounding climate change underline the importance of examining greenhouse gas (GHG) emissions across various sectors, with aviation causing approximately 1.9% of the global GHG emissions in 2020. To this modest figure, the Dutch aviation industry acknowledges its share to the climate impact and has gone ahead to objectify it. It has been shown that there has been a 13% surge in the 2018 total GHG emissions, and of the emissions attributable to the Netherlands, a staggering 75% has been emitted beyond its border. Remarkably 95.3% of these beyond-Dutch border emissions are attributable to its aviation sector. This showcases how a localized issue can have global impact.

This research explores the area of military aviation emissions, focusing on the Airbus A330 MRTT operated by the NATO Multinational MRTT Unit (MMU). While commercial aviation adheres to emissions monitoring policies, military aviation is exempted from such obligations. This research adopts a certain approach, focusing not necessarily on the identification of the 'right' methodology but more on the selection of methods tailored to identified goals. The core objective is a sensitivity analysis of emissions and climate impact concerning aircraft design and mission parameters.
In collaboration with the MMU and the Royal Netherlands Air Force (RNLAF), this research uses real-world data for model validation. This research addresses key questions around design and mission parameters with the focus on engine performance modeling, emissions modeling and sensitivity analyses.

The report is structured into four chapters.
The first chapter discusses the literature and background of emissions in commercial and military aviation. The focus will be on the critical role of emission and that of climate impact modeling.
The second chapter outlines the methodology, overall emission model reviews and a climate impact evaluation using Average Temperature Response (ATR).
The third chapter includes the validations using flight data and an external software tool for the emissions validations. The last chapter shows the results and a comprehensive sensitivity analysis. The obtained results aim to collectively present insights for Airbus Defence & Space, towards the conceptual design phase of their new military aircraft. This research contributes to the broader prevailing dialog on sustainable aviation.

Aviation is an important contributor to anthropogenic climate change. As indirect greenhouse gases, nitrogen oxides (NOx = NO + NO2) add to the Effective Radiative Forcing (ERF) induced by aircraft emissions. This work addresses a better understanding of emission mitigation by investigating dependencies between engine parameters and emitted nitrogen oxides as a part of the campaign VOLCAN. In-flight near field measurements are conducted using the DLR research aircraft Falcon, chasing an Airbus A321neo equipped with CFM LEAP-1A engines featuring lean combustion through staged fuel injection. Nitrogen oxide concentrations are measured applying the well-established chemiluminescence method. Emission indices are quantified for different fuels including Jet A-1, Sustainable Aviation Fuel (SAF) and two SAF blends with different levels of aromatics. Four combustor inlet temperature settings are tested and staged (lean) combustion is compared to unstaged (rich) combustion. Emissions are measured for two different but technically identical engines, deviating in terms of exhaust gas temperature margin. As expected, results indicate no significant differences in emitted nitrogen oxides for the investigated fuels. Measurements confirm that nitrogen oxide emission indices increase exponentially with combustor inlet temperature. Due to the forced nature of the analyzed rich burn mode, a reduction in nitrogen oxide emissions through lean combustion cannot be confirmed. Based on presented data, a relationship between engine degradation and nitrogen oxides is likely. Near field observations agree with well-established far field measurements and lead to lower uncertainties. Preliminary results of the ECO-Demonstrator campaign are in line with VOLCAN measurements. The performed research is a highly valuable contribution to extremely rare empirical in-flight emission data. Established nitrogen oxide dependencies support technical decision making to reduce aviation’s climate impact.

As society gets more aware of atmospheric pollution and the negative effects of the transport sector on the climate, new concepts are being innovated to mitigate these effects. One of these concepts is the Auxiliary Power and Propulsion Unit (APPU) project, in which the APU of the A321neo is replaced by a hydrogen powered turboshaft system that includes a propulsor and boundary-layer-ingestion (BLI) to alleviate the main engines, causing less kerosene to be burnt whereby less CO2 and soot are emitted.
As in most aircraft, certain parts of the engine system are in need of cooling, most notably the HPT blades. Concurrently, the onboard cryogenic hydrogen needs to be heated up before entering the combustor to avoid high thermal stresses. The cryogenic hydrogen can be used to cool these parts, while at the same time reaching a more appropriate temperature before entering the combustor. Alleviating conventional cooling methods by making use of the cryogenic hydrogen increases the thermal efficiency of the engine system. Moreover, increasing the temperature of the fuel increases the LHV, which increases the thermal efficiency of the engine system even further.
Three different cases are analysed: firstly, the cryogenic hydrogen is used to cool the bleed air, by which less bleed air is required, increasing the core flow, which increases the thermal efficiency of the cycle. Secondly, using the same principle, the TIT is increased, while the amount of (now cooled) bleed air stays constant to the baseline. In this case the thermal efficiency increases due to the higher LHV of the fuel. Thirdly, the cryogenic hydrogen is used to intercool the core flow between the booster and the HPC, after which the pressure ratio is increased accordingly.
It is found that intercooling and increasing the pressure ratio of both compressors to 8, increases the thermal efficiency with 3.6% with respect to the baseline. Performance complications due to increasing the OPR to 64 have not been analysed into great detail and might make this result hard to achieve in reality. The next best option is increasing the TIT 1840K, which increases the efficiency by 0.7%. Cooling and reducing the bleed flow however, results into a thermal efficiency increase of 0.2%.
It is concluded that the largest contributor to the thermal efficiency is the LHV of the hydrogen. This means that any process in which the hydrogen extracts the most amount of heat is most advantageous, efficiency-wise. Furthermore, it is concluded that adding intercooling and subsequently increasing the pressure ratio increases the thermal efficiency more than cooling and subsequently reducing the bleed flow.

Minimisation of the climate impact of flights in the short term may be achieved by contrail avoidance. This involves avoiding ice supersaturated regions (ISSRs), which cause contrails to persist. ISSRs occur when the relative humidity over ice is above 1, but numerical weather prediction (NWP) models struggle to predict such regions. Below 235.15 K, solely ice supersaturation can be considered. This study validates the prediction of ISSRs in the ERA5 reanalysis using IAGOS in-situ measurements from a pressure level (350 to 175 hPa), seasonal, yearly (2011 to 2022) and regional perspective. Validation of ERA5’s temperature showed a cold bias in all extratropic regions and at low altitudes in the tropics, which can result in ERA5 predicting ISSRs when none are observed. Increasing temperature deviations between IAGOS and ERA5 were observed between the years 2020 and 2022. In terms of relative humidity over ice, ERA5 and IAGOS showed good agreement below ice supersaturation, but ERA5 struggled in simulating values close to or above a value of 1. For the latter conditions, ERA5 showed a dry bias in the extratropics below the tropopause. A moist bias was found in some regions and seasons, including South Asia, in June, July, and August. This may be due to inconsistencies in the modelling of the atmospheric ice content in ERA5. Years 2013 and 2014 also showed a possibility of a moist bias in ERA5 in some regions, but this was most likely the result of regional changes in sampling by IAGOS. The moist bias caused false detection of ISSRs in ERA5. Meanwhile, the dry bias led to an underestimation of the occurrence of ISSRs, with 25 to 50% remaining undetected. This causes an overestimation of no persistent contrail regions and an underestimation of persistent contrail and reservoir regions. When ERA5 overestimates the ISSR occurrence, it leads to an overestimation of persistent contrail and reservoir regions but an underestimation of no persistent contrail regions. Hence, improvements are necessary to successfully avoid or ensure unnecessary avoidance of ISSRs, where the latter could cause an increase in the climate impact of flights. Improvements should be done before implementation in contrail avoidance strategies, otherwise the benefit of such strategies may be defeated.

The validity of current prediction methods for the formation of contrails from modern turbofan engines is investigated. A modelling framework has been developed for estimating the impact of engine configurations on contrail formation by analyzing the physics of the mixing between core and bypass flow. Within this framework, Engine Performance Modelling yields the flow conditions at exhaust nozzle exits. A 2D axisymmetric CFD Flow Field Solver then determines the flow parameters behind the engine. Water vapour dispersion is simulated using a species transport model, after which contrail locations are determined by a set of criteria for homogeneous ice crystal formation. Finally, particles are tracked to determine mixing lines, which are compared to those from current prediction methods. From a Leap-1A engine case study using this framework, it can be concluded that assumptions of instantaneous mixing underlying current methods are not valid, resulting in their overestimation of the mixing line gradient.

The aviation industry is shouting out its aim to reach ”net-zero carbon” by 2050. Nevertheless, air traffic is expected to grow up until then, and if fuel consumption is reduced by new technologies and aircraft, other sources of global
warming such as N Ox emissions and contrails are less considered. Therefore, the climate impact improvement of new technologies compared to older ones is not straightforward and requires a deep analysis. This work performs such an analysis via three steps: The selection of a new fleet to be compared with the actual fleet (2019), a comparison between the two fleets emissions via an Aviation Emission Inventory code, and a climate impact assessment with the tool AirClim. The new fleet analysed consists of the replacement of 14 old (entry in service before 2002) Airbus and Boeing aircraft with their new versions (entry in service between 2011 & 2018). The results show a reduction of 8.7% of fuel consumed by total aviation just by replacing the 14 old aircraft with the new ones. On the other hand, it leads to an 8.0% N Ox emissions increase. Nevertheless, the climate impact assessment concludes that this N Ox emissions increase lowers the surface temperature change due to aviation. This is explained by the strong influence of N Ox emissions location on its climate impact. Overall, this new fleet leads to a decrease in temperature change due to aviation in 2050 of 5.3 mK (-5.2%). This work gives important conclusions on the priorities that need to be set for the development of ’greener’ aviation technologies.

The aviation industry continues to contribute to anthropogenic climate change. Recent studies have shown that the total radiative forcing from aviation is around three times higher than that from CO₂ alone. To account for the full effect of aviation, climate metrics are needed, which equate the environmental impact of various emissions and effects. However, there is currently no consensus on which climate metric should be used in aviation policy. This thesis systematically analyses existing climate metrics by: 1) comparing the responses to simple emission profiles; 2) investigating the sensitivity to changes in high-level aircraft design variables; 3) using a Monte Carlo simulation to determine inherent biases in metric calculation methods; and 4) evaluating the ability of climate metrics to estimate CO₂-equivalent emissions. It is concluded that the Average Temperature Response (ATR) is the most appropriate climate metric for aviation climate policy. However, it is found that the time horizon remains a subjective choice that must be chosen carefully depending on the climate objective. The GWP*, a newly proposed climate metric, is concluded not to be suitable as a climate metric because of its high variability and secondary time horizon. Nevertheless, it is recommended to investigate the potential of using the GWP* as a Micro Climate Model to further climatic understanding.

Concerned about rapidly rising temperatures, international institutions, nations, and companies worldwide examine how to reduce emissions in all economic sectors. Inside the aerospace sector, it is believed that hydrogen technology has the potential to be the best asset to fight global warming. This thesis aims to create and use a methodology to analyze climate implications and uncertainties of a powered hydrogen aircraft. Results are conclusive. Hydrogen aviation reduces surface temperature change by 67\% compared to kerosene aviation by eliminating carbon dioxide emissions, reducing contrail climate impact, and lessening nitrogen oxide emissions. When analyzing uncertainties related to hydrogen emissions and climate effects, the study has demonstrated that even the worst-case situation for hydrogen aircraft is advantageous compared to kerosene aviation.

Contrail formation is one the largest warming contributions of aviation’s climate impact. Measures to mitigate contrail climate impact include the optimisation of flight trajectories to avoid the formation of warming contrails or to find air space where extra cooling contrails are formed. The latter option is only possible during daytime, due to the interaction of a contrail with the short-wave radiation from the Sun. Little research is done to evaluate the effect of the diurnal cycle on contrail climate impact mitigation. Moreover, models to predict this the contrail climate impact are still in the development face. This thesis aims to (1) find the daytime and nighttime contrail climate impact of eco-efficient flight trajectories, (2) to assess the prediction’s robustness and (3) to recommend a best practice for eco-efficient flying by using the difference between the daytime and nighttime contrail climate impact. To this end, simulations were carried out within the EMAC climate chemistry model, aided by the submodels AirTraf, CONTRAIL and ACCF. The robustness of the results were tested against a model parameter: the threshold time until sunrise (THsunrise). When a contrail is formed
during nighttime, THsunrise determines whether the contrail is formed sufficiently close to sunrise to be considered a daytime contrail. It is concluded that winter daytime mitigation of contrail climate impact is more eco-efficient than winter nighttime mitigation. Overall, daytime mitigation achieves a larger maximum reduction of contrail climate impact than nighttime mitigation. moreover, summer mitigation is more effective than winter mitigation and winter
mitigation has a larger reliance on the formation of extra cooling contrails. The thesis results are robust with respect to a varying THsunrise. However, overall results become biased to daytime results or nighttime results. Lastly, it is shown that differences between day and night contrail climate impact mitigation allow for the enhancement of mitigation results.

This report covers all major steps to establish an aviation emission inventory for 2019. This emission inventory is set up based on four consecutive steps. The first step is to gather all required data in the information model and this also includes some pre-processing of data to make it as complete as possible. The second step is to estimate the point performance of the aircraft at multiple waypoints along the trajectory based on the Base of Aircraft Data (BADA). This also allows for fuel consumption estimation. The third step uses the point performance data to estimate emissions under the respective flight condition. The last step addresses introduced uncertainties based on the different models. From a first principle perspective the uncertainty on a fleet wide scale (and for short and long haul flights) is found concerning the fuel consumption and various emission species (for example nitrogen oxides and carbon monoxide) using a Monte Carlo simulation.

The trajectory data is obtained from flightradar24 in which gaps were identified where the type of aircraft, origin airport or destination airport were missing. Complementing of the database is based around the provided flight numbers and call signs. Based on airline data a variety of assumptions is made relating to payload fraction (69%) and increase in flight distance (8%) compared
to the great circle distance. The trajectory is estimated using the rate of climb and descent provided in BADA. The emission model then uses constant emission indices, the boeing fuel flow method 2 (BFFM2) and the DLR method to compute all emissions according to:
• Constant emission index: carbon dioxide (corrected for emission index of carbon monoxide),
water vapor and sulfur oxide.
• BFFM2: carbon monoxide, unburned hydrocarbons and nitrogen oxides.
• DLR: black carbon emission.
The uncertainty analysis, finally, covers airline operational uncertainty, model uncertainty and engine aging uncertainty to find an average increase in fuel consumption of 4.2%. Due to the influence of fuel flow, other emission species are increased with a different fraction.

Due to computational limitations it has been decided to analyze one week, which will be representative of the entire year. Based on this analysis an annual fuel consumption of 272 Tg is simulated with corresponding carbon dioxide emission of 857 Tg. In addition, a nitrogen oxide emission of 5.3 Tg is found. All emission species are mainly emitted on the northern hemisphere on three geographical locations: north America, Europe and south-east Asia. The strongest recommendation is to include military flights and non-jet aircraft in the analysis (mainly turboprop aircraft). In addition, to decrease the dependency on data of a single week, it is advised to obtain more computational power to allow for analysis of multiple representative weeks preferably in both ICAO specified seasons.
Finally it is recommended to extend the uncertainty analysis to cover more individual uncertainties such as the uncertainty in cruise altitude (based on airline routing) and to find more research on the uncertainty of sulfur content in kerosene.

With an increasing complexity of systems, systematic design space exploration is required for fair analysis and comparison of architecture design options. However, there is still a need for a benchmark problem to support the development & evaluation of optimization algorithms and system architecture design space modeling methods, and to educate stakeholders in system architecture optimization. The thesis focus lies on the creation of such benchmark problem with an application to aircraft jet engine design, which is subsequently tackled by developing an MDO tool using a system architecting approach with mixed-discrete and multi-objective capabilities. The tool was built with the open-source software pyCycle and OpenMDAO and can generate, analyze and compare different aircraft engine architectures on several disciplines including engine thermodynamic cycle analysis, weight, geometry, emissions and noise. Therefore, it is able to tackle the black-box, mixed-discrete, multi-objective and hierarchical nature of system architecture optimization problems.

In the last few years, there has been a growing awareness regarding the climate impact of aviation in the general public. With global warming effects becoming more severe, it is important that aviation drastically reduce its emission footprint to keep the impact on the climate lower. There have been ongoing efforts by various organizations such as ICAO and ACARE which have led to the formulation of ambitious targets for reducing aviation emissions in the future. In the past, the main goal of improving aero-engine performance has generally been to increase the operating pressure and temperature, thereby improving the cycle efficiency leading to lower fuel consumption, and consequently, lower CO2 emissions. However, this increase also leads to more NOx emissions from the engine, as NOx emissions are sensitive to engine pressure and temperature variations. The climate impact of aviation is mainly driven by long-term impacts from the CO2 emissions and short-term impacts from the non-CO2 emissions. This thesis aims to analyze the sensitivity of the turbofan engine design parameters towards the impact on the climate in terms of near-surface temperature change due to the various emission species. A detailed methodology was developed for the thesis, encompassing different aspects such as aircraft performance, emission prediction, engine modeling, emission inventories, and climate analysis. The aircraft performance model, the emission prediction model, and the emission inventory model were developed specifically for the purpose of this thesis. The engine modeling was done in the Gas Turbine Simulation Program (GSP), which is a modeling tool used for the development and simulation of gas turbine systems. The climate analysis was carried out in AirClim, which is a surrogate model obtained from the results of Climate-Chemistry models, meant for comparing aviation technological options from a climate impact point of view. The results from the thesis are intended to develop a better understanding of the relationships in the field of aviation emissions, especially concerning the tradeoffs between the CO2 and the non-CO2 effects, since the relationship between design parameters, emissions, and climate impact is not straightforward.

Aviation has a growing impact on the earth’s climate, due to its emissions causing an increase in the global near-surface temperature. In order to better understand the dynamics by which different aircraft types contribute to this global warming and how this can be mitigated, the impact of different aircraft categories is analysed and compared. These categories are constructed by dividing aircraft into groups with a similar number of seats. Two approaches are employed to assess the climate impact of these categories. First of all, a global aviation emission inventory is used together with a climate response model, to evaluate the temperature change caused by each individual category. It is found that in absolute terms the middle category with 152-201 seats, and the largest aircraft with over 302 seats will cause cause the largest temperature change by the year 2100, compared to 1940. At the same time, per amount of generated capacity in the form of available seat kilometres, the middle category shows the smallest climate impact of all, with the largest aircraft being the second worst. From historical positional data of aircraft, flight trajectories are identified, to which an aircraft performance model is applied. This leads to the conclusion that the optimal distance in terms of fuel use is »2500 km, with an increase in fuel burn for both longer and shorter distance flights. The NOx emission increases for increasing flight distance, due to higher thrust settings and a higher rated thrust of the engines used. Next to being able to fly longer distances, the three largest aircraft categories cruise at a higher Mach number, increasing fuel use and NOx emission. Additionally, by flying in a less busy airspace, such as above the Atlantic, the impact of contrails is larger for these aircraft, as there is a smaller atmospheric capacity to form contrails in these areas. Another reason that the largest aircraft perform worse is the higher level of comfort provided to the passengers. It is shown that increasing the seating density to maximum capacity leads to a reduction in fuel use and NOx emission per available seat kilometre especially for the largest aircraft, narrowing the gap with the smaller aircraft categories which already make use of a high density seating. Based on the outcome it is suggested to adjust the policies dealing with aviation’s climate impact, to reflect the differences between the impact of the different aircraft types. Additionally, a direct reduction in aviation’s climate impact can be achieved by making use of the most climate efficient aircraft type for a givenmission.

Climate impact from aviation becomes increasingly important. The Flying-V is a promising concept with superior aerodynamic efficiency and lower weight, leading to lower fuel consumption and lower CO2-emission compared to a tube-and-wing aircraft like the A350. Climate impact from non-CO2 effects (NOx-emission, H2O-emission and contrails) depends on location and time of emission. Due to different design altitudes of the Flying-V and the A350, the impact from all effects have been assessed. At design conditions, the difference in climate impact is 1% in favor of the A350. The benefits of lower CO2- and NOx-emissions are trumped by increased impact from contrails. At identical conditions however, the Flying-V outperforms the A350 in both climate impact and fuel consumption. Also, lower altitudes showed substantially lower climate impact for both aircraft. It is recommended to redesign the Flying-V for lower altitudes and to operate existing civil aircraft at lower altitudes to reduce climate impact.