The aircraft’s environmental performance on fleet level is so far completely decoupled from the design process. The climate impact from aviation arising from non-CO2 effects are largely independent from CO2 emissions, but rather depend on the atmospheric state. Previously complex climate-chemistry models were used to evaluate the non-CO2 emissions impact on climate. This is far too computationally demanding for a multidisciplinary design optimisation (MDO) process, requiring a multitude of climate impact evaluations. The question then is, how to efficiently design the next generation climate optimal aircraft? In this paper, a new concept for designing aircraft with minimum climate impact using Climate Functions for Aircraft Design (CFAD) is presented. The content of this paper provides an overview of the development of these innovative CFAD and demonstrates the ability to be integrated in an existing MDO framework. The mitigation potential by optimising aircraft design using CFAD is analysed with respect to different cruise conditions and by minimizing the overall climate impact. To validate the CFAD, a higher fidelity assessment is carried out. Finally, the key performance indicators, i.e. fuel consumption, flight time and operating cost, of the optimised aircraft design are compared to that of the reference aircraft.

Aviation ensures mobility for both passengers and goods. It is important as a transport sector for connections on and between continents. Nevertheless, aviation also contributes to anthropogenic climate change. The effects are usually divided in CO2 and non-CO2 effects and therefore not only CO2 emissions but also other emissions (e.g., NOx , water vapour or soot) and contrails are covered. To reduce the effects of aviation’s climate impact, several mitigation options are applied. One approach are climate change functions, which will be addressed here. The concept of climate change functions was used in previous projects, e.g. REACT4C, WeCare, ATM4E. The goal of these functions was to optimize the aircraft routes regarding the calculated climate impact. Climate change functions measure the climate impact per unit emission for a specific day, which considers the current meteorological conditions. Climate change functions were previously used to optimize the aircraft routings. The concept should now be applied for the optimization of the aircraft design as well since the promising concept is currently missing for the application of aircraft design optimization. The climate functions for aircraft design will connect the aircraft design with the climate impact of various emission in order to be able to optimize the aircraft design. For the calculation of the functions, it is necessary to define a specific application. This application results from a combination of aircraft design parameters. Aircraft design parameters can be for example flight altitude, climb rate, speed or range. Based on a resulting emission inventory, the temperature response can be calculated with the model “AirClim”. This model calculates with the input, first, the radiative forcing and based on that the temperature change. The final development step is the verification of the climate functions.

Aviation is a highly necessary transport sector in our modern society. It guarantees mobility on a short- and long-range spectrum and is still a growing sector. However, aviation also contributes signi_cantly to the anthropogenic climate change via CO2 and non-CO2 e_ects. One possibility to reduce the climate impact of aviation would be to optimize the aircraft at the design level. Another possibility is to optimize the operations, e.g. to avoid climate sensitive regions in the ight route. To derive modelling capabilities, we review the climate impact of aviation with a focus on climate optimization of aircraft operations and design. The overall climate impact of aviation based on CO2 and non-CO2 e_ects is analyzed under consideration of contrails and di_erent emissions like CO2, NOx, and H2O. The connection to the related temperature change is shown via the climate sensitivity for each species. An overview over the most common climate metrics, including radiative forcing, global warming potential, global temperature potential, and the average temperature response is given in order to _nd the most suitable climate metric for aircraft design purposes. During previous studies within various projects, e.g. WeCare, REACT4C, and ATM4E, climate optimization strategies for aircraft operations were investigated. The aircraft routes regarding the ight path or altitude can be adjusted in regard to climate considerations, also in dependence on the current weather situation. In these projects, climate change functions and algorithmic climate change functions were developed which could potentially facilitate the climate optimized routings. The aircraft design for climate optimization di_ers from the approach to optimize the design for reduced cost or reduced fuel burn. For the climate impact, ying slow and low is bene_cial which was shown in the project CATS, but this is not reected in the current aircraft design. Therefore, previous studies propose redesigned aircraft. The relation between climate, aircraft operations and aircraft design is used to point out the requirements for modelling resulting from that. The focus is on the connection between climate and operations on one side, and on the connection between climate and design considerations on the other side. Currently, the model capacity for aircraft design does not support the climate optimized design. Therefore, deriving climate functions for aircraft design is highly important which will be one of the main goals in the Clean Sky 2 project GLOWOPT (Global-Warming-Optimized Aircraft Design).