To face the increasing environmental footprint of commercial aviation, industrial and research efforts have been focusing on exploring unconventional configurations and new propulsion paradigms, mostly based on electric technology. Such explorations require Overall Aircraft Design that has to be performed in an integrated multidisciplinary design environment. Such design environments are often limited to multidisciplinary analysis, adapted for a single aircraft configuration or require an important effort to be mastered. FAST-OAD is a software program developed by ONERA and ISAE-SUPAERO for aircraft sizing analysis and optimization that aims at user friendliness and modularity. It is an aircraft sizing code based on multidisciplinary design optimization techniques and the point mass approach to estimate the required fuel and energy consumption for a given set of TLARs. This paper presents the motivations for moving from the original software program, called FAST, to the open source code FAST-OAD based on OpenMDAO.

The aircraft environmental control system (ECS) is the second-highest fuel consumer system, behind the propulsion system. To reduce fuel consumption, one research direction intends to replace conventional aircraft with more electric aircraft. Thus, new electric architectures have to be designed for each system, such as for the ECS. In this paper, an electric ECS is modeled and then sized and optimized for different sizing scenarios with the aim of minimizing fuel consumption at the aircraft level. For the system and for each component, such as air inlets and heat exchangers, parametric models are developed to allow the prediction of relevant characteristics. These models, developed in order to be adapted to aircraft design issues, are of different types, such as scaling laws and surrogate models. They are then assembled to build a preliminary sizing procedure for the ECS by using a multidisciplinary design analysis and optimization (MDAO) formulation. Results show that the ECS design is highly dependent on the sizing scenario considered. An approach to size the ECS globally with respect to all the sizing scenarios leads to an ECS that accounts for around 200 N of drag, 190 kW of electric power, and 1500 kg of mass for the CeRAS aircraft.

Assessing mitigation strategies for aviation is a critical issue for the aviation stakeholders, while the debate continues on the most appropriate CO₂-equivalence metrics to address non-CO₂ effects. Here, we propose two lightweight climate models that can be parameterised to assess these strategies and move beyond the CO₂-equivalence metrics debate. A first approach relies on the use of the GWP* method, while a second one uses the FaIR climate emulator. These lightweight models, which should be considered as a new family of climate models for aviation that facilitate parametric studies, provide a straightforward and consistent means of evaluating mitigation strategies at the temperature level, although they are still limited for informing policymakers due to the significant uncertainties involved. They bypass the need for CO₂-equivalence metrics for comparing strategies. The latter should rather be used for other applications, such as policy mechanisms to encourage the emergence of strategies, as they are not suitable for assessing temperature changes from aviation. The debate on the choice of CO₂-equivalence metrics could then focus on methodological and ethical criteria. However, this paper demonstrates that the higher the traffic, the more appropriate it is to choose CO₂-equivalence metrics with high values for consistency with temperature estimates.