Mitigating Climate Impact through Intermediate Stop Operations and Fleet Optimization

Abstract

Longer range mission requires large aircraft with significant fuel tank capacity which subsequently increases the operating weight of the aircraft and the fuel required. This snowball effect leads to reduction in fuel efficiency with increasing range. By splitting the long-haul flights into shorter legs with intermediate stops, the aircraft can carry less fuel initially and refuel at an intermediate stop, thereby reducing the weight and increasing fuel efficiency for each individual leg. Multiple studies have considered the concept of Intermediate stop operation (ISO) to reduce the fuel burn, proportionally the CO2 and the resulting climate impact. However, the study in Linke et al. (2017) shows that in contrast to the CO2 emission, the climate impact of non-CO2 emissions increases for the ISO concept due to changes in emission location. In a recent study of Zengerling et al. (2022) an improvement to this concept with regard to climate impact mitigation of non-CO2 emission was considered by selecting intermediate stop airports and flight altitudes on climate-related criteria. An additional benefit from splitting long-haul flights into shorter legs can be enabled by use of smaller aircraft, which have better-fuel efficiency compared to the long-range aircraft. For instance, Linke et al. (2011) examines the potential for mitigating climate impact through the use of range-optimized aircraft within the ISO concept. In this study, we investigate the potential reduction in climate impact through a fleet and flight network optimization with the concept of ISO on airports which are selected based on climate-related criteria. A set of new aircraft designs with varying seat capacity and design range are developed using the conceptual design tool FLOPS. We consider the European flight plan of 2018 with mission lengths greater than 2500 NM and operated with wide-body aircraft as reference. For each combination of the origin-destination pair, a set of possible intermediate airport candidates are considered based on Zengerling et al. (2022). Subsequently, a network optimization is conducted to determine the optimal combination of aircraft (optimized in terms of size and range) and ISO airports. This optimization aims to minimize the overall climate impact, as indicated by the Average Temperature Response over 100 years, for each origin-destination (OD) pair.