Cost-Benefit Assessment of 2D and 3D Climate And Weather Optimized Trajectories

Abstract

Climate optimized flight trajectories are considered to be a promising measure to mitigate non-CO 2 emissions' environmental impact, which is highly sensitive to locus and time of emission. Within this study, optimal control techniques are applied in order to determine 2D (lateral) and 3D (lateral and vertical) cost-optimized flight trajectories while mitigating their climate impact by minimizing emissions and flight time in highly climate sensitive regions. Therefore, monetary and 4D-climate cost functions, describing the climate sensitivity in dependency of the emission location, altitude, time and weather situation, are integrated into the optimization algorithm.For both, 2D-and 3D-optimization, the cost-benefit potential (climate impact mitigation vs. rise in operating costs) is investigated for nine fictitious North Atlantic routes for eastbound and westbound directions in the presence of winds. The conducted study shows large potential for both measures as the reduction of climate sensitivities along the trajectory often predominates the additional emissions caused by headwinds, additional climband descent phases, additional flight distance, and off-design altitudes. Flight trajectories optimized within the horizontal plane can reduce the average temperature response (ATR) by approximately 15 % for a two percent increase in cash operating costs (COC). This mitigation potential is significantly improved by superposition of lateral and vertical optimization. 3D-optimized trajectories which are comparable in cost increase achieve a 20-35 % higher ATR reduction than their 2D-optimized counterparts. Further, they reduce global warming more efficiently (higher ATR reduction per unit cost increment) and to a higher extent. However, achieving maximum climate impact mitigation is linked with an disproportional rise of cash operating costs in both cases. Therefore, a careful consideration of the required climate impact savings as well as the accepted surcharges is necessary.

Mitigating the Climate Impact from Aviation: Achievements and Results of the DLR WeCare Project

“…The Trajectory Optimization Module (TOM) allows for a continuous four-dimensional optimization of aircraft trajectories (for more details see [66]). The underlying optimal control problem has the following general form:…”

“…As a use case, climate optimized trajectories for several routes within the North Atlantic region were investigated in order to compare the potentials of 2D (lateral) and 3D (lateral and vertical) trajectory optimization [66]. Therefore, models for the cash operating costs (COC) as well as CCFs (see Section 2.2.3) were integrated into the objective function J of the Trajectory Optimization Module (see Section 2.3.2) according to Equations (8) and (9).…”

“…Their results show very large reduction potentials, indicating that the Pareto Front is, by definition, to the right of the line of the 3D-optimization, but probably close to it. 2D and 3D average Pareto-fronts of climate impact reduction potential using the metric ATR relative to a reference and corresponding COC changes with respect to the same reference, i.e., the cost-minimal solution [66].…”

A Concept for Multi-Criteria Environmental Assessment of Aircraft Trajectories

“…Depending on the use case, further control, state and path limitations can be defined (see Equations (3)- (7)). A more detailed description of TOM is given by [33].…”

“…In cruise, step climbs are performed where required by monitoring and following the aircraft's optimum altitude profile. Emissions are modelled using the state-of-the-art Boeing Fuel Flow Method 2, which allows for the estimation of emission indices (EI) for the species NO x , HC and CO derived from EIs for sea level conditions obtained from the Engine Emission Databank by the International Civil Aviation Organization (ICAO) [33], whereas species that are produced proportionally to fuel burn, i.e., CO 2 , H 2 O are calculated using constant EIs. Four-dimensional (longitude, latitude, altitude, time) emission inventories are generated by simulating every flight in the traffic scenario and determining the corresponding emission distribution.…”