Significant progress has been made in reducing the specific emissions of aircraft, in particular CO2. However, the absolute emissions have been increasing rapidly during the recent decades and are projected to continue to grow. Furthermore, aviation substantially impacts upon climate from non-CO2 effects such as:
- Ozone formation and methane destruction from aviation's NOx emissions;
- Formation of contrails and contrail cirrus;
- Emission of H2O at high altitudes;
- Emission of aerosols (e.g. soot) and aerosol precursors (e.g. SOx), which modify cloudiness and cloud micro-physical and radiative properties.
Current flight planning is performed with the objectives of achieving maximum punctuality or minimizing operational costs. Minimal fuel consumption, minimal CO2 emissions or minimal climate impact have lower priority.
Impact of aircraft non-CO2 emissions on the atmospheric composition and on climate depends on the altitude and location of the emissions. Climate impact via NOx, contrails and contrails cirrus can therefore be reduced by flying lower and by avoiding contrail regions. But this results in a higher fuel burn and hence in higher CO2 emissions.
To reduce aviation's emissions and improve its environmental compatibility, the REACT4C project will investigate the potential of alternative flight routing to lessen the atmospheric impact of aviation. Hence the main objectives are:
- Explore the feasibility of adopting flight altitudes and flight routes that lead to reduced fuel consumption and emissions, and lessen the environmental impact;
- Estimate the overall global effect of such Air Traffic Management ('ATM') measures in terms of climate change.
The objective is to demonstrate that environmentally friendly flight routing is feasible, but does not address the operational implementation of such advanced ATM procedures. The operational implementation would require much more time than is available in the present project. However, REACT4C will deliver substantial scientific foundation and operational specification for novel ATM procedures, which might be explored in a later phase of the SESAR JU project. Analogously, REACT4C will deliver fundamental concepts of aircraft that are better suited for environmentally flight routing, which will have the potential to enter the Clean Sky JTI in a later phase.
The REACT4C project will perform an optimisation approach for alternative flight planning in order to assess the potential for reducing fuel consumption, CO2 emissions and climate impact from aviation.
For a set of typical weather situations, 4D (location and time) cost functions will be determined that reflect the environmental and climate impact of aviation emissions. Current operational flight planning tools will be extended to account for environmental effects via these cost functions. Flight trajectories will be calculated for several optimisation targets: operational, economic and environmental. The associated impacts on the environment will be calculated. Practical rules for an environmentally friendly flight planning will be deduced. Concepts of future (green) aircraft that will be adapted and optimised for the new environmentally compatible flight routing, will be developed. The associated mitigation gain of such aircraft will be estimated in terms of environmental and climatic impact.
The results will be disseminated to stakeholders in the aviation sector, the science community and the general public. Results will be prepared for further exploitation.
- An initial scoping study of expanding an operational flight planning tool by optimisation against criteria of fuel consumption and emissions was performed; the inclusion of climate cost functions enables environmentally friendly flight planning with respect to climate impact.
- The project quantifies the potential for improvements of inefficiencies in the air transport system with respect to fuel consumption, emissions and climate impact due to non-conventional flight trajectories under realistic atmospheric conditions on a regional and global scale.
- 4D climate cost functions (as functions of latitude, longitude, altitude and time) are calculated for realistic weather situations. These cost functions rely on different emission metrics of climate change, targets being time integrated marginal Radiative Forcing RF (in analogy to the Kyoto metric Global Warming Potential) and temperature change after a given time horizon (the Global Temperature Potential).
- The project provides the formulation of specific recommendations for stakeholders on flight planning, aircraft and engine design for future green aircraft.
- Cooperation is instigated between complementary experts required for environmental flight planning, which has the potential to initiate follow-up joint work in Clean Sky JTI and SESAR JU.
Innovating for the future: technology and behaviour: Promoting more sustainable development