ATM application-oriented Research for Aviation Green Deal

Project results are expected to contribute to the following expected outcomes.

• Environment. Project results are expected to contribute to the achievement of the objectives of a 55 % reduction in greenhouse gas emissions by 2030 and net-zero greenhouse gas emissions by 2050, by maturing concepts enabling optimal and optimum green trajectories, thus reducing CO₂ and non CO₂ emissions, as well as contributing to new and up-to-date models to tackle emissions and noise and improve local air quality. In addition, the impact of new entrants and new aircraft types / fuels on the environment should be assessed.
• Capacity. Project results are expected to contribute to the issue of sector capacity through the identification of optimal and environmentally friendly flight trajectories, including for new entrants (e.g. U-space flights).
• Safety. Project results are expected to contribute to the integration and improved interoperability of manned aviation with drones, and also to the integration of HAOs, thus keeping the level of safety of operations at least at the same level as today.

The SESAR 3 JU has identified the following innovative research elements that could be used to achieve the expected outcomes. The list is not intended to be prescriptive; proposals for work on areas other than those listed below are welcome, provided they include adequate background and justification to ensure clear traceability with the R&I needs set out in the SRIA for the aviation green deal flagship.

• Geometric altimetry. In current operations, aircraft cruising at a constant barometric pressure need to climb/descend when flying across isobars, which in the case of a climb causes extra fuel-burn. This extra fuel-burn may be offset if, thanks to it, the aircraft stays at its optimum (or at least closer to optimum) pressure altitude / temperature for a long enough time, but otherwise fuel may be wasted. The use of barometric altimetry has been the only option since the advent of aviation, but a move to geometric altimetry is deemed possible today because aircraft are nowadays for the most part equipped with GNSS, and this trend is expected to grow in the future. There is a need to assess the potential environmental benefits of moving to geometric altimetry, considering not only the impact on aircraft that are at cruising level but also the other concepts that would be unlocked by it, for example reduced vertical separation minima (RVSM 2) and elimination of the wasted airspace allocated to the ‘transition layer’. Research is also needed to develop an operational concept to move all aviation (en route and TMA, general aviation, airliners, civilian and military traffic, in all airspace classes) to geometric altimetry. Note that, in addition to the environmental benefits, the move to geometric altimetry is also expected to facilitate the approach and landing phases (e.g. no need to transition from barometric to geometric altimetry during the approach), which will have safety benefits. Geometric altimetry will also facilitate the integration of manned aviation with drones that are already using geometric altimetry in current operations, and also integration with HAOs (precision of barometric altimeters above Flight Level 800 is challenging). The research will need to consider aspects related to the transition from barometric to geometric altimetry (R&I need: optimum green trajectories).
• Evolution of separation minima, including RVSM 2. Building on the work of the SESAR 2020 ER project R-WAKE, the objective is to develop and validate a concept of operations to enable the reduction of vertical separation minima to 500 ft in a geometric altimetry environment, potentially in combination with a concept for new dynamic and/or geometry-dependent separation minima in the horizontal dimension. It is expected that the RVSM 2 concept will bring increased capacity (an estimated increase of 20 %) and reduced CO₂ emissions by making it possible for more aircraft to cruise at their preferred altitude. Safety benefits are also expected, because the concept also includes an increase in separation minima (e.g. vertical separation increases to 1 500 ft, or there is a requirement to add a small (e.g. 1 NM) horizontal separation to the 1 000-ft separation minimum for certain aircraft pairs when atmospheric conditions are known to be such that wake turbulence is especially persistent, thereby reducing the risk of wake encounters in the en-route phase of flight). The scope of the research includes investigating advanced modes of separation (e.g. dynamic separation) based on predictive modelling and ML techniques and enabled by further automation and improved connectivity. In addition, the dynamic calculation of the necessary separation parameters between aircraft (horizontal and vertical) to meet a minimum acceptable safety level (i.e. moving away from pre-determined separation standards) should be addressed. The separation minima to be developed include both minimum radar separation (MRS), which aims to keep the risk of collision sufficiently low to meet the target level of safety (TLS), and minimum wake separation (MWS), which aims to keep the risk of wake encounter sufficiently low to meet the TLS; the minima to be applied in operations will always be the maximum of the applicable MRS and TLS. Please note that it is expected that the RVSM 2 concept will not be possible with the precision that barometric altimetry can provide (it will require the increased precision provided by geometric altimetry, as described in the previous bullet point). The dynamic weather- and geometry-dependent pairwise distance-/time-based separation minima for en-route airspace and the TMA will allow the separation minimum between two aircraft to be reduced under certain weather conditions (e.g. depending on the location of the tropopause, on wind); the separation to be applied will be the greatest of the MRS and the MWS. The operational improvement will also require combined separation minima and consideration of flight-specific data (R&I need: optimum green trajectories).
• Introduction of environmental considerations into the European route-charging scheme. This element builds on the evolution of separation minima as described in the previous bullet point and covers research into the potential evolution of the route-charging scheme to incorporate environmental considerations, such as lower charges for flying at valley hours, lower charges for flying at suboptimal flight levels (or flying longer 2D routes) to reduce non-CO₂ impacts, lower charges for lighter flights accepting voluntary level-capping in order to make the best flight levels available to heavier aircraft and higher charges for aircraft with lower load factors or for business aircraft (R&I need: accelerating decarbonisation through operational and business incentivisation).