Airborne capabilities for supporting reducing ATM environmental footprint

Expected Outcome

To significantly advance the following development actions:

• IR-5-04 Airborne capabilities for supporting reducing ATM environmental footprint. This includes wake energy retrieval (WER), energy-based operations, and environment driven trajectory optimisation, etc.
• IR-3-08 Geometric altimetry.

Scope

The following list of R&I needs is proposed as an illustration of the potential project content, but it is not meant as prescriptive. Proposals may include other research elements beyond the proposed research elements below if they are justified by their contribution to achieve the expected outcomes of the topic and are fully aligned with the development priorities defined in the European ATM Master Plan.

• Environmentally driven trajectory planning

Research aims at developing technologies and operational concepts to allow the planning of more optimised trajectories by considering both CO2 / non-CO2 effects in the aircraft trajectory planning. Research shall assess the need and if required develop sufficiently accurate models (e.g., aircraft performance, climate impact, etc.) to support efficient trajectory optimisation. Research shall integrate different inputs (e.g., CO2 emission profiles, eco-sensitive regions (i.e., regions where non-CO2 effects (e.g., contrails, NOx, etc.) are significantly important), aircraft dynamical models, and define potential optimisation algorithms for trajectory planning. Airline trajectory optimisation plays an important role on the global environmental mitigations. However, and since adopting independently optimised trajectories may not be always operationally feasible, the proposed algorithms shall consider air traffic management aspects such as safety, traffic demand, complexity, etc. Environmentally driven trajectory optimisation shall include enroute and terminal areas. The optimisation in the terminal areas shall consider both noise, non-CO2 and CO2 including potential trade-offs. The research element should address the update of computerised flight plan service products, FMS updates and/or the development/update of EFB applications. The development of improved aircraft (e.g. for new aircraft, or more accurate models of existing aircraft) or climate models is also in scope. Note the integration of FOC, EFB and FMS is covered in WA 1-1.

Since adopting independently optimised trajectories may not be operationally feasible, the proposed algorithms shall be able to consider constraints expected from ATM (e.g. constraints from NM, be them RAD constraints or constraints imposed specifically to a flight, ATC constraints, LoA). The algorithms may incorporate a concept for considering the probability that an ATM constraint will actually be applied in execution as part of the planning. Potential use cases of the probabilistic approach to flight optimisation include, for example:

• If a LoA or RAD constraint for an early descent is expected to be waived, the flight plan could be optimised under the assumption it will be waived.
• if a shortcut is usually expected on a specific route, the flight plan may be optimised under the assumption the DCT will happen, even if the flight plan needs to file with the full route without the DCT.

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• Wake energy retrieval (WER)

WER operations allow aircraft to reduce fuel-burn by flying closely behind another aircraft, thus taking advantage of some of the residual lift of the leader. From an ATM point of view, the challenge is to identify WER candidate pairs, manage the rendezvous and then the pair when formed. In low-density airspace, continental airspace and/or oceanic/remote airspace, previous R&I has laid the operational foundations supporting WER entry into service for limited number of pairs. Research shall address the development and validation of a concept of operations for scaling up the WER concept to higher pair frequencies and the remaining en-route operational environments, considering the outcomes and results of previous projects on the topic. The research must cover both the ground and airborne technical developments and procedures, with a particular focus on support tool integration in common FDP systems as well as suitable automation steps to enhance ATCO efficiency when handling multiple WER operations or requests. The whole process must be addressed, starting with the flight planning phase (with inclusion of WER equipage information in the flight plan), the identification of candidate pairs, the actual ATC clearances required to put the two aircraft in a situation where the pairing manoeuvre can start, the ATC clearance for the pairing manoeuvre, the control of the flights by ATC during the WER operation and the ATC clearance to unpair. Tools for monitoring network WER operations for performance assessment purposes are also in scope.

Research shall address air to air (A/A) communication to enable new operations such as WER, defining the operation needs and requirements that should drive the developing of the associated technical capabilities.

In addition to contributing to the operational validation of such aircraft and ground capabilities, the research must pave the way to the standardisation and certification of the new airborne and ground systems, as well as support the adoption of WER at a global level through ICAO.

Note that there in on-going work under project GEESE.

This element would benefit from air-ground integrated validation activities integrating the ground prototypes (covered in WA 3) and the airborne prototypes (covered in WA 5).

• Environmentally friendly TMA operations through combined dynamic management of aircraft configuration and navigation and route structure

The research aims at enhancing flight management system on the one hand, which advises the pilots to perform the flight more optimally. It includes the required aircraft configuration with allowing a flight along the lateral path of the permanent resume trajectory (PRT) and the newly calculated optimal vertical profile from the FMS by the autopilot or (semi-)manual flight with commanded selections by the pilots. In both ways, modern aircraft flight control architectures can cope with the foreseen FMS enhancements for arrivals and departures as these have strong influence on the noise Impact. Furthermore, new communication ways will ensure the required data exchange to provide the enhanced functionalities. On the other hand, new airspace management techniques and related support tools open the path for more optimal routing of aircraft in the terminal manoeuvring area (TMA) enhancing the airspace capacity with more environmentally friendly operations at the same time while further maintaining and ensuring today’s safety level. The proposed solutions shall address not only arrivals but also departures as these have strong influence on the network capabilities. This research includes the development of avionics and procedures to improve vertical navigation in all phases of flight, including energy management in the descent, implementation of strategic or tactical vertical constraints and monitoring of their compliance, etc. Note that there is on-going work on this research element by projects DYN-MARS (working also on procedural aspects in relation with route structures dynamicity) and GALAAD.

This element would benefit from air-ground integrated validation activities integrating the ground prototypes (covered in WA 3) and the airborne prototypes (covered in WA 5).

• Voluntary mitigation of climate impact for individual flights in low-density/low complexity traffic situations at AU initiative

This research element covers the update of state-of-the-art FOC and/or EFB applications to implement a multi-objective flight planning via the integration of via the integration of climate impact models (e.g., algorithmic climate change functions) with the goal to consider the overall climate impact (CO2 and non-CO2 effects) of a flight while ensuring the compliance with conventional flight planning boundary conditions and operational constraints. The proposed solutions shall consider the impact on the uncertainty in weather forecast (e.g., persistent warming contrails forecasts based on any observation technologies available). From a conceptual point of view, the enabler solution developed could be implemented in different phases of the flight planning process, comprising strategic and tactical flight planning and even a revision of the flight plan during the execution phase.

The climate optimised trajectories may require unusual flight profiles in the vertical dimension (e.g. eco-yoyo flights, unusually low requested cruising level, longer track miles than expected by ATM). These unusual profiles are difficult to manage for ATM. The objective of the research is to facilitate that AU who so desire can fly these unusual profiles whenever safety is not compromised. Note that the concept could be applied to any airspace (including high density/complexity) at periods of low traffic demand/ low traffic complexity. Research should develop a concept to assess in operations until which level of traffic demand / traffic complexity this approach is operationally feasible. When not feasible, a coordinated approach should be applied as described in WA3-1 (research element “Network-orchestrated avoidance of eco-sensitive areas”).

Research considers:

• These unusual flight plan profiles may need to be flagged to avoid that they are rejected by the IFPS, and NM systems may need some adaptation to process them.
• ANSPs shall also have the information that these flights are flagged for environmental reasons.
• A process for local ATFM units to assess the increased workload/complexity caused by these flights and whether it is feasible to handle them (e.g., unusual profiles to be accepted whenever the sector demand is below XX% of the maximum capacity).
• ATC support tools to provide service to eco-yoyo flights (e.g., FDPS adaptation, ATC support to ensure timely climb or descent as per the yo-yo profiles, etc.).

The research may also include support for flights requesting unusual profiles directly to ATC instead of doing so in the flight plan (e.g., development of phraseology). A concept could be considered for declaring an eco-sensitive area of the airspace (i.e., areas where warming contrails are predicted) as eco-yoyo-friendly when traffic demand allows.

• Environmentally optimised operations with geometric altitude

Since the early days of aviation, barometric pressure measurements have been a simple and robust method for altimetry. Two drawbacks exist though: there is no direct reference to terrain, and the constant variations in pressure caused by the weather leads to increased vertical profile variability restricting capacity and flight efficiency in today’s high traffic density.

Research shall investigate the potential of extending the use of geometric altimetry enabled by satellite navigation to increase safety and deliver environmental benefits. The following elements are in scope:

• Earlier barometric to geometric transition in the approach: the objective is to facilitate a smoother descent by anticipating the switch from barometric to geometric guidance. It can also support a reduction of the length of the segment of the approach path that is required to be aligned to the runway. This element requires a proposal for an update of the procedure design in PANS OPS. The work of PJ.02-W2-04.3 “advanced curved approach operation in the TMA with the use of geometric altitude” must be considered. Note that there is on-going work on this research element by project Green-GEAR.
• Extension of the geometric altimetry concept in the climb/descent phase up to, or through, the transition layer: the objective is to eliminate the need for QNH setting, so that in geometric-altimetry airports/CTRs/TMAs aircraft would fly with respect to geometric altitude below a defined transition altitude (above which barometric altimetry with QNE would continue to be used). When going through the transition layer, aircraft would switch to/from geometric from/to barometric, or remain in geometric until enroute, instead of the current from/to barometric with respect to QNE to/from barometric with respect to QNH. The research should investigate if geometric altimetry based on GNSS without augmentation as per the current GNSS and IRS navigation paradigm in place (outside of specific approach procedures requiring augmentation, e.g. LPV, GLS) is sufficiently accurate or augmentation would be required. The flight-deck HMI needs to be developed to make both geometric altimetry and barometric altitudes available, and both altitudes should also be downlinked to ATC systems. The aircraft flight path control systems (FMS and autopilot) will also be affected (note that there is on-going work on the FMS by Project DYN-MARS). The research should also study the feasibility of a mixed barometric/geometric altimetry environment, including a quantification of the barometric vs. geometric altitude differences and research on how the vertical separation process would be affected. Impact on the development and readability of aeronautical charts should also be studied (e.g., publish both barometric and geometric minima vs. single geodetic/MSL minima with a sufficiently high transition altitude). The specific needs and constraints of general aviation must be considered.
• Geometric altimetry above the transition layer: in a geometric cruise, aircraft do not have to climb/descent when flying across isobars to maintain a constant altitude, but thrust settings need to be adapted to outside air pressure changes. The research must analyse the environmental impact in terms of fuel burn these two opposing effects would have and if possible, conclude with a go/no-go recommendation for this concept. If recommendation is to go ahead, the research should continue building on the previous point for geometric altitude below the transition layer.
• Potential reduction of separation minima thanks to more precise altimetry: the increased precision of the altimetry is expected to allow a reduction of vertical separation minima to 500 ft. for some aircraft type pairs (based on the results of a preliminary research on this topic conducted by SESAR project R-WAKE). The research should build on the R-WAKE project research to investigate this potential reduction of minima in different environments from the safety perspective and provide an estimation of the benefits it would provide.

Note that there is ongoing research on the transition to geometric altitude in SESAR project Green-GEAR and that in this call WA 6-2 there is an element addressing altimetry for drones. While it may not be required that open and specific category drones and certified aircraft use the same altimetry system, projects working in altimetry for drones and projects working in altimetry for certified aircraft should share information and consider interoperability at low altitude or applicable buffers for separation.

This element may benefit from air-ground integrated validation activities integrating the ground prototypes (covered in WA 3) and the airborne prototypes (covered in WA 5).