The European aviation sustainability Destination 2050 initiative identifies a route to achieving net zero CO2 emissions by 2050 through a combination of four key measures. These comprise: Improving aircraft and engine technologies, which could achieve emission reductions of 37%; using sustainable aviation fuels (SAFs), estimated to achieve emission reductions of 34%; implementing economic measures, contributing 8%; and improving air traffic management and aircraft operations, expected to achieve emission reductions of 6%. Air traffic management (ATM) uniquely provides an opportunity to deliver fast, measurable gains to help to meet interim targets in the next 15 years, writes Jenny Beechener. Measures already underway as part of the European Commission Single European Sky (SES) initiative – recently updated in September 2020 to take into account the objectives of the Commission’s Green Deal – have actually accelerated during the recent period of low traffic.
European air navigation service providers (ANSPs) have implemented more than three quarters of initial Free Route Airspace (FRA) – mandated by the end of 2022 under EC SES Implementing Regulation (EU) No 116/2021. While traffic flows must still be segregated for safety reasons, the FRA environment allows airspace users to plan more efficient flight paths between defined entry and exit points thanks to a reduction in intermediate waypoints. Eurocontrol estimates once free route airspace is fully implemented Europe-wide, potential savings could reach 3,000 tonnes fuel/day and 10,000 fewer CO2 tonnes/day.
Taking advantage of quiet skies, ANSPs managing the European core area introduced FRA in the region’s busiest airspace to enable airspace users to file optimised flight-plans and route profiles. Airspace users gained access to FRA on many night networks in addition to FRA around the clock in upper airspace controlled by Maastricht (since December 2019) and Karlsruhe (since February 2021) control centres, with major centres in both France and Switzerland preparing to implement similar procedures from the end of 2021.
The traffic downturn and increased availability of air traffic controller expertise during the pandemic enabled implementation of further airspace management projects aimed at building better foundations for sustainable operations going forward. ANSPs operating within Functional Airspace Block Europe Central (FABEC) airspace, an area handling more than 55% of European flights, removed over 500 flight level caps and air traffic flow and capacity management measures in the first six months. These measures are used to manage traffic during periods of high demand.
In addition, airspace users saved on advice of FABEC air traffic controllers 68 million track miles during the actual flight compared with filed airline flight plans, reducing carbon dioxide emissions by 1.4 million tonnes. By the end of 2020, horizontal flight efficiency in FABEC airspace reached 97.06%, exceeding SES performance targets and close to the optimum possible.
The challenge is to maintain the shorter flight-plannable route options as traffic returns, prompting several new initiatives involving neighbouring ANSPs. Among early measures, ANSPs in Switzerland and Germany shortened routes over the Alps by 15 nautical miles in June 2020, saving flight time and reducing fuel consumption. Flights destined for northern Italy now follow a more direct route across central and southern Germany, and similar changes are being considered for flights from north east Europe destined for airports in Spain and North Africa. The two ANSPs also introduced permanent procedures that enables airspace users to remain at fuel-efficient cruising heights for longer and to reach higher altitudes earlier across the international boundary. Flight arrivals cross the border 2,000-4,000 ft higher than previously and Frankfurt departures entering Swiss airspace are no longer held at FL320 but can enter at any altitude, generating an average saving of 32kg of fuel or 100kg of carbon dioxide per flight.
Graph showing the vertical profiles of daily Frankfurt departures to the south via Zurich ACC before (in red) and after (in green) the introduction of new cross-border procedures between Germany and Switzerland, saving 100kg of CO2 per flight.
New sector boundaries are being introduced as part of the Cooperative Optimisation of Boundaries, Routes and Airspace (COBRA) project. COBRA aims to reduce complexity and provide more efficient traffic management by replacing coordination between multiple sectors with bilateral handovers and the provision of new route options. For example, shorter routes along the Karlsruhe – Maastricht boundary simplify connections between adjacent approach centres and improve vertical profiles for several arrivals and departures to and from hub airports in the core area of Europe. The procedures are supported by validation simulations, controller training and new concept of operations with implementation expected in 2022. Maastricht Upper Area Control Centre (MUAC) is also engaged in a sectorisation review to identify improvements to flight planning which aims to deliver further network improvements in 2021/22.
Since March 2021, MUAC airspace sector organisation is better suited to the European concept of free route airspace and ready to support higher traffic levels as soon as commercial schedules resume. Benefits include a reduction in flight planning restrictions and the creation of several shorter flight-plannable route options. Simulations predict that on the basis of pre-pandemic traffic, the change will bring a weekly CO2 saving potential of 6,700 kg and offer flight-plannable gains of 280 nautical miles.
While these measures aim to save flight miles and reduce carbon emissions, other greenhouse gas emissions such as NOx and particulate matter provide the focus for separate ATM research. Preliminary findings show about half the climate impact of aviation originates from non-carbon dioxide effects of kerosene use, including the soot particles emitted from aircraft that lead to formation of contrails. The SESAR Exploratory Research project FlyATM4E is investigating the impact that weather situations and aircraft trajectories have on the formation of contrails and their persistence. The research partners aim to develop a concept to identify climate-optimised aircraft trajectories to enable an eco-efficient reduction in aviation’s climate impact, taking into account the balance between contrail avoidance and additional fuel burn.
In a practical application, MUAC is examining how relatively minor operational measures such as small flight level changes, for example diverting aircraft 2000 ft up or down from their normal flight path, can reduce persistent contrail formation and contrail cirrus. The trial includes creating a contrail prevention system; implementing operational procedures for contrail prevention; and the validation of the methodology with satellite image analysis by the project partner DLR.
Engaging with airspace users and ensuring network constraints are kept to a minimum are key steps in ensuring airlines take advantage of more efficient flight trajectories, enhance fuel efficiency and lower emissions. However, to be successful these measures depend upon more than just ANSP activities. Pan-European agency Eurocontrol published an assessment of benefits arising from operational ATM improvements examining fuel burn from take-off to landing across the whole ATM network in December 2020. The report concludes that reducing air transport emissions by up to 10% requires different tools, policy measures and the full collaboration of all the various involved aviation stakeholders. It emphasises the need for collaboration in the roles and responsibilities of each operational stakeholder, from ANSPs to airlines, including airports and the Network Manager, through mechanisms such as collaborative decision-making (A-CDM).
Photo: Eurocontrol Maastricht Upper Area Control Centre