These indicators have remained extremely stable for the last five years at just over 97% and 95% respectively, a level that EUROCONTROL sees as near optimum taking into account weather, military training and other safety constraints. However, using just two indicators overlooks progress in other areas where the aviation sector is reducing its environmental impact, and in particular its ongoing contribution to Europe’s goal of becoming climate-neutral by 2050.
"Aviation stakeholders are working together to deliver additional environmental benefits during the traffic downturn"
says Marylin Bastin, Head of Aviation Sustainability, EUROCONTROL
The environmental performance of the European sky is almost exclusively monitored using indicators based on horizontal en-route flight efficiency (HFE), which compare the length of actual (KEA) or planned (KEP) flight trajectories to the corresponding “achieved” distance.
The measures put in place to curb the spread of COVID-19 around the world nearly halted passenger air traffic for three months, and continue to slow significantly its rebound. As a result, capacity growth has become less urgent, with even the most optimistic forecasts predicting a return to pre-COVID-19 traffic levels unlikely before 2024. This leaves room for continuing and even accelerating efforts aimed at improving the efficiency of the aviation system, especially those that target reducing its environmental impacts. With this in mind, EUROCONTROL has taken the initiative to take a closer look at current system performance in order to establish a baseline of maximum achievable performance in different areas.
"EUROCONTROL has taken the initiative to take a closer look at current system performance in order to establish a baseline of maximum achievable performance in different areas."
For example, according to EUROCONTROL, average monthly taxi-out times dropped by a third between March and September 2020, and airport holding fell from an average of two minutes per arrival to almost zero. Most significant is the improvement in vertical flight efficiency, measured by the indicator developed by the European Continuous Climb Operations and Continuous Descent Operations (CCOs and CDOs) Task Force, now available on EUROCONTROL’s Aviation Intelligence Unit portal.
EUROCONTROL Head of Aviation Sustainability Marylin Bastin explains: “This new indicator, a proxy for vertical inefficiency, shows, for instance, a decrease of up to 60 seconds of level flight between February 2020 and April 2020, which clearly indicates that arrival flights were able to optimise their descent profiles and the associated fuel consumption by almost one minute during their descent to an airport.”
This is because CCOs and CDOs allow arriving or departing aircraft to descend or climb continuously to the greatest extent possible. Aircraft applying CCO employ optimal climb engine thrust and climb speeds until reaching their cruising level. With CDO, aircraft use minimum engine thrust, ideally from top of descent and in a low-drag configuration, prior to the final approach fix. Using these techniques reduces intermediate level-offs and gives aircraft the opportunity to spend more time at higher, more fuel-efficient, cruising levels, reducing fuel consumption and lowering emissions and costs.
Continuous climb and descent operations
Together with the members of the European CCO/CDO Task Force, EUROCONTROL has developed a detailed European CDO/CCO Action Plan, which aims at increasing the number of CCOs and CDOs, along with a toolkit, monthly performance tables and guidance material. The recommendations in the Action Plan require airlines, airports, air traffic control and the EUROCONTROL Network Manager all to play their part. “Sometimes the recommendations are obvious,” says Ms Bastin, “but it’s important to stress how collaborative the process is. All stakeholders have to work hand-in-hand to support optimised trajectories. This is particularly true during the crisis, but will also be necessary when traffic increases again. If we really want to achieve the ambitious goals set out in the European Commission’s Green Deal and reduce carbon dioxide emissions, we need to work closely together.”
Continuing the process when traffic starts to grow again is the challenge facing us. “We are using this time to look at how to maintain this level of optimised CCO/CDO and more efficient trajectories. In particular, we strongly believe in the potential of EUROCONTROL’s Specification for Collaborative Environmental Management (CEM) to establish working arrangements to discuss and explore solutions to minimise the environmental impact from local operations.” CEM brings together airport stakeholders to address issues such as greenhouse gas emissions, noise, and local air quality, “putting operational people from airports, airlines and air traffic around the same table”. The next version of the CEM platform will include Sustainable Aviation Fuel (SAF) among potential collaborative solutions and implementation strategies to address environmental challenges at airports.
Collaborative environmental management
Ms Bastin says each airport needs a local solution. “This is not a simple process, which is why we need to develop a platform at each airport and ensure that all stakeholders are working on the same objectives – reducing carbon dioxide emissions, reducing noise and improving local air quality.” The platform could also be used to introduce parallel research and innovation projects to focus on “more drastic changes,” she adds.
EUROCONTROL’s aviation sustainability unit is collaborating with industry on a number of ambitious projects that aim at implementing SAFs. Among these, the EUROCONTROL Experimental Centre is working with leading manufacturers including Airbus and Safran to assess the impact of new generation aircraft on airspace management. “SAFs are part of the future,” explains Ms Bastin. “We are in close contact with industry to better understand how we can help facilitate SAF implementation and how it affects aircraft performance. The key is to better understand and measure how SAFs, coupled with new kinds of aircraft technology, can contribute to the 90% in emissions reduction by 2050 as requested by the Green Deal.”
This activity includes gathering data and adapting tools and methodology to accommodate SAFs. “There are different types of SAF – biofuels and synthetic fuels – but exactly how environmentally friendly are they?” Ms Bastin asks. EUROCONTROL is examining future aviation models such as hydrogen and hybrid electrical aircraft to improve the understanding of future airspace operations.
"The key is to better understand and measure how SAFs, coupled with new kinds of aircraft technology, can contribute to the 90% in emissions reduction by 2050."
SAFs are part of the measures identified by the International Civil Aviation Organization’s (ICAO’s) Long-term Global Aspirational Goal Task Group (LTAG-TG) for international civil aviation to reduce carbon dioxide emissions. As an LTAG-TG working group member, EUROCONTROL contributes to the development of technologies, fuels and operational scenarios that could be implemented in the future. EUROCONTROL also participates in the ICAO Fuels Task Group (FTG) established in 2020, which is examining sustainability criteria and production methods for SAFs, as well as at Lower Carbon Aviation Fuels (LCAF). The Task Group is working on the classification of feedstock as waste, co-products and main products with the aim of providing policy-making guidance in coordination with LTAG-TG work for deployment.
EUROCONTROL is also working with airlines and air navigation service providers (ANSPs) to better understand condensation trails (contrails). These upper troposphere (8–13 km altitude) aircraft-induced ice-particle clouds form in icesupersaturated and low-temperature areas and can develop into larger cirrus clouds that have a net positive radiative forcing (i.e. warming) effect. According to research study by Imperial College London published in February 2020 (2), most contrail cirrus forcing can be attributed to a few largescale events. Accurate and timely identification of these events remains challenging but could help reduce contrails formation.
EUROCONTROL’s Maastricht Upper Area Control (MUAC) has in parallel launched a project to examine how relatively minor operational measures such as small flight path changes – e.g. diverting planes roughly 2,000 ft up or down from their normal flight path – can influence contrail formation, using weather forecasts to tactically push flights. Clearly, there has to be a positive balance between contrail avoidance and additional fuel burn, but Project Manager Rüdiger Ehrmanntraut believes the project will make a significant contribution.
“We want to have the best prediction model, because we want to minimise intervention and maximise the positive impact. We are working on an augmentation system for weather predictions, for example adding real-time sensors from Mode S data,” explains Ehrmanntraut.
MUAC is in the process of implementing the technology, and plans to validate the whole process by analysing satellite images after conducting live trials.
"EUROCONTROL has also developed two valuable environmental tools to evaluate noise and emissions. The first of these is IMPACT, a web-based platform that allows both the production of noise and noise contours and the evaluation of the mass of 25 species of pollutants along flight paths. This type of study is very relevant for "airports, ANSPs, national authorities and associations such as Airports Council International,” explains Ms Bastin. IMPACT helps identify sources of inefficiency, supports development of new operational solutions and measures their benefits.
The second is ALAQS, the Airport Local Air Quality Studies platform, which provides a four-dimensional inventory of emissions from various stationary and mobile airport sources, including aircraft operations and landside/airside activities. The model also includes non-airport sources such as road traffic to/from the airport. Moreover, ALAQS provides a connection to the dispersion model AUSTAL2000 and thus, once an emission inventory has been established, it can simulate pollutant concentrations at the airport and in the surrounding areas. It is an open-source airport local airquality tool which can be used to assess an airport’s relative contribution to total ambient concentrations according to legislative requirements.
Metrics play an important part in EUROCONTROL’s strategy towards a sustainable environmental future. The EUROCONTROL Aviation Intelligence Unit portal includes as a first step carbon dioxide metrics for States. However, to address air traffic management (ATM) performance, “we need to develop other measurements, indicators, metrics to inform the general public about the progress the aviation sector is making to reduce the environmental impacts of operations,” says Marylin Bastin. “If we want to improve, we need better data.”
"We need to develop other measurements, indicators, metrics to inform the general public about the progress the aviation sector is making to reduce the environmental impacts of its operations."
This is particularly relevant for ANSPs. “The indicators we currently have don’t reflect the impact of ANSP’s efforts to reduce emissions. They are working on reducing the carbon footprint of aviation, investing in new technologies and becoming more efficient.” This is the topic of a new EUROCONTROL working group looking at operational measures and their benefits.
"Sustainable aviation is a vast area of concern. We complement our work with training, including webinars on topics such as climate change and how stakeholders can adapt to the identified risks. We aim to launch training modules on the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) introduced by ICAO to help to explain its goals and how it works,” says Marylin Bastin.
It is important to place aviation in the broader transportation context.
“One of our main priorities in the year ahead is to produce think papers and studies to shake up the preconceptions about the aviation environmental impacts of aviation and the solutions to them and as well as more accessible ones that can help inform the public about all the efforts that aviation actors are making to deliver on the sustainability challenge. Environmental solutions must also address societal and economic needs. We want to increase public awareness about challenges and dilemmas facing the aviation sector when it comes to environment and sustainability. Two recent examples of this strategy are the European CCO/CDO Action Plan and our Think Paper on “Does taxing aviation really reduce emissions?”. The Action Plan is a valuable technical document that captures intensive work carried out with a large number of stakeholders, including airlines, airports and ANSPs on how to make CCO/ CDO work, with examples of best practices and how constraints can be overcome. It builds on the extensive experience Europe already has in optimising the efficiency of vertical flight profiles. The Think Paper, on the other hand, is firmly aimed at a wider audience. Using exclusive EUROCONTROL aviation data, it examines whether taxes on aviation fuel or air tickets, or equivalent measures, do effectively contribute to a direct reduction of aviation emissions – reaching some interesting findings for policy-makers, in particular that the best way to reduce aviation’s CO2 emissions is to support decarbonisation measures, with any European tax aimed at reducing emissions being ideally ring-fenced to fund such initiatives.”
Indeed, as the Think Paper underlines, investing heavily in greener aviation is central to the process. Air traffic management can influence less than 10% of all aviationderived carbon dioxide emissions in Europe, nevertheless it is an important part of the overall solution. According to Ms Bastin: “If we want to achieve a green transition, we must invest in new technologies and sustainable aviation fuels. The four ICAO pillars of market-based measures (the Emissions Trading Scheme (ETS) and CORSIA), disruptive technology, improved infrastructure and operations, and the uptake of Sustainable Aviation Fuels (SAFs) are key to aviation sustainability.”
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