air travel – greener by design

DESIGNbyGreenerGreener

ANNUAL REPORT 2020-2021

A I R T R AV E L – G R E E N E R B Y D E S I G N

2 Royal Aeronautical Society

Executive Committee

Prof Peter Bearman Jonathon Counsell Dr Cristina Garcia-Duffy Roger Gardner Dr John Green Ian Jopson Dr Ray Kingcombe Geoff Maynard Kevin Morris Prof Ian Poll Dr Marc Stettler Robert Whitfield Dr Richard Wilson Roger Wiltshire

Front cover: Contrails in stable air, from an A320, NE of Reno, NV, USA. Estimated altitude of FL 310. Robert J Boser.

Greener by Design

Heathrow

Airport

3 Greener by Design Annual Report 2020-2021

GREENER BY DESIGNANNUAL REPORT 2020-2021

Introduction 4Climate Change Conference 6Climate Impact of Non CO2 Conference 16Economic Measures – Carbon Pricing 30Technology 38Operations Report 46

Contents

Top: Aircraft taxiing at Heathrow Airport. NATS.


Introduction

Introduction

Aviation has experienced its most challenging year in living memory. Passengers were down by around 80%, although the effects on domestic traffic have been considerably less marked in many countries. Generally, Europe and Africa have been hit hardest, the Far East and China less so. With a third wave of Covid sweeping mainland Europe, concern over mutations of the virus circumventing the vaccination campaign resulted in a £5,000 fine being introduced if you leave, or attempt to leave England, without a special exemption. The legislation has now been repealed but a traffic light system for travel abroad remains, requiring many Covid-19 tests. Overall, prospects for a resumption of anything resembling normal international traffic seem a long way off, except for airfreight which has been affected much less.

If Covid wasn’t enough to contend with, environmental pressures have grown strongly during lockdown. Over 40 countries (emitting 75% of global CO2), have, or are in the process of, adopting a ‘Net Zero by 2050’ target. Governments are giving more thought – and investing cash – into how this is to be achieved.

The problem is especially serious for aviation, as there is no obvious solution, except batteries for short flights. Hydrogen has its advocates but it is inefficient, requiring at least four times the input energy compared with what you get out in thrust. Batteries do not have the required energy density for medium and longer distance flights. Sustainable aviation fuel (SAF) is a possible solution, but again requires a much higher energy input. Supplies are very limited at present, and attention is also being focused on just how ‘green’ some raw materials and production methods actually are.

Widespread use of SAF depends on radically higher production, and world-wide availability (with no SAF ‘nationalism’). Some countries, led by Norway, are mandating a small minimum percentage of SAF in all aviation fuel uplifted, rising to 30% by 2030. The

UK government has set up the Jet Zero Council to advise on the best way forward for aviation. Many of the issues were explored at our successful virtual autumn conference last year – Recovery strategy with climate gain – and a report of the conference is on page 6.

Climate change issues for aviation are further compounded by the non CO2 emissions, principally NOX and contrail cirrus, which are now known to exceed the CO2 warming effects. In view of their significance, we held a special conference in March this year to explore the issues in detail, and a report on this is on on page 16. Planning for our virtual and in person Autumn conference, to be held on 19 and 20 of October, is well advanced. The title is ‘Cutting Aviation’s Climate Change Impact’, and it will provide an informative and timely update (prior to COP 26). We very much hope you will be able to join us.

We are also very pleased to welcome Cristina Garcia-Duffy, of the Aerospace Technology Institute, to the GBD Committee. She will provide another valuable view on the challenges facing our industry.

Covid-19 shares many similarities with Global warming: invisibility (unless you look very closely), deadly consequences, and the capability to change our way of life for ever. They also both can be beaten by a well thought out scientific approach, implemented with vigour and determination. We must rise to the occasion and use our skills to defeat both.

Geoff Maynard Chair

Greener by Design

5Greener by Design Annual Report 2020-2021

Chris M

ale

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Royal Aeronautical Society 6

Greener by Design Climate Change Conference ReportINTRODUCTION

On 3-4 November 2020 the first virtual Climate Change conference was held. Speakers included representatives of government, industry, regulators and financiers and featured four panel discussions with: airline CEOs, airports, OEM companies and fuel suppliers. This online event was chaired by Geoff Maynard, Chair of the Greener by Design group, whose members had designed the conference programme. The title of the event, ‘Recovery Strategy with Climate Gain’, recognised that the industry is facing its greatest-ever crisis during the Covid-19 pandemic but also needs to address the longer-term climate crisis.

AIMING FOR JETZERO

Geoff Maynard introduced the first day’s opening speaker, the Rt Hon Grant Shapps MP – Secretary

of State for Transport, who gave a pre-recorded address. He drew parallels between the current Covid-19 situation and World War 2, both national and international crises. The Covid-19 crisis represents an opportunity for a similar change of direction for the UK aviation industry as that prompted by the war. The UK was the first major economy to set a 2050 ‘net zero’ commitment and as air travel returns, the industry must also deliver reduced emissions.

The UK air passenger market is expected to grow by 150 million passengers per year between 2017 and 2050. However, this time, the industry must also deliver reduced emissions. Up until now this was viewed as a constraint on the industry, now it is a passport to this future. Modernising the fleet and offsetting emissions (CORSIA) are one element of this process.

The UK government recently eestablished the Jet


He reported that industry CO2 emissions in 2020 could be half those in 2019 when it reached about 900m tonnes. Future CO2 emissions per revenue tonne-kilometre (RTK) will benefit from the early retirement of older, less efficient aircraft types with a low double-digit improvement expected this year compared with the normal 2-3%.

Clean fuels, eg SAF and electrification, are the long-term solutions. The introduction of SAFs, in particular, is potentially easy to incentivise.

Despite global government providing about $160bn of strategic aid, airlines are still ‘burning through their cash reserves’ and this raises serious questions about how some airlines will survive beyond the first quarter of 2021. Brian noted that climate change appears to have retained the airlines’ focus during this situation, possibly partly due to some governments linking financial aid to climate change commitments.

Brian highlighted the economic necessity of good air transport links but stressed that recovery has to be both with no infection transfer and with reducing emissions.

THE VIEW FROM ICAO

Jane Hupe, International Civil Aviation Organization (ICAO) – Deputy Director – Environment, provided an overview of the ICAO work on aviation’s green recovery and decarbonisation. Environmental protection, one of ICAO’s five statutory objectives, includes minimising community noise and

Zero Council to co-ordinate the UK’s capability. The vision is for a new generation of innovators in the aviation sector to address climate change as the industry and world recovers from the crisis with a goal to demonstrate zero-carbon flight across the Atlantic in the next ten years.

The UK needs to be part of the £4tn global future aircraft market by 2050 and the Secretary of State listed the significant recent investments in research and development made by government and industry. These included £2bn of research managed by the Aerospace Technology Institute (ATI) that includes Cranfield’s Project Fresson, to make commercial hydrogen fuel cell-powered electric flights a reality. Other supported activities include the Civil Aviation Authority (CAA) Innovation hub, ATI’s ‘Fly Zero’ programme and Zeroavia’s first hydrogen fuel-cell powered flight.

A strong Sustainable Aviation Fuel (SAF) production capability could also contribute £0.7-1.6bn to the UK economy by 2040, with maybe 11,000 ‘green jobs’.

The Secretary of State stated the government’s priority is to tackle Covid-19 and get aviation going again. The aviation recovery plan will support the sector and maintain the skills required to permit its future growth in the UK.

The day’s second speaker, Brian Pearce, International Air Transport Association (IATA) Chief Economist, described the Covid-19 crisis as “the greatest shock to the aviation sector since WW2,” with passenger demand down to 1/3rd of 2019 levels. However, cargo traffic volumes are down less than 20%, helped by the transportation of medical supplies, but limited by constrained capacity due to cancellation of most long-haul passenger flights with belly capacity.

A recovery to 2019 traffic, and CO2, levels is not expected until at least 2022-2024, ie much slower than the six-month recoveries following the 9/11 terror attacks and the 2007 financial crash. Future traffic growth trends may also include a permanent 10-15% hit that is a challenge for an industry with relatively fixed costs.

Left: ZeroAvia's Piper M-class six-seater converted to electric power. In March British Airways announced a partnership with ZeroAvia through parent company IAG’s Hangar 51 accelerator programme to explore how hydrogen-powered aircraft can play a leading role in the future of sustainable flying. ZeroAvia.

Air bp and Neste offered a five-fold increase in volume of sustainable aviation fuel during 2020 and 2021. Air bp.

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operations, SAFs and offsetting. This activity involves over 200 experts, 1,000 participants and 100 presentations. The process rates each on the extent of CO2 benefit, the level of finance required, the expected timescale and the potential challenges.

Jane described the future as ‘a flying future, but a sustainable flying future’.

UK CARBON ROAD MAP

Following the break Adam Morton, Chair of Sustainable Aviation (SA) – the environmental coalition formed in 2005 covering 90% of the broader UK aviation industry – explained how SA believes the net-zero target can be achieved for UK aviation. Morton focused on SA’s latest Carbon Road Map, published in February 2020. He explained each of the emission reduction pathways including – aircraft and engine efficiency; operational and airspace efficiency; carbon pricing and SAF.

Market-based measures would also contribute to achieving the 2050 target, through CORSIA initially, with carbon offsets increasingly using carbon removal technology.

Adam reported constructive discussions between SA and the UK’s independent Committee on Climate Change (CCC) over the past 18 months and said: “We look forward to the next report from the CCC later this year where we hope to see much less difference of opinion on how aviation can meet the net-zero target.”

SAF is seen as an important part of this strategy. SAF production itself can also be very positive economically. A study by E4Tech identified 14 possible plants at seven sites around the UK, with some 6,000 new jobs and strong export/licensing potential.

SA has asked the UK government for flagship funding for SAF pilot plants and continued support for aerospace R&D and leadership in airspace modernisation. SAF also needs Government support internationally, with ICAO, to ensure that UK leadership does not stand alone.

AIRLINE CHIEFS’ RESPONSE TO GRETA THUNBERG

The first panel discussion, which was chaired by Michael Gill, Executive Director of the Air Transport

greenhouse gases as well as maintaining local air quality.

Jane thought the Covid-19 crisis provides an opportunity to shift aviation’s focus on to environmental technology in a world where funding focuses on innovation delivering environmental benefits.

In 2010, ICAO defined two aspirational goals to combat climate change: a 2% fuel efficiency improvement per year and carbon-neutral growth from 2020. She explained their progress since 2010. The first-ever ICAO Committee on Aviation Environmental Protection (CAEP) CO2 standards for aircraft and the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) are two examples. There has also been progress on SAF with over 200,000 commercial flights using ‘drop-in’ SAF.

CORSIA’s pilot phase starts in January 2021 with 88 states participating. Each batch of SAF requires certification to determine the CO2 saving attributable within the CORSIA system.

A parallel process is ICAOs Long Term Global Aspirational Goal (LTAG) involving 600 scientists and specialists. It is currently reviewing the environmental data and scientific developments to support the 2022 CAEP meeting and 41st ICAO assembly. The process looks at improvement within the aviation sector, plus the capabilities of others, eg energy generation sector, and takes account of Governments’ emissions commitments. This process includes a ‘stocktaking seminar’ to review the diverse options to reduce carbon emissions across all threads, ie technology,

A recent review from industry coalition Sustainable Aviation has confirmed that the UK could be home to up to 14 sustainable aviation fuel (SAF) production facilities across the country. Velocys.

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want to continue providing the benefits of aviation but in a way that is sustainable.”

Johan Lundgren also stressed the social and economic benefits offered by air travel. The industry can adapt and change and also help combat inequality by maintaining people’s ability to travel. “In addition to the economic benefits, there are many people out there who are missing the contribution that aviation can give to people’s lives. People who are very vocal against aviation are missing the idea that we can adapt and do something. We need to tell anti-aviation protesters that not only can the airline industry do something about the environmental problems but aviation can also combat inequality by allowing people to fly and travel more. It’s up to our industry with the regulators and other stakeholders to ensure that we have less impact on the environment.”

“I am very glad that Greta has stood up to raise awareness of climate change,” said Rob Gurney “However, we shouldn’t just focus on the awareness but also on encouraging those areas where the airline industry has made commitments and where work is being done to improve sustainability.”

HOW GREEN IS MY AIRPORT?

The final session of the day was a panel discussion with managers responsible for the environmental strategy of six major UK airports. The session was

Action Group (ATAG), looked at airline strategies towards the achievement of net zero emissions. He explained how the whole airline industry is already committed to reduce CO2 emissions to 50% of 2005 levels (a target of 325m tonnes) and that this would be a tough target to meet.

However, the airlines are not short of ambition. As the new CEO of British Airways, Sean Doyle, reminded us “We, BA, are part of the first airline group to commit to Net Zero Emissions by 2050 in October 2019.” BA is focusing on newer more fuel-efficient aircraft which was one of the reasons why it has now retired all its fleet of older four-engined Boeing 747s. He was excited about new technological developments in electric and hydrogen-powered aircraft designs but they were not expected to come into service until the 2040s and, even then, may only replace smaller, short haul aircraft.

Sean also stressed the need for a portfolio of solutions. Since over 70% of aircraft carbon emissions come from medium and long-haul flights, one short-term priority was the development of SAF to replace fossil fuel-derived Jet A1. BA was involved in a joint venture with Shell in Lincolnshire to produce SAF.

Johan Lundgren, CEO of easyJet said that the feedback from passengers emphasised the need to tackle the environmental issue. “We need a whole range of technologies to solve the problem,” he said. “easyJet is committed to carbon offsets and, as a short-haul airline, we’re excited about the prospects offered by hydrogen and electric aircraft. We’re now looking at how we can operate such aircraft. There are plenty of opportunities for companies to take the initiative but we have to start acting today.”

Rob Gurney, CEO of Oneworld Alliance, agreed that the issue of tackling climate change remained a priority. “We are happy to be the first airline alliance to commit to Net Zero Emissions by 2050 in September this year.” he said. “The Covid crisis has reinforced that commitment.”

Each speaker was asked what message they had for environmental activist Greta Thunberg and the flygskam (flight shaming) movement. “We’re taking this very seriously,” responded Sean Doyle. “Aviation has been the first sector to create a global framework and to commit to achieving the regulatory targets by 2050. Aviation is also a very innovative sector and has a track record of efficiency improvements. Our commitment to the environment is genuine and sincere.” He added “We

Airbus A350 of British Airways. Four aviation decarbonisation projects supported by British Airways and designed to help the industry achieve its targets of net zero carbon emissions by 2050, have recently been shortlisted for Government funding. British Airways.


from long haul flights.” As an incentive, Heathrow has decided to reduce airport charges for airlines which are using SAFs. “We’re also looking to better understand electric/hydrogen technology. We need to prepare for when that technology comes to market.”

“The decarbonisation of flight is our biggest challenge and we are one part of that strategy as we aim to have a carbon net zero airport by 2033” said Kirstin McCarthy, Head of Sustainability at Birmingham Airport. “We are in unusual times, so let’s have unusual ways of thinking. Now that everything has slowed, we can concentrate on carbon reduction but to do that we need collaboration and thinking things differently.” The priority for 2021 recovery is to clarify the work needed for net zero operations in 2033. Future infrastructure requirements are unclear. However, Kirstin stressed, “Airports are very adaptable.”

Rachel Thompson, Head of Sustainability, Gatwick Airport agreed. “Airports have always adapted infrastructure for changes in aircraft technology. We think that SAF may start to come into use around 2025, followed by the infrastructure for electric aircraft by 2030. However, SAF has to become able to compete with Jet A1.” The panel all called for government to encourage its development. Rachel also described a project at Gatwick introducing hydrogen-powered buses. “It is very interesting to see the familiarisation and safety-conscious journey that is needed to use hydrogen as a fuel source. When we start using hydrogen aircraft, the airport will already be familiar with its operation on the ground and the infrastructure needed. The development of hydrogen power in other sectors will help aviation learn but will also lead to competition for hydrogen with other users.” In summary, she said “There is no one silver bullet; we will have to look at a range of solutions.”

GREENER BUT ALSO MORE PROFITABLE?

The second day started with a keynote presentation from Chris Stark, CEO of the Committee on Climate Change (CCC), which advises Government on climate change matters. His presentation, entitled ‘The role of Aviation in Achieving Net Zero’, focused on its next report to Government due in early December. This will take into account the impact of Covid-19 and the result of the presidential election in the USA. It will make a number of recommendations to support achievement of the UK’s sixth Carbon Budget (mid-2030s) and its net zero target in 2050. These will include: international

chaired by Karen Dee, CEO of the Airport Operators Association (AOA), who said: “This has been an extraordinary year for airports. Post Covid, meeting the climate change commitment is going to be high up on the agenda.”

Adam Freeman, Head of Environmental Strategy at the Manchester Airport Group (MAG) (which operates Manchester, East Midlands and London Stansted), explained their aim of making Manchester a net zero airport by 2038. “However, it has to be remembered that airport emissions are only a small part of the whole pie. We also have to focus on the 99% of emissions which are airport relevant but don’t belong to us.” We can use SAFs in aircraft today but for new sources of power such as hydrogen you need to create the infrastructure. Hydrogen is versatile and has a lot of potential, for example to store renewable energy, generate clean electricity and take peaks off demand. It could also power the many vehicles used to load and unload cargo aircraft at East Midlands Airport. You could look at an airport not just as an airport but as an energy hub as part of a broader energy network.

Matt Gorman, Carbon Strategy Director at Heathrow Airport, said: “As a result of Covid, we’ve now seen what a situation with traffic reduction is like. Covid-19 has elevated the climate agenda ... post Covid-19, we will need to earn our licence to recover and also grow. New designs for electric and hydrogen-powered aircraft will only come in later so we need to concentrate for the moment on sustainable fuels. SAF is also currently the only solution for the 70% of emissions that come

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ZEROe is an Airbus concept aircraft. In the blended-wing body configuration, two hybrid hydrogen turbofan engines provide thrust. The liquid hydrogen storage tanks are stored underneath the wings. Airbus.


He discussed three future propulsion systems: battery, fuel cell and high bypass gas turbine and predicted that the gas turbine system would remain in operation for long distance flights due to that fuel’s higher power density.

Simon completed his presentation by describing the ATI FlyZero project which is to realise the design of a zero-emission commercial aircraft by the end of the decade. A team with a range of key capabilities has been established and he expected this project to contribute to the innovation recovery in UK aerospace needed to meet the challenge of net zero by 2050.

WHAT CAN INDUSTRY OFFER?

The first panel discussion of the day, entitled ‘Where Carbon Reduction Features in OEM’s Strategy’, featured speakers from the sector’s leading companies. Panel Chair, Colin Smith, Chair of the Aerospace Growth Partnership, noted the industry’s past performance and current situation but asked “Should a step-change in technology now be grasped to address the climate challenge?”

Rising to this challenge, Jacqueline Castle, Chief Engineer at Airbus UK, illustrated the continuous improvement in airframe development with the 20% increase in fuel efficiency of latest A320 design compared with forerunners. But this scale of improvement was not keeping pace with growth in demand or in emissions. She explained the Airbus intention to produce the world’s first zero emissions aircraft by 2035 and to look at hydrogen propulsion,

aviation and shipping within UK climate targets, supporting further R&D and deployment of new aircraft technology including SAF and managing demand and airport capacity as a backstop if efficiency gains plus SAFs and greenhouse gas removal under-deliver. The sixth Carbon Budget is a key milestone on the way to net zero in 2050 and Chris warned that a steeper decline in UK emissions is needed if we are to achieve net zero.

In response to audience questions, he was confident there would be sufficient green energy available to meet the demand by 2050 based mainly on offshore wind and the utilisation of hydrogen. Asked what impact hydrogen-powered aircraft would have on policy recommendations he felt that they would not play a significant role before 2050. He expected SAF to play an important role in aviation and also expected the 2050 net zero target to be achieved.

The next presentation was given by Michael Eberhardt, a Director of BlackRock Inc, the global investment management corporation and the world’s largest asset manager with $7.8tn under management. He explained sustainable investing at BlackRock and the importance to investors of Environmental, Social and corporate Governance (ESG). The following quote from his presentation summarises the BlackRock view: “Our investment conviction is that sustainability and climate-integrated portfolios can provide better risk-adjusted returns to investors. With the impact of sustainability on investment returns increasing, we believe that sustainable investing is the strongest foundation for client portfolios going forward.”

Michael described sustainability over the past ten years as the tectonic shift transforming investing and how returns on green equity were out-performing market-wide benchmarks. His concluding slide predicted that “confluence of forces across banking and the investment sector will likely drive rising expectations on climate for aviation.”

Dr Simon Weeks, Chief Technology Officer, Aerospace Technology Institute (ATI), gave a presentation entitled ‘Setting the Ambition for Sustainable Air Transport Technology’. He explained how sustainability targets had advanced over the past 12 years and described how ATI is helping to progress technologies that improve aerodynamic efficiency. One of the examples he presented was more efficient aerodynamics and this included higher aspect ratio wings, the introduction of folding wing tips, a laminar flow demonstrator and rear fuselage boundary layer ingestion. Simon showed the Airbus zero- emission blended-wing body concept aircraft.

The Pratt & Whitney PW1000G geared turbofan is delivering a 16% fuel burn improvement. Rafael Luiz Canossa.


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alternative fuels and enhanced operations. Multiple actions will be needed to dramatically reduce emissions.

Geoff Hunt, SVP Engineering and Technology at Pratt & Whitney, stated that while aircraft CO2 may only be about 2% of manmade global totals, the 4.5% compound annual growth rate requires revolutionary change. He reported that the hugely expensive geared turbofan developed over ten years is delivering a 16% fuel burn improvement with less pollutant emissions and noise. However, the scaling up of drop-in alternative fuels is also imperative.

Sean Newsum, Director of Sustainability Strategy at Boeing, identified with the strategies of fellow panel members flagging up the harmonised global approach through ATAG and ICAO. Pressures from Covid-19 would be felt for a while but he believed that commitments to net zero are solid within the sector and that achieving 2050 goals through one or two generations of technology will still need a massive boost in the penetration of alternative fuels.

ELECTRIC AND HYDROGEN SOLUTIONS

Electrification was discussed with energy density of batteries agreed to be a limiting factor. The E-FanX project has laid the Airbus groundwork now being taken forward through hydrogen. Geoff Hunt pointed out the challenge for longer flights where weight on landing would pose a big design challenge. Sean Newsum saw electrification being introduced in

EcoPulse is a distributed hybrid-propulsion aircraft demonstrator developed in partnership with Daher and Safran with the support of France’s CORAC and DGAC. Airbus is providing battery technology and overseeing aerodynamic modelling. Airbus.

small fixed wing aircraft as a proving ground for use in civil regional aircraft. Hybrid may add a few percentage points efficiency gain but the panel took the view that this is not a game-changer.

Hydrogen shows potential but huge technical challenges exist. Jacqueline Castle acknowledged the difficulties linked to the need for greater fuel carrying capacity. Airbus has set five years to tackle this and other design challenges if the target of a 2035 aircraft is to be realised.

The panel agreed that water vapour climate effects and possible enhancement of contrails require further academic work. Discussion of contrails noted that the debate was moving towards avoidance by changing flight altitudes together with advanced combustors. SAF could also reduce contrail generation but research remains critical and tests with aircraft using 100% SAF are taking place.

FALSE PROMISES?

The view from the NGO community was given by Cait Hewitt, Deputy Director of the Aviation Environment Federation (AEF), under the title ‘Can we rely on airlines’ promises to decarbonise?’ She reminded the conference that 2019 had the highest CO2 concentration on record and that September 2020 was the hottest September on record. She welcomed the airline sector's commitment to net zero but questioned if future significant growth should be allowed without additional taxes and charges.

Hewitt also questioned the industry’s confidence, noting that proposed solutions are not delivering as envisaged. Electric aviation may serve short-haul needs in time and hydrogen production would require green electricity to be of real value. Biofuels potential is limited and synthetic fuels derived from carbon capture may mature but the sector is still in its infancy. That means that airlines rely upon offsets but these are not a long-term solution and, while greenhouse gas removals are assumed for 2050, the incentive for airlines to be involved is not there.

Global level discussions and goals are important but small step actions at the national level are essential and the UK can lead. Aviation should be included in the UK 2050 goals, better regulation on caps and non-CO2 emissions are needed and ticket prices should not be cheaper for air than rail. Environmental costs should be internalised and better information made available to the public. A smaller leaner sector with less flying should


be seriously considered. On taxation, the AEF is awaiting the Treasury view but generally, if there are carbon removal costs ahead, money should be drawn from the sector to pay.

Cait also warned the industry of potential noise issues (from AEF members) associated with airspace modernisation for greater efficiency. On acceptance of flight path changes, the AEF view was that the rationale of greater environmental efficiency may actually be more about achieving greater capacity.

In summary, she agreed with and welcomed the SA vision of net zero but regulatory and financial mechanisms do not exist to ensure delivery. The AEF participates in the Jet Zero Council looking at radical approaches but still advocates less aviation overall to make the problem manageable.

THE ROLE OF SUSTAINABLE AVIATION FUEL

The final panel session of the conference considered the outlook for SAF. The Chair, Robert Boyd, Manager Environment – Alternative Fuels at IATA, explained that, with airlines set to lose $100bn this year, the outlook for SAF has never been more challenging – yet SAFs have never been more needed. He explained that he was looking to hear about real projects, how SAF stacks up against hydrogen and electric, and an assessment of what needs to happen in the next five to ten years to meet the 2050 goals.

Both fuel companies on the panel sounded positive. Tom Parsons, Commercial Development Manager – Low Carbon (Air bp), said that the industry is aligned on the need to take action with multiple stakeholders helping to develop the sector. BP has recently signed a deal with Swedavia to supply renewable fuel and their first Municipal Solid Waste project is coming on stream in the coming months. The industry would need clear policy, as much global alignment as possible and significant investment in SAF production. Air bp will partner with SAF suppliers and be a SAF supplier itself, and will be co-processing with renewable diesel, that is to say simultaneous conversion of biogenic residues and intermediate petroleum distillates in existing petroleum refineries for the production of renewable hydrocarbon fuels. Air bp’s aim is for 20% of their aviation fuel to be SAF by 2030.

Bryan Stonehouse, General Manager Sustainability and Risk, Shell Aviation, underlined Shell’s own commitment to be zero carbon by 2050. Shell is linked up with Velocys, has its own proprietary

waste to fuel technology in Bangalore, and has an arrangement with Amazon to provide renewable fuels in San Francisco. In addition to SAF, they are also working on synthetic fuels and renewable hydrogen. He anticipates more change in the sector in the next ten years than has been experienced in the past 50 years and sees this as a real licence to operate issue. A range of technologies will be needed together with regulatory certainty and a closure of the cost gap. Co-processing is an interesting pathway for Shell but not the only one. There does not seem to be any winning technology, in Bryan’s view. Some of the newer technologies are not at the scalable level, but hopefully they will get there. In the meantime, there is the Hydrogenated Vegetable Oil (HVO) process using cooking oils and tallow that is available today.

There is a need to create the correct landscape for demand, which is a current area of focus for Shell.

Rachel Soloman Williams, Head – Low Carbon Fuels, Department for Transport (DfT), confirmed that the UK government is keen to show the way in aviation. As head of all low carbon fuels within the DfT, her focus has been on road fuel until recently, but now the balance is shifting. She is expecting the Jet Zero Council to come up with some key suggestions. Also there has been a positive response to changes in the Renewable Transport Fuels Obligation (RTFO), where aviation fuel is now encouraged but not mandated. A new category of development fuel has been created,

Airbus has taken the next step in reducing its industrial carbon footprint with the maiden flight of a Beluga super-transporter using sustainable aviation fuel (SAF) from its Broughton plant in the UK. Airbus/Jane Widdowson.


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Robert Boyd felt the UK is a global leader in terms of ambition and that after February 2021, he expects the SAF innovation and development momentum to shift from the USA’s West Coast to Europe. Panellists’ views on the likely speed of SAF penetration varied but all agreed that 2% by 2030 was a reasonable ambition which would trigger much larger use of SAF in later years.

At the end of the conference the Chief Executive Officer of the Royal Aeronautical Society, Sir Brian Burridge, gave a presentation linking the current crisis, the climate change response and the need for future careers in aerospace and aviation.

Geoff Maynard closed the conference by saying “We’ve had a good look at the vision that many people have for the industry over the next 20/30 years.” He thanked sponsors, speakers and delegates for a very enjoyable event.

with such fuels being eligible for a much higher number of certificates than standard biofuels. There have been no renewable aviation fuel submissions (claims) to date but there has been a lot of interest in the past year. If these fuels receive certificates, someone will then need to buy them and that is the bit that needs to be addressed now.

Leigh Hudson, Sustainable Fuels and Carbon Manager, International Airlines Group (IAG) spoke encouragingly about the sustained commitment to low carbon across the sector, in this very difficult period. There is great interest in electric and hydrogen but customers are also interested in both SAF and offsets. She echoed the view that there is no sense of there being a winning fuel solution: all are necessary. IAG are encouraging a diverse approach and now have 12 low-carbon projects: most are SAF, with the Velocys waste-to-fuel project in Lincolnshire receiving planning permission earlier this year. But there are also Carbon Removal and Carbon Capture projects.

Leigh pointed out that in the UK a lot of waste is used for producing electricity. This approach leads to high carbon emissions and there are much lower carbon sources of electricity such as offshore wind. If the waste were used as an aviation fuel feedstock these high emissions could be avoided. IAG is also looking at Low Impact Land Use Change options, including new crop strains and drawing upon the UK’s plant science expertise.

The panel discussed Europe’s Green Deal and the proposed ReFuelEU initiative. The chair and panel could all see both benefits and risks in the proposal. Overall, they felt that the initiative could, with care, be helpful but there was a risk of perverse incentives and new technologies would need to operate at scale.

Household waste could be turned into feedstock for aviation fuel. D’Arcy Norman.


Bill Read


Mitigating the climate impact of non-CO2 – Aviation’s low-hanging fruitConference ReportOn 23-24 March 2021 the Royal Aeronautical Society hosted a joint conference shared between its Greener by Design group and the Institute of Atmospheric Physics of DLR, the German Aerospace Centre at Oberpfaffenhofen. The event was organised by the Contrail Avoidance Group, an informal body formed after the GBD conference in 2015 by members of Greener by Design with members from DLR, NATS and UK universities. Several members of the group gave presentations to the conference. The rationale for the conference was that within the scientific community there was now fairly solid agreement that the non-CO2 effects of aviation are responsible for two thirds of its impact on climate. The strongest impact is from contrails

and contrail cirrus, with the impact of NOX emissions at altitude also contributing. For both these impacts, the prospects of substantial reductions are real and potentially realiseable within a far shorter timescale than the options for reducing CO2 emissions. Hence the ‘low hanging fruit’ in the title of the conference.

The conference was a virtual, online event divided between two afternoons. The presentations were grouped under the headings ‘The Science Base’ on the first day and ‘Mitigation Possibilities’ on the second. The event was chaired by Geoff Maynard, chairman of Greener by Design. In his opening remarks, he emphasised that, while the subject of aviation’s non-CO2 effects was potentially wide-


ranging, he wanted the conference to concentrate on its theme of mitigating the climate impact of these effects.

DAY 1: THE SCIENCE BASE

Keynote address

The meeting opened with a keynote address by Robert Sausen, Head of the Institute of Atmospheric Physics at DLR. The talk, entitled ‘Climate impact of aviation’s non-CO2 emissions-An overview’, covered all aspects of aviation’s climate impact but then focussed on the non-CO2 impacts and the options for mitigating them.

For CO2 emissions, he showed that, even with carbon-neutral growth after 2020 as projected by ICAO, the impact of aviation’s CO2 on temperature will continue to grow for the rest of the century. By 2100 the projected temperature increase will be more than three times the increase in 2020 There is quite a spread in the projections to 2100, depending on the assumed IPCC RCP (Representative concentration pathway), but the importance of CO2 emissions from aviation is starkly clear.

He presented the most recent estimate by Lee et al(1) of the impact of the various contributors to warming, expressed (Fig 1) as the now-preferred Effective Radiative Forcing (ERF). Alongside the figure he made three points:1. The non-CO2 effects contribute at least 2/3 of

the total aviation ERF.2. Non-CO2 effects also occur if alternative fuels

are used, in particular H2.3. The magnitude of the non-CO2 effects depends

on location and time of the emissions.

Among the non-CO2 impacts he highlighted the evolution of the perceived climate impact of NOX. This is shown in Fig.1 as a net positive contribution, the result of the effect of the increase in ozone being greater than that of the reduction in methane, both greenhouse gases influenced by NOX emissions. After a re-evaluation that increased some of the negative methane effects, the NOX contribution in 2005 had fallen from an estimated 13.8mW/m2 in 2009 to a value of 4.0mW/m2. This effectively demoted NOX as a climate issue, leading to the

conclusion that besides CO2 only contrails play a significant role in aviation’s contribution to climate change. However, in 2019 Volker Grewe and his colleagues at DLR published a paper(2) drawing attention to two methodological flaws in the analysis underlying this conclusion. Their analysis increased the estimated positive contribution of ozone and reduced the negative impact of the methane reduction, leading to an increase in the NOX RF in 2005 to 26.7mWm2, very similar to that of CO2. This is discussed further below.

He discussed various mitigation measures, including the concepts for Europe set out in the EASA report of 2020(3), demonstration of contrail avoidance by ATM and eco-efficient flight trajectories. All of these were presented by other speakers and are covered later in this report.

In his closing remarks he re-emphasised the importance for the aviation sector of its non-CO2 effects, the need for suitable metrics to support strategic decisions on mitigation measures and the range of mitigation measures available.

Oxides of nitrogen

The next two presentations addressed different aspects of the climate impact of NOX. This is the mixture of NO and NO2 that is produced in the high pressure and temperature conditions in an engine combustion chamber by the combination of atmospheric nitrogen and oxygen. They are not greenhouse gases but at altitude enter into complex chemical reactions that result in an increase in ozone concentration and a reduction in methane concentration, both strong greenhouse gases.

Left: The DLR Advanced Technology Research Aircraft (ATRA) A320 leaving contrails while using alternative fuels. The photo was taken from a DLR Falcon during the 2015 ECLIF-I research flights. DLR.

Figure 1. Current estimate of contributions from aviation to effective radiative forcing. Lee et al (2021).


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Agnieska Skowron of Manchester Metropolitan University discussed the effect of future atmospheric background composition on NOX climate impact in the longer term. Emissions from aircraft and from sources on the ground both influence the background level of NOX at cruise altitude, the emissions from aircraft having about twice the effect of those on the ground. The NOX emissions at ground level are expected to reduce by 2050 leading to a cleaner upper atmosphere, which will reduce the climate impact of NOX, but this will be offset if NOX emissions in cruise continue to increase.

Higher background NOX causes increased RF from ozone but also reduced RF from methane, this reduction being greater when the most recent modelling of the effect of methane is adopted. The projected background concentration of NOX in 2050 is rather uncertain and Agnieska’s analysis indicates great uncertainty in the RF due to aviation NOX. Because of the predicted stronger negative effect from methane, the net RF might even be negative in 2050. The paper notes that measures to reduce engine NOX emissions increase fuel burn and CO2 emissions, which undoubtedly have an adverse climate impact. Combined with the above uncertainly in the NOX RF in 2050, the paper argues that the priority for industry should be to reduce CO2 emissions rather than NOX.

One point that may be noted in the presentation but was not discussed at the meeting is that the baseline adopted in the modelling gave a net NOX RF of around 4. This is the modelling that, as noted above by Robert Sausen, had been challenged by Grewe et al in 2019. By correcting for what they argued were two methodological flaws, they had proposed that NOX RF in 2005 should be put at 26.7 rather than 4.0. This discrepancy needs investigation and resolution. It could have an important effect on the paper’s main conclusion.

The next presentation was by Volker Grewe of DLR, who addressed the current assessment of NOX impact and its dependence on time and place of emissions. The talk was divided into two parts, the first discussing the important effect of weather and the second revisiting the diagnostics to calculate NOX RF.

The importance of weather was illustrated by observing the climate impacts of NOX emissions at two locations on the same flight path on the same day. The first location was in a branch of the jet-stream that was diverted northwards by a blocking region of high pressure, the second location was in

the centre of the high-pressure region, from which air eventually moved southwards towards the topics. Over a lifetime of 90 days, the different histories of ozone formation and methane reduction along the trajectories of the packets of NOX emitted at the two locations was striking.

The observation of this strong dependence on weather at the point of NOX emission led to the development of the concepts of climate change function and of climate optimised routeing. The substantial body of work supporting these concepts was summarised in the presentation. It has been followed by an exploratory ‘proof of concept’ investigation, comparing cost-optimised routes with climate optimised routes which direct traffic around ‘climate sensitive’ regions. The preliminary indications are that a 2% reduction in NOX RF can be achieved in this way. This topic of climate optimised routeing will be studied further at DLR in the CLIMOP and ACACIA projects and also in the European FlyATM4E programme.

The second part of the presentation considered the way that the contributions of NOX emissions to ozone and methane are diagnosed. Differences in approach can lead to very different results. A key issue is the evolution of methane, which is a relatively long-lived gas with the steady state perturbation from current emissions not reaching an equilibrium level for more than 30 years. He compared the radiative forcing calculated for methane in 2018 on the basis of the NOX emission levels in 2005 taken as a reference for three different models. The first was with NOX emissions held steady at their level in 2005, the second was for their growth being linear through the 2005 level from zero in 1940 and the third was for their real growth since 1940 which by 2018 have reached

Crisscrossong contrails. Erik van Wees.


about twice the level given by linear growth. The difference in the calculated methane negative RF between steady state and linear growth in emissions by 2018 was a reduction of around 21%. The linear transient growth was the basis of the modelling in Ref 1. The difference between steady state and real growth by 2018 was a difference of 42%.

A further point in the presentation was the difference in the predicted ozone impacts between the ‘perturbation’ method and the ‘tagging’ or ‘contribution’ method. This was illustrated by modelling the hypothetical case of eliminating the ozone emissions from road traffic, which account for about 12% of the contribution to the atmospheric ozone column. The effect of removing road traffic as a source was a compensating response in which the efficiency of ozone creation by other sources increased. The result, applying the contribution method, was that the reduction in the ozone column was 2% rather than the 12% given by the perturbation method. At present only one study of aviation’s climate impact has been published that has used the ozone contribution method. The results were noted in ref 2, cited already by Sausen and set out in Table 1.

Volker went on to note that what he asserts are the correction of flaws shown in this table would, if applied to the results shown in Fig 1, double the ERF of NOX, from 17.5mW/m2 to 35.2mW/m2. This would make the ERF from NOX slightly greater than the 34.3mW/m2 attributed in Fig 1 to CO2. He did not say so, but if accepted, this would substantially change views on the priority to be given to reducing NOX emissions at cruise. He ended with a proposal that there should be further research into the methods of diagnosis used to assess the impact of NOX emissions. The present divergence needs to be resolved.

Contrails and contrail cirrus

The next three papers considered current evidence on persistent contrail occurrence, beginning with a presentation by Klaus Gierens of DLR on ‘Contrail Statistics, Big Hits and Predictability’. He began by noting the 58% downward adjustment in Ref 1 from radiative forcing (RF) to effective radiative forcing (ERF) for contrail cirrus, an adjustment that does not apply to the RF from CO2. With this adjustment, the global values given in Ref 1 for 2018 are 34.3mW/m2 for CO2 and 57.4mW/m2 for contrail cirrus. Contrail cirrus provides by far the largest contributor to aviation’s ERF in 2018 which, in total, Ref 1 puts at 100mW/m2. He highlighted the units here – aviation’s total global ERF is measured in mW/m2.

For individual contrails, he went on to show that the net RF can be two to three orders of magnitude greater than this, in the range. 10 to 100W/m2. This includes both strong cooling cases in the daytime and strong warming at night. These strong effects arise only from persistent contrails, with lifetimes of the order of several hours, which form only in ice supersaturated regions (ISSRs). About 15% of all flight distances are in ISSRs, but a minimally invasive strategy would be to avoid only those contrails with the strongest warming effect. This idea, to avoid only the ‘Big Hits’, emerged from a conversation with a DLR colleague, the late Hermann Mannstein. Big Hits comprise only 1-2% of all flown flight distances and offer a powerful handle for reducing climate impact. To pursue a strategy of avoiding them requires the ability to:n predict contrail formation (Schmidt-Appleman

criterion);n predict contrail persistence (ice supersaturation);n predict individual contrail forcing.

The first two of these can be provided by the ECMWF. The DLR CoCiP (Contrail Cirrus Prediction) code provides the latter.

Lee et al 2009 Additional Revised methane Correction of flaws (PMO, SWV) processes RF formula #1 methane #2 ozone lifetime contribution method

Ozone 26.3 26.3 26.3 26.3 41.2Methane –12.2 –12.5 –15.4 –10.0 –10.0PMO –5.0 –5.0 –3.3 –3.3SWV –1.9 –1.9 –1.2 –1.2Total NOX RF 13.8 6.9 4.0 11.8 26.7

Table 1. Radiative forcing of aviation NOX emission in 2005 in mW/m2.


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The presentation reported a recent assessment of the accuracy of the ECMWF forecasts. Relative humidity data collected in flight on instrumented civil aircraft in the IAGOS programme were compared with predictions for the same time and place drawn from the ERA-5 (EMCWF re-analysis) data set. Predictions of the Schmidt-Appleman criterion were found to be reasonably good but not predictions of ice supersaturation. The conclusion was that the current ability to make on-the-point and bang-on-time prediction of ISSR location needs to be improved. Further assessment led to a more positive conclusion. Regional contrail forecasts by ECMWF, seeking regions where persistent contrails might appear, are satisfactory for planning research flight campaigns. Further analysis showed that forecasting accuracy was improved by using a threshold of less than 100% for RHi (relative humidity with respect to ice). The basic forecasting capabilities are sufficient for giving ATM instructions on contrail avoidance but further work to improve ISSR forecasting is needed. Further work is also needed to build a statistically robust characterisation of Big Hit situations. However, even at this stage, the avoidance of night-time contrails in the winter months, when most of the impact of Big Hits occurs, appears to be practicable with present weather forecasting capability.

The presentation which followed, by Ulrich Schumann of DLR, reviewed the evidence on contrails that has been provided in 2020 following the drastic reduction in air traffic under the Covid-19 restrictions. He began by emphasising the importance of observation.in developing an understanding of the radiative effects of contrail cirrus. This was strikingly illustrated by the demonstration, from satellite data, of a double hump in the graph against time of cirrus formation and outgoing long wave radiation over the Atlantic. The double hump was shown to correlate with the two peaks, morning and evening, in transatlantic air traffic. The peak in the contrails lagged about three hours behind the peak in the traffic, corresponding

to the time needed for the contrails to grow to be observable by satellite.

The Covid shutdown caused a reduction of 92% in air traffic over Europe in April 2020 and a reduction of 72% over the six-month period from March to August, an unprecedented event. Contrail coverage over Europe with an optical depth greater than 0.1 decreased from 4.6% in 2019 to 1.4% in 2020. The reduced contrail coverage caused 70% less longwave, 73% less shortwave and 54% less net RF. Demonstrating the impact of the shutdown was complicated, however, by the very different European weather in 2019 and 2020, which made it difficult to quantify the difference in the contrail impact between the two years. The study confronted this challenge by using two tools to evaluate contrail thickness and outgoing radiation. One used the DLR CoCiP model together with weather data from the IFS (Integrated Forecasting System) of the ECMWF, the other used the Meteosat-SEVERI observation results. Comparisons between the two methods were shown for six-month averages, for 2019 and for the differences between 2020 and 2019, of contrail optical thickness (OT), outgoing long-wave radiation (OLR) and reflected solar radiation (RSR). The positive effect of introducing the CoCiP model is clear from Table 2, which shows the statistics of the difference between the satellite observations and predictions by the IFS, with or without CoCiP. The tables show that, particularly for optical thickness and outgoing long-wave radiation, the correlation coefficient r, Normalised Mean Bias and Root Mean Square Error are all considerably better for the predictions which include CoCiP.

The air traffic reduction during the Covid-19 pandemic has provided a test case for aviation RF that will generate further studies, including a planned assessment of the 2019-2020 contrail differences over a 12-month period. Results to date are encouraging, however, showing that contrail signatures are identifiable despite strongly different atmosphere and surface conditions in 2019 and

Period Parameter Without contrail model With contrail model RMSE unit r2 NMB RMSE r2 NMB RMSEMAR-AUG OT 77.7% –21.4% 0.024 85.4% 9.8% 0.022 1 OLR 93.1% 29.6% 1.46 95.2% 13.5% 0.98 Wm–2

RSR 82.8% 5.5% 3.57 82.9% 12.9% 3.60 Wm–2

MAR-MAY OT 88.7% –30.8% 0.040 91.1% –12.8% 0.034 1 OLR 97.7% 9.1% 1.81 97.9% 1.3% 1.55 Wm–2

RSR 92.7% 4.2% 5.31 92.4% 7.7% 5.42 Wm–2

Table 2. Statistics of the effect of the Covid shutdown of air traffic on the radiative characteristics of contrails over Europe.


2020. The implications of the study are:n Contrails RF is highly variable, locally far larger

than any other aviation RF;n Contrails RF can be predicted for given traffic for

the next days with IFS/CoCiP;n Contrail cirrus cover/irradiance predictions can

be validated with METEOSAT CiPS/RRUMS.

The overriding message is that the mitigation potential is large and the methods now available are capable of testing it.

The third presentation on contrails was by Luca Bugliaro of DLR, whose subject was contrail and contrail cirrus observations by satellite. The presentation was in two parts, the first on the potential and challenges of contrail evaluation tools and the second on the properties and radiative effect of a contrail cluster during its life cycle.

The first part, on contrail avoidance strategy, reviewed practical requirements discussed by earlier speakers but then focussed on the challenges of identifying, measuring and monitoring the development of contrails by satellite. The basic tool is the automated contrail detection algorithm (CDA) developed by Mannstein at DLR in 1999 and since adapted to Meteosat Second Generation and MODIS and used internationally in a wide range of studies. There is a difference in resolution between images from orbiting and geostationary satellites. The first pass over an area four times a day and have higher spatial resolution. The latter produce images every five minutes of the same area of land and have high temporal resolution, enabling close tracking of contrail development and movement. Sample images showed that this process on its own is not wholly reliable, missing some contrails and in other

cases producing false alarms. It can be improved by using air traffic data and also combining weather data with the contrail prediction tool CoCiP, which helps to account for the spatial and temporal shift with respect to air traffic and also helps to reduce false alarms. Even so, Bugliaro’s current view is that evaluating contrail avoidance measures in ISSRs, is a challenging task that requires much effort and large statistics. It cannot be taken for granted.

The second part of the presentation was on a case study of a contrail outbreak on a particular day, which was explored by the DLR HALO research aircraft and by a range of satellite-based methods. The satellite observations provided information on contrail properties and radiation through the day, from 05.00 to 18.00, supplemented by observations by the HALO aircraft in mid-afternoon. The contrail cluster formed in an initially clear sky, its optical thickness predicted by CoCiP increased steadily until about 15.00 and then declined to about 1/3 of its maximum value by 18.00. In parallel there was a growth in natural cirrus from zero at 11.00 to a significant plateau by13.00. The results for the radiative effect for the cluster was that the outgoing long-wave radiation stayed at 20W/m2 between 09.00 and 17.00. The reflected solar radiation fell below –20W/m2 between 13.00 and 16.00 but then reduced in magnitude rapidly in the evening. The net radiative effect was thus a warming of around 10W/m2 in mid-morning, falling to a slightly negative value in early afternoon and then rising again to around 10W/m2 by 17.00. While listing areas in which further research was needed, he echoed the point made by Klaus Gierens and Ulrich Schuman that the observed outgoing radiation, at 20W/m2, is about 200 times the total RF attributed to aviation.

The afternoon session concluded with a round table discussion chaired by Professor Helen Rogers of NMITE and involving all the day’s speakers except Agnieska Skowron. It was a lively and wide-ranging discussion which ended with a fair degree of consensus. To avoid repetition, the outcomes of the discussion are reported in the presentation by Helen Rogers which opened proceedings on the second day.

DAY 2: MITIGATION POSSIBILITIES

To provide a background to the day’s discussion of mitigation, the day began with a summary by Helen Rogers entitled ‘What have we learnt during Day 1: The Science Base?’. This was a review of the perceptions agreed in the round table discussion

Boeing 777 of Air France. Sergey Kustov.


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that closed proceedings on Day 1. Her conclusions were:n Major improvements in the science

understanding have been made;n Non-CO2 effects are very large for aviation and

depend on location and time;n Our understanding of contrail cirrus has improved

significantly, as evidenced using data from the Covid-19 pandemic lockdown;

n We now have the first calculations of the indirect effect of aerosols on cirrus although the range is very large;

n Air traffic is not always fuel optimised, so mitigation is possible without increased CO2 emissions, although this still requires validation.

What still remains:1. We need to define an appropriate optimal

metric(s) depending on our endpoint goals;2. Additional/better Relative Humidity

measurements in the UTLS region are required if we really want to focus on accurately determining Ice Super Saturation and testing model predictions;

3. Weather predictions of Relative Humidity in the UTLS need further validation;

4. Important to consider emission contribution when modelling aviation’s impact;

5. Aviation needs a step change approach to reduce its climate impact significantly.

What can we do to address these issues?1. Focused science research on optimal metrics;2. Aviation can help improve observations by in

situ measuring during operations as well as supporting other measurement initiatives;

3. Aviation should call for validation of RH predictions from NWP providers;

4. Perturbation and contribution methods are both of value and can help answer different questions;

5. Industry should prepare for SAF.

Possible first steps:n Minimising contrail RF by route changes may

be an option for future sustainable air transport but industry needs to demonstrate the route optimisation can be implemented operationally;

n Further research is required to determine appropriate, reliable metrics and estimates of aviation’s climate impact, together with accurate predictions of regional and temporal distributions.

In the discussion that followed it was agreed that demonstrating the practicality of contrail avoidance with minimum fuel burn penalty was a top priority, along with the need for improved relative humidity

forecasting in the UTLS and the development of appropriate metrics from the climate impact of short-lived emissions.

Emissions Reduction by Engine Technology

The next presentation, with the above title, was by Paul Madden of Rolls-Royce. He reviewed the company’s wide range of activities to reduce emissions. For smaller aircraft they are exploring more electric pathways with emphasis on battery technology. They are also investigating hydrogen powered gas turbines for regional aircraft. For larger aircraft, which will rely on kerosene powered gas turbines for the foreseeable future, they are working to clear the way for the use of 100% SAF as against the current 50% limit.

As regards the non-CO2 emissions at cruise, which are determined primarily by the design of the combustor, the one with greatest climate impact is NOX. Emissions of NOX in the landing and take-off area (LTO) are constrained by ICAO regulation. The regulation applies only to LTO NOX and, although there is some link between this and NOX at cruise, there is currently no proposal to limit its level at cruise. ICAO has now also established limits on nvPM (non-volatile Particulate Matter) in the LTO area, again as a health measure. Whether or not this limit has any bearing on contrail formation is unclear, but LTO NOX and nvPM are now two emissions that are regulated by ICAO and potentially subject to increased stringency in future.

The presentation briefly described the technology of the RQL (Rich Burn Quick Quench Lean Burn) combustor, which is the low NOX combustor in the current family of large Rolls-Royce engines. This was a significant advance on previous designs but has reached its limits. The paper went on to describe in detail the lean burn combustor developed in the ALECSys (Advanced Low Emissions Combustion System) programme. This combustor has fuel staging, with a rich burning pilot at its core for low power stability, switching to the lean burning main burner for low NOX and near zero nvPM at high powers. An important part of the ALECSys programme was the development of the control laws and control system to ensure that the cross-over from pilot to main occurs at the right power level. This is dictated by efficiency, operability and nvPM emissions. The near zero nvPM emissions at cruise power should reduce contrail formation, but this needs further study to confirm.

Current in-production engines are being improved to reduce the LTO nvPM at the expense of some


increase in LTO NOX. What effect if any this has on cruise NOX was not stated. For the ALECSys engines, however, the reduction in NOX emissions at cruise will be appreciable. The ALECSys combustor system has been through an extensive ground testing programme on two Trent 1000 engines, which included fully satisfactory tests on a 100% HEFA SAF (Sustainable Aviation Fuel derived from Hydro processed Esters and Fatty Acids). Flight testing of the two ALECSys demo engines on the Rolls-Royce Boeing 747 flying test bed is planned in the coming months.

Mitigating Contrail Impact

The first of four presentations addressing this subject was given by Christiane Voigt of DLR. Her title was ‘Reducing the climate impact of contrails by SAF and contrail avoidance’. Her first theme was the beneficial effect of substituting a sustainable fuel for Jet A1. She showed results from the international multi-agency ECLIF2/NDMAX campaign in 2018 which included flight tests in which an instrumented DC-8 captured data in the wake of DLR’s ATRA A320 aircraft. These were the first experiments to provide in-flight measurements of soot and ice particle numbers for a range of alternative SAFs. They showed a linear reduction in soot particle number and a steeper reduction in ice particle number with reducing % volume naphthalene content of the fuel. When translated into impact on contrail formation, however, the effect is found to be non-linear, a 50-70% reduction in ice numbers leading only to a 20-40 reduction in contrail RF. Key messages from this work are: substitution of biofuels can provide a reduction in

contrail RF without any question of it being offset by increased CO2 emission; fast implementation in the fuelling system is possible; non-linearity requires stronger reductions in aromatics, hence regulations to lower the maximum levels of aromatics in fuels, with a certification target of 100% SAF.

In support of this aim, a joint programme between Airbus, Rolls-Royce, DLR and the SAF supplier NESTE began in January 2021. The programme, ECLIF3, is based at Toulouse and involves ground and flight trials with an Airbus A350-900 as the test vehicle and the DLR Falcon 20-E as the chase plane. It will be the first in-flight study of 100% sustainable aviation fuel on a commercial passenger jet and will investigate all aspects of emissions, including those relevant to contrail formation. First in-flight measurements are planned for April 2021.

The effect of the lockdown in 2020 was studied by a multi-agency project in BLUESKY, using the DLR HALO and Falcon aircraft to collect atmospheric data. The data relevant to contrail formation were for one day only and are consistent with the data for a longer period reported by Schumann above. Future DLR flight programmes include the multi-institute CIRRUS-HL mission on the HALO aircraft which will investigate contrail cirrus particle microphysics and shape, and soot cirrus. There will also be day-night flights to investigate cirrus radiative effects and it is intended to have a dry run of a contrail avoidance test, In addition, data will be gathered to extend previous DLR work to assess the quality of weather forecasting in the UTLS, which is believed to need improvement, particularly for relative humidity. The presentation concluded with an outline of the studies of cloud physics currently planned in five flight programmes involving DLR. These are ECLIF 3 and CIRRUS-HL described above; ECO2FLY investigating emissions from lean combustors on a bizjet, due to begin in October 2021; H2CONTRAIL, an investigation from 2021 to 2025 of contrails from hydrogen; and from 2022 to 2026 Project WandeLH2B, a further investigation of hydrogen propulsion.

Mitigating aviation contrails was the title of the following presentation, by Marc Stettler of Imperial College, London. He outlined the physics behind the formation of persistent contrails and contrasted the effects of daytime and night-time contrails. Daytime contrails both cool the earth by reflecting incoming sunlight and warm it by trapping outgoing long-wave radiation. After sunset, night-time contrails only trap the long-wave radiation. Not all contrails are created equal. Their impact on climate depends on meteorological conditions, engine particle

The view of the A320 ATRA’s exhaust plume taken from the trailing DLR Falcon during their ECLIF flight campaign in 2015. DLR.


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emissions, diurnal and seasonal cycles and surface albedo.

Options for mitigation include alternative fuels to reduce particle emissions, cleaner engines for the same reason, and flight diversion to avoid ice supersaturated regions (ISSRs). Only the latter two options were addressed in this presentation. Figure 2 illustrates the idea of diverting to avoid an ISSR, as proposed by the late Hermann Mannstein of DLR

The paper(4) on which the presentation is based describes a study of this kind of diversion, applied to six one week periods of air traffic between May 2012 and March 2013 in Japanese airspace. The climate impact of the contrails created by this air traffic was calculated using the DLR CoCiP code. The metric for the impact was the energy forcing EF of an individual contrail, determined by the integration with time over its life of the product of its length and width and its local RF. The energy forcing from the CO2 emitted during the flight is determined from the Global Warming Potential of the mass of CO2 emitted during the flight integrated over time horizons of 20, 100 and 1,000 years The main comparisons in the paper adopt a time horizon of 100 years.

The paper showed the fleet-level results in terms of the distributions in time of flights forming contrails and of their contrail EF. Overall, only 17.8% of flights produced contrails. A more striking finding, however, was the concentration of the energy forcing into a still smaller proportion of flights. Figure 3 shows the results of ranking contrails in terms of their energy forcing EF, with cumulative EF plotted against the proportion of total flights. The chart shows that 2.2% of flights account for 80% of the total contrail EF. This aligns with the Big Hits concept advocated on Day 1 by Gierens and leads to the conclusion that a fleetwide diversion strategy is not necessary.

The study found that the contrails producing the largest EF were produced typically between 15.00 and 06.00. A small-scale diversion approach was adopted. For every flight which produced a high EF contrail, the EF was calculated for diversions of ±2,000ft and the trajectories with the lowest EF selected. Up to 10% of all flights were allowed to divert at a time. Overall, it was found that diverting up to 1.7% of flights could reduce the contrail EF by 59%. The average fuel burn penalty and additional CO2 emissions for each diverted flight was 0.27%. For the fleet overall, the fuel burn and CO2 penalty was 0.014%. The effect of introducing cleaner engines into the calculation was assessed by applying the diversion strategy to those aircraft with DAC (double annular combustor) engines, which reduce contrail EF by about 40%. Table 3 compares the effects of diversion, DAC engines and a combination of the two. It is assumed there is no change in fuel efficiency for DAC engines.

The presentation which followed was by Rüdiger Ehrmanntraut of Eurocontrol. Its subject was the 2021 live trials for contrail prevention at Maastricht Upper Area Control (MUAC). This control centre handles all air traffic above 24,500ft over Belgium, Luxembourg, the Netherlands and north-west Germany. It is the third busiest upper area control centre in Europe.

Airlines were informed by NOTAM that, from 18 January 2021 to 31 December 2021 between 15.00 to 05.00 UTC in winter and 14.00 to 04.00 UTC in summer, MUAC will be running a contrail prevention trial. During this period, flights may be tactically requested by the sector controller to deviate from the planned/requested flight level. The purpose of the project is to establish and test a procedure that avoids persistent contrails in

Figure 2. Contrail avoidance concept proposed by Mannstein. DLR (Mannstein et al).

Selected FLs according to fuel use

optimum

Figure 3. Distribution of cumulative contrail energy forcing across fleet.


the MUAC area of responsibility. The trial is being run jointly with DLR, using numerical predictions of relative humidity and temperature by DWD (Deutscher Wetterdienst – ICON).

The trial aims to answer a number of questions:n Can we organise air traffic such that areas which

allow the formation of persistent contrails can be avoided?

n Can we predict the formation of contrails with a reasonable skill?

n Can we predict the formation of persistent contrails with a skill that is sufficient for deviating air traffic?

n Alternatively, can we detect ISSRs and avoid them in real time?

It is too early to have validated results (after six weeks of trial, every other day, in the winter season with low ISSR). Traffic downturn due to the pandemic allows for tuning systems and procedures while minimising impact for airline operators. The feasibility of adapting operational working processes needs to be assessed, while avoiding additional workload and impact on ATM capacity. The climate benefit of contrail avoidance must be validated against additional CO2 emissions and the costs of additional fuel burn plus the CO2 charging scheme on top.

A key issue is the accuracy of ISSR prediction. The MUAC concept is for tactical air traffic control with real-time online decision making. The preference therefore is to have a real-time online ISSR observation system in addition to a predictive system. The question is raised as to whether this can be achieved by current generation satellites and ground-based cameras, Looking forward, the MUAC perception is that operational decision making needs to be improved by moving from central supervisory towards local sector decisions. This requires a solid ISSR detection or prediction system and better integration into the controller working

position.Work with DLR will continue to validate the process,particularly when traffic starts to build up again. Continued work to tune and validate ISSR predictions, seek alternative validation of ISSR predictions and work towards real-time online ISSR detection are all in the outlook.

The session on mitigating contrail impact was concluded by Ian Poll of Cranfield University with a paper on the accurate prediction of fuel burn and emissions. His motivation for the paper was to provide the atmospheric science community with a modern, accurate, open source and independently verifiable method for predicting fuel burn. He listed a number of desirable attributes which made the method preferable to the ‘black box’ methods that had been used in previous studies. Citing the motto of the Royal Society, Nullius in verba, take no one’s word, he asserted that science that depends upon ‘black box’ methods can never be considered to be sound. The new method he described was developed jointly with Ulrich Schumann of DLR and was fully documented in four peer reviewed articles in The Aeronautical Journal. Ref 5 sets out the fundamental aspects of the method.

The underlying principle is that, for a given fuel, the rate of fuel burn in straight and level flight at constant speed depends only on the mass of the aircraft and the product of its propulsion efficiency and its lift to drag ratio (η0L/D). This key quantity is a function of the aircraft lift coefficient CL, the flight Mach number M∞ and the flight Reynolds number Rac. The simple idea underlying the method is that curves of (η0L/D) against CL, when normalised with respect to the optimum, defined as the maximum value attainable of (η0L/D), collapse fairly closely to a single curve, Fig 4.

The variation with Mach number in Fig 4 can be largely eliminated by expressing the ratio of the best values of (η0L/D) and CL as two functions of the ratio of flight Mach number to optimum Reynolds number.

Approach % flights % change in % change in % change in total diverted contrail EF fuel burn EF (CO2, 100yr TH)1 Small-scale 1.7% –59% [–66, –52%] +0.014% diversion [0.010, 0.017%] –36% [–44, –28%]2 Cleaner DAC 0 –69% 0 –42% engines [–82, –45%] [–53, –33%]3 Diversion ~2% –92% [–96, –87%] + 0.027% + cleaner [0.021, 0.033%] –57% [–70, –44%] engines

Table 3. Calculated effects of climate impact reduction measures in a sample of Japanese air traffic.


Conference Report

These two functions, together with the function defined in Fig 4, are ‘near universal’, ie they apply to all aircraft. For an individual aircraft, the problem is reduced to finding the values of (η0L/D), CL and M∞ when (η0L/D) has its absolute maximum, or optimum value. These optimum values have been found and published for 53 turbofan aircraft.

Applying the method to aircraft flying at the usual long-range cruise Mach number and lift coefficient, the fuel used per unit distance is approximately 1% higher than that at the optimum. The effect of a reduction in cruise altitude of 2,000ft to avoid an ISSR is an increase in fuel burn of 1.4%, for a reduction of 4,000ft it is 5.5%. A reduction is preferable to an increase in cruise altitude because the effect on fuel burn is less and the descent reduces the climate impact of NOX. The presentation also discussed the alternative to flying around rather than under or over an ISSR. Two alternative avoidance strategies were considered, one ‘tactical’, the other ‘strategic’, showing how a decision could be made on the contrail avoidance measure with the lowest fuel and time cost. Usually, the lowest increase in fuel will be by flying under the ISSR but it was emphasised that the addition trip fuel usage of both the ‘tactical’ and ‘strategic’ diversion options are very small, typically less than 1%, adding less than five minutes to a transatlantic flight. These conclusions are consistent with results reported by Stettler. They should be set against some of the more alarmist statements on fuel burn and schedule disruption that have been made in recent times.

Regulation

The subject of the next presentation was the potential to reduce non-CO2 climate impact by regulation. To fulfil the requirement of Article 30(4)

of the EU ETS Directive, a report was commissioned by the European Union Aviation Safety Agency (EASA) in 2019(3). This report was prepared by a 16-strong team of specialists from six institutions, supported by a stakeholder group of similar size. The presentation was given by Stephen Arrowsmith of EASA, the project team leader (three others from the team had given presentations at the conference on the previous day).

The terms of reference of the study set out three tasks: Task1: Current status of science and remaining uncertainties on climate change effects of non-CO2 emissions; Task 2: Existing technological and operational options used to limit or reduce non-CO2 impacts from aviation and related trade-off issues; Task 3: Potential policy action to reduce non-CO2 climate impacts, pros/cons and associated knowledge gaps. The topics of the first two tasks were well covered in the preceding presentations and the potential to reduce climate impact by regulation is the essence of Task 3. Six policy options were shortlisted to be considered in greater detail.

Financial related measures were seen as primarily addressing NOX emissions. A NOX emissions charge or possibly the inclusion of NOX in ETS had been considered. Key issues were: to reduce scientific uncertainty on climate impact from aircraft NOX emissions; select appropriate CO2 equivalent emissions metric and time horizon; agree on climate damage costs to determine level of charge.

Fuel related measures included reductions in aromatics through fuel specification or SAF blending mandate. Key issues were: to reduce scientific uncertainty on climate impact from a reduction in persistent contrail cirrus formation as a result of cleaner fuels and lower aircraft nvPM emissions; facilitation initiative to ensure uptake of SAF by the aviation sector; system to monitor fuels used and environmental benefits delivered.

ATM related measures included avoidance of ice supersaturated regions and a climate charge. Key issues were: to reduce scientific uncertainty on climate benefit from optimisation of flight paths; enhanced meteorological forecast model capabilities needed to predict persistent contrails correctly in time and space; select appropriate CO2 equivalent emissions metric and time horizon to assess trade-offs; agree on climate damage costs to determine level of charge.

A pilot project operating over the Atlantic is needed to assess the feasibility and costs/benefits. The feasibility is more limited within congested

Figure 4. Normalisation of (η0L/D) against Cl through optimum values.


European continental airspace. Communication on benefits as well as incentives are needed to ensure buy-in.

In summary, regulators need regularly to review latest scientific understanding of non-CO2 impacts. They need to maintain and regularly review existing ICAO environmental standards (CO2, NOX, nvPM). The use of Sustainable Aviation Fuels (SAF) has shown a reduction in both CO2 and non-CO2 emissions. The ReFuelEU initiative is currently considering policy options to incentivise the uptake of SAF. Further research should be pursued, potentially through Horizon Europe at EU level, to: increase certainty on climate impact from non-CO2 emissions; consider different metrics and time horizons that could be used to assess the impact of potential policy measures; enhance existing analytic methods to estimate aircraft non-CO2 emissions in cruise based on certified LTO emissions data; enhance capability to predict accurately the formation of persistent contrails.

Governance issues

This presentation was followed by one from Robert Whitfield of Greener by Design, who chairs the Governance Sub-Group of the Greener by Design Contrail Avoidance Group. When the Contrail Avoidance Group first met, two options for reducing climate impact were on the table. The first was changing cruise altitude to avoid forming evening and night-time warming contrails, as in Fig 2. The second was, earlier in the day, deliberately flying into ISSRs in order to form contrails to reflect sunlight – ie cooling contrails. Both options had been proposed by Hermann Mannstein. It emerged that half the group thought that both options should be explored but half the group foresaw political reluctance to consider deliberately forming contrails on the grounds that it could be considered geoengineering. Consequently, a governance sub-group was formed to consider the sensitivities in this area.

Geoengineering is the deliberate large-scale intervention in the Earth’s natural systems to counteract climate change.n The large-scale removal of carbon dioxide from

the atmosphere (‘carbon dioxide removal’ – CDR);n The reflection of more sunlight back into space

to cool the planet (‘solar geoengineering, or solar radiation modification’ – SRM).

There are big questions about significant risks and potential trade-offs some of these approaches would bring, and how they compare with the risks of a warming world.

Figure 5 is a schematic produced by the proponents of SRM. They argue that, despite aggressive measures to cut greenhouse gas emissions and a programme of CO2 removal, SRM will need to be deployed for a period to keep climate impact within tolerable limits.

The presentation traced the evolution of thinking on geoengineering governance from the Royal Society report and the evolution of the Oxford Principles in 2009 through a range of successive stages: the Code of Conduct for Responsible Geoengineering Research (CCRGR) in 2015/7; the Carnegie Climate Governance Initiative (C2G) et al in 2017; the 2018 IPCC report on 1.5 degrees; the UN Environmental Assembly (UNEA) of April 2019; most recently SCoPEx, the Stratospheric Controlled Perturbation Experiment, led by the Keutsch Group at Harvard. Some of the principles developed in the above initiatives are now the subject of international agreement, others are voluntary.

The conclusion on governance in the context of this conference are:n Creating persistent cooling contrails at scale may

be considered as solar geoengineering, but it could help to address temperature overshoot;

n Pending internationally negotiated governance for solar geoengineering, the SCoPEx project governance approach provides key learning;

n Avoiding persistent warming contrails at scale is not geoengineering but a significant mitigation opportunity;

n The motivation of governance measures should be to avoid doing harmful things;

n The SCoPEx project may have some suggestions for governance;

n The key watchword is transparency, transparency, transparency.

Figure 5. Buying time with solar geoengineering.


Conference Report

GBD-CAG objectives

The final presentation was given by John Green of Greener by Design. Its subject was the Contrail Avoidance Group linked to Greener by Design, how it came to be, what it had achieved and what it aims to achieve.

Greener by Design (GBD) first came together in March 2000 as a co-operative group representing the civil aerospace community, under the title ‘Air Travel – Greener by Design’,, with aim of reducing air travel’s environmental impact. Its Technology Sub-Group produced a report in July 2001 addressing design and technology possibilities to reduce noise and air pollution around airports and also to reduce impact on climate. The last of these was taken by the Sub-Group as the most important. NOX was the only non-CO2 emission discussed in the report.

In 2004 the Aerospace Innovation and Growth Team (AEIGT), a UK government body, asked the GBD Technology Sub-Group, to address a list of environmental questions and make recommendations for future research. The Sub-Group report, issued in July 2005, contained many recommendations including one, prompted by research at DLR and Imperial College London, on contrail avoidance. “The practicalities and difficulties of adapting the European air-traffic-control system to enable contrail formation to be reduced by denial of critical flight levels and by re-routing.” The recommendation met a general pushback. It would be too difficult, too costly for airlines and the science base was not secure enough.

In June 2011, at a workshop held at the Royal Society by the COSIC (Contrail Spreading Into Cirrus) project led by Leeds University, Ulrike Burghardt of DLR presented a prediction of radiative forcing by contrail cirrus. This, the first quantitative treatment of the problem, was generally recognised as a potential game changer.

Four years later GBD held a workshop/conference in London with the title ‘Contrail-cirrus, other non-CO2 effects and smart flying’. In the round table discussion that concluded the meeting, the majority view was that the science base was now secure enough to support a policy of contrail reduction by ‘smart flying’. It was agreed that the aim should be to begin regionally in the north Atlantic, with Europe taking the initiative. Someone had to start the process and GBD undertook to do so. This led to an informal meeting in April 2016 at Gatwick Airport of a group of key participants in the workshop and the

formation of the Contrail Avoidance Group (CAG).

The founder members of the group were from the DLR Institute of Atmospheric Physics, the GBD Executive Committee, NATS and the University of Reading. The conclusions of the meeting were: (1) the science base is now good enough to justify proceeding; (2) the ultimate aim is to stage a flight demonstration of contrail reduction by ATM in the Shanwick OCA of the north Atlantic; (3) paper studies, a ‘virtual demonstration’, are needed to make the case for a real demonstration; (4) a sub-group will be formed to review broader ethical and governance issues, eg geoengineering.

CAG has met four times since then. There has been no external funding, all work has been done within existing research funds or pro bono, but the presentation listed a substantial volume of research and publications that has been stimulated by the CAG. The presentation noted two important recent developments, the EASA study(3) and the formation of a plan by the Aerospace Technology Institute at Cranfield to build a consortium to conduct the contrail avoidance trial that the CAG has envisaged.

The CAG take-home messages are:n The non-CO2 climate impact of aviation is about

twice as important as that of CO2 alone and the greater part of it is from contrails and contrail-cirrus;

n Contrails can be substantially reduced by a small alteration in cruise altitude or route with minimal effect on CO2 emission and airline costs;

n This change in operational procedure can be adopted by the world fleet in less time and at a fraction of the cost needed for equivalent improvements via new technology;

n The development of safe, worldwide ATM procedures for contrail avoidance will require enlightened leadership. A high profile, scientifically driven demonstration in the Shanwick OACC, managed by NATS, would be an excellent starting point.

It is time to take the next step.

Day 2 Roundtable

The conference concluded with a roundtable of the Day 2 speakers, under the chairmanship of Iain Gray, Director of Aerospace at Cranfield University.

There was a general sense that regulators were engaged but were not moving fast enough. Paul Madden argued that there was close contact with the regulators regarding NOX standards but he


acknowledged that on SAF more could be done, a view shared by Christiane Voigt. Christiane stressed the need to put incentives in regulatory agreements. Stephen Arrrowsmith acknowledged that Non-CO2 is back in the political spotlight but there is a need to maintain momentum. Regulators are looking for confidence that they have the appropriate context to measure (metrics, time horizon) and that the options that are being considered will have the environmental benefits attributed to them – a no regrets policy.

Turning to ATM capacity, it was agreed that a key learning point from a trial will be how ATM copes with an additional role. Rudiger Ehrmanntraut proposed a KPI on how well the centre can operate in avoiding contrails. Ian Poll noted that the new system capability across the North Atlantic should help improve capacity.

Regarding the science, Helen Rogers acknowledged that there were some known unknowns, particularly soot, but that there is a very good understanding of a lot of these effects. She did not see significant changes coming that would lead to incorrect policy decisions. She did, however, recommend that a task force be appointed to address the issue of metrics and time frames, possibly leading to a basket of metrics, some for regional impacts and others global. Marc Stettler broadly agreed, acknowledging the limitation of the detail and accuracy of the computer models and confirming the need to do

more projects like the MUAC trial, expanding into larger regions with more flights to both improve the science and understand better how it can be operationalised.

For John Green contrail avoidance is the really low hanging fruit of aviation. The bogey-man is that people still talk about it involving problems and costs for the airlines. People need to understand that recent work shows that you can achieve a substantial reduction in warming from air travel at very little cost to the airlines. The downside for the airlines is very small, which, on top of the positive impact of this change on the perception of aviation’s contribution to the world’s problems, should lead to the airlines getting behind this.

Iain Gray concluded that the science is sufficiently mature now to support moving to the operational side of things. COP 26 later this year invites an announcement around a physical demonstration of contrail avoidance. This is not a trade-off but something that we have to do. He vowed to never again attend a meeting on aviation’s emissions without taking the opportunity to introduce the subject and importance of the Non-CO2 agenda. Furthermore, he committed himself to be a champion of the need to rapidly establish a big demonstration project that brings to life the issues discussed at the conference.

References1. D S Lee et al, The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018, Atmospheric Environment, 244 (2021) 117834.2. V Grewe et al, The contribution of aviation NOX emissions to climate change: are we ignoring methodological flaws? Environmental Research Letters, Volume 14, Number 12, December 2019.3. S Arrowsmith et al, Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures pursuant to EU Emissions Trading System Directive Article 30(4), 2020, www.easa.europa.eu/document-library/research-reports/report-commission-european-parliament-and-council.4. R Teoh et al, Mitigating the climate forcing of aircraft contrails by small-scale diversions and technology adoption, Environmental Science and Technology, https://dx.doi.org/10.1021/acs.est.9b05608.5. D I A Poll and U Schumann, An estimation method for the fuel burn and other performance characteristics of civil transport aircraft in the cruise. Part 1 Fundamental quantities and governing relations in a general atmosphere, The Aeronautical Journal, Vol 125, No 1284, pp 296-340, February 2021.

A heavily instrumented HU-25 Falcon measures chemical components from the larger DC-8's exhaust generated by a 50/50 mix of conventional JP8 and a plant-derived biofuel. NASA/Lori Losey.

Economic measures – Carbon pricing


1. INTRODUCTION

For a long time, greenhouse gas emissions (GHGs) have remained unpriced. This allowed companies to emit GHGs at no cost. As a result, products were priced below the social optimum, which led to levels of supply and demand above the social optimum. Economic measures assign a monetary value to emissions. This internalisation of emission costs ensures that producers explicitly take these costs into account in their business decisions, and it incentivises producers to reduce their emissions.

The pricing of GHGs is increasingly recognised as a key mechanism to reach the Paris climate goals (CDP(10), 2017; World Bank Group, 2019; IMF, 2019a). In 2019, 57 carbon pricing initiatives were implemented or in preparation(1). More initiatives are expected as countries seek cost-effective ways to reach their climate goals. Out of the 185 Parties that submitted their Nationally Determined Contributions (NDCs) to the Paris Agreement, 96

Parties (representing 55% of global GHG emissions) have stated that they are planning or considering carbon pricing as a tool to meet their commitments (World Bank Group, 2019).

Although carbon pricing is seen as a key component to decarbonise, literature indicates that it needs to be complemented with a mix of other policies to drive the required changes in a 1.5°C scenario (IPCC, 2018a). The large-scale transformation of sectors also requires policies that, for instance, support research and development. Such complementary policies mean that the reduction goals can be achieved with a lower carbon price (CDP, 2017). Studies suggest a combination of measures and policies is required.

This report focuses on economic measures. Section 2 describes smart economic measures of emissions trading and offsetting in more detail and indicates how these measures and carbon prices may develop until 2050. Required policies and actions are presented in Section 3.


Kiefer


2. SMART ECONOMIC MEASURES

Emission trading and offsetting reduce carbon emissions most efficiently and at the same time ensure that emission targets or climate goals are being met. Such measures are therefore referred to as ‘smart’ economic measures and are to be preferred over taxes. This section describes emission trading and offsetting schemes in more detail.n Emission trading: Emission trading schemes

or cap-and-trade schemes require producers to cover their emissions through emission allowances. Allowances are certificates that allow the holder to emit one unit of a particular pollutant, such as a tonne of CO2. The number of available allowances is capped at a level which corresponds to the emissions target. This ensures that the target will be met. Producers can either reduce their emissions or buy allowances on the market (trade). Governments can either sell allowances or give them away for free. Allowances sold at auctions generate revenues for the government that can be used to support innovations or reduce existing taxes. In 2019, 20 emission trading systems were in force spanning 27 jurisdictions and covering around 8% of global GHG emissions (ERCST, et al, 2019). The systems in the EU and South Korea are the only ones that include the aviation sector (World Bank Group, 2019). Over the next five years six more jurisdictions are putting in place emission trading systems, including China and Mexico. The Chinese system initially only covers the power sector; later it will be expanded to other sectors including aviation. Another 12 jurisdictions are considering a system as part of their climate policy (ERCST, et al, 2019);

n Offsetting: Offsetting schemes require producers to offset emissions that exceed a certain threshold through carbon credits. A carbon credit represents the certification that a tonne of CO2 has been reduced or avoided compared to a scenario without the offsetting scheme. The overall threshold is translated in thresholds for individual producers. When producers want to increase their output, they will either have to reduce their emissions to the threshold level and/or buy credits on the market to offset any emissions over and above the threshold.

In both systems producers will reduce their emissions when the cost of doing so is lower than the cost of acquiring allowances or carbon credits on the market. When emission targets become more ambitious, the price of allowances and carbon

credits increase. Consequently, more emission reduction projects become economically viable. Smart economic measures therefore ensure that the most cost-effective measures are taken first(2).

The effectiveness of smart economic measures depends on their design. First, compliance should be high to ensure that the majority of emissions are covered and producers cannot evade the system and undermine its working. Second, when an airline buys an allowance or carbon credit, this should respectively reduce the right to emit of its seller or represent actual emission reductions realised by a project which would not have taken place without the scheme. Third, the market for allowances or carbon should be sufficiently large. The market is broadened when more sectors and countries take part in the measure.

2.1 EU Emissions Trading Scheme (ETS)

ETS is the cornerstone of EU’s policy to combat climate change and its key tool to reduce GHG emissions in a cost-effective way. At present it is the world largest carbon market.

Initially the ETS only covered the power industry and heavy industry. Since 2012, aviation has also fallen under the EU-ETS and it is still the only transport mode included in the scheme(3). Originally it was designed to cover the emissions of all flights from, to and within the EEA(4) (full scope). In 2013, the scope was reduced to intra-EEA flights through the ‘stop-the-clock’ decision after strong opposition from various countries outside the EU.(5) With the ‘stop-the-clock’ decision the EU also allowed the International Civil Aviation Organization (ICAO) to develop a global measure (CORSIA, see below). Airlines active in the European Economic Area (EEA) need to monitor, report and verify their emissions and surrender allowances for those emissions. The

Boeing 757-200 at Paris-Orly Airport. Olivier Cabaret.



reduced scope shall remain in place until the end of 2023, after which it reverts to its full scope unless there is a revision in light of CORSIA.

Two types of emission allowances exist within the EU-ETS system. General allowances (EUAs) and aviation allowances (EUAAs). Fixed installations (power and heavy industries) need to cover their emissions through general allowances. Airlines can use both the general and aviation allowances for compliance. In the current trading period (2021-2030) fixed installations are also allowed to use aviation allowances.

In the previous trading period (2013-2020) operators were also allowed to use international offset credits from the Clean Development Mechanism (CDM).(6) According to the provisions in the revised EU ETS Directive, international credits can no longer be used for compliance in this trading period (2021-2030) as the EU has a domestic emissions reduction target (UNFCCC, 2017; Carbon Tracker, 2018; EC, 2018a).

2.2 CORSIA

The Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) is an offsetting scheme. This global market-based measure was agreed upon at the 2016 ICAO Assembly to address CO2-emissions from international aviation. CORSIA aims to stabilise net CO2-emissions from international flights from 2020 onwards. CORSIA requires airlines to offset any emissions above the 2019 threshold by purchasing carbon credits generated by projects that reduce emissions in other sectors. This should ensure that the ICAO target of carbon-neutral growth from 2020 onwards (CNG2020) is being met. No further targets have been specified for the period after 2020.

International carbon credits are financial instruments that represent a tonne of CO2 reduced or removed from the atmosphere as a result of an emissions reduction project. The credits are generated by emission reduction projects and are available through various offsetting programmes. The Kyoto Protocol set the basis for two of such

programmes, the Clean Development Mechanism (CDM) and the Joint Implementation (JI) in 1997. The most widely used programmes today are the Verified Carbon Standard (VCS) and the Gold Standard.(7)

In October 2020, 88 states (including all EU Member States) representing 77% of international aviation activity applied to voluntarily participate in the pilot phase (2021-2023) and first phase (2024-2026) of CORSIA. The second phase (2027-2035) is mandatory, although exemptions exist for states with a small aviation industry, Least Developed Countries (LDCs), Small Island Developing States (SIDS) and Landlocked Developing Countries (LLDCs). These states may however still participate on a voluntary basis.

Initially the price of carbon credits developed in line with the price of EU-ETS allowances, as they could be used for compliance within the EU-ETS system. Prices plummeted after the financial crisis. But where the EU-ETS prices recovered when the oversupply of allowances was addressed, the prices of credits remained low due to oversupply and the fact that they could only be used to a limited extent during the third trading period of the EU-ETS (2013-2020). In early February 2020, carbon credits were traded for as little as €0.23, roughly 100 times less than the price of EU-ETS allowances. Projects that adhere to higher quality standards regarding environmental and social integrity generate more expensive credits and could trade at up to $70 per tCO2e (Energies Nouvelles, 2017). However, around half of the credits were sold below $1 per tCO2e (World Bank Group, 2019). CORSIA might lead to a large increase in demand for carbon credits. The more stringent the criteria for the credits, the more expensive these credits will eventually be.

In 2018 the ICAO Council adopted standards and recommended practices (SARPs) for CORSIA. In 2019 ICAO invited offsetting programmes to apply for assessment by the Technical Advisory Body (TAB) based on its eligibility criteria (ICAO, 2019c). It received 14 responses, which included the aforementioned Clean Development Mechanism (CDM), Verified Carbon Standard (VCS) and the Gold Standard. Although the Ökö-Institut e.V. (2019) concluded that many programmes did not guarantee environmental integrity, six out of the 14 programmes were approved in March 2020.

The implementation of the scheme is ongoing and not yet complete. Uncertainties remain regarding its coverage, robustness and compliance policy. Certain

Figure 1. Illustration of cap-and-trade scheme.

Cap on emission allowances

Trading of emission allowances


countries with a large aviation industry might not participate or delay the implementation of CORSIA into national law.

As mentioned above, carbon removal projects may lead to the issuance of allowances or carbon credits which can be used by the aviation sector to compensate for a part of its emissions that cannot be mitigated before 2050. This means that even under a net zero target, there may still be allowances and credits available stemming from carbon removal projects.

2.3 Comparison of EU-ETS and CORSIA

Table 1 summarises the main differences between the two schemes. These relate to:n Ambition level: EU-ETS aims to reduce absolute

GHG emissions by 43% (compared to 2005) levels in 2030 for the sectors covered by the system (power generation, heavy industry and aviation). The European Green Deal may lead to a more ambitious target. CORSIA is less ambitious as it aims to stabilise net CO2-emissions at the 2019 level;

Scheme

Applicability

Target

Certainty on reaching target

Coverage

SAFs

Table 1. Main differences between EU-ETS and CORSIA.

EU-ETSCap and trade

Caps the level of emissions. Operators reduce their emissions or buy EU Allowances in the market (trade). International credits (CERs and ERUs) can be used to offset up to 1.5% of emissions (until 2020)

’12-‘23

Reverts to full-scope in ’24 unless there is a revision in light of CORSIA

2020: –5% compared to ‘04-’062030: –43% compared to ‘05

From 2021-2030 general and aviation caps are reduced by 2.2% each year

Available allowances (cap) correspond to target, ensuring that target is met under full compliance

Legally binding system, penalties in case of non-compliance

Intra-EEA flights and within Outermost Regions

Initially all flights to and from EEA airports. ‘Stop the clock’ decision limited the scope in 2013 to give ICAO time to develop a global MBM (CORSIA). Reverts to full-scope in ’24 unless there is a revision in light of CORSIA

SAF are attributed zero emissions if matching RED requirements

CORSIAOffsetting

Operators buy international carbon credits to offset their emissions above 2019 levels. Conditions apply to offsetting programmes.

‘21-’26 (voluntary), ‘27-’35 (mandatory)

Carbon-neutral growth from 2020 (CNG2020)

Cap remains fixed at 2019 level

Depends on the quality of the carbon credits and compliance level

Only legally binding when implemented in national law. Uncertain how compliance is to be enforced

International flights between participating states

In June 2019, 80 states representing 76.63% of RTKs, announced their intention to participate from the outset. Exemptions apply for domestic flights, least developed countries, small island states, landlocked developing countries, small operators and aircraft, flights with public purpose

Reduced offsetting obligation for ‘eligible fuels’ depending on life-cycle emissions


n Certainty on reaching emission target: In EU-ETS the number of available allowances (cap) is fixed and corresponds to the target. This ensures that the target is met under full compliance. As mentioned before compliance levels are high due to the fact that the system is legally binding and penalties apply in case of non-compliance. For CORSIA much is still uncertain. The quality of the carbon credits greatly determines its efficiency. Furthermore, the system is not legally binding until countries have implemented it into national law. If CORSIA is not implemented in all countries at the same time, this could lead to market distortions (EC, 2017). Also it is yet unclear how compliance will eventually be enforced;

n Geographic coverage and timing: EU-ETS covers CO2-emissions from intra-EEA flights until the end of 2023, after which it reverts to its full scope unless there is a revision in light of CORSIA. CORSIA has a global reach and covers the growth in CO2-emissions of international flights between participating states after 2020. The global scope of CORSIA limits the risk of market distortions and carbon leakage. However, emissions from domestic flights are not covered by CORSIA.(8) This allows airlines with a large domestic network to pass-through part of the costs to their domestic routes. This gives them a competitive advantage on international routes. The same holds true for airlines that serve international markets through indirect flights whereby one of the flights is domestic. This means that they only need to offset their emissions for the non-domestic flight leg, whereas competitors that operate direct need to offset emissions on the entire route. This introduces new risks of market distortions and carbon leakage. Both systems are in place at least during the 2021-2023 period. Over these

years the growth in CO2-emissions of intra-EEA flights between two EEA states is covered by both systems, unless the EU ETS is revised. However, CO2-emissions from the EEA states to states not participating in CORSIA (and vice versa) are neither covered by ETS nor CORSIA;

n Use of international credits: EU-ETS is based on emission allowances that can be traded among sectors in the EU. The system only allows operators to cover a small part of their obligations through the use of international credits until 2020. Thereafter such credits are no longer allowed. This means that as of 2021, all of the emission reductions achieved will occur within the EU. The offsetting under CORSIA is based on international credits. These credits will to a large extent stem from projects outside the EU. This means that CORSIA mainly offsets emissions through reductions outside the EU and thus has only a limited potential to contribute to the EU GHG reduction targets.

n Exceptions for SAF: The EU-ETS attributes zero emissions to SAFs that comply with the sustainability criteria defined in the RED. The purchase of SAF thereby reduces an aircraft operator’s reported emissions, and the number of ETS allowances required (EEA, EASA & EUROCONTROL, 2019). Under CORSIA, airlines can reduce their offsetting requirements by claiming emissions reductions from the use of CORSIA eligible fuels (CEF)(9). The emission reduction that can be claimed depends on the life-cycle emissions of the specific SAFs used compared to the life-cycle emissions of conventional fuels. When the life-cycle emissions of a SAF are for instance 70% lower than those of conventional fuels, airlines only need to offset the remaining 30% of the emissions resulting from the combustion of the SAF through CORSIA. Excluding emissions from the combustion of SAFs partly or completely acts as a financial incentive for airlines to use SAF (EEA, EASA & EUROCONTROL, 2019).

2.4 Development of existing measures

As mentioned above, work at ICAO is ongoing to develop the implementation rules and tools for CORSIA. Within 12 months after its adoption, the European Commission will re-assess its rules, tools, ambition and environmental integrity. Based on the outcome of this assessment, the European Commission may revise the scope of EU ETS for aviation, consistent with the EU climate targets (EU, 2017). In the absence of a new revision, EU-ETS would revert back to its original full scope from 2024. Although the EU favours a global measure, it is


Transavia Airlines Boeing 737-800 landing at Skiathos.Tim

o Breidenstein


unlikely it will accept CORSIA in its current form as the sole mechanism to reduce aviation emissions in the EU. First, this is because of its lower ambition level and the exclusion of domestic flights. With the European Green Deal the European Commission shows that it aims for more ambition instead of less. This may lead to a reinforcing of EU ETS and a further reduction of free allowances, which will further increase the difference in the level of ambition with CORSIA. Second, this is because of CORSIA’s reliance on international credits which are generated in part by emission reduction projects outside the EU. For the EU the European ambition is key. Policy is therefore aimed at reducing intra-EU and domestic emissions.

3. POLICIES AND ACTIONS

Aviation is a global industry which requires global solutions. National economic measures, such as aviation taxes often lead to market distortions and carbon leakage. Ideally policy-makers and industry should work together towards one global all-encompassing smart economic measure which yields actual emission savings. Such a global measure not only has the largest scope for emission reduction, it will also ensure that emission reductions are achieved against the lowest cost. Compared to a situation in which multiple systems co-exist, it has the added benefits of limited administrative costs and a reduced risk of market distortion and carbon leakage. When all emissions

from flights departing from EU airports are covered by a smart economic measure, national economic measures need to be reconsidered to prevent that the same external cost is priced twice.

Until an all-encompassing global measure is available, the EU should aim for a package of measures that covers the emissions from all flights departing from EU airports to reach the EU climate goals. This might mean revising EU ETS to complement CORSIA in such a way that ETS addresses all emissions which are not covered under CORSIA. This would prevent double counting of the same emissions. Furthermore, while both systems co-exist, it is important that the reporting mechanisms are aligned to limit administrative costs for the airlines. When deciding on the way in which ETS and CORSIA will interact, the risk of carbon leakage and distortion of competition has to be minimised. This will ensure the highest environmental effectiveness of the two systems, while also avoiding social and economic disadvantages for European aviation.

The EU should also try to improve the existing measures. With respect to CORSIA this means (1) striving for an ambition level that goes beyond carbon neutral growth from 2019 onwards, (2) urging third countries to also put in place economic measures that cover their domestic emissions and (3) to agree on a high standard for carbon credits, with all credits to be sourced from high-quality carbon removal projects by 2050.

Russell Lee


There is also room for improvement regarding EU ETS. First, to reduce the number of allowances to zero in 2050 to ensure climate neutrality is achieved. This should be complemented with a policy which allows any remaining carbon emissions to be compensated by negative emissions. For instance, by allowing carbon removal projects to lead to the issuance of additional allowances. Second, to reduce the amount of freely allocated allowances. Third, to enhance the cost-effectiveness of ETS by increasing its scope through the inclusion of more sectors and/or by linking it to similar schemes elsewhere in the world. The latter might however lead to emission reductions outside the EU financed by the European aviation sector. Fourth, to require Member States to invest all proceeds of the auctioned allowances in sustainability projects.

EU ETS has proven that it yields actual emissions reductions in a cost-effective way. Further improvements to the scheme (lowering the cap and the number of free allowances) will help the EU to reach its 2050 climate goals.

4. ECONOMIC MEASURES IMPACTS AND NEXT STEPS

Economic measures lead to higher costs for air passengers, and – depending on the measure – could also lead to lower (net) emissions per flight.

The cost increases resulting from measures taken are assumed to be fully passed through to the passenger. This is likely with global measures that affect all competitors. However, national or regional measures may only affect part of the market which leads to market distortions. In such cases, airlines may not be able to pass the cost increases on to their customers in full in the affected markets. However, due to the small profit margins in the aviation industry, airlines will need to recover the cost increases elsewhere in their networks.Economic measures may result in in-sector and out-of-sector emission reduction. Out-of-sector reductions are achieved through investing in other sectors. Through an economic measure, the aviation sector may for instance invest in carbon removal projects. In theory, if all CO2 emissions from a flight are removed from the atmosphere, the net CO2 impact of this flight is zero. Economic measures act as an incentive for technological development, operational improvement and SAF uptake.

Although there has been some significant development of market-based measures for aviation, ultimately the industry needs a global solution to

ensure all of its emissions are carbon priced. So there will need to be a significant development of CORSIA so that it covers all of the industry’s emissions and not just the growth, and in this way it can better incentivise the sector to deliver the Net Zero Emissions by 2050 challenge.

This report is a summary of the Economic Measures section of European Aviation’s Destination 2050 report published in February 2021.

References1. Prices differ significantly between jurisdictions. Most are still too low to incentivise investments at the scale needed to reach the Paris climate goals (OECD, 2018a; UNEP, 2018; World Bank Group, 2019). The IPCC, International Monetary Fund (IMF) and the OECD all pushed for strengthening and accelerating carbon pricing.2. In a well-functioning system, prices tend towards the marginal abatement cost of carbon (Synapse Energy, 2016).3. EU-ETS covers CO2-emissions from the power and heavy industry as well as aviation. In addition it covers N2O-emissions from the production of various acids and glyoxal and perfluorocarbons (PFCs) from aluminium production. For aviation EU-ETS only covers CO2-emissions.4. The EEA includes the EU Member States plus Iceland, Liechtenstein and Norway.5. The United States for instance adopted the ‘EU ETS Prohibition Act’ which would allow its authorities to forbid airlines based in the United States to comply with the system.6. The credits are no longer surrendered directly, but may be exchanged for allowances at any time during the calendar year.7. Offset credits may also be used by companies and organisations to voluntarily offset (part of)


Alfonso Eguino


It is recognised that the design of CORSIA was a compromise to gain agreement of all the UN member states, the main elements of compromise being:1. It covers only the growth in emissions as opposed to all emissions2. It applies from 2021 to 2035, and a revised scheme will be needed post 20353. It is a carbon offset scheme4. It begins with a voluntary phase from 2021 to 2026 prior to the mandatory phase in 2027

However, it is a significant achievement that a global agreement to address C02 emissions has been implemented and there is additionally a three yearly in-built mechanism to review the effectiveness of the scheme, with the first review taking place in 2024. Critical to the effectiveness of CORSIA will be the quality and integrity of the carbon offsets. Post 2035, availability of offsets will reduce as more countries move towards net zero, and alternative C02 removal solutions such as Direct Air Carbon Capture and Storage (DACCS) powered by green electricity will be needed to offset aviation emissions.

The limitations of CORSIA.

their carbon footprint. The size of the voluntary carbon market is much smaller than the compliance markets. Over the 2005-2018 period around 2,000 projects worldwide had issued over 430MtCO2e of voluntary credits. This is relatively modest compared to the 11GtCO2 covered each year by emission trading schemes and carbon taxes (Energies Nouvelles, 2017).8. Reducing these emissions is a responsibility of individual states. Domestic emissions are covered by the Nationally Determined Contributions (NDCs) that States have to meet under the Paris Agreement. The ambition levels of the NDCs differs per state and are not legally binding. Around two thirds of all flights are domestic and 40% of aviation emissions can be attributed to domestic flights (ICCT, 2019). 9. Specific certification processes determine whether a SAF meets the CORSIA eligibility criteria.10. CDP was formerly the Climate Disclosure Project.


During the past year, the Covid-19 crisis caused massive disruption to the air transport market, posing huge challenges to the airline and aviation industries (and everyone else). However, disruption also brings opportunities, and this is true for the associated environmental matters. The ‘build back better’ or ‘build back greener’ messages are widely quoted by governments and trade associations. The following looks at the short- to mid-term aviation technological progress and options.

The challenges will be how to build back better and greener despite greatly diminished revenues since March 2020, relative to 2019 levels. Many Governments also committed substantial funds to shore up and sustain their economies, possibly constraining their scope for future investment. Government support to the aviation and aerospace industry may perhaps be at the expense of lower future support during the repair of national finances.

There is clearly a balance to be struck between the benefits of positioning companies and economies to exploit future reduced emissions aerospace applications and the upfront costs associated with establishing (or maintaining) the capability and perhaps capacity to deliver the necessary technological improvements.

IN-SERVICE FLEET FUEL EFFICIENCY

Most years, the in-service fleet fuel efficiency improves by 1-1.5% due to the replacement of older aircraft with newer, more fuel-efficient alternatives, plus the general expansion of the fleet size with newer aircraft. Hence, its coverage in this report is usually limited.

However, last year’s events are likely to have caused a more significant change, with a probably larger than usual net improvement in fleet efficiency, although it may be short-term unless there are permanent structural changes. Consequently, the following considers the potential changes in more detail than usual.

Clearly, reduced total aviation missions are the principal environmental effect of the disruption: fewer aircraft movements mean lower emissions, especially for more severely affected long-haul flying. Whether the air traffic recovery returns to pre-Covid trends or the crisis causes a permanent displacement remains to be seen. Although not strictly concerned with fleet efficiency, its direct impact on global emissions is important.

Secondly, the crisis has accelerated the retirement of numerous older, less efficient aircraft, e.g. few

Technology

Technology


passenger 747-400s will remain in service post-Covid, replaced mainly by A350, 787, and 777 aircraft with up to 30% improved fuel efficiency per seat mile. Such changes will improve fleet fuel efficiency. Even considerably younger A380 superjumbo aircraft are being retired, considered too large for the traffic levels on many routes. The associated fleet efficiency benefits will be smaller due to the more recent technology included.

Logic also suggests that airlines will retain their newer, more efficient aircraft to minimise their fuel bills and to offset the higher associated ownership costs. Newer aircraft should return to service (from storage) sooner for the same reasons. If true, this process will also improve fleet fuel efficiency.

Airlines may also choose to return leased aircraft with pre-Covid costs to manage their capacity or seek lower-cost options afforded by the large, parked fleet. This consideration could worsen the fleet fuel efficiency should airlines opt for less efficient aircraft with lower lease rates. Conversely, the availability of newer, more efficient models at reasonable acquisition costs might benefit the overall fleet efficiency. However, it could also increase pressure on new efficient aircraft orders, especially for airlines with limited funds, potentially slowing the fleet’s efficiency improvement.

The return of the 737 MAX to operations should also significantly improve the overall fleet efficiency as the aircraft they were originally intended to replace can be retired or sold.

While passenger traffic experienced massive passenger traffic reductions in 2020, the considerable decrease in wide-body passenger aircraft flights constrained the available global freight capacity as they include substantial freight capacities. Pre-Covid, they accounted for about half the global air-freight; the other half carried in dedicated freighters.

The lack of freight capacity in modern, high-efficiency passenger aircraft caused increased usage of older, less efficient freighter airframes to fill the capacity gap. Some passenger aircraft also operated as dedicated freighters, filling their belly holds with cargo but with empty passenger cabins (possibly with hand loaded freight strapped to seats).

The lack of passenger aircraft freight capacity also often increases the total distance travelled by freight. The much-reduced network density provides fewer opportunities for direct carriage of smaller freight loads to many destinations,

necessitating more 'hub and spoke' style or multi-mode movements. These effects increase the total aviation emissions due to increased payload tonne-kilometres.

More positively, the availability of parked passenger aircraft is a potential opportunity for freight carriers to replace existing fleets with more fuel-efficient models. Freighter aircraft efficiency tends to be worse than passenger variants as they are either conversions of over ten-year-old passenger aircraft or new-build freighters introduced as demand for the passenger variants wanes. For both cases, the introduction of more efficient, competing passenger aircraft causes the shift of older aircraft to freighter variants.

ONGOING LARGE AIRCRAFT PROGRAMME DEVELOPMENTS

The long development timescales of aircraft and their engines require continued spending during economic downturns to ensure they are ready for the industry’s recovery.

The aviation supply industry has been massively affected by Covid-19, especially the engine manufacturers who rely heavily on the revenue generated by engine overhaul activities.

Consequently, Boeing substantially slowed the 777X (-8 and -9) programme pushing certification and entry into service back by one to two years due to depressed traffic volumes and limited need for 400-seat aircraft. Mitsubishi also paused

United Airlines Boeing 737-9 MAX. The 737 MAX will improve overall fleet efficiency. Konstantin von Wedelstaedt.

Opposite: An artist's impression of the Airbus A321XLR. Airbus.


their regional jet SpaceJet programme for similar reasons, ie airlines’ current reluctance to commit huge investment with much-reduced revenues.

Airbus’s short-term focus is the A321XLR due for certification in late 2021, or early 2022, that will offer substantial improvements on some medium-range (3,000-4,000nm) routes with little freight traffic. Airbus claim >20% fuel burn per seat improvements relative to the 1980’s technology Boeing 757-200.

The Comac 919 and Russian Irkut MC-21 flight-test programmes continue with certification for both currently planned for 2021. Both aircraft target the A320neo and 737 MAX market.

FUTURE LARGE AIRCRAFT DEVELOPMENTS

The following discusses aircraft programmes at a conceptual or early stage of design, ie the final configurations are not yet publicly presented. All will include aerodynamic, propulsive and mass efficiency improvements.

In early 2021, various press outlets reported Boeing's renewed interest in tackling the A321’s market success, especially the A321XLR. Few details exist publicly for the Boeing aircraft, ‘dubbed’ the -5X, except for its nominal 225-seat, small twin-aisle fuselage (possibly similar to the 767) and ~5,000nm range capability.

Importantly, to be competitive with the A321XLR, Boeing will likely focus on the passenger payloads with limited freight capability.

The reports indicate the extensive use of composite structure but conventional propulsion, with Boeing stating an explicit reliance on sustainable alternative fuels. The long-range requirement effectively rules out hybrid-electric or hydrogen propulsion.

The A321XLR and potential -5X should offer significant improvements to transport aircraft fuel efficiency on some routes. The fuel efficiency of any medium-range routes with limited or no freight traffic will benefit from a more appropriate aircraft, ie wing and engines not sized for the additional freight capacity incorporated into all wide-body aircraft.

These aircraft are also particularly suited for point-to-point flights, improving efficiency by shortening the total flight distance compared to an indirect hub and spoke routing. These smaller aircraft are

also ideal for opening up new routes, ie smaller passenger volumes and an undeveloped direct freight market.

Conversely, in September 2020, Airbus released conceptual images of three hydrogen-powered aircraft intended for 2035 entry into service. All address regional and relatively short-range operation with small aircraft. Two appear as relatively conventionally configured regional turboprop (ATR42/72) and single-aisle (A320) configurations, while the third resembles a less conventional hybrid-wing body concept. Although not committed aircraft programmes, they probably reflect ongoing Airbus studies.

Embraer developments target a new turboprop with an estimated ~70-seat capacity to compete with the DHC-8 Q400 and ATR72. The propulsion system and energy source are not yet specified, but its 2027 target entry into service suggests conventional fuel as the most likely.

In December 2020, Deutsche Aircraft unveiled its Do328eco programme with emissions and economics improved through a ten-seat stretch relative to the Do328 turboprop fuselage and a reported modest 2-3% propulsion efficiency improvement. The company provided little information on specific aerodynamic enhancements.

RESEARCH ACTIVITIES

UK Jet Zero, FlyZero and the ATI Programme

The UK government set up the Jet Zero Council (JZC), a partnership between government and industry, to bring together ministers and chief executives from the industry to deliver zero-emission transatlantic flight within a generation (targeting 2040). It currently has sub-groups addressing environmental improvements through two main threads, a technology strand developing more energy-efficient aircraft and zero-emissions aircraft, led by the UK Aerospace Technology Institute (ATI), and commercialisation of sustainable aviation fuels (SAFs).

FlyZero is a project led by the ATI and funded by the Department for Business Energy and Industrial Strategy. It intends to gather about 100 secondees from across the UK aerospace sector for a 12-month programme (delivering in early 2022) to look at the design challenges, the market opportunities and the commercial feasibility to deliver a zero-carbon emission aircraft by 2030.

Technology


Areas covered by the strategic research project include determining the technical and commercial viability of a future zero-carbon emission aircraft design; technology and industrialisation roadmaps; and assessments of the sustainability issues, the UK industrial capability, and the market and economics aspects.

FlyZero’s focus is not on the advanced air mobility area (for which commercial opportunities are already in development and partly funded by the ATI Programme in some cases). Neither does it consider long-range, large passenger commercial airliners (which will rely primarily on SAF and more energy-efficient aircraft technologies, also part of the ATI Programme). FlyZero focuses on aircraft in the regional market up to the short-range, single-aisle market where the limits of zero-carbon propulsion solutions have yet to be explored in detail.

The ATI Programme continues with circa 320 projects launched and £2.9bn allocated since its establishment in 2014. Projects are spread across technology solutions for aircraft propulsion and power, aerostructures, advanced systems and technology integration at the whole aircraft level.

In March 2021, the EU launched its ‘Clean Aviation initiative’ with the following description:

‘The European Partnership for Clean Aviation will build on the work done to date by the Clean Sky and Clean Sky 2 Joint Undertakings, pursuing innovative and impactful research to ensure climate neutrality by 2050’. (https://www.cleansky.eu/eu-to-set-up-a-new-european-partnership-for-clean-aviation)

It is part of the broader Horizon Europe programme with specific subjects identified as:i) Hybrid- and full-electric propulsion concepts.ii) Ultra-efficient aircraft architectures.iii) Disruptive technologies to enable hydrogen-

powered aircraft. Ongoing Clean Sky 2 integrator technology demonstrator programmes finishing in the last year or planned to deliver in the coming year, primarily focus on regional aircraft systems and structures, business jet structures, as well as the Airbus Racer high-speed rotorcraft. The Airbus Racer compound helicopter should make its first flight in late 2021.

Some industry-led technology programmes have been cancelled or slowed during the Covid-19 crisis. Last year’s Annual Report mentioned the April 2020 cancellation of the planned Airbus-Rolls-Royce led EfanX flight test programme. It planned to replace one of the four BAe146 engines with an electric propulsor.

Infographic of three hydrogen-powered studies by Airbus. Airbus..


Technology

In August 2020, Raytheon and Collins reported a slowing of ‘Project 804’ activity due to the Covid epidemic. Work will continue at a reduced pace rather than an outright cancellation. The project intends to introduce a parallel hybrid-electric system to one engine on a DHC-8-200 aircraft.

Boeing performed their ecoDemonstrator 2020 flight tests with a 787-10 in partnership with NASA and Safran. Its prime objective addresses aircraft community noise with around 200 microphones on the aircraft’s external surface and on the ground. Perforated aerodynamic fairings attached to the undercarriage structure also targeted landing noise improvements by smoothing the complex flow around this part of the airframe.

NASA

The all-electric distributed propulsion X-57 Maxwell demonstrator continues its progress towards flight test. The programme, launched in 2016, is planning for ground and taxi tests followed by flight tests with its ‘Mod II’ wing in 2021. These tests involve demonstrating an all-electric propulsion system on a conventionally configured aircraft with two high-power electric motors directly replacing the baseline piston engines at around 30% semi-span. The wing also looks very similar to the baseline Tecnam 206 wing.

After this test phase demonstrates high power electric motors in flight, the installation of the cruise optimised (Mod III) wing will occur with the cruise motors moved to the wingtips. The new wing includes distributed propulsion propeller installations along the wing leading edge.

SUPERSONICS

Development continues of the various supersonic demonstrators such as the NASA X-59 QUESST and Boom XB-1. The latter was ‘rolled out’ in October 2020, with a first flight planned for 2021. The X-59’s first flight remains scheduled for 2022. These aircraft claim use of Sustainable Alternative Fuels will allow them to achieve lower emissions, despite their inherent increased energy usage per passenger mile relative to high-subsonic aircraft.

ALTERNATIVE PROPULSION DEVELOPMENTS

The considerable interest levels associated with the various electric and hydrogen-related propulsion

systems continues as the aviation industry targets lower future emissions.

However, unless massive battery technology improvements occur before 2030, it is unlikely that any form of electric propulsion will enter the market on anything other than small, short-range aircraft. Consequently, their impact on global aviation emissions will be minimal, although a helpful initial step.

Most hydrogen propulsion concepts include one or more fuel cells. These convert a hydrogen fuel flow into electrical power distributed to propulsors driven by electric motors. Alternatively, direct combustion of hydrogen fuel in a gas turbine is also possible. Much of the associated technology exists.

However, green hydrogen’s principal challenges are its ‘wind to tank’ efficiency, the tank to fuel mass ratio, and the tanks’ volume. Only about one-half of the clean energy to create the hydrogen fuel arrives in the hydrogen tank. The necessary electrolysis, compression to LH2 (or high-pressure gas), and transportation to the end-user consume the rest. By contrast, electrical energy has minimal losses once generated, and its highly efficient transmission through the standard electrical grid incurs low losses – provided the grid has the capacity.

If clean energy is plentiful and cheap, then hydrogen is viable. If the clean energy supply is limited, using it to produce hydrogen diverts the clean energy away from other environmental improvements. Across Europe in 2020, renewable energy supply accounts for only about 20-30% of total electrical annual energy demand, with it occasionally approaching 100% demand for an individual country when the local wind and sunlight conditions are optimal.

The hybrid-electric Ampaire Electric Eel demonstrator, which is based on a six-seat Cessna Skymaster, made a flight from Kirkwall Airport on the Orkney Islands to Wick John O’Groats Airport on 12 August 2021. Ampaire.


Consequently, without huge clean electrical demand reductions and massively increased renewable generating capacity and associated backup, the additional electrical power needed for aviation seems a considerable challenge. Nuclear power may hold the key for such substantial clean energy increases or possible fossil fuels with a highly effective carbon capture system.

Although hydrogen specific energy (kWh/kg or MJ/kg) is almost three times greater than kerosene-based jet fuel, its tank mass is considerable, often significantly exceeding that of the fuel within, thus reducing the hydrogen’s specific energy advantage. The installed mass may be even higher due to requirements to secure the tank under the loads associated with a survivable accident.

Reducing hydrogen tank mass is clearly a priority for hydrogen-fuelled aircraft concepts, along with an acceptable, ie economic, tank cyclic-life driven by the high-pressure or cryogenic storage requirements.

The associated mass penalty of jet fuel storage on a large airliner is no more than a few hundred kilogrammes, mostly sealant to prevent leakage through the structure.

Liquid hydrogen’s volumetric specific energy (MJ/litre) is poor, only about a quarter of jet fuel, ie four times the volume for the same energy storage. High-pressure hydrogen gas is even worse. Jet fuel storage typically inside the wing structure is convenient with no competing demands, with fuel mass delivering structural load relief.

By contrast, the conventional Airbus Zero-E configurations place their cylindrical hydrogen tanks

(with hemispherical ends) inside the rear fuselage, displacing passenger volume. The resulting tank and fuel mass drive the concepts’ wing position further aft, relative to existing aircraft.

During 2020 and early 2021, various airlines, eg International Airlines Group (IAG – British Airways and Iberia) and All Nippon Airlines, recently invested in SAF projects to support the scaling up of the associated production capacities. United Airlines made a similar investment in 2019. Many other airlines are also pursuing increasing SAF usage.

The principle SAF challenges are land use for bio-fuel SAFs and the considerable energy requirements associated with both synthetic and bio-fuel production. Completely replacing global fossil fuels with SAFs is very likely unfeasible without vast amounts of clean electrical energy.

However, the limited use of SAFs to reduce short-term CO2 emissions on existing aircraft fleets has a helpful contribution. Future SAF usage may also focus on longer-range aircraft, less suited to short- to mid-term electric or hydrogen technology that may work for smaller, short-range aircraft.

Rolls-Royce reported that its Ultrafan research and demonstrator programme should be essentially complete by 2022. At that time, the architecture and technology involved will be available for any future engine proposals requiring conventional propulsion systems. The programme also includes testing their ALECSys lean-burn combustion technology supported by the EU Clean Sky and UK ATI.

SMALL CONVENTIONAL TAKE-OFF AND LANDING (CTOL) AIRCRAFT DEVELOPMENTS WITH ALTERNATIVE PROPULSION SYSTEMS

Electric and hydrogen aircraft concepts have focused on smaller, short-range aircraft due to their relatively low energy and power requirements. The following represent those fixed-wing programmes that have caught the author’s attention during the last year. Many others exist with similar targets to those discussed.

Many higher-profile projects covered in last year’s Annual Report released little extra public information during the previous year, possibly busy progressing their work, perhaps disrupted by the Covid restrictions. These projects include the all-electric DHC-2 e-Beaver (a floatplane) and Cessna e-Caravan electric developments that first

The Harbour Air eBeaver first flew with a MagniX EPU replacing its normal piston engine in December 2019. MagniX.


Technology

flew in late 2019 and early 2020, respectively. The Eviation Alice aircraft project also released no updates during the last year, although a 2021 first flight is possible.

The plan for electric air operations on the UK’s Orkney islands, Project Fresson, was also discussed in last year’s Annual Report. It is a UK ATI-funded project involving a consortium, including Britten-Norman, Rolls-Royce and Ferranti.

In March 2021, the project reported a switch from a hybrid-electric to hydrogen fuel-cell propulsion and likely linked to the launch of Project SATE (Sustainable Aviation Test Environment). SATE centres around Kirkwall airport, in the Orkneys, and intends to provide and evaluate the necessary infrastructure for hydrogen and synthetic aviation fuels, in addition to all-electric.

The largest electric aircraft is the 19-seat Heart ES-19 regional all-electric turboprop with up 250nm range. It is a conventionally configured high-wing aircraft with four electric motor-driven propellers. Its batteries are reported mounted in extended nacelles aft of the electric motor and propellers to enable rapid change and access. This location also isolates the batteries from the fuselage and occupants. Heart’s intent is commercial certification by 2026.

The similar-sized (18-seat) Faradair BEHA (Bio-Electric Hybrid Aircraft) MIH aircraft has a ‘triple box-wing’ to reduce span while delivering Short Take-Off and Landing (STOL) capability. A low or carbon-neutral footprint is forecast by using composite structures and series hybrid-electric propulsion; the use of bio-fuels necessary to achieve carbon neutrality. The company plans a 2024 first flight for the prototype with operational trials in 2026.

ZeroAvia achieved the world’s first flight of a hydrogen fuel-cell-powered aircraft in September 2020 in the UK with a modified six-seat Piper Malibu aircraft fitted with ZeroAvia’s hydrogen fuel cell powertrain connected to a 300kW Magnix electric motor. In December 2020, ZeroAvia secured an additional £12.3m UK Government grant from the Aerospace Technology Institute and the Department for Business Energy and Industrial Strategy (BEIS) to support further development of ZeroAvia’s hydrogen fuel cell powertrain. The project considers aircraft of up to 19-seats, targeting a market-ready date as soon as 2023. British Airways offered its support to the broader ZeroAvia programme through a partnership agreement in late 2020.

Rolls-Royce and Tecnam reported a joint development programme study in March 2021. It will develop a fully electric commuter aircraft (probably six to ten seats) to address Widerøe airlines’ requirements, to meet a Norwegian government ambition for zero-emission domestic flight by 2040. Its planned 2026 entry into service builds on a joint EU clean sky funded research programme involving Rolls-Royce and Tecnam to install electric propulsion on a Tecnam P2010 aircraft.

One interesting alternative development path broke cover in August 2020 involving the six-seat Otto Celera 500L aircraft. Its use of a new diesel piston

United Airlines has signed an agreement to acquire 100 of Heart Aerospace’s ES-19 aircraft, a 19-seat all-electric airliner. Heart Aerospace.

The Faradair BEHA features a ‘triple box-wing’. Faradair.


engine with a less conventional configuration claims massive efficiency improvements over competing aircraft. It achieves US trans-continental range with fuel mileage similar to an SUV, ie 4X4 vehicle. Otto claims up eight times lower fuel consumption than similar jet aircraft with speeds as high as 0.7 Mach number.

The Celera’s primary new technology is extensive laminar flow around its bullet-shaped forward fuselage and over its wing. Its single pusher propeller positioned on the rear fuselage avoids the propeller outflow disrupting the airframe’s laminar flow.

Otto reports more than 30 flights completed and expected benefits demonstrated. If it maintains its claimed benefits through certification into service, it substantially raises the bar for judging future small electric aircraft.

Indeed, Otto also reports potential future variants with hybrid or electric propulsion included once available, applying new propulsion technology to what would be an already proven airframe concept. Although the battery weight and energy capacity would very likely shorten the resulting range capability, customers could mix different aircraft variants to suit mission distance requirements.

The Otto website also describes a 20% larger (maybe eight to ten seat) Otto 1000L development. The laminar flow fuselage benefits will likely diminish as the aircraft size increases from this.

EVTOL/URBAN AIR MOBILITY

Much of the new propulsion technology discussed above for CTOL aircraft also applies equally to the many eVTOL/UAM development programmes currently underway. During the previous year, several projects completed first flights (mainly with no occupants aboard).

However, the propulsion systems challenges reported for the CTOL aircraft are equally valid for eVTOL aircraft, even more so due to their substantially higher thrust/weight requirements. Hence, these aircraft primarily focus on relatively short-range requirements.

SUMMARY

The current levels of considerable uncertainty pose substantial challenges for the aerospace and

aviation industry. However, opportunities also tend to occur with challenges and the increasing political and societal pressure to ‘grow back greener’ or ‘better’ offer benefits for those able to address the opportunities.

Reducing global aviation emissions, both CO2 and non-CO2, requires the application of various technologies to appropriate specific classes of civil aircraft to address the global challenge. Improving technology levels will also modify the contribution of each as time passes.

If the scaling up of SAF is feasible, they offer short- to mid-term improvement in emissions levels for the larger (>100-seat aircraft). It is especially relevant for existing aircraft types that will likely remain in service up to 2050 and beyond.

Electric and hydrogen energy storage with 2020 technology levels will likely appear initially on relatively small, short-range aircraft. However, improving technology, especially significantly lower battery and hydrogen tank mass, may extend their usage up to the 150-seat aircraft class in the 2030s.

It is worth remembering that SAFs, electric and hydrogen energy storage options all require large quantities of clean electrical energy to reduce emissions relative to fossil fuels. All will also significantly increase aviation energy costs, although this should also attract more investment to explore the challenges.

The Otto Celera 500L. Otto Aviation.


Operations Report

COVID-19 AND THE DEMAND FOR AIR TRAVEL

Covid-19 has turned into a major disaster everywhere. It has halted all but the most essential international travel throughout much of the world. 4.6m deaths have been reported, with the figures in many countries still rising fast. There have been reported cases from very nearly every state. Deaths in some 67 countries have exceeded 1,000 per million inhabitants, and in 22 countries in excess of 2,000 deaths per million inhabitants. Only about 25% of the world’s adult population has had at least one dose of the vaccine. It is against this sombre background that this report is compiled.

Last year’s report accurately anticipated many of the issues and actions which were taken over the past 12 months. Periodic closures of borders with next to no notice, the need to prove you are Covid-19 free before you travel, the introduction of vaccine passports, testing before you travel and compulsory quarantine when you arrive are all features of 2021. Indeed because of the great risk of virus mutations in countries where the virus is rampant,

the UK Government took unprecedented peace-time measures to restrict international travel. This included a £5,000 fine in force earlier in the year if you left, or attempted to leave, England without a valid exemption. Compulsory quarantine in Government-approved hotels (at your own expense) for returning citizens was also a legal requirement from ‘red list’ countries. For a time, entry was banned for non-British passport holders, with limited exceptions. All this is designed to avoid new variants of the virus, which may be more resistant to the vaccines, entering the country and nullifying the excellent progress that has been made so far in controlling Covid-19 with the vaccines.

However, many states are struggling with their vaccination programme, with doubts about side-effects and much resistance to being vaccinated within some communities adding to governments’ problems. The net result is a third wave of infections in many European nations, and further lockdowns being announced. Now the results show the vaccines to be highly effective, all states are anxious to vaccinate their citizens quickly, so vaccine supply problems are adding to the difficulties.

Operations Report


The biggest outstanding issue – to which we don’t know the answer yet – is how long is the vaccine effective for? Eight to ten months seems to be the best estimate, with more learned sources suggesting the lower end of the range. This suggests that everyone will require a booster dose later this year, preferably of a type that is effective against newly emerging strains of the virus. This will provide another challenge for governments around the world, and plenty more scope for things to go wrong – and hence restrictions re-imposed. The other worrying feature is that with the older half of the population immunised, the virus is circulating and mutating in a younger age group. Variants that target younger people could emerge to add to the problems. It will take many years and a world-wide effort to bring this virus fully under control. Its not just going to fade away by itself.

The Civil Aviation Authority’s statistics for 2020(3) clearly show the damage this has caused to the aviation industry. Despite over two months ‘pre-Covid’ travel, and wholesale repatriations for several weeks thereafter, the figures make grim reading. Overall UK passenger traffic was down by 75% across all airports. Heathrow was down by 73%, Gatwick 78%. The top ten airports were all in the range 70%–78%, Luton being the least affected, and Gatwick and Glasgow being the worst. Outside the top ten there was more variety: Cardiff recorded an 87% drop and Prestwick 86%, while those servicing oil and gas installations showing less reduction: Aberdeen was down only 66%, Sumburg 57%, but in part this was due to the permanent closure of Scatsta – combining the figures gives an overall 71% drop. Lands End, with its service to the Scilly Isles, showed the smallest drop (46%), no doubt in part due to the length of time Cornwall and the Scillies stayed in the least restrictive Tier 1 restrictions.

With restrictions tightening dramatically just before Christmas 2020, it is unsurprising that bigger drops have been recorded this year. For January and February 2021, Heathrow was down 85% on the same period last year, Gatwick 90%, and Cardiff and Southampton down 95%. Almost all airports of size have reported a reduction of over 80%. The reductions in business rates and the Government furlough scheme are helping but with the financial strain airlines and airports are under, unless there is a speedy easing of restrictions, potential bankruptcies seem inevitable.

Against this background, what are the likely outcomes? It is very clear the threat of mutations undermining the vaccinations policy will keep many borders firmly shut for most of this year, especially in states where vaccination rollout is so painfully slow. A one jab vaccine will help the situation, but after almost all governments have being severely criticised for imposing restrictions too little and too late, it seems many will be more cautious and ease restrictions slowly. While the prospects for the UK seem much more promising, the resumption of international travel is going to be dependent on finding other states where the virus is equally under control and both governments are happy to lift restrictions. That will not be easy and is likely to be a constantly changing situation, which will compound the problems facing would be travellers, so only very limited international travel will be possible, mainly later in the year.

Another issue will be the public’s reaction to borders reopening. While there are plenty of people who can’t wait for their holiday in the sun, others are much more cautious. If travel requires some sort of vaccination certificate, this may bar many younger people who will not have had a vaccine. The red tape surrounding travel, the uncertainty and the need to get a negative test a few days before you travel out, and again for the return journey, is bound to deter some for hassle or cost reasons – or both. A proportion of people with long-term health issues may be advised against or prefer not to travel. On the other hand, visiting relatives will recover more quickly: you can’t crawl round the floor playing with the children on Zoom! However, overall it all points to a slow recovery, and considerable marketing and reassurance will be needed if leisure travel is to return to more than 75%–85% of pre-Covid demand within five years.

The issues for business travel resumption are more complex. Many companies have found they can run

Left: British Airways and its sister airline Iberia both use Mototok remote-controlled battery-powered push back vehicles. British Airways/Stuart Bailey.

Heathrow

Airport


Operations Report

their business quite satisfactorily with virtual on-line meetings. It is much cheaper, and many employees are now working from home permanently, so saving on office costs. Home working also makes attending meetings in different time zones easier: a 6am meeting with a Far East customer is much easier from home – no need even to get fully dressed! Many organisations have found that attendance at virtual meetings is higher. This also extends to conferences, where many of those who attended our recent conference on aviation’s non-CO2 climate impacts have said they wouldn’t have attended if the event had been live because of the travel and accommodation costs. Of course, many technical specialists need to travel because they must be there in person, and they will resume quickly. But many businessmen will not, so the airlines will find it difficult to attract more than 70%–80% of their former customers back. The loss of premium class passengers will be keenly felt by full-service airlines. All this presupposes that all countries do return to normal: many commentators think the virus will be with us long term and will periodically flair up causing further border closures, and further depress demand.

The only brighter spot is that the demand for air freight has held up well, with tonnages last year down only 6% compared with 2019. However, with many fewer passenger flights, cargo has had to be switched from passenger planes to dedicated freight services. Overall, in 2019 68% of freight was carried on passenger aircraft, 32% on freight, but last year there was a reversal, with 30% on passenger planes and 70% on dedicated freight services (despite some 11 weeks of pre-Covid traffic levels). So far this year this split is being

maintained, but there has been a further fall in air freight tonnages, probably due in part to Brexit distortions issues around the end of the year.

There has also been a significant impact on individual airports: some like East Midlands, already a freight hub, have seen tonnages rise by 41%, and at nearby Doncaster by 117%. At the other end of the scale, Gatwick and Newcastle, with many fewer passenger flights, have seen freight traffic tumble by 90% and 81% respectively.

Overall air traffic has been very badly affected with no immediate prospect of things returning to pre Covid levels for many years. Airline and airport finances will be stretched and with low throughput, unit costs will rise, impacting the price customers will have to pay in the medium and longer term.

CLIMATE CHANGE COMMITTEE (CCC) REPORT

Established under the Climate Change Act 2008, and reporting to Parliament, this committee advises the UK Government on how to meet its Climate Change targets, including complying with Paris agreements and the UK’s net zero commitment by 2050. In December last year it published its Sixth Carbon Budget, covering the years 2033-2037. The report was formally laid before Parliament in June 2021.

This includes recommendations on what the maximum CO2 emissions can be in this period, consistent with meeting the Paris Agreement and the UK’s Net Zero commitment by 2050, and how to achieve the necessary reduction. Not unsurprisingly the targets have been tightened, as the previous target was only an 80% reduction. In the past five years emissions have fallen by 16MtCO2e per annum, whereas to meet Net Zero by 2050 the reduction must be 21MTCO2e per annum. This will be especially challenging as previous reductions have mainly been in the power generation sector, which is now extensively decarbonised, and scope for further reduction is more limited.

The report is inevitably controversial, as it is the first time the CCC have set out the detail on how Net Zero is to be achieved. Although all sectors are covered, transport comes in for special attention as its emissions are showing no signs of reducing because for many years growth has offset all the efficiency gains.

The CCC goes further by recommending that all outward International flights are included in the Net Zero target. This goes beyond what is required under

Demand for air freight has risen. British Airways.


the Paris Agreement, but the CCC argues this meets the ‘higher ambition’ provision in the Agreement. Meeting this target will be very challenging. The central scenario considered – called ‘Balanced Net Zero Pathway for Aviation’ assumes demand returns to close to pre-Covid levels by 2024. Thereafter emissions gently decline from 38MtCO2e to reach 23MtCO2e by 2050. These remaining emissions will have to be offset by greenhouse gas removals.

To meet this target, passenger demand will need to be constrained by demand management – only 25% growth is accommodated, compared with an unconstrained growth forecast of around 65%. CCC further assumed that ‘this (increase) occurs without any net increase in UK airport capacity, so that any expansion is balanced by reductions in capacity elsewhere in the UK(1)’. This implies a significant brake on airport expansion. On efficiency, CCC assumed a 1.4% per annum improvement, compared with 0.7% anticipated in the baseline. ‘This includes 9% of total aircraft distance in 2050 being flown by hybrid electric vehicles(1)’. Sustainable Aviation Fuels (SAF) are planned to contribute 25% of the fuel by 2050, with two-thirds derived from biofuels and the balance from carbon neutral synthetic jet fuel, produced via direct air capture of CO2 combined with low-carbon hydrogen(1).

CCC also considered four further scenarios, two of which assume negative growth (–17%), one the same growth rate as in the baseline (25%), and one (Widespread innovation) with 50% growth compared with 2019. It should be noted that this figure assumes significant efficiency improvements, along with extensive use of SAF – hence the scenario name ‘innovation’.

Although this may appear fairly draconian, aviation is not alone in having to supress demand – a 9% reduction in car travel is assumed by 2035, rising to 17% by 2050 (as a result of more home working, more walking and cycling and transfer to low carbon public transport). There are also reductions in other sectors – eating a third less meat, and a quarter less dairy products to reduce farming emissions.

CCC identified Aviation as one of the sectors that could benefit financially, as they think the added costs of SAF will be offset by efficiency gains. While this may be true, this does not include the costs of removing all the residual GHG. If this is included, costs are likely to higher, but the CCC calculate still affordable. Even if full decarbonisation were paid for using GHG removals to offset remaining emissions, the net added cost would be around £56 for a return ticket from London to New York.by 2050.

CCC also considered the non-CO2 impacts of Aviation. While some of their observations are at variance with the conclusions from our conference reported earlier in this Annual Report, they conclude that while significant, constraining the total distance flown each year has a greater relative benefit each year to the climate than measures that reduce the carbon intensity of flying. ‘Action to limit these non-CO2 climate effects will be necessary, although not at the expense of reducing CO2 emissions, which have a longer lasting impact on the climate’ (p 422(1)). They conclude that trying to consolidate non-CO2 effects into a single multiplier of CO2 emissions would not be robust, and therefore do not currently recommend inclusion of non CO2 effects in the aviation budgets (p 423(1)). They also note earlier in the report that for consistency with the carbon budget, aviation non-CO2 effects should target stopping contributing to global warming by 2050. In the absence of mitigation, ‘this would require year-on-year demand growth to be reduced to essentially zero by or before 2050’ (p 374(1)).

It is very clear that the challenge of meeting net zero for the aviation industry will not be easy, nor cheap. It is also important that the stricter approach advocated in this report does not encourage passengers to travel via a hub where less stringent rules and therefore lower costs – and fares – apply.

MOTOTOKS

It is often overlooked that while high level policies for eliminating CO2 are essential, small schemes also have an important role to play. One such innovation is the use of Mototoks by British Airways (BA) and its


Operations Report

sister airline Iberia. Mototoks are remote-controlled battery-powered push back vehicle, with two high torque electric motors on each side(2). They have a hydraulic platform which supports the nose gear wheel and are operated remotely. It is more efficient than a traditional diesel-powered tug.

BA are currently using them at Heathrow Terminal 5. Besides the environmental benefit, they are easy to use and control, so improving ramp safety, and have contributed to a 54% reduction in delays. Iberia is using them at Madrid and Barcelona. Aer Lingus is using them at Heathrow, and All Nippon airways has recently started using them at HSG Saga Airport in Kyushu.

The manufacturers claim very low maintenance costs, suggesting maintenance and fuel amount to less than one Euro per pushback, based on 30 pushbacks a day. The battery will, on average, push back 28 aircraft before the 80 volt battery requires recharging.

Another advantage is that they can be operated by one man (unlike tugs that require two). The driver does not need a driving licence and can be trained in 3 hours. The loading process is quick, taking 10-15 seconds, and is activated using a single button. It is also considerably safer as the vehicle is much smaller than a tug, and so less likely to damage an aircraft if an error is made in moving the vehicle.

An excellent example of how innovation can bring benefits all round: safety, economics and the environment.

AIR TRAFFIC MANAGEMENT & GLOBAL WARMING

Air Traffic Management (ATM) services throughout the world have a major role to play in reducing Global warming. There are two strands to achieving this reduction. The first is the offering of a ‘perfect green flight’ to all aircraft. This means enabling aircraft to fly both the shortest route and with the optimum flight level throughout. Typically, this means climbing away from the airport of origin in a Continuous Climb Operation (CCO), cruising at an optimal level for the type and weight of the aircraft and descending in a Continuous Descent Operation (CDO). It also requires the shortest route. Note that does not necessarily mean the shortest geographic route (a great circle), as less fuel will be used on a longer route if there is a good tailwind, or indeed if headwinds are a factor, selecting a longer route which avoids the worst of them will be beneficial.

The route with the lowest fuel consumption will be the route with least air miles (ie speed of the plane relative to the air the plane is flying in). To achieve this, decontrolling upper air space is critical to allow each aircraft to take its own optimum route, along with good metrological data and forecasts of wind speeds to identify this route.

Today routes are frequently selected on other criteria. The quickest route is often required, especially after earlier delays. This may not mean the shortest route, as airspace is busy and many ATMs impose quotas on how many flights can be handled safely over each route/sector. An earlier arrival can often be achieved by selecting an uncongested but longer route, rather than wait to take off later on a shorter route. Another factor considered by airlines in route choice is the cost of ATM for each route. Because charges vary considerably by national ATM providers, a longer route can be cheaper (despite higher fuel costs) and therefore will be favoured by airlines. However, the position is slowly changing. CORSIA and the various ETS schemes are set to penalise fuel use more heavily. Fuel costs themselves are set to rise, as more expensive SAF is gradually used in JET A, with various proposals for an increasing mandatory SAF component. The key requirement is the ATM’s ability to offer the ‘perfect green flight’. More work needs to be done to be routinely able to offer this to all flights, although as there will always be some congested areas coupled with the need to avoid military airspace, 100% cannot be achieved.

Stansted Airport control tower. Air Traffic Management services have a major role to play in reducing global warming. NATS.


The next Annual Greener by Design Conference ‘RAeS Climate Change Conference 2021 – Cutting Aviation’s Climate Change Impact’ – will be held both virtually and in person on 19 and 20 October 2021.

The Greener by Design GroupGreener by Design was formed in 1999 by the Royal Aeronautical Society and bodies representing airports, UK airlines and the aerospace industry, bringing together experts from every part of the aviation industry with Government bodies and research institutions. The initiative is supported by the Department for Business, Energy and Industrial Strategy and other bodies in the aviation sector but it is non-aligned, researching and advising independently of any interest.

Greener by DesignResearches, assesses and advises Government and industry on operational, technological, economic and regulatory options for limiting aviation’s environmental impact.Promotes best practice across the aviation and aerospace sectors.Promotes a balanced understanding of aviation’s true environmental impact and its environmental programmes, in liaison with other groups with similar objectives.Issues an annual report and holds an annual conference and workshops on sustainable aviation.

The second area where ATM can make a major contribution is in minimising contrails. The GBD conference held jointly with DLR (summarised on p 16 in this annual report), identified that only a small proportion of flights cause contrails. Those that do increase the average contribution to global warming of all aircraft by over 100%. Meteorological data, identifying areas where conditions are conducive to contrail formation, can be used by ATMs to divert traffic around specific areas/levels, so dramatically reducing the incidence of contrails (and hence the global warming impact of aviation). A trial is currently underway to identify how practically this can be achieved, taking advantage of the currently

reduced level of European air traffic. Although the diversion may use a small amount of extra fuel, in practice the amount is tiny, and negligible in comparison to the dramatic reduction achievable in the non-CO2 warming effect of aviation. With current metrological forecasts, this is a very quick and practical way of halving the total global warming effect of aviation.

References1. Climate Change Committee Report: Sixth Carbon Budget: The UK’s route to Net Zero2. Mototok website: accessed 10 March 20213. Civil Aviation Authority: Traffic statistics


Global Market-Based Measures

DESIGNbyGreenerGreener

Air Travel – Greener by Design draws on the expertise of industry and academia.Any views expressed in this report are those of Greener by Design and do not necessarily represent the view of the Royal Aeronautical Society as a whole.

For further information or comments on this paperAir Travel – Greener by DesignROYAL AERONAUTICAL SOCIETYNo.4 Hamilton PlaceLondon W1J 7BQ, UK+44 (0)20 7670 4300www.aerosociety.com/get-involved/specialist-groups/air-transport/greener-by-design/

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