MONTRÉAL 2010

REPORT

REPORT OF THE INDEPENDENT

EXPERTS ON THE MEDIUM AND

LONG TERM GOALS FOR

AVIATION FUEL BURN REDUCTION

FROM TECHNOLOGY

INTERNATIONAL CIVIL

AVIATION ORGANIZATION

Doc 9963

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MONTRÉAL 2010

REPORT

REPORT OF THE INDEPENDENT

EXPERTS ON THE MEDIUM AND

LONG TERM GOALS FOR

AVIATION FUEL BURN REDUCTION

FROM TECHNOLOGY

INTERNATIONAL CIVIL

AVIATION ORGANIZATION

Doc 9963

(ii)

Published in English only, by the INTERNATIONAL CIVIL AVIATION ORGANIZATION 999 University Street, Montréal, Quebec, Canada H3C 5H7 For ordering information and for a complete listing of sales agents and booksellers, please go to the ICAO website at www.icao.int Doc 9963 Report of the Independent Experts on the Medium and Long Term Goals for Aviation Fuel Burn Reduction from Technology Order Number: 9963 ISBN 978-92-9231-765-2 © ICAO 2011 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, without prior permission in writing from the International Civil Aviation Organization.

G OA L S F O R AV I A T I O N F U E L B U R N

R E D U C T I O N F R O M T E C H N O L O G Y

PROF N. CUMPSTY

PROF J. ALONSO

MR S. EURY

DR L. MAURICE

MR B. NAS

MR M. RALPH

PROF R. SAWYER

I C A O C O M M I T T E E O N AV I A T I O N E N V I R O N M E N T A L P R O T E C T I O N

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GOALS FOR AVIATION FUEL BURN REDUCTION FROM TECHNOLOGY

EXECUTIVE SUMMARY

The seventh meeting of the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP/7) held in February 2007 requested advice from Independent Experts (IEs) on the prospects for reduced aviation fuel burn from technology advances over the medium term (MT) and long term (LT), specifically ten and twenty years. The assessment by the IEs of the reduction in aviation fuel burn from technology advances followed a two-step process: an industry led Fuel Burn Reduction Technology Workshop held in London UK in March 2009 and then a formal Fuel Burn Reduction Technology Goals Review, held in Atlanta U.S. in May 2010 led by the IEs. There were seven IEs drawn from France, Sweden, the UK and the U.S.; in addition a representative from Singapore took part up to the initial workshop but then withdrew and representatives from PR China and Italy withdrew around the beginning of the study.

Because the IEs had limited resources they considered only two aircraft types: the single-aisle aircraft (110-210 seats) and a relatively small twin aisle (211-400 seats). Together these aircraft categories are responsible for around 85% of the global fuel burn by commercial aircraft. The goals are expressed as reductions from current levels, which are taken to be those from reference aircraft in service in 2000. The medium term goal therefore represents some 20 years progress whereas the long term goal is only a further ten years on. The single-aisle reference (referred to as SA) is the 737-800 and A320-200 class whilst the so-called small twin aisle (referred to as STA) is the 777-200ER and A330 class. Given that the single aisle aircraft have earlier origins than the twin aisles the potential efficiency gains from new technology for the SA are expected to be larger.

The IEs developed three basic Technology Scenarios (TS). One, referred to as TS1, corresponds to the expectation of a continuation of the current trend where industry continues to introduce new technologies. TS2 represents the effect of increased pressure to reduce fuel burn. TS3 represents even greater pressure for fuel burn reduction and is considered in two parts: the pure technology strand which includes consideration of technology improvements currently deemed likely to be non-viable or unaffordable but might become acceptable under increased pressure; the other strand envisages modest changes to the specification of aircraft and aircraft mission which have the potential to reduce fuel burn. This is in line with the IEs Terms of Reference (ToR), as detailed in CAEP-SG/20082-WP/20 which states “Only operational changes as necessitated by fuel burn reduction technologies need be considered”.

Technology improvements were presented by industry at the workshop and these were augmented and refined on the basis of further discussion and the input from other bodies. These and other future technology improvements were used in the modelling carried out by the IEs and by International Coalition for Sustainable Aviation (ICSA), Georgia Institute of Technology (GaTech), German Aerospace Centre (DLR), and Qinetiq. For incorporation into the models, the numerous technologies were grouped into baskets for aspects of the engine, for the airframe aerodynamics and for the aircraft weight. The judgement of the IEs was required for this, since some technologies are exclusive, some are additive and others are conditional in the sense that more than one must be introduced. Some allowance was made for the probability of achievement as well as for the likely benefit and in some cases likely associated penalties.

In the absence of any standard, it was necessary to define some airplane reference for each airplane category (Regional Jets, Single Aisles, Small Twin Aisles) to benchmark the technology potentials for future milestones (2020 and 2030). Technology potentials were evaluated based upon assumed baseline airplanes in 2020 and 2030. The IEs adopted a fuel burn metric for the purpose of their study, whilst recognising that discussions are ongoing within CAEP to choose a metric for setting a Standard for CO2 emissions. For this

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study the metric used was kilogram of fuel burned per available-tonne-kilometre (kg/ATK) to be calculated at the maximum payload maximum range condition.

It was found that the different calculations of fuel burn for the baseline aircraft agreed reasonably well in terms of absolute kg/ATK but it was also found that if the precise inputs were matched (e.g. lift/drag ratio, empty weight/maximum take-off weight, engine specific fuel consumption, reserve fuel assumptions) then the agreement in absolute values was very close even when different models were used. Even when the absolute values did not agree exactly, the differences predicted for the introduction of the new technologies were sufficiently close that the overall predictions were considered to be sufficiently accurate for the goal-setting exercise. It was considered that the similarity of results despite the differences among assumptions and models tended to support the robustness of the estimates.

The resulting predicted reductions in fuel burn are set out in the report in the form of graphs with lines showing reductions corresponding to the different technology scenarios. The lines are anchored at shorter design ranges (2125 nm) by the single-aisle reference aircraft and at longer design ranges (5750 nm) by the small twin-aisle reference aircraft. The values at the anchor points are detailed below.

2020 2030

SA STA SA STA

TS1 23 19 29 26

TS2 29 25 34 35

TS3 41 41

TS3 Open rotor 48

Estimated percent reduction in fuel burn metric at the single aisle (SA) and small twin-aisle (STA) anchor points relative to 2000 baseline at maximum payload maximum range

Whilst TS1 represents what would happen with continued and consistent funding and dedicated programs, and without additional pressure other than market forces, TS2 does represent a clear challenge. Therefore the goal has been set as a band in kg/ATK below TS2 for 2020 and for 2030 as a band between TS2 and TS3. Achieving the goal has been defined by the IEs as having a value of kg/ATK below the TS2 line, but additional progress would be indicated by moving down towards the TS3 line and the band has been included to indicate what level of further progress might be possible. The IEs felt that reaching the level corresponding to TS2 by technology alone was possible though by no means certain, but, when coupled with the potential arising from the changes in aircraft mission specification and aircraft configuration, the probability of achievement is substantially higher. Therefore the goal will be said to have been achieved in 2020 if the fuel burn reduction relative to the 2000 baseline exceeds 29% for the single aisle reference aircraft and exceeds 25% for the small twin-aisle aircraft with suitable interpolation and extrapolation for other aircraft categories. In 2030 the goal will be achieved with similar interpolation across the range of aircraft from single- to twin-aisle aircraft if the reduction exceeds 34% to 35% relative to the 2000 baseline. A 35% reduction by 2030 corresponds to an annual compound reduction of about 1.4%, which may be compared with the ICAO aspirational goal of 2% per annum fuel efficiency improvement out to 2050. The ICAO aspirational goal relates to the entire commercial aircraft/air-traffic system as a whole, whereas the IEs have only considered individual aircraft design and only its technology aspect. The modelling by the IEs and other organisations confirms the view that technology on its own is not able to deliver the reductions which are judged to be required by the ICAO goals.

Further reductions are possible and the ultimate goal for 2030 with TS3 could be as large as 41% with a turbofan engine or 48% if open rotors were used. In addition, it has been found that quite modest changes in design Mach number, design range and wing span (the latter having an effect on airport layout) can lead to additional savings which are comparable to a change in TS level from 1 to 2 or from 2 to 3.

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The IEs believe that these goals must be regarded as interim. The topic should be revisited with full participation and engagement with industry when the CO2 certification parameter has been resolved. The IEs also believed that it is important to conduct system analyses to evaluate the contributions of various strategies toward meeting these goals, particularly the overall system effects of changes in Mach number and design ranges, including the potential effect on the number of operations, which could affect safety, operating costs, noise exposure and air quality impacts.

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ACKNOWLEDGEMENTS

In carrying out this review the Independent Experts (IEs) have been helped by people in a number of organisations, including the Georgia Institute of Technology, the German Aerospace Centre – DLR, the International Coordinating Council of Aerospace Industries Associations, the International Council on Clean Transportation (part of the International Coalition for Sustainable Aviation) and QinetiQ. The IEs wish to express their gratitude to all of them, but especially to Dr. Michelle Kirby for also hosting the review meeting in Georgia Tech in May 2010.

An essential part of the review has been carrying out calculations specifically for the IEs under the direction of Professor Juan J. Alonso. The IEs particularly wish to thank Sean R. Copeland and Thomas D. Economon, both graduate students in Stanford University, for their excellent work.

It is possible that the review would not have taken place without the work of Peter Newton who, until his retirement early in the review, was employed by the UK Department for Business, Innovation and Skills. In addition Peter Newton played a key part in setting up the workshop in March 2009. It is also true that the review would have foundered without the excellent work of Dr. Samantha Baker, also of the UK Department for Business, Innovation and Skills. Her contribution in facilitating and supporting the meetings and telephone conferences, and in preparing the report is gratefully acknowledged.

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TABLE OF CONTENTS

Executive Summary ............................................................................................................................................................ 2 Acknowledgements ............................................................................................................................................................. 5 Table of Contents ............................................................................................................................................................... 6 List of Figures ...................................................................................................................................................................... 7 List of Tables ....................................................................................................................................................................... 7 1 Introduction .......................................................................................................................................................... 8 2 Fundamentals...................................................................................................................................................... 13 3 The Goal Setting Process ................................................................................................................................. 17 3.1 Fuel Efficiency Metric ....................................................................................................................................... 17 3.2 Fuel Burn per ATK ........................................................................................................................................... 17 3.3 Fuel Efficiency versus Range ........................................................................................................................... 17 3.4 Technology Scenarios ........................................................................................................................................ 18 3.5 Making Use of the Technology Scenarios ..................................................................................................... 19 3.6 Constraints and Business Trade-offs .............................................................................................................. 19 3.7 Technology Readiness Levels (TRLs) ............................................................................................................. 19 4 Methodology ....................................................................................................................................................... 21 4.1 Reference Aircraft .............................................................................................................................................. 21 4.2 Technological Possibilities ................................................................................................................................ 22 4.3 Technologies and Concepts Considered ........................................................................................................ 23 4.4 Modelling Software ............................................................................................................................................ 27 5 Results .................................................................................................................................................................. 29 5.2 IE Analysis .......................................................................................................................................................... 29 5.3 Medium Term ..................................................................................................................................................... 31 5.4 Long Term .......................................................................................................................................................... 32 6 TS3 – Doing Things Differently ..................................................................................................................... 35 7 Presentation of Goals ........................................................................................................................................ 40 7.2 2020 MT 10 Year Goal ..................................................................................................................................... 41 7.3 2030 LT 20 Year Goal....................................................................................................................................... 42 7.4 Meeting the Goals .............................................................................................................................................. 42 7.5 Beyond 20 Years – Achieving Greater Ambition 2030-2050 ..................................................................... 42 7.6 System Goals ...................................................................................................................................................... 43 8 Conclusions ......................................................................................................................................................... 44 9 Recommendations ............................................................................................................................................. 46 Glossary of Terms ............................................................................................................................................................ 47 List of References ............................................................................................................................................................. 49 Appendix A-1: List of Presentations for the March 2009 Workshop held in London, UK ............................ 50 Appendix A-2: List of Presentations/Agenda for the May 2010 Review held in Atlanta, U.S. ...................... 53 Appendix A-3: List of Attendees for the May 2010 Review held in Atlanta, U.S. ............................................ 56 Appendix B: Key Data for the Reference Aircraft ............................................................................................. 58 Appendix C: Basket of Technologies ................................................................................................................... 59 Appendix D: Summary of Modelling Results ....................................................................................................... 63 Appendix E: TRL scale ........................................................................................................................................... 64

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LIST OF FIGURES

Figure ‎1.1: Diagrammatic payload-range diagram for a commercial airliner. (Maximum structural payload also corresponds to maximum zero-fuel weight. For a given mission, take-off weight is zero fuel weight plus the weight of fuel, which is fuel to be consumed in the mission plus reserve fuel.) .................................................... 11 Figure ‎2.1: Fuel burn (kg-fuel/ATK) versus range for a hypothetical aircraft. Take-off and climb fuel 0.02MTO; reserve fuel 0.05MTO; aircraft empty weight=0.45(MTO)max. .................................................................... 15 Figure ‎3.1: Fuel burn versus distance profiles for a selection of aircraft types. (Note the fuel metric here is based on payload derived relative to operating empty weight.)................................................................................. 18 Figure ‎5.1: Values of the fuel burn metric for all aircraft analyzed by IEs and participating organizations. Fuel burn metric plotted against R1 range. Note payload is defined here as MZFW - MWE ..................................... 30 Figure ‎5.2: Fuel burn metric changes plotted against R1 range for the 2020 MT time frame in TS1 and TS2. Results from aircraft optimized by IEs and participating organizations with same R1 range have been averaged. ............................................................................................................................................................................. 31 Figure ‎5.3: Fuel burn metric changes plotted against R1 range for the 2030 time frame and in TS1, TS2, TS3, and TS3-OR. Results from aircraft optimized by IEs and participating organizations with same R1 range have been averaged. ................................................................................................................................................................... 33 Figure ‎6.1: Comparison between fuel burn metric improvements achieved by technology alone and with aircraft mission specification changes. Single aisle reference aircraft (B737-800). This figure reflects the calculations carried out by the IEs only. ....................................................................................................................... 35 Figure ‎6.2: Comparison between fuel burn metric improvements achieved by technology alone and with aircraft mission specification changes. Small twin aisle reference aircraft (B777-200ER). This figure reflects the calculations carried out by the IEs only.................................................................................................................. 37 Figure ‎7.1: MT 10 year and LT 20 year fuel burn technology goals versus R1 ...................................................... 40 Figure ‎7.2: MT 10 year and LT 20 year fuel burn technology goals versus ATK*1000........................................ 41

LIST OF TABLES

Table ‎4.1: IE Assumptions for expected percent improvements in propulsion, aerodynamic, and structural efficiencies in each Technology Scenario, time frame and for the two aircraft categories (SA and STA). The percentage changes refer to the parameters listed in the table. ................................................................................. 23 Table ‎5.1: Summary of SA aircraft optimized under different technology scenarios and time frames. This table reflects the calculations carried out by the IEs only. ................................................................................................... 33 Table ‎5.2: Summary of STA aircraft optimized under different technology scenarios and time frames. This table reflects the calculations carried out by the IEs only. ......................................................................................... 34 Table ‎6.1: Summary of improvements and resulting designs for SA changes to mission specifications including span, cruise Mach number, and R1 design range beyond TS1 2020 and TS2 2030 technology improvements. This table reflects the calculations carried out by the IES only. .................................................... 36 Table ‎6.2: Summary of improvements and resulting designs for STA changes to mission specifications including span, cruise Mach number, and R1 design range beyond TS1 2020 and TS2 2030 technology improvements. This table reflects the calculations carried out by the IEs only. .................................................... 38 Table ‎8.1: Estimated percent reduction in fuel burn metric at the SA and STA anchor points relative to 2000 baseline for maximum payload maximum range based on all contributing sources (see Appendix D). ............ 44 Table ‎8.2: Annual compound percentage reductions in fuel burn metric for SA/STA categories and 2020/2030 based on all contributing sources. ............................................................................................................. 44

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1 INTRODUCTION

1.1 The seventh meeting of the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP/7) held in February 2007 requested advice from Independent Experts (IEs) on the prospects for reduced aviation fuel burn from technology advances over the medium term (MT) and long term (LT), specifically ten and twenty years from 2010. The CAEP Steering Group provided guidance on the remit for this task: the Review should consider the effects of “major technologies” on fuel burn/efficiency, as well as combinations of improvements from aircraft and engine, including best possible integration. The panel of experts were to focus their analyses only on technologies and not on operations or new types of fuels. Only operational changes required to implement and derive the benefits of fuel burn reduction technologies needed to be considered and interdependencies were to be qualified where quantification was not possible.

1.2 The assessment of the reduction in aviation fuel burn from technology advancements over ten and twenty years was to follow a two-step process:

a) An industry-led Fuel Burn Reduction Technology Workshop to be held in early 2009;

b) A formal Fuel Burn Reduction Technology Goals Review, to be held early in the ninth CAEP cycle (CAEP/9) led by the IEs.

1.3 The first step, the Fuel Burn Reduction Technology Workshop was led by ICCAIA and held in London, UK between 25 and 26 March 2009. The workshop was an opportunity for industry and research organizations to share information on the status of the technologies for fuel burn reduction explored by airframe and engine manufacturers and government researchers. The IEs attended the Workshop for familiarisation with the materials presented. A list of presentations from the Workshop can be found in Appendix A-1. The IEs provided CAEP with a formal report reflecting on the Workshop and information received subsequent to it at the meeting of the CAEP Steering Group in 2009 (SG2009), CAEP-SG/20093-WP/21.

1.4 The CAEP/8 Steering Group in 2008 required a final report from the IEs to be delivered to the first meeting of the CAEP/9 Steering Group in 2010 and specified that the review should address the following:

a) the status of technology developments for fuel burn reduction that will be brought to market within ten years from the date of review, and the twenty year prospects for fuel burn reduction technologies suggested by research progress.

b) assessments for fuel burn reductions in the future, stated as improvements against an identified performance metric.

c) recommending mid- and long- term fuel burn/efficiency technology goals at the overall aircraft level, taking into account the information presented and using their judgment as appropriate.

d) assessment of the possibility of success in achieving the recommended mid and long term technology goals, based on experience from past research and development programs

e) comment on the importance of fuel burn as the primary technology focus, based on current scientific understanding of environmental impact of aircraft engine emissions.

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f) report on the status of understanding of environmental impacts of aircraft engine emissions and identify areas where further research is needed to help focus ongoing and future technology development efforts.

1.5 The policy importance of this IE review is clear. Many governments now advocate that to avoid the most dangerous climate change it will be necessary to hold temperature rise to less than about 2°C above pre-industrial values, and this is reflected in the UNFCCC Copenhagen Accord. To date, over half of the amount of CO2 which corresponds to this temperature rise has been released. In 2009, ICAO agreed to a global goal for an annual improvement of 2% in fuel efficiency of the international civil aviation in-service fleet for the medium-term (up to 2020) and an aspirational global goal for an annual improvement of 2% in fuel efficiency of the international civil aviation in-service fleet for the long-term (up to 2050) as part of the contribution of the sector to stabilize and subsequently reduce aviation‟s absolute emissions contribution to climate change. (It is noteworthy that the metric for efficiency was not defined.) This will require significant resources and investments to improve all aspects of the aviation sector. ICAO has committed to undertake further work on medium and long-term goals, including exploring the feasibility of goals of more ambition including carbon-neutral growth and emissions reductions. It is therefore important to understand what reductions in fuel burn and hence CO2 emissions technology can be expected to deliver.

1.6 The title of the review refers only to Fuel Burn Reduction Technology, whereas the underlying concern of the review is climate change impacts. Items e) and f) of the remit, in section 1.4 above, support this wider understanding. As is well known, several emissions contribute to climate change; only in the case of CO2 is the impact known with a high level of confidence and for other emissions considerable uncertainty remains. Moreover the persistence of the pollutants varies, with CO2 being most long lived, so the impacts differ depending on the time over which they are assessed. There are several metrics available to represent the impacts of emissions, including Radiative Forcing (RF), Global Warming Potential (GWP), and Global Temperature change Potential (GTP). The importance of different species and operations varies depending on the metric adopted and on assumptions adopted (e.g., time horizon).

1.7 The complexity involved in looking at climate change and the difficulties inherent in considering only the creation of CO2 convinced the IEs that the narrower remit of fuel burn, referred to in the title of this Review, is more appropriate. Their wish to consider only fuel burn was endorsed by SG/2009.

1.8 A second progress report was provided to CAEP in February 2010 via CAEP/8-WP/11. The IEs identified that progress had not been as significant as they would have liked, largely due to a conflict in resources for ICCAIA with work to develop CO2 Standards (CAEP/8 WG3 Remit E.08). The meeting noted the perceived lack of coordination between the industry and the IEs, and urged that the preparatory work for the review be accelerated by the industry in order to deliver the review within the timescale requested by CAEP. The formal Review was held in Atlanta, U.S. between 25 and 27 May 2010. A list of attendees and presentations from the Review can be found in Appendix A-3.

1.9 Throughout the process, engagement with stakeholders was critical. Attendees at the Workshop and the Review included representatives from government, industry, academia, research establishments and NGOs. They have also been kept informed of progress at a working group level, predominantly through WG3 which has responsibility for the delivery of the review to CAEP. In addition, regular teleconferences between the IEs and ICCAIA were instrumental in preparing for the Review.

1.10 The Fuel Burn Reduction Technology Independent Experts (IEs) nominated by various CAEP Members and Observers are:

Nick Cumpsty, UK (Elected by the IEs as Chair)

Juan J. Alonso, U.S.

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Serge Eury, France

Lourdes Maurice, U.S.

Bengt-Olov Nas, IATA

Malcolm Ralph, UK

Robert Sawyer, ICSA

1.11 IEs were also nominated by Peoples Republic of China, Singapore and Italy, and useful inputs were made in the early stages but unfortunately they were not able to take part in the Review or in the preparation of this report.

1.12 The IEs are aware that the task given them, assessing prospects for fuel burn reduction technologies and setting fuel burn goals, is one of great complexity. Earlier IE Reviews to establish medium and long term technology goals have looked at oxides of nitrogen (NOx) or noise, but this Review looks at an issue which is central to the competitive position of all stakeholders: engine makers, airframe makers and airlines. Furthermore, fuel burn does not lend itself to convenient demarcation between engines, airframes, aircraft mission specification and the way the aircraft is operated; all these impact fuel burn and therefore need to be considered.

1.13 The IEs were conscious that this goal-setting review differs from earlier ones in another way: the lack of an existing regulatory standard to provide a baseline. The IEs concluded that the baseline should be in-production technology of 2010, while recognising that the technologies embodied were matured and design decisions were made long before. In practice the IEs judged the reference aircraft to embody, on average, 2000 technology.

1.14 The IEs are aware of the discussions going on within CAEP on the most appropriate metric for CO2 Standard. In order to proceed and to be able to report in 2010 the IEs urgently needed a fuel efficiency metric applicable to technology goals within the review process. The IEs had extensive discussion on the metric to be used for fuel burn and elected to use kg-fuel/Available-Tonne-Kilometre (kg/ATK). This is simple and the use of available-tonne focuses on the aircraft, and its technology, rather than the operation of the airline. The metric used for this review does not pre-empt discussions elsewhere in CAEP and the IEs have co-ordinated with WG3 to keep abreast of relevant developments. The fuel burn metric was evaluated at the maximum-payload maximum-range point, denoted by A at range R1 in Figure 1.1. This is a simple and hypothetical version of a plot widely used in the industry to show range and payload variation for a given aircraft. The line shown corresponds to the aircraft taking off with the maximum allowable payload for the range. In the horizontal portion the payload is unaltered as more fuel is added to allow the range to be flown, but when point A is reached, at range R1, the aircraft has reached its maximum take-off weight. For greater range than R1, when increased fuel must be carried, there must be a compensating reduction in payload to limit the take-off weight to its maximum value. As the mission requires additional range beyond B, where the maximum fuel capacity has been reached, further decreases in payload become necessary. The payload used here is based on the manufacturer‟s empty weight (MWE), making the payload larger than the frequently used operating empty weight (OWE) and which includes operational items determined by the airline customer.

1.15 Aircraft operations are outside the scope of this review, but issues related to operations impinge on any assessment of fuel burn. For short flights the way in which take-off, climb and descent are managed influences the mission fuel burn strongly. For all flights the reserve fuel which is carried, fuel which would not normally be burned during the mission, has been considered. However, none of these factors was varied for this review as they were felt to be too close to purely operational issues. On the other hand, the effects of

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varying cruise Mach number and of varying the maximum range achievable at maximum payload were investigated (referred to later as R1).

Figure ‎1.1: Diagrammatic payload-range diagram for a commercial airliner. (Maximum structural payload also corresponds to maximum zero-fuel weight. For a given mission, take-off weight is zero fuel weight plus the weight of fuel, which is fuel to be

consumed in the mission plus reserve fuel.)

1.16 Technology Readiness Level (TRL), described in Appendix E, was extensively discussed. It was recognized that anticipating the TRL for a new and immature technology in ten or twenty years time is a matter of expert judgment as discussed more fully in section 3.7. The IEs decided for the setting of both the 10 year (MT) and 20 year (LT) goals they should consider the levels of fuel burn performance thought likely to have been achieved by the due dates and matured to TRL 8 – ready for service which is in line with the approach adopted for the NOx IE review. In making this judgment it is necessary to combine the present TRL with some assessment of likelihood of the advances being made. Some greater confidence was achieved in the validity of judgment by independent assessments being made by government, non-governmental organisations, university and industry experts as well as the IEs.

1.17 The IEs concluded that four classes of aircraft should be considered: regional jets, single-aisle aircraft, small twin-aisle (211-400) seats and large twin-aisle (more than 400 seats). This division is in line with the CAEP Forecasting and Economic Support Group (FESG) categories. Because of limitations of resources, the IEs have focussed the majority of their work on the single-aisle (SA) and the smaller twin-aisle categories (STA), since these together account for 85% of the total fuel burn by commercial aircraft. Supplementary analysis on the regional jets was provided by some participants.

1.18 The IEs adopted three Technology Scenarios (TS) for 2020 and 2030, which are intended to reflect a range of possible future scenarios and represent technology responses to increasing pressure for improvement dependent on, for example, a variety of future environmental pressures and fuel prices. The formulation of these scenarios has adapted somewhat as the study has progressed and they are described in more detail in sections 3.4 and 3.5:

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TS1 – „Continuation‟ - a continuation of the current trend of improvement, resulting from current market forces and environmental pressures.

TS2 – „Increased pressure‟ - increased pressure to incorporate more technologies to reduce fuel burn though still with „tube and wing‟ architecture.

TS3 – „Further increased pressure‟ justifying more radical technology innovations and allowing „doing things differently‟ - including modest alterations to aircraft configuration and/or modest alterations to aircraft mission specifications. The open rotor applied to the single-aisle aircraft is included in this category.

1.19 The IEs have discussed issues which relate to the specification of the aircraft, a feature of consideration under TS3. Whilst the remit of the task is to develop goals that can be delivered through technology progress, there are significant inter-relationships with other variables: changing the specification of the mission or the aircraft can change the technologies available and the magnitude of the benefits produced. The IEs have come to realise that a considerable part of the benefit of improved technology introduced in the past has been used to improve the performance of the new aircraft, mainly range, rather than to reduce fuel burn per ATK. They therefore believe it is essential to look at alterations in terms of aircraft mission specification, particularly for the longer term, which is in line with their ToR and is discussed further in Section 3.5.3. Consideration of operational issues consequent upon changes of specification should, it was felt, be postponed until the potential benefits are quantitatively estimated.

1.20 Aircraft design is frequently a trade-off among conflicting requirements and in the present context concern has been raised that noise or NOx emissions might be increased by the alterations to reduce fuel burn. For the purposes of this review, the IEs have assumed that aircraft would continue to be specified and designed so as to meet existing regulatory standards and goals for NOx and noise.

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2 FUNDAMENTALS

2.1 It is possible to get insight into some of the controlling features of commercial aircraft fuel burn by simple analytic methods based on some idealisations. The approach adopted is set out in a paper by Poll1. The aircraft is assumed to operate in an idealised manner during cruise, which is the majority of the flight, at constant lift-drag ratio, L/D. Likewise the engines are assumed to operate at a constant overall efficiency, which corresponds to operating with constant specific fuel consumption, sfc. To achieve this there is a continual climb during cruise to maintain optimum L/D and sfc as the weight of the aircraft decreases – an idealised procedure referred to as cruise-climb. Most aircraft on long flights change altitude in steps as their weight decreases.

If (MF)cruise is the weight of fuel burned during cruise and M1 is the aircraft weight at start of cruise, then the long-established Breguet2 equation gives for optimum cruise-climb

(MF)cruise/M1 = 1 – exp{–R/H},

where R is the range and H is the range factor which is given, for flight speed V, by

H = (V . L/D) / sfc

If plausible assumptions are made for lift/drag ratio and engine specific fuel consumption, numerical values may be created: it is assumed in this section that L/D=20 and sfc= 0.525 kg h-1kg-1, which are values representative for cruise of the latest twin-aisle aircraft. In addition cruise speed is taken to be 252 m/s, corresponding to a Mach number of 0.85 at 35000 ft in a standard atmosphere. It then follows that

H = 34.6×103 if R is in kilometres and 18.65×103 if R is in nautical miles.

2.2 Fuel is also burned during taxi, take-off, climb and landing and here it will be assumed that fuel equal to 2% of take-off weight is used in a way which exceeds that needed for optimum cruise between take-off and landing points. It is also necessary to carry reserve fuel, with the amount dependent on rules and the region of operation. The weight of reserve fuel can have a significant impact on the fuel burn and here this weight is taken to be 5% of the take-off weight, a value which corresponds quite closely with the assumed reserve used in section 5 of this Report. It is assumed that take-off occurs with the minimum weight of fuel consistent with range and reserves; increasing range invariably requires an increase in the weight of fuel at take-off.

2.3 The Breguet equation allows the weight of fuel consumed on a mission to be found subject to the stated assumptions. Three key weights determine the performance of the aircraft: maximum take-off weight (MTOW), empty weight (ME) and maximum payload (MPL)max. At maximum take-off weight, as an idealisation, the wing lift, engine thrust and structure should be approaching their acceptable limits. Empty weight is taken here as the manufacturer‟s empty weight before items like seats are added and maximum payload, (MPL)max therefore includes cabin fittings as well as passengers, baggage, and freight. The ratio of empty weight to maximum take-off weight ME/MTOW is a measure of the level of technology; improving the material properties, joining technology and structural design all lead to a reduction in ME/MTOW. For the results presented in this section the ratio is taken to be 0.45, which is typical of a recent twin-aisle aircraft.

1 Poll, D.I.A. The optimum aeroplane and beyond. Lanchester Lecture of the Royal Aeronautical Society. 2009 Aeronautical Journal 113. 2 Breguet, L. Calcul du poids de combustible consumme par un avion en vol ascendant. 1923 Comptes Rendus de l’acadmie des sciences, 177, pp. 870-872

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The ratio tends to be a bit higher for single-aisle aircraft than twins and the ratio tends to fall as aircraft are stretched to make better use of the structure.

2.4 For the present it will be assumed that the aircraft is operating at the highest payload allowable for the range chosen. Operation is therefore along the line shown in Figure 1.1. Along the horizontal part of the line, from the axis to point A, the payload is constant and as range is increased the fuel weight is increased until at point A the maximum take-off weight is reached. Point A is the maximum-payload maximum-range point and the range here is denoted by R1. For the present report point A is taken to be the design point. The weight of fuel for range R1 is denoted by (MF)R1 so the maximum take-off weight is given by

MTOW= ME + (MPL)max+ (MF)R1

2.5 For operation between points A and B the maximum take-off weight is assumed constant so that any increase in range beyond R1 implies a reduction in payload coupled with a corresponding increase in fuel load.

2.6 In considering a new aircraft design the selection of design range, here taken as R1, is a decision about how the difference between maximum take-off weight and empty weight is used, that is how payload and weight of fuel are split at point A. Design range is therefore a decision on the ratio of the weight of fuel for range R1 to the maximum payload (MF)R1/(MPL)max at point A in Figure 1.1. Long range designs have larger values of this ratio than short range designs. The ratio of fuel weight for R1 to maximum payload, (MF)R1/(MPL)max, and the ratio of empty weight to maximum take-off weight, ME/MTOW, therefore determines maximum payload as a fraction of maximum take-off weight.

2.7 Figure 2.1 shows the fuel burn parameter kg-fuel/ATK plotted against range derived by the approach outlined above. There are two sets of curves. The solid line corresponds to region AB in Figure 1 where maximum take-off weight is constant (in this case such that the empty weight is equal 0.45MTO). Each broken line corresponds to operation where the payload is held constant at its maximum value; the three lines shown correspond to different ratios of fuel weight for range R1 to maximum payload, (MF)R1/(MPL)max: a value for this ratio of 0.75 corresponds to a single aisle aircraft like the Boeing 737 or A320 whilst 2.25 corresponds to a long-range version of a twin aisle, like the Boeing 777-200LR. As stated earlier, the curves shown are for hypothetical aircraft flown in an idealised manner. In practice, and particularly for very long ranges, many engineering design constraints need to be considered and these may limit the achievement of some theoretical performance improvements.

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Figure ‎2.1: Fuel burn (kg-fuel/ATK) versus range for a hypothetical aircraft. Take-off and climb fuel 0.02MTO; reserve fuel 0.05MTO; aircraft empty weight=0.45(MTO)max.

2.8 The broken and solid lines in Figure 2.1 intersect at range R1 and, as the fraction of fuel at point A increases, so too does R1. The fuel burn parameter rises steeply for range in excess of R1, primarily because the payload is being reduced in the denominator in the fuel burn parameter. For ranges below R1 there is a minimum in the fuel burn parameter, which is slightly below the value at R1, and the small rise in fuel burn prior to reaching R1 is a consequence of the cost inherent in carrying fuel which is burned late in the flight. What is more striking is that the minimum level of fuel burn increases with the increase in design range, i.e. with increase in (MF)R1/(MPL)max, even though the technology assumed in all cases is the same.

2.9 The steep rise in fuel burn parameter for ranges below about 1500 nm is a consequence of the fuel required for take-off, climb and descent. This increase is very dependent on the assumptions made for the excess, which in turn depends strongly on the way the aircraft is flown and the air traffic management constraints imposed. The pilot has some control over the engine thrust, speed and climb (or descent) rate, and these should be optimised, but additional requirements of air traffic management may also constrain the flight to be far from that for lowest fuel burn. If these phases of the flight can be optimised there is potential to reduce the excess fuel with significant impact on fuel burn for short flights, for example, flights under 1000 nm.

2.10 As already noted, in Figure 2.1 all parameters related to the technology level of the aircraft (lift/drag ratio, engine specific fuel consumption, empty weight/maximum take-off weight) are held constant for this comparison. The differences in fuel burn parameter for the three curves are an ineluctable consequence of the specification of design range in terms of (MF)R1/(MPL)max. The absolute levels in Figures 2.1 depend, of course, on the parameter values assumed and these could be easily varied to agree with measured data. The values of input parameters correspond to a modern twin-aisle aircraft and for single-aisle, shorter range aircraft L/D is typically lower than 20 and sfc is typically higher than 0.525. As a result, data from in-service aircraft, such as Fig.3.1, tend to obscure the consequence on the fuel burn parameter directly attributable to range.

2.11 In Figure 2.1 it is assumed that the maximum permissible payload is being used; for the shorter ranges this is the maximum payload for the aircraft and for ranges above R1 it is the payload which with the

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

kg-f

uel

/ATK

Range in nautical mile

Maximum Take-off Weight fixed

Fuel weight for R1=0.75 Max.Payload

Fuel weight for R1=1.5 Max.Payload

Fuel weight for R1=2.25 Max.Payload

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fuel load leads to maximum take-off weight. Aircraft often operate with the payload below the maximum allowed (load factor less than unity) either because the airline has chosen to configure the aircraft in such a way that the maximum payload cannot be achieved or because the requisite number of passengers and weight of cargo has not been loaded. In either case the value for the metric for this case, fuel burn per revenue ton kilometre, will be higher. Put another way, the lowest fuel consumption will occur when the ratio of payload to empty weight is as high as possible.

2.12 The results presented here do not remove the need for more complete modelling of aircraft. They are presented to show how many features of aircraft performance are determined by quite fundamental features of the system at cruise: lift-drag ratio, engine specific fuel consumption, the ratio of empty weight to maximum weight and the specification of design range R1. They also demonstrate that design decisions regarding range determine the minimum level of fuel burn which can be achieved for a given level of technology: long range designs inevitably have increased kg-fuel/ATK compared to medium range aircraft at the same technology level.

2.13 The most efficient operation in terms of fuel burn always occurs when the aircraft is operating at its maximum payload, although airlines can in many cases increase profitability by operating at different conditions. For long range aircraft minimum kg-fuel/ATK is only slightly smaller than the value of kg-fuel/ATK at R1 and occurs at a range which is approaching R1. For shorter range designs minimum fuel burn is at R1. Increasing range beyond R1, where payload is reduced to allow the necessary extra fuel to be carried, inevitably leads to rapidly increasing values of kg-fuel/ATK.

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3 THE GOAL SETTING PROCESS

3.1 FUEL EFFICIENCY METRIC

3.1.1 There is currently no existing ICAO Standard for fuel burn and therefore there is no prescribed ICAO metric by which it should be measured for an individual product. Work on fuel/CO2 efficiency metrics for specific application to CAEP work has been ongoing since CAEP/8, and is covered by an ad-hoc group under WG3. Progress on fuel efficiency metrics was reported to CAEP/8 in CAEP/8-IP/20. The additional task in CAEP/9 to develop a CO2 Standard means that there is now additional urgency to agree on the metric. The choice of a metric continues to be studied and, it is understood, there is a long list of possibilities still under consideration. It was apparent to the IEs early on that in order to be able to set fuel burn goals in the required timescale they would need to make an early choice of metric which, if necessary, might require later amendment to fall in to line with an ICAO CO2 certification parameter, if and when, one is eventually agreed.

3.2 FUEL BURN PER ATK

3.2.1 The IE report to CAEP SG2009 (CAEP-SG/20093-WP/21) proposed that the fuel burn technology goals should be based on fuel quantity burned (kg) per Available Tonne Kilometre (ATK) flown, as the IEs believe this best reflects the efficiency of the aircraft at its technology level. This metric excludes effects of airlines‟ business models such as load factors, seating configurations, and freight policies. Available Seat Kilometre (ASK) was also considered but was not selected as it would be influenced by, and require information on, the variability of seat counts between airlines.

3.2.2 In many ways it was felt that the choice of this metric was straightforward; how it should be computed and applied were felt to be the more difficult questions. It was necessary to standardise on a point on the characteristic payload /range diagram from which to compute ATK. It was decided to use the maximum payload maximum range R1, point A in Figure 1.1. It was well understood that in airline operations many flights are not at MTOW, and arguments could be made for a point below this weight. Using MTOW has the crucial advantages of it being a certification data point, and the fuel burn parameter at R1 will be a good indicator of minimum fuel burn at ranges below R1.

3.2.3 A definition of payload was needed with there being two leading contenders: MZFW-OWE (where MZFW is maximum zero fuel weight and OWE is operating empty weight) which is commonly used, or alternatively MZFW-MWE (where MWE is manufacturer‟s empty weight). It was noted there is a significant disadvantage in using OWE as, for any given aircraft, this figure varies for each airline as it is dependent on the individual cabin layout and buyer furnished equipment. It was for this reason that it was decided to use MZFW-MWE – which the IEs have termed the „Ultimate Payload‟.

ATK is therefore defined as [(MZFW – MWE) × R1 range] with weight in tonnes and range in kilometres.

Estimates for MWE were used recognising the variability of MWE across airplanes.

3.3 FUEL EFFICIENCY VERSUS RANGE

3.3.1 Fuel efficiency initially increases with mission distance, as progressively the climb and take-off portions of the flight have less impact. At longer distances the fuel burn parameter rises slowly until maximum payload maximum range R1, point A in Figure 1.1, is reached. Beyond R1, where the available tonne payload is limited and traded for more fuel to increase range, the fuel burn parameter increases more rapidly. In practice, many flights will be operated below the maximum take-off weight (MTOW) though airlines do not generally plan operations with significant payload limitations as these are often not economically viable. Figure 3.1 illustrates some typical fuel burn versus distance profiles for generic aircraft

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types of regional Jet (RJ), single aisle (SA), and twin aisle (TA). The initial rapid improvement of fuel efficiency with distance is clearly evidenced by the downward slopes on the left of the figure; in contrast the effect of trading payload for fuel can be seen in the steep upward slopes at the right hand portion of the curves. For the single aisle and the regional jets, the optimum is close to or at the maximum payload maximum range, R1, which, as it happens, is well beyond the average stage length for these types.

Figure ‎3.1: Fuel burn versus distance profiles for a selection of aircraft types. (Note the fuel metric here is based on payload

derived relative to operating empty weight.)

3.4 TECHNOLOGY SCENARIOS

3.4.1 For setting goals the IEs decided that, particularly for the 20 year horizon, they should consider a range of technology scenarios. These were to be related to technology and not directly to economic, societal and political situations, though it was recognised that these factors will determine some of the pressure to incorporate new technologies. The IEs decided to avoid trying to predict the precise level of future environmental pressures and particularly future fuel prices.

3.4.2 The scenarios were developed with the intention of representing technology responses to increasing pressure for improvement. It was anticipated that the application of these scenarios would help identify the spread of possible outcomes and hence provide information on the width of the (assumed to be) goal bands. The three Technology Scenarios developed by the IEs follow:

TS1 – „Continuation‟ - a continuation of the current trend of improvement, resulting from current market forces and environmental pressures.

TS2 – „Increased pressure‟ - increased pressure to incorporate more technologies to reduce fuel burn though still with „tube and wing‟ architecture.

TS3 – „Further increased pressure‟ justifying more radical technology innovations and allowing „doing things differently‟ - including modest alterations to aircraft configuration and/or modest alterations to aircraft mission specifications. The open rotor applied to the single-aisle aircraft is included in this category.

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3.5 MAKING USE OF THE TECHNOLOGY SCENARIOS

3.5.1 The scenarios were used in conjunction with consideration of technologies as assessed for predicted level of impact (high, medium, low) and predicted likelihood of adoption (high, medium, low), with more technologies being assumed to be harvested when moving from 10 years to 20 years and from TS1 to TS3. The 10 year and 20 year outlooks were compiled as follows:

10 year medium-term, MT, technology outlook developed from TS2

20 year long-term, LT, technology outlook developed from TS2 and elements of TS3.

3.5.2 This categorisation of technologies by their likely impact and likelihood of achievement (and guided by current TRL) is discussed more fully in Sections 4.2 and 4.3 and in Appendix C.

3.5.3 The intention underlying TS3 is that the pressure to reduce fuel burn is so large that two approaches might be adopted: one is the introduction of technologies currently judged uneconomic and the other was alteration in aircraft configuration or mission specification. Examples of changing aircraft configurations included non-tube-and-wing and open-rotors. Furthermore, some technologies become practical when there is a change in the mission specification; for example reducing cruise speed makes laminar flow easier to achieve and consequently more plausible as an option. This is not an operational change for existing aircraft as the required technologies would need to be incorporated in new aircraft types. It was considered that speed, or flight Mach number, is the obvious variable which needs to be included, for this affects the geometry (e.g. wing sweep, wing thickness) directly. From the flight speed the cruise altitude is also determined, with consequent effects on global warming from NOx and contrails over and above those from CO2. The induced drag of the aircraft is affected strongly and predictably by the wing span, and considering the direct impact on fuel burn of relaxing the airport box size to allow longer wings for different classes of aircraft seems an important consideration. Less obvious specifications, which have not been considered here, include such things as rate of climb at cruise altitude and the ratio of take-off thrust to maximum take-off weight since these affect size and design of engines and therefore the fuel burn.

3.5.4 To assist consideration of such radical changes, a survey was conducted with a number of airlines and following the Review itself there was follow-up dialogue with selected airlines.

3.6 CONSTRAINTS AND BUSINESS TRADE-OFFS

3.6.1 It was understood that many apparently straightforward changes may have significant adverse effects on other business aspects; for example, reducing cruise speed may reduce aircraft productivity, increase crew costs, increase world fleet size, and affect passenger acceptance. Clearly, it would not have been possible to analyse fully all of these broad factors so the IEs were required to exercise judgement and restraint when considering possible changes in an imagined TS3 world.

3.7 TECHNOLOGY READINESS LEVELS (TRLS)

3.7.1 To bring some measure of standardisation to the goals setting process the various goal reviews have utilised the NASA originated TRL scale as the basis for judging the maturity of technologies. This scale attributes a maturity rating from 1 through 9, with 1 being an understanding of basic principles and 9 being flight proven in operation. A text description of each individual TRL level is also provided in the NASA scale, a copy of which is given in Appendix E. In very general terms it has been accepted that for technologies to be considered as potentially viable in a ten year horizon, they would be expected to lie between TRL5 to TRL8 today. For a twenty year horizon, they may today lie at TRL3 or possibly even TRL2.

3.7.2 Despite this NASA TRL scale being methodical and progressive, the IEs noted some significant limitations. Technologies progress at very different rates with some reaching maturity without major

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difficulties in development, while others stall for very many years. Furthermore, the application of a single TRL number to system level technologies was not found to be particularly useful, for in reality, at the sub-system level, the individual technology elements may be at very different levels of maturity. Also in many instances in-service issues such as cost and maintenance may be the overriding barriers. Future reviews would benefit from visibility of the maturity levels of the full spectrum of individual technologies and in-service issues relating to any one system level technology.

3.8 The IE panel was required to take a view on which fuel efficiency improvement technologies would be likely to be sufficiently mature by the end of the 10 and 20 year periods, as well as taking a view on the likely levels of impacts they might achieve. In terms of TRLs, this was interpreted as a requirement, that by the due date, the technology was to have reached TRL8 which is „flight qualified‟, and therefore in ICAO language, has been proven to be technically feasible. It should be noted however that impediments to be overcome to reach TRL8 may not be purely technological but could be other issues such as reliability and maintenance.

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4 METHODOLOGY

4.1 REFERENCE AIRCRAFT

4.1.1 CAEP uses generic aircraft categories in the CAEP/FESG forecast and has defined different categories by seat capacities:

Regional Jet (RJ) <100 seats

Single Aisle (SA) 101-210 seats

Small-Medium Twin Aisle (STA) 211-400 seats

Large Twin Aisle (LTA) >400 seats

4.1.2 In order to establish fuel efficiency baselines reference aircraft were used. The reference aircraft have been chosen to represent the 4 major categories. The IEs concentrated on two categories, the SA and STA aircraft in which, according to CAEP 2006 goals, 85% of the aviation fuel is burned. Additional modelling of RJ and LTA categories has been carried out by some organizations and research establishments involved in the Review.

4.1.3 Originally the plan was to use generic (i.e. hypothetical) Technology Reference Aircraft (TRA) representative of aircraft in service in 2010 so as to avoid competitive issues. It was, however, found to be more practical to use current in-service aircraft as references because of availability and consistency of input data. Also, by using current aircraft, the different participating organizations were in a position to provide additional data points that could be used to establish the baseline. No Very Large Twin Aisle Aircraft (LTA) was modelled but it is, however, expected that such aircraft are not significantly different in the scope of their fuel burn reduction potential compared with the larger Small Twin Aisle Aircraft (STA). Some key parameters for the reference aircraft are given in Appendix B.

4.1.4 The current reference aircraft types include:

RJ CRJ900

SA A320-200 and 737-800 with and without winglets

STA A330-300 and 777-200ER and a High Gross Weight (HGW) version

4.1.5 The Technology Reference Aircraft are the SA and STA aircraft in production in 2000 which, in both cases, have not as of 2010 been replaced in service by aircraft of higher technology. In both cases they are based on earlier technologies available at introduction into service. Most obviously the 737-800, a version of the 737NG (Next Generation) family, is derived from earlier 737 models like the “Classics” and the original 737-100, which dates back to the 1960s. Notably the wing for the later 737NG family was redesigned and more recently blended winglets have been introduced. The current production Standards for the 737-800 and A320-200 have been upgraded over time, primarily regarding the engine build Standard. The current engine Standards are at similar technology Standard. Considering the wing and engine upgrades, the SA reference technology aircraft could be regarded as a few years more current than the original Entry Into Service (EIS) dates. The STA reference aircraft entered service in 1994 in the case of the A330 and in 1997 for the 777. Most of the STA modelling is based on the 777 aircraft.

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4.1.6 The paragraphs above indicate how difficult and imprecise it is to put a single date on the technology embodied in the reference aircraft. It has therefore been decided for the purpose of this report to denote the reference aircraft as 2000 Standard, recognising the limitations associated with this specification of a unique date.

4.2 TECHNOLOGICAL POSSIBILITIES

4.2.1 During the industry-led London Workshop and the IE-led Atlanta Review, a number of organizations including DLR, Georgia Tech, ICCAIA, ICCT (part of ICSA), NASA and QinetiQ presented their evaluation of possible technologies for improving fuel burn.

4.2.2 All technologies of potential interest that were presented at the Workshop and the Review are listed in Section 4.3 and an analysis of the technologies by the IEs using publicly available information and expert knowledge confirms that this list may be considered comprehensive with respect to technologies that could be utilized up to 2030.

4.2.3 The technologies have been grouped according to their impact on five aircraft performance parameters that affect fuel burn. The technologies are grouped as:

Propulsion

o thermodynamic efficiency

o propulsive efficiency (where propulsive efficiency includes transfer efficiency of the LP turbine and fan)

Aerodynamics

o viscous drag

o induced non-viscous drag

Weight

4.2.4 The figures given for engines by the industry were for fuel burn, rather than engine fuel consumption, and therefore make allowance for expected change in weight of the engines and installation and the aerodynamic drag changes associated with new engines

4.2.5 By evaluating each technology in turn, with respect to both its level of maturity and likely time frame for implementation, it was possible to identify those technologies that were already in use (and which could thus be dropped from the list, for example winglets), those that could be in use in 2020 and 2030, and those for which likely implementation would be beyond the 2030 time horizon. Decisions regarding implementation of certain technologies or solutions (for example, eliminating reverse thrust) would be absolute, that is to say, they would either be implemented or not. However, implementation of most (for example, use of composites) could be incremental and of varying extent.

4.2.6 Possible progress for each technology was evaluated for the 10 cases selected for analysis (single aisle and small twin aisle, entry into service in 2020 or 2030, and the 3 scenarios TS1, TS2, TS3. The details of each of these can be found in Appendix D. Some technologies judged unlikely to be implemented during the envisioned time horizon were not included in the overall accounting. In particular, at the 2020 horizon, the TS3 scenario was not evaluated because of its low probability within the next 10 years.

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4.2.7 For each technology category (propulsion, aerodynamics, weight), the potential progress for the entire category was evaluated taking into account, the fact that not all of the potential progress on the various technologies would be attained– and the result of these assessments can be found in Table 4.1.

4.2.8 This global evaluation, based on an “engineering judgment”, has made possible an evaluation of the potential progress on the five key performance parameters for each scenario. These data have been used to re-size and re-optimize aircraft and to obtain their fuel burn performance.

SA STA

2020 2030 2020 2030 2030 2020 2030 2020 2030 2030

TS1 TS1 TS2 TS2 TS3 TS1 TS1 TS2 TS2 TS3

Propulsive efficiency

13 14 14 15 28* 6 9 7 10 12**

Thermodynamic efficiency

3 4 4 5 3* 2 3 3 4 5**

Induced non-viscous drag

2 4 4 6 7 2 4 4 6 7

Viscous drag

2 4 4 7 9 2 6 4 8 10

Structural Weight

10 15 15 20 20* 10 15 15 20 25**

* With Open Rotor compatible with the level of thrust of SA ** Without Open Rotor incompatible with the high thrust requirement of twin engined STA

Table ‎4.1: IE Assumptions for expected percent improvements in propulsion, aerodynamic, and structural efficiencies in each Technology Scenario, time frame and for the two aircraft categories (SA and STA). The percentage changes refer to the

parameters listed in the table.

4.3 TECHNOLOGIES AND CONCEPTS CONSIDERED

4.3.1 Propulsion

Advanced Turbofan

Geared Turbofan

Open rotor

4.3.1.1 Basket of Technologies which improve Propulsive Efficiency

Improved global design through advanced analytical tools

Optimized components through advanced analytical tools

Reduced nacelle weights which displace the optimum towards decreased FPR and increased BPR

o Advanced composites (Phenolic matrix , Metallic matrix, Ceramic matrix)

o Advanced alloys

o Increased loading

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o Manufacturing technology

Combined feature functionality

Integrated installations

Zero Hub Fan

4.3.1.2 Basket of Technologies which improve Thermodynamic Efficiency

Improved materials to allow higher temperatures

Improved compressor and turbine with 3D aerodynamics, blowing and aspiration

Active tip clearance

4.3.2 Airframe

4.3.2.1 Basket of Technologies which improve Viscous Drag

Riblets

Active turbulence control

Natural Laminar Flow

Hybrid Laminar Flow Control

4.3.2.2 Basket of Technologies which improve Non-viscous Drag

Increased wing span (increased aspect ratio)

Improved aero tools

Excrescence reduction

Variable camber with new control surfaces

Morphing wing

4.3.2.3 Basket of Technologies which improve Weight

Optimization of geometry through

o Reduction of loads (Active smart wing)

o New joining processes (removal of riveting) by Stir welding process, Super-plastic Forming, Diffusion Welding, Laser beam welding.

o Metallic technologies (Al-Li, Al-Mg-Sc, Advanced alloy)

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o Composites technologies (PMC, Fluoro-polymers, Glare, ARALL, CentrAl )

Multifunctional materials/structures

Nanotechnologies

Health monitoring

4.3.2.4 Aircraft concepts

More electric aircraft (MEA)

Fuel cells

4.3.3 For propulsion, the technologies listed above have, to some extent, already been included by engine manufacturers in their predictions for fuel burn improvements for the new ATF (Advanced Turbofan) and the new GTF (Geared Turbo Fan). The TS1 scenario uses directly the engine manufacturers‟ assumptions, while for TS2 and TS3 the IEs have forecast a higher level of improvement resulting from a greater use of these new technologies. The airframe manufacturers provided percentage drag reductions for various aerodynamic technologies and weight reductions but these were not converted by the manufacturers into future fuel burn reductions at the aircraft level. The IEs have assumed that the relevant technologies will be used to varying degrees in the different scenarios and time periods.

4.3.4 Comments on two particular technologies and concepts

4.3.4.1 Two particular technologies stand out with large potential benefits: for propulsion the Open Rotor and for aircraft drag the hybrid laminar flow control. These two concepts or technologies each offer a large fuel burn improvement and both are feasible, but it is still not clear that they will be used in the future.

4.3.4.2 It was presented in the review that the “Open Rotor” could improve the fuel burn by roughly 10% relative to a new turbo-fan engine, but with a potential penalty on noise. The concept is feasible and has already flown as a demonstrator. If Open Rotors were used for twin aisle aircraft with an acceptable diameter of propeller, four engines would be required. When taken into account, the Open Rotor was given a benefit of 13% in propulsive efficiency but a penalty of 2% on thermal efficiency and 5% on global weight for the aircraft. It may be noted, however, that if some reduction in cruise Mach number were allowed, single rotor propellers could be used, a proven technology avoiding many of the complexities and the noise concerns of the twin rotor.

4.3.4.3 The “hybrid laminar flow control” could reduce drag by roughly 10%. The concept is also feasible and some demonstrations in flight have already been made. The uncertainties of the concept are linked to the real weight of the aspiration system, to the behaviour of the aspiration holes versus time in operation due to pollution and dirt, and to the real possibilities of easy and cheap cleaning on ground. If “hybrid laminar flow control” will not be practically feasible, then natural laminar flow could be implemented for SA but extensive natural laminar flow for bigger STA is improbable, though possible. In the natural laminar flow case the assumption of drag improvement at 2030 in scenarios TS2 and TS3 should be reduced by at least 5% relative to hybrid laminar flow.

4.3.5 Technologies and concepts not considered

4.3.5.1 Some technologies or concepts were not taken into account for the overall evaluation because there appears little likelihood of their implementation. These include:

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Water injection. No support for industry was received for this technology, which was an unfortunate omission. Water injection is a proven technology (used on the Boeing 747-100 and the BAC-111) which can be employed in several ways. It can be used at compressor inlet to reduce compressor work and delivery temperature; it can be used to cool the turbine cooling air; and it can be used to reduce NOx by injection into the combustor. It may be seen as an enabling technology for higher overall pressure ratios and higher turbine inlet temperatures, both routes to higher engine efficiency. (In this respect it is an alternative to intercooled engines or heat exchangers to cool the cooling air.) In the context of reducing NOx, studies were carried out by Boeing, NASA and Massachusetts Institute of Technology3. As well as reducing NOx, water injection was found to be capable of reducing operating costs by reducing turbine deterioration. In other words, in spite of a higher aircraft system complexity, for the engine the use of water is perfectly practical as a route to improving efficiency by reducing temperatures during take-off and climb.

Intercooled Turbofan. The intercooled turbofan is being considered as a European research project, but it is far from clear that this is going to be a practical technology due to the volume and weight of the intercooler and aspects related to life and reliability.

UHB (FPR<1.3 ≈ BPR>18). The Ultra High Bypass engine is possible, but currently it is judged to lead to additional penalties in weight, drag and constraints on aircraft configuration that may preclude it. The issues here are primarily to do with the installation because the nacelle becomes so large that there are issues of wing height from the ground, the interference drag is increased and the weight will be larger (including weight increase from likely increased undercarriage length). A variable area nozzle is also an essential enabling technology.

Variable cycle. Variable cycle engines are used in military applications, but the benefits beyond those achievable with variable compressor vanes and a variable bypass nozzle are not clear for the commercial aircraft engine

Integrated propulsion, blended wing body and boundary layer ingestion installation concepts. These topics are linked: they are possible but are still well in the future. No support from industry was received for these. There are major concerns with the weight and losses in the intakes of the engines. There are concerns for acceptability of the blended wing body.

Active Stability. No support was received from industry for active stability. This technology is likely to be complicated and to give only modest potential gains but to raise serious issues of safety and acceptability by authorities

Truss-Based Wing was not considered due to dimensions of wings incompatible with box sizes on airports.

Cruise Efficient Short Take-Off and Landing did not appear to address the issue of reducing fuel burn overall and was not considered.

Rhomboid wing. No support from industry was received and the concept currently suffers from a lack of flight demonstration for stability and flight control.

3 Dagett, D L, Hendricks, R C, Mahashabde, A and Waitz I A. “Water Injection – Could it Reduce Airplane Maintenance Costs and Airport Emissions?”. NASA/TM-2007-213652, International Symposium on Air-Breathing Engines, ISABE-2005-1249.

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4.4 MODELLING SOFTWARE

4.4.1 Different conceptual-aircraft analysis and design optimization tools were used to calculate the effectiveness of new technologies aimed at reducing fuel burn. Several organizations have gratefully agreed to supply modelling data to supplement the IEs own analysis carried out by Stanford University (using the PASS program). These institutions include the German Aerospace Centre – DLR (using the PrADO software), the International Council on Clean Transportation (part of the International Coalition for Sustainable Aviation, using the PIANO tool), the Georgia Institute of Technology (using the EDS system) and QinetiQ (also using the PIANO tool). The four tools used by these organizations all target the conceptual analysis and design of current and future tube-and-wing configurations and aim at providing information that is appropriate for conceptual-level assessment of aircraft designs and the technologies that are used in those designs. Note that different kinds of data are used in all the analyses and optimizations. Firstly, data for the reference aircraft are taken from the existing literature and from years of accumulated flying experience and they are, therefore, deemed to be accurate. Data for future technology improvements have been collected from many different sources (including the Workshop held in 2009) and have been assigned to technology “baskets” by the IEs; these data are subject to interpretation. Finally, the quality of the data that results from the use of the modelling software depends on the assumptions made inside each piece of software; as will be shown later, these results appear to be very consistent between different modelling packages. Brief descriptions of each of the modelling tools follow.

4.4.2 PASS: the Program for Aircraft Synthesis Studies is a conceptual design tool capable of analyzing the performance of existing or future aircraft that are described in terms of their mission, geometry/aerodynamics, propulsion system, structural design, and a detailed set of weights and performance constraints (climb gradients, stability margins, take-off and landing field lengths, engine-out safe operations, among many others) and is able to describe many aspects of the resulting performance of the airplane, including block fuel burn and other environmental impacts. PASS was developed at Stanford University in the Aircraft Design Group and is typically used to study the performance of future aircraft under a wide variety of technology and mission assumptions.

4.4.3 PrADO: the Preliminary Design and Optimization Program, PrADO, was developed at the Institute of Aircraft Design and Lightweight Structures of the Technical University Braunschweig, with contributions from DLR, incorporates a number of correlation-based and low-to-medium fidelity tools to analyze and redesign all types of aircraft including conventional wing-fuselage configurations and advanced concepts such as blended wing bodies, supersonic transports, and ultra-green vehicles. PrADO makes use of methods ranging up to a higher-order subsonic/supersonic singularity method for the calculation of the three-dimensional aerodynamic properties, and can perform many kinds of multi-disciplinary analyses and designs including multi-objective optimizations (such as trade-offs between fuel burn and cost that would be relevant to this effort).

4.4.4 PIANO: PIANO is a commercially-available tool developed by Lissys Ltd. for the analysis of commercial aircraft. It is used in preliminary design, competitor evaluation, performance studies, environmental mission assessments and other conceptual development tasks by some airframers and engine manufacturers. PIANO has been accepted in CAEP and has been used for AERO2k and FAST modelling. It has also been used by aviation research establishments and decision-making institutions throughout the world. PIANO contains a comprehensive database of existing aircraft that includes the various baseline/reference aircraft investigated in this report, including several engine options. PIANO can also be used to redesign the baseline aircraft to maximize a measure of efficiency subject to technology improvement assumptions and multiple design constraints.

4.4.5 EDS: The Federal Aviation Administration's Office of Environment and Energy (FAA/AEE), in collaboration with Transport Canada and the National Aeronautics and Space Administration (NASA) and through the Partnership for AiR Transportation Noise and Emissions Reduction (PARTNER) Centre of

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Excellence are developing a comprehensive suite of software tools that will allow for the thorough assessment of the environmental effects of aviation. A basic building block of this suite of tools that provides an integrated analysis of fuel burn, noise, and emissions at the aircraft level is the Environmental Design Space (EDS). EDS provides a physics-based capability to estimate fuel burn, source noise, exhaust emissions, performance, and economic parameters for potential future aircraft designs under different policy and technological scenarios. While the primary focus of EDS is future aircraft designs (including technology modifications to existing aircraft), the tool is also capable of analyzing existing aircraft. EDS has been extensively validated using input from a variety of industry stakeholders. EDS presently contains well-validated models for single aisle as well as large twin aisle aircraft.

4.4.6 Expected accuracy of predictions and optimizations. All tools used in this study/report have been developed independently to predict the performance of similar classes of aircraft. Given the conceptual nature of the tools and the fact that certain modelling assumptions (exact amount of fuel reserves, exact values of specific fuel consumption and aircraft aerodynamic performance, component weights, etc.) can vary slightly from tool to tool, the IEs expect relative variations in the baseline values (see Figure 5.1) of the predicted fuel burn metrics to be around 3-4%. However, as will be shown in Section 5 (Figures 5.2 and 5.3), the variations in the fuel burn metric improvements are within 1-2% of each other, making the predictions of these tools perfectly appropriate for goal-setting exercises that focus on improvements of 19-48%.

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5 RESULTS

5.1 As a first step in the goal-setting process, each participating organisation created models of the reference aircraft to establish the baseline from which improvements in 2020 MT and 2030 LT goals would be measured. The majority of the work focused on the single-aisle SA (including the 737-800 with winglets, the A320-200, and the ICCAIA SA Technology Reference Aircraft) and small twin-aisle STA (including the B777-200ER and the A330-200) categories. Some data was also supplied for regional jets RJs (including the CRJ900 and the ICCAIA RJ Technology Reference Aircraft). The calculations to establish these baselines were also used as a validation exercise in order to understand the differences among the predictions of the various modelling tools described in Section 4.4. As mentioned in Section 4.4.6, these small differences result principally from the slightly different assumptions for the same reference aircraft and only slightly from the different models or aircraft performance. The baseline data can be seen in Figure 5.1.

5.2 IE ANALYSIS

5.2.1 To establish the values of the fuel burn metric the IE group created its own models of representative aircraft in the SA and STA categories using available or pre-existing information. In all cases, the MTOW, MZFW, and MEW for the reference aircraft, the engine thrust-specific fuel consumption and the aerodynamic characteristics were matched to existing data within 1-2%. The aircraft were “flown” through their typical missions (including taxi, take-off, climb, cruise, descent, landing, and taxi to the gate). The selected total range for each mission was the R1 value for each particular aircraft and the aircraft were assumed to be carrying their maximum payload. Fuel reserves equivalent to 4% of the aircraft MTOW were carried in all missions for the SA reference (a B737-800 with winglets) while reserves of fuel equivalent to 3% of the aircraft MTOW were used for the STA reference aircraft (a B777-200ER). The resulting block fuel burn from the simulations was used together with the design R1 range and a total payload equal to the difference between MZFW and MEW to compute the fuel burn metrics presented with diamond shapes (and the solid line) shown in Figure 5.1. Additional calculations for all the reference aircraft submitted by all participating organizations are also plotted in Figure 5.1. Note that the baseline trend for RJs with shorter R1 range is drawn as a dashed line since only two data points are currently available. Several conclusions can be drawn from Figure 5.1:

5.2.2 Although five separate organizations, four different tools, and varying assumptions are represented in Figure 5.1, the spread in the fuel burn metric results is relatively small. In particular, the small variations in the weights, notably empty weights and the amount of fuel reserves assumed by each participating organization have been seen to account for most of the variation in the results. The IEs concluded that, regardless of the modelling tool, very similar results are achieved. Therefore, future discussions in this report will not focus on the appropriateness of the particular tools for the goal-setting exercise but, rather, on the assumptions that are provided to these modelling tools; for goal-setting purposes, the baseline exercise, based on existing reference aircraft, provides sufficient confidence in the results submitted.

5.2.3 The trend is for a decrease in the value of the fuel burn metric with increasing R1 range. While this result differs from the idealized results presented in Figure 2.1, it represents the widely accepted values of the baseline aircraft included in this Figure, with lower lift-to-drag ratio and higher specific fuel consumption for smaller aircraft, which have shorter range.

5.2.4 Additional simulations by the IEs, not included in Figure 5.1, have shown that there is a significant dependence of the actual value of the fuel burn metric on the precise amount of fuel reserves carried by the aircraft. The IEs have assumed that 4% and 3% of the MTOW is carried as fuel reserves for the SA and STA reference aircraft respectively, which is representative of typical reserve fuel loads for such aircraft. However, the IEs understand that different operators rely on different algorithms to determine the actual reserve fuel carried and therefore the actual values of the fuel burn metric may change.

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5.2.5 It must be noted that, while all reference aircraft are plotted in the same Figure 5.1, these aircraft represent technologies that first entered into service anywhere between 1988 and 1998. The reference aircraft chosen for analysis by the IEs, the B737-800 and the B777-200ER, entered into service in 1998 and 1997. The version used in the modelling is assumed to be the current production standard, including the latest engine build Standard and the use of winglets. Both aircraft types, however, have had improvements in technology introduced after the initial date of EIS (winglets, engine packages, etc.) For purposes of dating the baseline and computing annual rates of improvement, the technology level for currently in production B737-800 and B777-200ER aircraft will be assumed to be the year 2000.

Figure ‎5.1: Values of the fuel burn metric for all aircraft analyzed by IEs and participating organizations. Fuel burn metric plotted against R1 range. Note payload is defined here as MZFW - MWE

5.2.6 Two data points for the RJ category are shown in Figure 5.1. As stated above, the IEs have carried out modelling only for the SA and STA aircraft classes and later graphs omit the RJ.

5.2.7 Based on these reference aircraft, the modelling by the IEs then applied efficiency improvements as indicated in Table 4.1 for the 5 parameters chosen: propulsive efficiency, thermal efficiency, viscous drag, non-viscous induced drag, and structural weight. These improvements were selected taking into account the “baskets” of new technologies described in Section 4.3 for the different technology scenarios and for both the 10- and 20-year timeframes. For each “basket” of technology the aircraft configurations were re-optimized for minimum mission fuel burn. Average lines drawn for 2020 MT can be seen in Figure 5.2 and for 2030 LT in Figure 5.3. It must be noted that Figures 5.2 and 5.3 include the average of the results obtained by the IEs and those supplied by other participating organizations. The results of all optimizations are presented in Figures 5.2 and 5.3 in the form of percentage improvements in the fuel burn metric, relative to the baseline curve shown in Figure 5.1 (which, as described earlier, does not necessarily represent 2010 technology but, rather, is more closely associated with technology availability dates around the year 2000.) The results represent the average percent improvements obtained by all the participating organizations, although the individual values were found to be in very close agreement (within 2-4% of each other) even when individual technology efficiency improvements were selected independently by most of the participants.

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The IEs believe that these results constitute a broad consensus on the technologically-achievable fuel burn reductions for the 2020 MT and 2030 LT time frames

5.2.8 The lines in Fig. 5.1 and 5.2 are shown without the computed points on which they are based but the same lines are shown in Appendix D with all of the points superimposed. Each point represents a complete optimization of the aircraft configuration with the corresponding technology improvements for each Technology Scenario. The plots show the results computed by the IEs and by the other participating organisations. Throughout these optimizations the cruise Mach number and altitude, payload, R1 range, wing span, and tube-and-wing configuration were maintained. The optimization tool was allowed to vary the wing area and shape parameters, aircraft weights, initial and final cruise altitudes (complying with current ATM procedures), engine sea-level static thrust, take-off and landing speeds, and some details of the high-lift system. The resulting optimized aircraft were all required to maintain the baseline aircraft values for take-off and landing field lengths, minimum stability, wing span, operating margins at all major critical conditions, and 2nd segment climb ability. In all, 19 design parameters were varied, and 21 quantities were constrained to arrive at each aircraft design. The optimizations carried out by other organizations followed the same approach but used their own modelling tools. It should be noted that ICSA used identical efficiency improvements to those used by the IEs, while DLR, GaTech, and Qinetiq chose their own technology baskets (derived from previous and/or current studies conducted by each organization) to obtain efficiency improvements appropriate to the time frames and technology scenarios specified by the IEs.

5.3 MEDIUM TERM

5.3.1 Figure 5.2 presents the results from the projected percentage improvements in the aircraft fuel burn metric for the 2020 MT time frame in technology scenarios TS1 and TS2. The trend is for these improvements to decrease with increasing R1 range because of the more recent technology applied at the time in the more range capable STA reference aircraft.

Figure ‎5.2: Fuel burn metric changes plotted against R1 range for the 2020 MT time frame in TS1 and TS2. Results from aircraft optimized by IEs and participating organizations with same R1 range have been averaged.

5.3.2 Significant improvements are expected in the 2020 MT time frame from aerodynamic, propulsion, and structural technology advances. For TS1, which is what industry is likely to achieve with significant work

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and continuous funding, but without increased external pressure, the expected improvements are approximately 23% and 19% for the SA and STA respectively aircraft classes. Additional technology improvements contained in TS2 would provide further decreases in the fuel burn metric of approximately 6%. It must again be noted that these results are relative to the baselines presented in Figure 5.1 that correspond to technology availability dates around the year 2000. Because major improvements with aircraft fuel burn come in large but infrequent increments, the IEs have considerable reservation about expressing improvements as compound annual rates. Because, however, others express goals in this way, the changes have also been expressed in this form.. Considering a span of 20 years between 2000 and 2020, TS1andTS2 correspond to compounded annual rates of fuel burn reduction of 1.29% and 1.70% respectively for the SA category, and 1.05% and 1.43% for the STA category4.

5.4 LONG TERM

5.4.1 Figure 5.3 presents the results from the projected percentage improvements in the aircraft fuel burn metric for the 2030 LT time frame and for technology scenarios TS1, TS2, TS3, and TS3-OR (Open Rotor). For TS1, the trend is for the improvements to decrease with increasing R1 range, as for 2020, whereas for TS2, TS3, and TS3-OR, the averaged predicted percentage improvements are practically independent of the R1 design range.

5.4.2 More significant improvements are expected in the 2030 time frame from aerodynamic, propulsion, and structural technology advances. For TS1, for example, the expected improvements are approximately 29% and 26% respectively for the SA and STA aircraft classes. Additional technology improvements contained in TS2 would provide further decreases in the fuel burn metric to approximately 34 - 35% from the baseline. TS3 technologies enable improvements of approximately 41%, while these same technology improvements, with the possible addition of open rotor technology, result in total reductions in the fuel burn metric of approximately 48% for the SA category. While the TS3-OR data extends to ranges appropriate to the STA category, the IEs understand that very significant challenges would need to be overcome in order for large diameter rotors to be practical in aircraft of that size. It must again be noted that these results are relative to the baseline presented in Figure 5.1 that corresponds to year 2000 technology. With this in mind and considering a span of 30 years between 2000 and 2030, TS1 corresponds to compounded annual rates of fuel burn reduction of approximately 1.14% and 1.00% for the SA and STA respectively, whilst TS2 results in 1.38% and 1.43% annual reductions. If TS3 and TS3-OR can be achieved then 1.74% and 2.16% annual reductions respectively are possible Put another way: a cumulative year-on-year reduction of more than about 1.5% is exceedingly difficult to maintain for more than a few years and this needs to be borne in mind when future commitments for efficiency improvements are considered.

5.4.3 In the results contributed by all participating organizations (for both the 2020 and 2030 time frames) the differences are relatively small (typically no more than 3%) compared to the overall improvements levels predicted. Once again, it is even clearer now that the assumptions drive the results, not the tools used to re-optimize the aircraft. The data submitted by all participating organizations has been included in Appendix D for completeness.

4 Annual compound % reductions in fuel-burn metric, i, computed according to the following formula: metrict = metricref (1-i)t-tref , with tref = 2000, and t=2020 (MT) or t=2030 (LT).

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Figure ‎5.3: Fuel burn metric changes plotted against R1 range for the 2030 time frame and in TS1, TS2, TS3, and TS3-OR. Results from aircraft optimized by IEs and participating organizations with same R1 range have been averaged.

5.5 Some key parameters of the aircraft optimizations carried out by the IEs are displayed in Tables 5.1 and 5.2 below. In these Tables, the fuel burn metric and the major characteristics of the designs for all technology scenarios and time frames are presented. Note that the efficiency improvement factors result in better aerodynamics (increasing cruise L/D ratio and higher aspect ratios while holding span constant), better propulsion (decreasing thrust-specific fuel consumption), and improved structural efficiencies.

1998 EIS 2020 2020 2030 2030 2030 2030

Baseline TS1 TS2 TS1 TS2 TS3 TS3-OR

Kg Fuel / ATK 0.1401 0.1027 0.0962 0.0962 0.0902 0.0871 0.0777

% Reduction 0% -27% -31% -31% -36% -38% -45%

Range (nmi) 2125 2125 2125 2125 2125 2125 2125

Mcruise 0.785 0. 785 0. 785 0. 785 0. 785 0. 785 0. 785

L/D 17.4 18.3 18.7 18.7 19.2 19.5 19.3

SFC 0.600 0.506 0.495 0.495 0.484 0.479 0.419

Span (ft) 117 117 117 117 117 117 117

AR 9.4 11.8 12.4 12.4 12.6 12.7 12.8

MEW/MTOW 0.492 0.481 0.476 0.476 0.471 0.469 0.479

Table ‎5.1: Summary of SA aircraft optimized under different technology scenarios and time frames. This table reflects the calculations carried out by the IEs only.

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1997 EIS 2020 2020 2030 2030 2030

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Kg Fuel / ATK 0.1245 0.0999 0.0925 0.0888 0.0822 0.0754

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Range (nm) 5750 5750 5750 5750 5750 5750

Mcruise 0.84 0.84 0.84 0.84 0.84 0.84

L/D 19.5 20.0 20.4 20.6 21.1 21.6

SFC 0.530 0.488 0.478 0.468 0.458 0.443

Span (ft) 199 199 199 199 199 199

AR 8.6 9.9 10.1 10.1 10.3 10.6

MEW/MTOW 0.460 0.455 0.452 0.455 0.452 0.449

Table ‎5.2: Summary of STA aircraft optimized under different technology scenarios and time frames. This table reflects the calculations carried out by the IEs only.

5.6 It must be noted that all these results were obtained assuming tube-and-wing configurations with identical missions (and mission parameters) to the baseline aircraft. Additional improvements are possible by changing the aircraft configuration and by altering some of the mission parameters (range, payload, cruise speed, wing span). In particular, cruise speed reductions are implicitly required to realize the gains in the TS3-OR scenario. Additional improvements that may result from relaxing mission specifications and span constraints are briefly discussed in Section 6 of this Report.

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6 TS3 – DOING THINGS D IFFERENTLY

6.1 The results in Section 5 describe the percent improvements from the baseline that are expected in different technology scenarios (TS1, TS2, TS3, and TS3-OR when applicable) for the two time frames (2020 MT and 2030 LT) when the appropriate technology efficiency improvements are considered during the full re-design of future tube-and-wing aircraft. However, throughout the optimizations presented in Section 5, the mission characteristics of the reference aircraft (R1 design range, cruise Mach number, maximum payload, and wing span) were held constant. Further opportunities to reduce the fuel burn metric can be exploited if these mission specification constraints are relaxed and if non-conventional aircraft configurations are considered. This section describes the potential effect of relaxing these constraints in the design of future vehicles should a TS3 scenario (“Doing Things Differently”) materialize.

6.2 It is noted that mission specification changes could be applied to the reference aircraft directly (with no technology improvements) or to the resulting designs of any of the Technology Scenarios. In this section, however, we focus on the application of such mission specification changes to the aircraft resulting from the 2020 TS1 and 2030 TS2 scenarios. The improvements in the fuel burn metric due to change in mission specification have been seen to increase with decreasing aircraft technology level (i.e. improvements are larger for the reference aircraft than for a TS3-optimized one).

6.3 The results presented in this section assume that a pre-specified level of technology improvement is available and that, in addition, the wing span, cruise Mach number, and R1 design range can be altered by the modelling/optimization software in order to achieve lower values of the fuel burn metric. The rest of the optimization procedure is similar to that described in Section 5.3.

Figure ‎6.1: Comparison between fuel burn metric improvements achieved by technology alone and with aircraft mission specification changes. Single aisle reference aircraft (B737-800). This figure reflects the calculations carried out by the IEs only.

TS1 2020 TS2 2030

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Span Span + Mach

Span + Range

Span + Mach + Range

Span Span + Mach

Span + Range

Span + Mach + Range

Kg Fuel / ATK 0.1006 0.0980 0.1034 0.1007 0.0889 0.0867 0.0919 0.0896

% Reduction -28% -30% -26% -28% -37% -38% -34% -36%

Range (nm) 2125 2125 1594 1594 2125 2125 1594 1594

Mcruise 0.785 0.724 0.785 0.720 0.785 0.720 0.785 0.718

L/D 19.8 20.7 19.0 20.1 20.5 21.3 19.9 20.9

SFC 0.506 0.489 0.506 0.488 0.484 0.467 0.484 0.466

Span (ft) 133.8 139.6 129.8 136.7 133.8 137.6 130.5 134.5

AR 14.0 16.1 13.9 15.9 14.7 16.9 14.5 16.6

MEW/MTOW 0.496 0.494 0.503 0.503 0.486 0.481 0.493 0.489

Table ‎6.1: Summary of improvements and resulting designs for SA changes to mission specifications including span, cruise Mach number, and R1 design range beyond TS1 2020 and TS2 2030 technology improvements. This table reflects the calculations

carried out by the IES only.

6.4 Figure 6.1 and Table 6.1 show the results of relaxing wing span and mission specification constraints beyond the technology improvements provided by TS1/2020 and TS2/2030 for the SA aircraft category. In these optimizations, the R1 range was lowered to 75% of the value of the baseline (from 2,125 nm to 1,594 nm), the cruise Mach number was allowed to vary to a minimum of 0.72, and the wing span was allowed to increase to a maximum of 140 ft. Optimizations were repeated by considering the technology improvements plus:

a) relaxing the wing span constraint;

b) relaxing the wing span and cruise Mach number constraints;

c) relaxing the wing span and the R1 design range constraints; and

d) relaxing all three quantities simultaneously.

6.5 As can be seen, the effect of decreasing the R1 range value for the SA aircraft is rather small since the reference aircraft is already at a design range that is close to the optimum and a decrease of the R1 range by 25% yields slightly higher values of the fuel burn metric. However, the effects of relaxing the constraints on wing span and cruise Mach number are significant: for the 2020/TS1 case an additional (beyond TS1) 3.5% improvement in the fuel burn metric is achieved. For the 2030/TS2 case, the further improvements, as expected, are slightly smaller and in the neighbourhood of 2%. What is more striking and can be seen in Figure 6.1 is that for both design cases, the combined effect of modest span and cruise Mach number modifications is roughly equivalent to the improvement that would be obtained from technologies included in the next TS. In other words, relaxing span and cruise Mach number constraints in the 2020/TS1 case yields comparable results to those that would be obtained if the technologies in the TS2 technology baskets were also available. The same is true of the 2030/TS2 case where span and cruise Mach number can result in similar improvements to those that would be obtained by adding the TS3 technologies to the design.

6.6 Figure 6.2 and Table 6.2 show the results of relaxing specification constraints regarding wing span and mission range beyond the technology improvements provided by TS1/2020 and TS2/2030 for the STA aircraft category. In these optimizations, the R1 range was lowered to 75% of the value of the baseline (from 5,750 nm to 4,312 nm), the cruise Mach number was allowed to vary to a minimum of 0.76, and the wing span was allowed to increase to a maximum of 240 ft. Optimizations were repeated by considering the

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technology improvements plus (i) relaxing the wing span constraint, (ii) relaxing the wing span and cruise Mach number constraints, (iii) relaxing the wing span and decreasing the R1 design range, and (iv) relaxing all three quantities simultaneously. As can be seen in Table 6.2 and Figure 6.2, the effect of decreasing the R1 range value for the STA aircraft is now more substantial since the reference aircraft is at a design range more significantly beyond the optimum. The effects of relaxing the wing span and cruise Mach number constraints, and decreasing the R1 design range are quite large: for the 2020/TS1 case an additional (beyond TS1) 7% improvement in the fuel burn metric is achieved. For the 2030/TS2 case the additional improvements, as expected, are slightly smaller but still sizable and in the neighbourhood of 5%. Just as was observed for the SA aircraft and as can be seen in Figure 6.2, for both design cases the combined effect of span, cruise Mach number, and R1 range is roughly equivalent to or slightly larger than the improvement that would be obtained from technologies included in the next TS. In other words, relaxing span, cruise Mach number, and R1 range constraints in the 2020/TS1 case yields comparable results to those that would be obtained if the technologies in the TS2 technology baskets were also available. The same is true of the 2030/TS2 case where these changes can result in similar improvements to those that would be obtained by adding the TS3 technologies to the design.

Figure ‎6.2: Comparison between fuel burn metric improvements achieved by technology alone and with aircraft mission specification changes. Small twin aisle reference aircraft (B777-200ER). This figure reflects the calculations carried out by the

IEs only.

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TS1 2020 TS2 2030

Span Span + Mach

Span + Range

Span + Mach + Range

Span Span + Mach

Span + Range

Span + Mach + Range

Kg Fuel / ATK 0.0998 0.0946 0.0961 0.0913 0.0821 0.0774 0.0800 0.0757

% Reduction -20% -24% -23% -27% -34% -38% -36% -39%

Range (nm) 5750 5750 4312 4312 5750 5750 4312 4312

Mcruise 0.84 0.76 0.84 0.76 0.84 0.76 0.84 0.76

L/D 19.9 22.4 19.4 21.8 21.0 23.5 20.5 23.0

SFC 0.488 0.467 0.488 0.467 0.458 0.438 0.458 0.438

Span (ft) 193.8 224.7 187.3 217.3 192.2 222.9 186.8 216.9

AR 9.6 12.9 9.7 12.9 10.0 13.6 10.0 13.6

MEW/MTOW 0.451 0.461 0.472 0.481 0.447 0.457 0.466 0.475

Table ‎6.2: Summary of improvements and resulting designs for STA changes to mission specifications including span, cruise Mach number, and R1 design range beyond TS1 2020 and TS2 2030 technology improvements. This table reflects the

calculations carried out by the IEs only.

6.7 While the IEs themselves did not investigate the possibilities of the potential improvements in the fuel burn metric that would result from dramatically altering the aircraft configuration from a traditional tube-and-wing arrangement, results were presented at the Workshop (by the NASA Subsonic Fixed Wing Project and the NASA Environmentally-Responsible Aviation Initiative) that are worth repeating here for completeness. Assuming a reference aircraft for the STA category (“777-200LR-like”) NASA contributed results for aggressive technology goals (TRL=6 in 2020) for both an advanced “tube-and-wing” configuration and two Hybrid Wing Body configurations (HWB), another name for the better-known family of Blended Wing Body concepts. As is natural in a research organization and, given the orientation of the NASA programs to achieve significant gains in aircraft performance and environmental impact, it is fair to consider these goals to be in line with the IEs TS3 for 2030 or even slightly beyond. They showed that fuel burn reductions of 42.5% are achievable using a conventional tube-and-wing configuration, while 48-53% might be possible by the adoption dramatically changed configurations (HWB). Since these numbers are referenced to an aircraft of the same vintage as the one chosen by the IEs for the STA, the results can be compared directly. The studies conducted by the IEs and other participating organizations resulted in fuel burn improvements of 41% for NASA‟s 42.5%, albeit at different time frames: NASA‟s aggressive technology goals are meant to allow the production of an airplane for entry into service in 2025, while the IE results were meant to represent technologies with TRL 8 in 2030. Nevertheless, the agreement is remarkable in terms of what is technologically feasible in comparable time frames. Much like the IE efforts in investigating “Doing Things Differently”, NASA‟s results for the HWB configurations (additional fuel burn reductions of approximately 10%) could be obtained by altering the aircraft configuration significantly.

6.8 NASA‟s efforts in their N+3 program (EIS beyond the time frame of this study, potentially 2035 and beyond) also provide a glimpse of what may be possible in such a time frame. While the NASA efforts are only moving on to Phase II at the time of this writing, preliminary studies have shown that fuel burn reductions of up to 60-70% compared to the same baseline could be possible around the year 2040 if very aggressive technology development is pursued now.

6.9 In summary, this section shows some of the potential of “Doing Things Differently / TS3”. The benefits are found in all technology scenarios and these further improvements are approximately equivalent to adding the technologies in the next TS. It should be noted that the examples of doing things differently considered here are not the only ones which have the potential to reduce fuel burn, nor do the changes appear large enough to be an unimaginable disruption to air transport. Clearly, the level of disruption which

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will be judged acceptable will be related in the future to the pressure to reduce CO2 emissions and fuel burn. An important but different view of these mission specification changes is that they can serve as an alternative path to reach the fuel burn goals that may prove very hard to obtain by technology improvements alone. Because of the existence of this dual path (technology and mission specification changes) to the attainment of significant fuel burn metric percentage reductions, the certainty with which technology goals can be achieved increases. This fact has been taken into consideration by the IEs when setting the goals recommended in Section 7.

6.10 Changes in the mission specification, the span of the aircraft, and the overall configuration of future vehicles will undoubtedly have operational implications as noted in Section 3.7. The IEs are well aware of this situation and understand that more complete modelling may be necessary to understand the full operational implications. However, in a future scenario where we may be forced to “Do Things Differently / TS3”, these are further improvements and alternative approaches that should be considered.

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7 PRESENTATION OF GOAL S

7.1 Figure 7.1 shows the two bands anchored at the single-aisle (SA) and small twin-aisle (STA) reference aircraft as a function of R1 range and in Fig.7.2 as a function of ATK. These bands were derived by the panel of experts for the medium term (MT) 10 year and the long term (LT) 20 year fuel burn technology goals. As with other goal setting efforts, the goals are expressed in terms of bands to account for uncertainties. However, unlike goals previously set for NOx and noise, there is no current certification line or agreed measured values against which to reference the goal bands. Hence the goal bands are referenced against the curve fitted to represent current baseline data (Figure 5.1) and the reference aircraft discussed above. The goals are expressed in terms of percent fuel efficiency improvement over the baseline at the maximum payload maximum range point, R1. Goals are also shown against ATK for reference. As with other goal setting efforts, the goals represent levels of potential achievement by the industry, not individual companies or designs. There is also an inherent assumption of sufficient funding to develop, mature and commercialize the technologies. However, the underlying technologies or different aircraft configurations considered in setting the goals are firmly based on those presented by the industry both at the London 2009 Workshop and the Atlanta 2010 Review. In addition, altered aircraft mission specifications, grounded in analyses as discussed in Section 6, were used to explore some of the additional fuel efficiency potential which exist. These in turn increase the likelihood of meeting the predicted goals from technology and hence influenced the goal setting.

Figure ‎7.1: MT 10 year and LT 20 year fuel burn technology goals versus R1

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Figure ‎7.2: MT 10 year and LT 20 year fuel burn technology goals versus ATK*1000.

7.2 2020 MT 10 YEAR GOAL

7.2.1 The upper edge of the 2020 MT goal band (that is the minimum level of reduction in fuel burn metric to be aspired to) in Figure 7.1 coincides with the TS2 line for 2020. The IEs expect that TS1 2020 technology improvements would be realized by manufacturers without any additional external pressure and, therefore, TS1 would not be appropriate as a goal. The lowest edge of the MT band would rely on additional external pressure and less certain technologies, but still using a conventional tube-and-wing configuration. The IEs did not believe that a TS3 scenario was appropriate for 2020, but nonetheless placed the lower edge of the band 4% below the top, a range judged reasonable when compared with the suit of available modelling results. The goals could be achieved with a variety of technology baskets featuring the technologies and levels of improvements discussed above. If the new technologies are not delivered or fully implemented, altered aircraft mission specifications may still allow achieving similar 2020 TS2 levels (although some of the changes would not be easy because of the infrastructure changes needed, which take many years to accomplish). Hence, the IEs felt that this increased the likelihood of meeting the goal and were comfortable setting the lower edge of the goal band below TS2 2020 level.

7.2.2 The goal bands are anchored at the Single Aisle (SA) and Small Twin Aisle (STA) reference aircraft analyzed by the IEs. For the SA the upper edge of the MT goal band was anchored at 29% below the reference line with the lower edge of this band set at 33%. The reductions achievable for twin-aisle designs are likely to be more modest since technologies embodied in the STA baseline aircraft are relatively more recent than those in the SA baseline. The upper edge of the MT STA goal band was set 25% below the reference line and the lower edge was set at 29%. The 4% variation reflects a relatively tight range of uncertainty as technologies likely to be incorporated into products in the next ten years are generally well defined as discussed above. However uncertainties in potential performance as well as the effects of integration still result in a band rather than a discrete point or line.

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7.3 2030 LT 20 YEAR GOAL

7.3.1 The 2030 long-term LT band again also calls for more ambition than a continuation of current trends, which would be at TS1. The band width in this case considers TS2 and both scenarios TS3 and TS3 OR. TS3 includes changes to mission specification and design constraints as well as new technology. There are therefore more potential baskets of options to achieve the LT goals and although the spread in likely-achieved reduction is larger, the confidence in achieving these goals should be rather higher. As noted, altered aircraft missions and infrastructure changes to support these missions can also lead to more efficient conventional configuration aircraft designs that rival the performance of new configurations. The less constrained aircraft and/or altered aircraft mission improvements are small for the SA (about 2%) but much larger for the STA (about 7%). As noted above, the IEs realize that some of the changes in aircraft and mission specification require infrastructure alterations to realize these gains. Although some changes to infrastructure and air traffic management may be costly and require many years, they are plausible by 2030.

7.3.2 Again, the goal bands are anchored at the SA and STA reference aircraft. The upper edge of the SA LT goal band was set 34% below the reference line, and the upper edge of the STA LT goal band was set 35% below the reference line. The goal band width was set at 8%, making the lower edge of the band 42% and 43% for the SA and STA respectively. The upper edge of the LT band, a reduction of 34% / 35%, is only 5-10% below the upper edge of the MT band. This decrease in relative level of ambition reflects that the LT band relies on just another 10 years of technology development, versus the longer period of technology development available from the baseline to 2020 to set the MT band. The lower edge of the goal band does go beyond TS3, but is well within TS3 OR and there are multiple approaches to meet this ambition. The greater band width for the LT band (8% versus 4%) reflects the greater level of uncertainty.

7.4 MEETING THE GOALS

7.4.1 The IEs had some discussion on criteria for determining when the fuel burn technology goals are met. Again, this is more complex than determining when the NOx or noise goals are met, as there are no aircraft CO2 certification parameters, with agreed measured values, against which to judge performance improvement. Although there was an understanding that an individual technology would be considered as achieved when it reached a TRL level of 8, progress toward meeting goals for an aircraft would, it was presumed, rely on a calculated fuel burn metric of the new aircraft design (fully optimised with appropriate TRL) considering a number of technologies rather than a measured certification number. Any calculated fuel burn metric above the goal line would demonstrate progress toward meeting the IE specified goals. Achieving the goal, however, has been defined by the IEs as having a value of kg/ATK below the TS2 line. Additional progress would be indicated by moving down towards the lower line and the goals have been given as bands to indicate what level of further progress might be possible. However the bands, as well as the levels, should be given further consideration when a certification parameter, which will likely be at least partially dependent on computations and may lead to reconsideration of the goal metric, is agreed upon.

7.5 BEYOND 20 YEARS – ACHIEVING GREATER AMBITION 2030-2050

7.5.1 As indicated earlier, the Copenhagen Accord noted that to avoid the most dangerous climate change it will be necessary to hold temperature rise to less than 2°C above pre-industrial values.5 The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) indicates that to achieve this goal will require global greenhouse gas emissions to be 50% to 80% lower in 2050 than in 2000, and to begin declining by 2015.6 Hence there is a period beyond the 20 year, (2030) goal where there is a need for a further

5 http://www.denmark.dk/en/menu/Climate-Energy/COP15-Copenhagen-2009/cop15.htm 6 IPCC-Synthesis. (2007). Climate Change 2007 Synthesis Report: Summary for Policymakers. Contributions of

Working Groups I, II, and III to the Fourth Assessment Report of the IPCC. Geneva, Switzerland: Intergovernmental

Panel on Climate Change.

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reduction. Technologies and concepts not taken into consideration in setting the 20 year LT goal could become viable beyond 2030 and contribute toward meeting the challenging aspirational goals the aviation industry is trying to achieve to mitigate its impact on the earth‟s climate. However, even this ambition is unlikely to keep up with even the least ambitious growth scenarios. Meeting the system goals will require continued advances in operations and air traffic management.

7.6 SYSTEM GOALS

7.6.1 A number of system goals were conveyed by various presenters. ICAO has adopted an aspirational global goal for an annual improvement of 2% in fuel efficiency of the international civil aviation in-service fleet from 2021 to 2050. The U.S. is advocating a goal of achieving carbon neutral growth on the basis of 2005 by 2020, with net reductions by 2050. The European Union has called for a net reduction of carbon emissions of 10% by this time frame. The International Air Transport Association (IATA) is calling for carbon neutral growth from 2020 and a 50% reduction by 2050 from a base of 2005. Regardless of the proponent, these are extremely ambitious goals. Aircraft technology has been responsible for the majority of the gains made in the last three decades in reducing aviation‟s environmental impacts. The 10- and 20-year technology goals discussed above are an essential contribution to towards meeting ambitions for global aviation system efficiency goals and technology must be pushed for further improvements beyond 2030. Nevertheless the rate of change in gains from technology appears to be diminishing with time and technology alone will not be sufficient to meet these ambitions. Other approaches, including further consideration of aircraft configuration and mission specification, must be introduced, along with air traffic management and operational improvements and possibly sustainable fuels and market measures. The IEs feel that it would be important to conduct system analyses to evaluate the realism of the goals as well as the contributions of various strategies toward meeting these goals. Particularly it would be important to evaluate the overall system effects of changes in Mach number and design ranges, including potential effect on number of operations, which could affect safety, operating costs, noise exposure and air quality impacts.

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8 CONCLUSIONS

8.1 Based on the Workshop held in March 2009, the Formal Review in May 2010, many additional interactions with stakeholders and the calculations carried out by the Independent Experts and by other parties, the IEs have arrived at the conclusions described in the following paragraphs.

8.2 The predicted reductions in fuel burn are set in section 5 of the report in the form of graphs with reductions shown against maximum payload maximum range, R1. The lines, which show reductions corresponding to the different technology scenarios (TS), are anchored at shorter design ranges (2125 nm) by the single-aisle reference aircraft and at longer design ranges (5750 nm) by the twin-aisle reference aircraft. The values at the anchor points are set out in table 8.1 below.

2020 2030

SA STA SA STA

TS1 23 19 29 26

TS2 29 25 34 35

TS3 41 41

TS3 Open rotor 48

Table ‎8.1: Estimated percent reduction in fuel burn metric at the SA and STA anchor points relative to 2000 baseline for maximum payload maximum range based on all contributing sources (see Appendix D).

8.3 The IEs have some reservations about expressing reductions in fuel burn in terms of annual compound reductions, because changes in technology can result in large but infrequent step changes. However, for comparison with goals given by other organisations the present goals are presented in table 8.2 below as annual percentage changes.

Annual Compound % Reductions in Fuel Burn Metric4

SA STA

2020

TS1 („Continuation‟) 1.29% 1.05%

IE Recommended Goal 1.70% 1.43%

2030 TS1 („Continuation‟) 1.14% 1.00%

IE Recommended Goal 1.38% 1.43%

Table ‎8.2: Annual compound percentage reductions in fuel burn metric for SA/STA categories and 2020/2030 based on all contributing sources.

8.4 TS1 is taken to be what the industry is likely to achieve without further increased pressure, but continued effort and funding. It will be seen that most of the reduction is represented by TS1, with comparatively small additional reductions from the aggressive use of new technologies in TS2 and TS3. TS3 also allows different aircraft specifications and doing things differently, but it was judged that 2020 is too soon to make consideration of TS3 appropriate.

8.5 The „doing things differently‟ option in TS3, allowing altered aircraft specifications and changed aircraft mission specification, shows benefits comparable in magnitude to the differences in achievements attributable to technology alone between TS1 and TS2 and between TS2 and TS3. If the „doing things differently‟ approach were adopted in tandem with the new technologies the IEs believe that achieving the levels of TS3 is reasonably probable and achieving the levels of TS2 highly likely. This requires the changes to be accepted by airlines (and customers) as well as by other aspects of the air transport industry.

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8.6 The IEs conclude that setting the goal as a band between TS2 and TS3 is both plausible and challenging. The goal would be met by obtaining a value of kg/ATK below the line for TS2. The bottom of the band placed at TS3 in 2030 has been included to provide some insight of what additional reductions might be possible. For 2020 the goal should be considered to have been met if an aircraft at maximum payload maximum range achieves a reduction in excess of between 29% and 25% (with the former being for the SA size and the latter for the STA) relative to baseline aircraft of 2000. For 2030 the goal would be achieved if the corresponding reduction were 34% and 35% (with the former being for the SA size and the latter for the STA).

8.7 The aspirational global goal of 2% fuel burn reduction up to 2050 which ICAO has committed to is believed to relate to the whole system and the IEs have not taken into account such factors as fleet replacement. However, the highest annual rate found by the IEs for technology goals corresponds to around 1.4% (for best-in-class individual aircraft), confirming that technology alone cannot achieve the reduction.

8.8 It has become clear that past technology improvements have partly been used to increase performance, primarily design range. Because of this the reductions in fuel burn have been smaller than they might have been, particularly for long-range twin-aisle aircraft. In assessing future reductions in fuel burn and the potential for these it is important to include the effect of the specified design range.

8.9 The IEs have been made aware that the majority of flights for both the single-aisle and twin-aisle aircraft are substantially below the maximum payload range of the aircraft. Both manufacturers and airlines have opted for long range since a long range aircraft can always operate a short flight, but not the other way around. The IEs have identified that design for long range comes at a substantial price in terms of minimum fuel burn.

8.10 The issues of fleet commonality and aircraft flexibility, which are related to conclusion 8.8 above, are partly the result of the cost of developing, manufacturing and certifying new aircraft. A real engineering challenge is to find ways to reduce this cost whilst producing a range of aircraft with specifications for range and payload which would more closely match the needs of different airlines. The requirement was referred to by one airline, with which the IEs discussed this issue, as a “Lego kit” of parts to allow different wing areas and spans.

8.11 The review would have been easier and the conclusions might have had greater acceptability if there had been more input from industry. Some aspects, such as engine-airframe integration issues are only fully understood and quantified by industry. It is desirable to repeat the study with calculations being carried out inside the industry when the CO2 Standard has been agreed. The study should also look at regional jets and large (>400 seats) twin-aisle aircraft.

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9 RECOMMENDATIONS

9.1 Based on the Workshop held in March 2009, the Formal Review in May 2010, many additional interactions with stakeholders and the calculations carried out by the Independent Experts and by other parties, the IEs offer the following recommendations:

a) The independent experts recommend that the fuel burn reduction goals should be expressed as a percentage reduction in the fuel burn metric (kg/ATK) at maximum payload maximum range relative to 2000 baseline aircraft. It is acknowledged that the metric and evaluation point(s) should be re-examined once the ICAO CO2 certification procedure is finalised.

b) The IEs recommend that the goal should be expressed as a band of percentage reduction versus (R1) design range or ATK. The goal would be judged to have been achieved when an aircraft achieves a reduction equal to or greater than the upper edge of the band.

c) The IEs recommend that the 2020 goal should be met if an aircraft at maximum payload maximum range achieves a reduction in excess of between 29% and 25% (with the former anchoring the band for the SA size and the latter for the STA) relative to baseline aircraft of 2000. For 2030 the goal would be achieved if the corresponding reduction were between 34% and 35% (with the former anchoring the band for the SA size and the latter for the STA) relative to baseline aircraft of 2000.

d) The IEs recommend that when the CO2 certification procedure has been agreed to, the goals should be re-examined. This should also include the regional jet and the large twin-aisle.

e) The IEs also believed that it is important to conduct system analyses to evaluate the contributions of various strategies toward meeting these goals, particularly the overall system effects of changes in Mach number and design ranges, including potential effect on number of operations, which could affect safety, operating costs, noise exposure and air quality impacts.

f) If there is another goal-setting review carried out by IEs, it is recommended that the review should have the full commitment and engagement of industry.

g) The present study would have been virtually impossible without the IEs having direct access to modelling capability. It is recommended that for any future fuel burn review carried out by IEs, it is ensured that the team has access to modelling capability and appropriate resources to use this.

h) Any future review should consider the combined effects, on fuel burn goals, of new technology and changes to aircraft capability and mission specification.

i) Based on the knowledge gained the IEs recommend that any future review has as one of its members someone familiar with the business of taking potential new commercial aircraft from concept through to delivered products.

j) The present review was carried out entirely by IEs from Western Europe and the U.S., and it is recommended that any further review should have wider geographical representation.

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GLOSSARY OF T ERMS

ASK Available Seat Kilometre ATF Advanced Turbofan ATK Available Tonne Kilometre ATM Air Traffic Management BPR ByPass Ratio CO2 Carbon Dioxide CAEP Committee on Aviation Environmental Protection DLR German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt e.V.) DOC Direct Operating Cost EDS Environmental design space EIS Entry Into Service FAA Federal Aviation Administration FESG Forecasting and Economic Support Group FPR Fan Pressure Ratio GaTech Georgia Institute of Technology GTF Geared Turbo Fan GTP Global Temperature change Potential GWP Global Warming Potential HGW High Gross Weight HWB Hybrid Wing Body IATA International Air Transport Association ICAO International Civil Aviation Organization ICCAIA International Coordinating Council of Aerospace Industry Associations ICCT International Council on Clean Transportation ICSA International Coalition for Sustainable Aviation IE Independent Expert IPCC Intergovernmental Panel on Climate Change L/D Lift/Drag LT Long Term LTA Large Twin Aisle MEA More Electric Aircraft

MPR Maximum Payload Range MT Medium Term MTOW Maximum Take-Off Weight MWE Manufacturer‟s Empty Weight MZFW Maximum Zero Fuel Weight NASA National Aeronautics and Space Administration NOx Oxides of Nitrogen OEW Operating Empty Weight OR Open Rotor PARTNER Partnership for AiR Transportation Noise and Emissions Reduction PASS Program for Aircraft Synthesis Studies PrADO Preliminary Design and Optimization Program RF Radiative Forcing RJ Regional Jet SA Single Aisle STA Small-medium Twin Aisle TA Twin Aisle TOR Terms of Reference

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TRL Technology Readiness Level TS Technology Scenarios TRA Technology Reference Aircraft UHB Ultra High Bypass

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LIST OF REFERENCES

Breguet, L. Calcul du poids de combustible consumme par un avion en vol ascendant. 1923 Comptes Rendus de l’acadmie des sciences, 177, pp. 870-872 Dagett, D L, Hendricks, R C, Mahashabde, A and Waitz I A. “Water Injection – Could it Reduce Airplane Maintenance Costs and Airport Emissions?”. NASA/TM-2007-213652, International Symposium on Air-Breathing Engines, ISABE-2005-1249. http://www.denmark.dk/en/menu/Climate-Energy/COP15-Copenhagen-2009/cop15.htm IPCC-Synthesis. (2007). Climate Change 2007 Synthesis Report: Summary for Policymakers. Contributions of Working Groups I, II, and III to the Fourth Assessment Report of the IPCC. Geneva, Switzerland: Intergovernmental Panel on Climate Change. Poll, D.I.A. The optimum aeroplane and beyond. Lanchester Lecture of the Royal Aeronautical Society. 2009 Aeronautical Journal 113.

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APPENDIX A-1 : LIST OF PRESENTATIONS FOR THE MARCH 2009 WORKSHOP HELD IN

LONDON, UK

FUEL BURN REDUCTION TECHNOLOGY WORKSHOP AGENDA

London, March 25-26th, 2009 DAY ONE

08:30 08:40 Host Welcome / Logistics P. Newton 08:40 08:50 ICCAIA Workshop Opening ICCAIA / F. Viscotchi / D. Allyn INTRODUCTION 08:50 09:00 Reminder of the CAEP remit WG3 / D. Lister/ C. Holsclaw 09:00 09:20 Environmental needs / D. Lee 09:20 09:30 Section Q&A 09:30 09:45 Fuel Burn and Technology - Historical Trends IATA / T. Roetger 09:45 09:55 Section Q&A 09:55 10:25 Airline Fleet Planning IATA / M. Pfeifer 10:25 10:35 Section Q&A COFFEE BREAK (15 min) 10:50 11:10 Performance retention ICCAIA / W. Lord 11:10 11:20 Q&A FUEL BURN - BASELINE AND METRIC 11:20 11:40 Baseline ICCAIA / D. Allyn 11:40 11:50 Q&A 11:50 12:15 Metrics ICCAIA / D. Allyn 12:15 12:25 Q&A LUNCH BREAK (1 hour) TECHNOLOGIES AND THEIR POTENTIAL CONTRIBUTION TO REDUCING FUEL BURN (Session1) 13:25 13:50 Introduction to Propulsion System and Aircraft Level Technologies ICCAIA / F. Viscotchi 13:50 14:00 Q&A Engine and Propulsion System 14:10 14:30 Propulsive Efficiency ICCAIA / R. Clough 14:30 14:40 Q&A 14:40 15:00 Thermal Efficiency ICCAIA / G. Johnson 15:00 15:10 Q&A 15:10 15:35 Powerplant Installation/ integration effects ICCAIA / E. Hermant 15:35 15:45 Q&A COFFEE BREAK (20 min)

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Engine Architecture concepts examples 16:05 16:25 Open Rotor ROLLS ROYCE / R. Clough 16:25 16:35 Q&A 16:35 16:45 The Contra Fan or Counter-Rotating Turbofan SNECMA / E. Hermant 16:45 16:50 Q&A 16:50 17:05 Advanced Turbofan (ATF) GENERAL ELECTRIC / G. Johnson 17:05 17:15 Q&A 17:15 17:40 Ultra-High BPR Ducted Propulsor PRATT & WHITNEY / W. Lord 17:40 17:50 Q&A 17:50 18:00 Wrap up of the day 1 and plan for day 2 ICCAIA / F. Viscotchi/ D. Allyn DAY TWO 08:30 08:40 ICCAIA Introduction of Fuel Burn Workshop Day 2 ICCAIA / F. Viscotchi / D. Allyn TECHNOLOGIES AND THEIR POTENTIAL CONTRIBUTION TO REDUCING FUEL BURN (Session2) Aircraft 08:40 09:20 Structural Technologies for weight efficiency ICCAIA / S. Barre 09:20 09:30 Q&A COFFEE BREAK (20 min) 09:50 11:00 Aerodynamics / Flight Physics technologies ICCAIA / P. Vijgen 11:00 11:10 Q&A OVERALL EFFECTS AND ENVIRONMENTAL INTERDEPENDENCIES 11:40 11:55 Overall Effects and Environmental Interdependencies ICCAIA / P. Madden 11:55 12:00 Q&A ICCAIA – TECHNOLOGIES SUMMARY 11:10 11:30 Summary presentation ICCAIA / F. Viscotchi 11:30 11:40 Q&A LUNCH BREAK (1 hour) RESEARCH PROGRAMS 13:10 14:10 US Research Programs NASA / F.S. Collier 14:10 14:20 Q&A COFFEE BREAK (20 min) 14:40 15:40 EU Research Programs / D. Chiron / N. Kumar 15:40 15:50 Q&A CONCLUSIONS and NEXT STEPS 15:50 16:10 Conclusions and next steps ICCAIA / D. Allyn 16:10 16:30 Q&A

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QUESTIONS AND ANSWERS SESSION 16:30 17:00 Questions and Answers session FUEL BURN WORKSHOP CLOSURE 17:00 17:15 Meeting Closure ICCAIA / F. Viscotchi/ D. Allyn

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APPENDIX A-2: LIST OF PRESENTATIONS/AGENDA FOR THE MAY 2010 REV IEW HELD

IN ATLANTA, U.S .

CAEP Fuel Burn Reduction Technology Goals Review Final Agenda Day 1: Tuesday 25th May Introduction and Scene Setting 08:30 – 08:40 Welcome and practical arrangements - S. Baker, IE Secretary 08:40 – 09:00 CAEP requirements and relationship between goals and Standards - C. Holsclaw/D. Lister,

WG3 co-rapporteurs 09:00 – 09:20 The IE approach and aims for meeting - N. Cumpsty, IE 09:20 – 09:35 ICCAIA perspective on the FBRT review – O. Husse, ICCAIA 09:35 – 10:15 Aviation and climate change impacts and the pressure for fuel burn reductions – D. Lee,

MMU 10:15 – 10:45 Discussion – led by M. Ralph, IE 10:45 – 11:15 Break Review of technologies and their impact on key efficiency parameters to 2020 and 2030 11:15 – 11:35 Technology Reference Aircraft – O. Husse, ICCAIA 11:35 – 11:55 Alternative aircraft for studies – B. Nas, IEs 11:55 – 12:30 Discussion – led by S. Eury, IE 12:30 - 13:30 Lunch 13:30 – 14:00 Presentation of IE technology matrix - S. Eury, IE 14:00 – 15:30 Technology matrix and trends

Aerodynamics – P. Vijgen/J. Conlin, ICCAIA

Structures/weights – O. Husse, ICCAIA

Propulsion – R. Clough, ICCAIA 15:30 – 16:00 Break 16:00 – 16:45 The TERESA project - E. Stumpf, DLR 16:45 – 17:45 Discussion – led by N. Cumpsty, IE

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Day 2: Wednesday 26th May 08:30 – 09:00 The role of new technologies for airlines‟ emissions reduction goals - T. Roetger, IATA 09:00 – 09:45 N+1 story (A joint NASA/FAA CLEEN presentation on the background/development of

the N+1 goals and the CLEEN program activities) - R. Jefferies, FAA and M. Guynn, NASA

09:45 – 10:30 NASA‟s Environmentally Responsible Aviation Project Impact on Midterm (N+2) National

Goals with Focus on Fuel Burn – F. Collier, NASA 10:30 – 11:00 Break 11:00 – 11:45 NASA‟s Subsonic Fixed Wing Vision For Long Term (N+3) National Goals with Focus on

Fuel Burn - R. del Rosario, NASA 11:45 – 12:15 Discussion – led by J. Alonso, IE 12:15 -13:15 Lunch Application of new or enhanced technology to 2020 aircraft 13:15 – 13:45 Design studies - B. Nagel, DLR 13:45 – 14:15 Impact of selected technology innovation on fuel burn for different mission ranges - G.

Horton, Qinetiq 14:15 – 14:45 EDS assessment of fuel burn technology roadmaps - M. Kirby, Georgia Tech 14:45 – 15:15 PIANO design studies using the IE technology matrix - M. Zeinali, ICCT 15:15 – 15:45 Break 15:45– 16:30 Modelling with PASS to inform IE analysis - J. Alonso, IE 16:30 – 17:30 Discussion of results of modelling to 2020 and consideration of goals – led by L. Maurice,

IE

TS1 Single Aisle and Twin Aisle

TS2 Single Aisle and Twin Aisle

TS3 Single Aisle and Twin Aisle Day 3: Thursday 27th May 08:30 – 09:00 Game changing technologies for airlines‟ long term perspectives – K. Echtermeyer, IATA 09:00 – 09:45 Fuel burn dependence – a first principles, first order approach - I. Poll, Greener by Design 09:45 – 10:15 Discussion – led by B. Sawyer, IE 10:15 - 10:45 Break

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Application of new or enhanced technology to 2030 aircraft 10:45 – 11:15 Modelling with PASS to inform IE analysis - J. Alonso, IE 11:15 – 11:45 Design studies - B. Nagel, DLR 11:45 – 12:15 Impact of selected technology innovation on fuel burn for different mission range – G.

Horton, Qinetiq 12:15 – 13:00 Lunch 13:00 - 13:30 EDS assessment of fuel burn technology roadmaps - M. Kirby, Georgia Tech 13:30 – 14:00 PIANO design studies using the IE technology matrix- M. Zeinali, ICCT 14:00 – 15:00 Discussion of modelling to 2030 and consideration of goals – led by B. Nas, IE

TS1 Single Aisle and Twin Aisle

TS2 Single Aisle and Twin Aisle

TS3 Single Aisle and Twin Aisle 15:00 – 15:15 Break Recommendations for further modelling and calculations 15:15 – 15:45 Discussion – led by N. Cumpsty, IE 15:45 – 16:15 Way forward to formulation of technology goals 16:15 Close

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APPENDIX A-3: LIST OF ATTENDEES FOR THE MAY 2010 REVIE W HELD IN ATLANTA,

U.S .

Name Organisation

Nick Cumpsty IE

Malcolm Ralph IE

Lourdes Maurice IE

Juan Alonso IE

Bengt Nas IE

Serge Eury IE

Robert Sawyer IE

Sam Baker IE Secretary

Bjoern Nagel DLR

Eike Stumpf DLR

Bryan Manning Environmental Protection Agency

Curtis Holsclaw Federal Aviation Authority

Thomas Roetger IATA

Betty Hawkins IATA

Michelle Kirby Georgia Institute of Technology

Fay Collier NASA

Olivier Husse Airbus

Ruben Delrosario NASA

Steve Csonka GE Aviation

Rhett Jefferies FAA

David Lee MMU

Dom Sepulveda Pratt & Whitney

Wes Lord Pratt & Whitney

Mazyar Zeinali ICCT (ICSA)

Dan Rutherford ICCT (ICSA)

Gareth Horton Qinetiq

Anders Andersson Swedish Transport Agency

Dave Lister UK CAA

Karl Echtermeyer Lufthansa

Arturo Benito Universidad Politécnica de Madrid

Ian Poll Greener by Design

Professor Riti Singh Cranfield University

Tetsuya Tanaka ICAO secretariat

Chris Hughes NASA

Craig Nickol NASA

Mark Guynn NASA

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Roger Worth UK DfT

Richard Clough Rolls Royce

Paul Vijgen Boeing

David Anvid Delta Airlines Sean R. Copeland Stanford University Thomas D. Economon Stanford University

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APPENDIX B: KEY DATA FOR THE REF ERENCE AIRCRAFT

Category RJ SA SA STA STA

Type CRJ900 737-800W A320-200 A330-300 777-200ER

Typical seat count 90 160 150 295 300

MTOW tonne 36,51 79,017 73,5 230 288,036

R1 range km 2250 3936 3273 6800 10649

R1 payload kg 10399 21319 19099 48320 58740

Engine max thrust 27000 25000 68000 92000

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APPENDIX C: BASKET OF T ECHNOLOGIES

Propulsion

o Advanced Turbofan o Geared Turbofan o Open rotor

Basket of Technologies which improve Propulsive Efficiency

o Improved global design through advanced analytical tools o Optimized components through advanced analytical tools o Reduced nacelle weights which displace the optimum towards decreased FPR and increased BPR

o Advanced composites: o PMC, Phenolic matrix composite o MMC, Metallic matrix composite o CMC, Ceramic matrix composite o Composite frames

o Advanced alloys o Increased loading o Manufacturing technology

o Combined feature functionality o Integrated installations o Zero Hub Fan

Basket of Technologies which improve Thermodynamic Efficiency

o Improved materials to allow higher temperature. o Improved compressor and turbine with 3D aerodynamics, blowing and aspiration o Active tip clearance

Aerodynamic Basket of Technologies which improve Viscous Drag

o Riblets o Active turbulence control o Natural Laminar Flow o Hybrid Laminar Flow Control

Basket of Technologies which improve Non-viscous Drag

o Increased wing span (increased aspect ratio) o Improved aero tools o Excrescence reduction o Variable camber with new control surfaces o Morphing wing

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Basket of Technologies which improve Weight

o Optimization of geometry through o Reduction of loads (Active smart wing) o New joining processes (removal of riveting) by:

o Stir welding process, o Super-plastic Forming, o Diffusion Welding, o Laser beam welding.

o Metallic technologies

o Al-Li, o Al-Mg-Sc, o Advanced alloy

o Composites technologies

o PMC

o Fluoro-polymers,

o Glare (glass-fibre-reinforced),

o ARALL (aramid-fibre-reinforced),

o CentrAl (aluminium-based composite material with alternating high-quality aluminium and

composite layers in a fibre metal laminate)

o Multifunctional materials/structures

o Nanotechnologies

o Health monitoring Other concepts

o Electric landing-gear drive o More electric aircraft (MEA)

o Fuel cells

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Technological improvement in propulsion

Technologies emphasised by ICCAIA

Probability

High Scope 2020 2030 2020 2030 2030 2020 2030 2020 2030 2030

Medium Scenario 1 1 2 2 3 1 1 2 2 3

Low Cases 3 6 4 7 8 9 12 10 13 14

Propulsion Improvement in Efficiency 16% 18% 18% 20% 31% 8% 12% 10% 14% 27%

SFC 0.51 0.48 0.51 0.48 0.4 0.50 0.48 0.50 0.48 0.4

Advanced Turbofan 16%

Geared Turbofan Gain of 0 - 2% / ATF 18%

Open rotor Gain of 10% / ATF 26%

UHB (BPR 18)

Variable cycle

Intercooled Turbofan 2% 2%

Integrated propulsion

Buried, boundary layer ingesting installation concepts (4%)

Increase of BPR BPR 10 13 10 13 35 12 13 12 13 35

Propulsive efficiency 0.82 0.85 0.82 0.85 0.97 0.84 0.86 0.84 0.86 0.97

Increase of propulsive efficiency 13% 14% 14% 15% 28% 6% 9% 7% 10% 25%

Active laminar flow control on nacelle

Variable nozzle

Supression of reverse 2% 2% 2% 2%

Increase of OPR OPR 40 50 50 60

Increase of thermal efficiency 3% 4% 4% 5% 3% 2% 3% 3% 4% 2%

Active tip clearance

Water injection 3% 3%

Single aisle aircraft Twin aisle aircraft

Technological improvement in Aerodynamics

Technologies emphasised by

ICCAIA

Probability

High Scope 2020 2030 2020 2030 2030 2020 2030 2020 2030 2030

Medium Scenario 1 1 2 2 3 1 1 2 2 3

Low Cases 3 6 4 7 8 9 12 10 13 14

Aerodynamic - non viscous 2% 4% 4% 6% 7% 2% 4% 4% 6% 7%

Improved aero tools 1% 2% 2% 3% 4% 1% 2% 2% 3% 4%

Excessence reduction 1% 1% 1.3% 1.3% 1.3% 1% 1% 1.1% 1.1% 1.1%

Variable camber with new control surfaces 1.3% 1.5% 1.5% 1.8% 2.0% 1.3% 1.5% 1.5% 1.8% 2.1%

Morphing wing

Winglets/Spiroid wingtips

Aerodynamic - viscous 2% 4% 4% 7% 9% 2% 6% 4% 8% 10%

Coating

Riblets 1.4% 2.3% 1.7% 2.5% 1.6% 2.5% 1.9% 2%

Active turbulence control

Natural Laminar Flow 4% 7% 6% 10% 0.5% 1% 6% 1.5%

Hybrid Laminar Flow Control 0.5% 1% 7% 11%

Single aisle aircraft Twin aisle aircraft

62

Technological improvement in Weight

Technologies emphasised by

ICCAIA

Probability

High Scope 2020 2030 2020 2030 2030 2020 2030 2020 2030 2030

Medium Scenario 1 1 2 2 3 1 1 2 2 3

Low Cases 3 6 4 7 8 9 12 10 13 14

Weight Improvement 10% 15% 15% 20% 17% 10% 15% 15% 20% 23%

Wings and empenages

Optimisation of geometry

Reduction of loads (Active smart wing) 2% 4% 4% 5% 6% 2% 4% 4% 5% 6%

New bounding process (suppression of riveting)

Metallic technologies 1% 2% 1% 2% 3% 1% 2% 1% 2% 3%

Composites technologies 3% 4% 4% 5% 7% 3% 4% 4% 5% 7%

Multifunctional materials/structures 1% 2% 3% 4% 7% 1% 2% 3% 4% 7%

Nanotechnologies 1% 2% 4% 1% 2% 4%

Health monitoring 1% 2% 4% 1% 2% 4%

Active Stability

Cabin and fuselage

New materials 2% 3% 2% 3% 4% 2% 3% 2% 3% 4%

Systems

Landing gear in Ti 1% 1% 1% 1% 1% 1% 1% 1% 1% 1%

More electric aircraft (MEA) 1% 1% 1% 1% 1% 1% 1% 1%

Fuel cells

Single aisle aircraft Twin aisle aircraft

63

APPENDIX D: SUMMARY OF MODELLING RESULTS

Fuel Burn Metric Changes Plotted Against R1 Range for the 2020 MT Time Frame in TS1 and TS2. Results from Aircraft Optimized by IEs and Participating Organizations with Same R1 Range Have Been Averaged.

Fuel Burn Metric Changes Plotted Against R1 Range for the 2030 Time Frame and in TS1, TS2, TS3, and TS3-OR. Results from Aircraft Optimized by IEs and Participating Organizations with Same R1 Range Have Been Averaged.

-60%

-50%

-40%

-30%

-20%

-10%

1 000 2 000 3 000 4 000 5 000 6 000

% c

han

ge

R1 distance nm

Stanford

ICSA

GaTech

DLR

Qinetiq

TS1

TS2

-60%

-50%

-40%

-30%

-20%

-10%

1 000 2 000 3 000 4 000 5 000 6 000

% c

han

ge

R1 distance nm

Stanford

ICSA

DLR

Qinetiq

GaTech

TS3

TS1

TS2

TS3OR

64

APPENDIX E: TRL SCALE

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© ICAO 2011

Order No. 9963

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