MEFUL: Minimizing Flight Emissions while Sustaining Guaranteed Operational Safety as a Contribution to an Environmental Friendly Air Transport System
PROJECT INFORMATION
- Sponsoring authority: German Federal Ministry of Economic Affairs and Energy (BMWi)
- Financial and technical partner: Lufthansa Cargo AG (LCAG)
- Project term: 36 months, January 2014 - December 2016
Urgency and necessity for environmentally sustainable transport offers are highly evident today. The research cluster “eco-efficient air transport”, part of the current 5th German aviation research program (BMWi ‘s LuFo V), mainly focusses promising technologies for an environmentally friendly air transport system until the year 2050. In order to meet future demands, technical adjustments need to be complemented with operational developments.
Figure 1: Comparison of a operating cost minimum vertical profile with a emission minimum aircraft trajectory. In red a conventional trajectory is shown.
Currently, numerous operational constraints result in economically and ecologically imperfect flight operations. While some constraints are legitimized by the state of the art in safety and technology, capacity limits of the European airspace induce further, significant deviations from the ideal flight trajectory. “Ecologically” optimized flight plans are established almost exclusively with respect to minimal CO2 emissions – basically, equivalent with minimal fuel consumption. At the ground level, the aspects of aircraft noise and the NOx pollution play a role in the context of procedure design (e.g. arrival/departure routes) and airport charges at some airports (e.g. daytime and noise dependent pricing). A comprehensive ecological framework has not yet been established; today’s metrics for environmental sustainability are hardly sufficient to evaluate the big picture: Future flight trajectory planning and implementation will have to quantitatively balance safety, cost effectiveness, and environmental sustainability. The ambitious research project MEFUL aims for minimizing negative ecological impacts of flight operations while simultaneously managing operational safety at acceptable levels. The research focuses on conceptual design, parameterization and validation of legitimate metrics which will encompass the ecological footprint of air traffic and form the basis for continuative multi-criteria optimization of flight profiles holding partially conflicting target criteria. The project relies on the extensive preliminary work at the Institute regarding Aircraft Performance Modelling (EJPM), flight efficiency evaluation and identification of the climate impacts of air transport. As a main result, the potential of an ecological optimization should be determined in consideration of the discrepancies of safety and economy requirements. The project is partially funded by the Lufthansa Cargo AG. The airline further supports the project and participates with several professionals (flight operations, safety & quality, engineering). In times of globalization and rethinking environmental awareness, the ecological indicators being developed by MEFUL have the potential of a competitive side advantageous product differentiation for airlines.
The 4D trajectory of an aircraft consists of the three spatial dimensions plus time as a fourth dimension. In MEFUL, flight trajectories are determined by using a multi criteria optimization approach. In many cases the aircraft trajectory management can have two or more conflicting objectives and a decision need to be taken in the presence of trade-offs. In the network, fleet and trajectory optimization this multi objective optimization more than one objective functions are involved and optimized simultaneously. Therefore, operating costs, safety criteria, and environmental sustainability can affect the trajectory design.
Conventional flight paths are included in the given air traffic route structures and fix waypoints to ensure a high level of safe air traffic flow. In the best case, these flightpaths are optimized according to the currently wind vectors to minimized flight time and total fuel consumption.
MEFUL furthermore takes environmental sustainability and external costs for emissions in consideration. Therefore, emissions with radiative forcing are transformed in their global warming potential and included in an emissions trading scheme. Now, additional to conventional operating costs also emission costs exist and can be respected in target objective function. Thus, for example, ice supersatured regions and the formation of contrails can be avoided. Compared with this, additional emissions by flight path modification occur and a trade-off between contrails and other emissions with radiative forcing can be made.
Area of tension considered by a multi criteria trajectory optimization
The optimization of the air transport system considering the conflicting objective functions Safety, Ecology and Costs requires a comprehensive and detailed assessment the of air traffic network, fleet and flight path. For this purpose, a variety of indicators of the above objective functions will be developed. The assessment always has to take into account all interacting indicators, to identify interdependencies. Besides the assessment of conventional cost efficiency and safety also emissions indicators are taken to be in account. The following picture 1 shows the CO2 equivalent emissions for a short distance flight of an Airbus A320 with 400 km distance. Short distance flights are classified in the air traffic system as least environmentally acceptable.
Figure 1: Type and amount of emission of a A320 flight with 400 km flight distance
The emissions generated by the aircraft are basically to be distinguished in their kind of impact. Some emissions affect the radiation budget of the Earth atmosphere system and cause a cooling or warming of the Earth's surface temperature. Other emissions affect the air quality or the health of life on Earth, especially in the vicinity of airports. This differentiation constitutes a differentiated assessment of the emissions and consideration in the optimization.
Emissions with significant impact on the radiation budget of the Earth atmosphere system 1are carbon dioxide, water vapor, nitrogen oxides, soot, as well as sulphur-containing connections (precursor of radiation-effective aerosols) and effects of the condensation trails. Emissions with significant effects air quality or the health of life on Earth are carbon monoxide, unburned hydrocarbons and noise. Sulphur dioxide is washed out in lower troposphere and is a component of acidic rain. The emissions are quantified for every considered flight. For comparability, the Global Warming Potential GWP of each emission is estimated, using the emission specific radiative forcing (RF). The GWP quantifies the CO2 equivalent mass with the same radiative forcing. The emission sources H2SO4, NOX and BC are quantified according to [1] and [2]. The climate cost functions depend on altitude and latitude and are implemented according to [3], [4] and [5]. With the help of emission trading system, these emissions can be formulated as external environmental costs.
Literaturverzeichnis
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[1] |
M. Schaefer, „Methodologies for Aviation Emission Calculation- A comparison of alternative approaches towards 4D global investigations,“ Diploma Thesis , Berlin University of Technology, 2006. |
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[2] |
A. Kugele, F. Jelinek und R. Gaffal, „Aircraft Particulate Matter Emission Estimation through all Phases of Flight,“ EUROCONTROL Experimental Centre, 2005. |
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[3] |
J. Fuglestvedt, K. Shine, T. Berntsen, J. Cook, D. Lee, A. Stenke, R. Skeie, G. Velders und I. Waitz, „Transport Impacts on Atmosphere and Climate: Metrics,“ Atmospheric Environment, 44, pp. 4648-4677, 2010. |
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[4] |
A. Skowron, D.S. Lee und R. R. De León, „Variation of radiative forcings and global warming potentials from regional NOx emissions,“ Atmospheric Environment 104, pp. 69-78, 2015. |
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[5] |
T. Stocker, D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex und P. Midgley, „The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental,“ Cambridge, United Kingdom and New York, NY, USA, Cambridge University Press, 2013, p. 1535 pp. |
For trajectory optimization, a flight performance model and a lateral pathfinding algorithm are used iteratively by the simulation environment TOMATO (TOolchain for Multicriteria Aircraft Trajectory Optimization). Originally developed for the purposes of MEFUL, TOMATO is used in further projects of the institute and adapted if necessary.
The aircraft performance model COALA (Compromised Aircraft performance model with Limited Accuracy) enables the modeling of optimized waypoint-less trajectories for each aircraft-engine combination using real weather conditions. Developed in MEFUL, COALA is being extended by new functions for extensive research purposes at the institute.
Airline networks represent the strategy of the airline (network carrier, low-cost carrier, hybrids). The basic aim of a network modeling is to minimize costs or maximize revenue. In MEFUL, the network optimization is connected with a fleet assignment considering their optimum range of application. This bi-objective non-strict model finds regular line connections of synchronous traffic flows and serves the demand.
Figure 1: NOx emission assessment in a global network
The optimization to an eco-efficient network is based on a cost minimizing approach for a given demand. Thus, regional effects of NOx are applicable and can be expressed as additional costs. Results from an economical and market model can be included. The implementation and solution of the network problems follows a linear programming approach for one airline. Because the model is allowed to choose between the knots to be served, only the cost optimal routes are selected during optimization and connections with high costs will be neglected. The main functionalities are:
- A part of given demand shall be served by a number of flights between established connections.
- Detection of local hubs for a limited number of variable possible hubs.
- Connections are added to hubs involving hub-destination connections, as well as point-to-point links.
- Aircraft types and the required number of flight are basically assigned.
Figure 2: Example network design with hubs (dark grey) and connected nodes (light grey circles), crossed nodes are not connected in the current network. Flight-connections are marked with dark grey lines for hub-to-hub and hub-to-point connections, point-to-point-connections are enhanced with light grey lines
A parameter study, solved for a network including 40 nodes, shows that the optimum hub factor is 0.2-0.35 for this network. The hub factor is the ratio of number of hub and spoke connections (grey) and point to point connections (yellow). Therewith, increasing emissions costs reduce the hub factor because of higher cost weighting of hub connections.
Figure 3: solved network problem
Furthermore, the example above shows that regional effect of NOx does not change the network structure significant, even if emissions costs are set really high. However, given the fact that the global warming potential of nitrogen oxide is in Asia higher, a few flights were relocated to Europe in this example. Otherwise, the transportation costs increase.
During the project, following activities and results were publicated:
- Judith Rosenow, Stanley Förster, Martin Lindner, Hartmut Fricke (2016): Impact of Multi-critica Optimized Trajectories on European Traffic Density, Efficiency and the Environment, 12. USA/Europe Air Traffic Management Research and Development Seminar (ATM2017), Seattle
- Judith Rosenow, Stanley Förster and Hartmut Fricke (2016): Continous Climb Operations with Minimum Fuel Burn, SESAR Innovation Days, Delft
- Stanley Förster, Judith Rosenow, Martin Lindner, and Hartmut Fricke (2016): A toolchain for optimizing trajectories under real weather conditions and realistic flight performance Greener Aviation Brussels
- Martin Lindner, Stanley Förster, Judith Rosenow and Hartmut Fricke (2016): Ecological impact of air traffic control en-route charging zones in multi criteria optimized flight paths, Greener Aviation Brussels
- Martin Lindner, Stanley Förster, Judith Rosenow and Hartmut Fricke (2016): Potential of integrated aircraft rotation and flight scheduling with modeled tailsign performance, DGLR Kongress Braunschweig
- Judith Rosenow and Hartmut Fricke (2016): Flight performance modeling to optimize trajectories, DGLR Kongress Braunschweig
- Judith Rosenow, Hartmut Fricke (2016): Trajektorienoptimierung mit multikriteriellen Zielfunktionen, Symposium ATM Research & Industrie
- Judith Rosenow, Stanley Förster, Martin Lindner and Hartmut Fricke (2016): Multi-objective trajectory optimization, International Transportation,Special Edition 1, Volume 68
- Sabrina Groth, Judith Rosenow and Hartmut Fricke (2016): Aviation-induced nitrogen oxide emissions and their effect on the energy budget of the Earth-atmosphere system, International Conference on Research in Air Transportation (ICRAT), Philadelphia; USA - Pennsylvania
- Martin Lindner and Hartmut Fricke (2016): Potenziale und Herausforderungen der Integration von Formationsflügen in den Luftraum, 25. Verkehrswissenschaftliche Tage Dresden
- Judith Rosenow, Franziska Dieke-Meier, Christian Seiß and Hartmut Fricke (2015): Auf der Suche nach der optimalen Flugbahn, DFS Transmission 02/2015
- Judith Rosenow, Martin Linder and Hartmut Fricke (2015): Assessment of Air Traffic networks considering multi- criteria targets in network and trajectory optimization, submitted to the CEAS Aeronautical Journal
- Judith Rosenow and Hartmut Fricke (2015): Angle dependence of the extinction of solar radiation of individual condensation trails, Proceedings of the 4th International Conference on Transport, Atmosphere and Climate, 22-25 June, Bad Kohlgrub, Germany
- Valentin Minning (StA): Optimierte Einsatzplanung des A320 NEO am Beispiel der Lufthansa Passage
- Matthias Asmus (StA): Überführung existenter Algorithmen zur Konflikterkennung auf wegpunktlose Flugtrajektorien
- Yannic Brodersen (DA): Entwicklung und Bewertung von Formationsflugszenarien unbemannter Frachtluftfahrzeuge mit Hilfe eines Schnellzeitsimulationstools
- Robert Brühl (DA): SMS Umsetzung identifizierter flugbetrieblicher Sicherheitskennzahlen (SPI)
- Carina Hieke (DA): Entwicklung eines Algorithmus zur Konflikterkennung und -lösung wegpunktloser Flugtrajektoren
- Sebastian Wilker (DA): Lokale Verbesserung der Einsatzplanung von Luftfahrzeugen durch sequentielle Handlungsempfehlungen
- Felix Steinmeier (StA): Entwicklung einer methodischen Verfahrensweise zur Ermittlung von Ausweichrouten im Falle eines Triebwerkausfalles auf der standartisierten Abflugroute (SID)
- Richard Hofmann (StA): Visionäre Luftfahrtzeug-Konzepte - Verlagerung des innerdeutschen Luftverkehrs auf die Schiene weiterhin nachhaltig?
- Jan Bumke (StA): Erweiterung von Flughafen-Entgeltstrukturen um eine standardisierte und verstärkte Internationalisierung externer Umweltkosten
- Philipp Schubert (DA): Optimierung der Flottenzuordnung und Umlaufplanung einer Luftverkehrsgesellschaft unter Berücksichtigung von Instandhaltungsintervallen
- Fabian Kalb (StA): Ökologische Auswirkungen einer kostenfallbasierten Entscheidung zur Instandhaltung der Luftfahrzeugzelle
- Hannes Braßel (StA): Functional Failure Analysis Regarding Airworthiness, Airspace Integration and Air Traffic Control for Remotely Piloted Aircraft Systems (RPAS) Sustaining a Partial Loss of Information Transfer on the C3-Link
- Dominik Link (StA): Potential der Bereitstellung von aufbereiteten Flugverlaufsdaten als Informationsquelle für Cockpitpersonal am Beispiel der Lufthansa Passage
- Carina Hieke (StA): Entwicklung einer Entscheidungsempfehlung für die Verwendung der APU im Fahrzeugabfertigungsprozess am Beispiel der Lufthansa Passage
- Philipp Büttner (DA): Implementierung von Safety Performance Indikatoren zur Bewertung von mittels Flugleistungsmodell generierten Flugtrajektorien
- Sascha Pohlers (DA): Zeitkosten- und Kraftstoffeinsparpotential ferngesteuerter Luftfahrzeuge
- Alexander Pilz (DA): Modellbildung und Anwendung einer weiterführenden Internationalisierung externer Kosten im Luftverkehr
- Marco Jany (StA): Lokale Optimierung von mittels Heuristiken generierten kostenseitig suboptimalen Airline Netzwerken
- Sebastian Wilker (StA): Bewertung der operationellen Flexibilität von Luftfahrzeug-Flotten anhand möglicher Konfigurationen in einer Fluggesellschaft
- Johannes Albrecht (StA): Multikriterielle Optimierung von Flugtrajektorien moderner Strahlflugzeuge
- Sabrina Groth (DA): Luftverkehrlich emittierte Stickoxide und deren Einfluss auf den Strahlungshaushalt der Atmosphäre
- Nadine Parpat (DA): Konzeption von ökonomisch optimierten Routenstrukturen für Luftverkehrsgesellschaften im Jahr 2050 unter Berücksichtigung minimaler ökologischer Auswirkungen
- Jonas Trost (DA): Konzeption und Implementierung eines Flottenkonfigurators für Luftverkehrsgesellschaften im Jahr 2050
- Bruno B. Hass (StA): Potentialanalyse von FODA Flugverlaufsdaten zur analytischen Beschreibung des Betriebsverhaltens von Triebwerken
- Sabrina Groth (StA): Identifikation von flugbetrieblichen Leistungskennzahlen (EPI) zur Bemessung des ökologischen Fußabdrucks eines Einzelfluges
- Stefano Bianchi (MA): Calculation of the resulting thrust of a turbo-jet aircraft