Flight network-based approach for integrated airline recovery with cruise speed control

Airline schedules are generally tight and fragile to disruptions. Disruptions can have severe effects on existing aircraft routings, crew pairings, and passenger itineraries that lead to high delay and recovery costs. A recovery approach should integrate the recovery decisions for all entities (aircraft, crew, passengers) in the system as recovery decisions about an entity directly affect the others' schedules. Because of the size of airline flight networks and the requirement for quick recovery decisions, the integrated airline recovery problem is highly complex. In the past decade, an increasing effort has been made to integrate passenger and crew related recovery decisions with aircraft recovery decisions both in practice and in the literature. In this paper, we develop a new flight network based representation for the integrated airline recovery problem. Our approach is based on the flowof each aircraft, crewmember, and passenger through the flight network of the airline. The proposed network structure allows common recovery decisions such as departure delays, aircraft/crew rerouting, passenger reaccommodation, ticket cancellations, and flight cancellations. Furthermore, we can implement aircraft cruise speed (flight time) decisions on the flight network. For the integrated airline recovery problem defined over this network, we propose a conic quadratic mixed integer programming formulation that can be solved in reasonable CPU times for practical size instances. Moreover, we place a special emphasis on passenger recovery. In addition to aggregation and approximation methods, our model allows explicit modeling of passengers and evaluating a more realistic measure of passenger delay costs. Finally, we propose methods based on the proposed network representation to control the problem size and to deal with large airline networks. © 2017 INFORMS

Integrated Disruption Management and Flight Planning to Trade Off Delays and Fuel Burn

In this paper we present a novel approach addressing airline delays and recovery. Airline schedule recovery involves making decisions during operations to minimize additional operating costs while getting back on schedule as quickly as possible. The mechanisms used include aircraft swaps, flight cancellations, crew swaps, reserve crews, and passenger rebookings. In this context, we introduce another mechanism, namely flight planning that enables flight speed changes. Flight planning is the process of determining flight plan(s) specifying the route of a flight, its speed, and its associated fuel burn. Our key idea in integrating flight planning and disruption management is to adjust the speeds of flights during operations, trading off flying time (and along with it, block time) and fuel burn; in combination with existing mechanisms, such as flight holds. Our goal is striking the right balance of fuel costs and passenger-related delay costs incurred by the airline.We present both exact and approximate models for integrated aircraft and passenger recovery with flight planning. From computational experiments on data provided by a European airline, we estimate that the ability of our approach to control (decrease or increase) flying time by trading off with fuel burn, as well as to hold downstream flights, results in reductions in passenger disruptions by approximately 66%-83%, accompanied by small increases in fuel burn of 0.152%-0.155% and a total cost savings of approximately 5.7%-5.9% for the airline, may be achieved compared to baseline approaches typically used in practice. We discuss the relative benefits of two mechanisms studied-specifically, flight speed changes and intentionally holding flight departures, and show significant synergies in applying these mechanisms. The results, compared with recovery without integrated flight planning, are because of increased swap possibilities during recovery, decreased numbers of flight cancellations, and fewer disruptions to passengers

Energy efficient transport technology: Program summary and bibliography

The Energy Efficient Transport (EET) Program began in 1976 as an element of the NASA Aircraft Energy Efficiency (ACEE) Program. The EET Program and the results of various applications of advanced aerodynamics and active controls technology (ACT) as applicable to future subsonic transport aircraft are discussed. Advanced aerodynamics research areas included high aspect ratio supercritical wings, winglets, advanced high lift devices, natural laminar flow airfoils, hybrid laminar flow control, nacelle aerodynamic and inertial loads, propulsion/airframe integration (e.g., long duct nacelles) and wing and empennage surface coatings. In depth analytical/trade studies, numerous wind tunnel tests, and several flight tests were conducted. Improved computational methodology was also developed. The active control functions considered were maneuver load control, gust load alleviation, flutter mode control, angle of attack limiting, and pitch augmented stability. Current and advanced active control laws were synthesized and alternative control system architectures were developed and analyzed. Integrated application and fly by wire implementation of the active control functions were design requirements in one major subprogram. Additional EET research included interdisciplinary technology applications, integrated energy management, handling qualities investigations, reliability calculations, and economic evaluations related to fuel savings and cost of ownership of the selected improvements

Cruise speed reduction for air traffic flow management

Avui dia un considerable nombre d’infraestructures del transport aeri tenen problemes de congestió. Aquesta situació es veu empitjorada amb l’increment de trànsit existent i amb la seva densitat deguda al sistema de hub i spoke utilitzat per les companyies aèries. Aquesta congestió es veu agreujada puntualment per disminucions de capacitat per causes com la meteorologia. Per mitigar aquests desequilibris, normalment són implementades mesures de gestió del flux de transit aeri (ATFM), sent el retard a l’aeroport d’origen una de les més utilitzades. Assignant retard previ a l’enlairament, el trànsit d’arribada és repartit durant un interval de temps superior i les arribades es distribueixen. Malgrat això, la predicció de quan aquestes reduccions de capacitat es solucionaran una tasca dificultosa. Això comporta que es defineixin regulacions que són més llargues del necessari i per tant, porta a la realització de retard innecessari i al desaprofitament de capacitat. La definició de trajectòries precises ofereix noves oportunitats per gestionar aquests desequilibris. Una tècnica prometedora és la utilització de variacions de velocitat durant el creuer. Generalment, es considera que volar més lent que la velocitat de màxim abast (MRC) no és eficient. En aquesta tesis es presenta una nova aproximació. Quan les aerolínies planifiquen els seus vols, consideren el cost del temps junt amb el del combustible. Per tant, és habitual seleccionar velocitats més ràpides que MRC. Així és possible volar més lent de la velocitat de MRC tot mantenint el mateix consum inicialment planificat. Aquest retard realitzat a l’aire pot ser considerat a la fase pre-tàctica per dividir el retard assignat a un vol en retard a terra i retard a l’aire durant el creuer. Amb aquesta estratègia, el retard és absorbit de manera gradual durant el vol fent servir el mateix combustible que inicialment planificat. Si la regulació es cancel•la abans del que estava planificat inicialment, els vols que estan a l’aire es troben en una situació més favorable per tal de recuperar part del retard. La present tesis es centra en l’estudi d’aquest concepte. En primer lloc, s’ha realitzat un estudi de la relació entre el combustible utilitzat i el temps de vol quan es modifica la velocitat nominal de creuer. A continuació, s’ha definit i analitzat el retard que pot ser realitzat sense incorre en un consum extra de combustible en l’absència i en la presencia de vent. També s’ha considerat i analitza la influència de triar un nivell de vol diferent del planificat inicialment i la utilització de combustible extra per tal d’obtenir major quantitat de retard. Els resultats mostren que per vols de curt i mitja distància, la quantitat de retard realitzable és d’entorn a 5 minuts, aquesta quantitat augmenta a uns 25 minuts per vols de llarg recorregut. El nivell de vol s’ha identificat com un dels paràmetres principals que afecten a la quantitat de retard que pot ser absorbit a l’aire. A continuació es presenta l’aplicació de la tècnica a regulacions d’ATFM realistes, i particularment a ground delay programs (GDP). Per tal de mostrar resultats que siguin significatius, els GDPs implementats en 2006 en el espai aeri nord-americà han sigut analitzats. Han sigut detalladament estudiats escenaris als aeroports de San Francisco, Newark i Chicago. Aquests tres aeroports van ser els que van declarar més GDPs durant el 2006 i per la seva situació geogràfica presenten trànsits amb diferents característiques. Per tal de considerar el trànsit s’ha utilitzat dades de la Federal Aviation Administration i característiques aerodinàmiques i de consum realistes provinents d’Airbus. Finalment, la tesis presenta l’efecte d’utilitzar radis d’exempció en els programes de regulació de trànsit i l’ ús de polítiques de priorització de vols diferents a la utilitzada actualment (ration-byschedule). Per concloure, s’ha realitzat una breu discussió sobre l’impacte d’aquesta estratègia en la gestió del trànsit aeri.Nowadays, many air transport infrastructures suffer from congestion. This situation is worsened by a continuous increase in traffic, and, traffic density due to hub and spoke systems. Weather is one of the main causes which leads to punctual capacity reduction. To mitigate these imbalances, air traffic flow management (ATFM) initiatives are usually undertaken, ground delay at the origin airport being one of the main ones used. By assigning delay on ground at the departure airport, the arrival traffic is spread out and the arrivals are metered at the congested infrastructure. However, forecasting when these capacity drops will be solved is usually a difficult task. This leads to unnecessarily long regulations, and therefore to the realisation of unnecessary delay and an underuse of the capacity of the infrastructures.The implementation of precise four dimension trajectories, envisaged in the near future, presents new opportunities for dealing with these capacity demand imbalances. In this context, a promising technique is the use of speed variation during the cruise. Generally, it is considered that flying slower than the maximum range speed (MRC) is neither efficient nor desirable. In this dissertation a new approach is presented. When airlines plan their flights, they consider the cost of time along with the cost of fuel. It is therefore common practice to select speeds that are faster than MRC.Thus, it is possible to fly slower than MRC while maintaining fuel consumption as initially planned. This airborne delay can be considered at a pre-tactical phase to divide the assigned air traffic flow management delay between ground and airborne delay. With this strategy, the delay is absorbed gradually during the flight using the same fuel as initially planned, but with the advantage that, if the regulation is cancelled before planned, the flights which are already airborne are in a better position to recover part of their assigned delay.This dissertation focuses on the study of this concept. Firstly, a study of the trade-off existing between fuel consumption and flight time, when modifying the nominal cruise speed, is presented. Secondly, the airborne delay that can be realised without incurring extra fuel consumption is defined and assessed in the absence and presence of wind. The influence of selecting a different flight level than initially planned, and the use of extra fuel consumption to obtain higher delay, are also considered and analysed. Results show that for short and mid-range flights around 5 minutes of airborne delay can be realised, while for longer flights this value increases up to around 25 minutes. The flight level is identified as one of the main parameters which affect the amount of airborne delay realisable.Then, the application of the suggested cruise speed reduction on realistic ATFM initiatives, and, in particular, on ground delay programs (GDP) in the United States, is presented. In order to obtain significant results, the GDPs implemented in North American airspace during 2006 are analysed. Scenarios for San Francisco International, Newark Liberty International and Chicago O'Hare International are studied in detail, as these airports were the ones where the most GDPs were implemented in 2006. In addition, due to their location, they present different traffic behaviours. In order to consider the traffic, Federal Aviation Administration data and the aerodynamics and fuel consumption characteristic form Airbus are used.Finally, the use of radius of exemption in the GPDs and the use of ration policies different from the operative ration-by-schedule, are also analysed. To conclude, a brief discussion about the impact of this speed reduction strategy on the air traffic management is presented.Hoy en día un número considerable de infraestructuras del transporte aéreo tienen problemas de congestión. Esta situación se ve empeorada por el incremento de tráfico existente y por su densidad producida por el sistema de hub y spoke utilizado por las compañías aéreas. Esta congestión se ve agravada puntualmente por disminuciones de capacidad debidas a causas como la meteorología. Para mitigar estos desequilibrios, normalmente se implementan medidas de gestión del tráfico aéreo (ATFM), siendo el retraso en el aeropuerto de origen una de las más utilizadas. Asignando retraso en tierra previo al despegue, el tráfico de llegada se distribuye durante un intervalo mayor de tiempo y se controlan las llegadas. Pese a esto, la predicción de cuando estas reducciones de capacidad se solventarán es generalmente una tarea compleja. Por esto, se suelen definir regulaciones durante un periodo de tiempo superior al necesario, comportando la asignación y realización de retraso innecesario y el desaprovechamiento de las infraestructuras. La definición de trayectorias precisas permite nuevas oportunidades para gestionar estos desequilibrios. Una técnica prometedora es el uso de variaciones de velocidad durante el crucero. Suele considerarse que volar más lento que la velocidad de máximo alcance (MRC) no es eficiente. En esta tesis se presenta una nueva aproximación. Cuando las aerolíneas planifican sus vuelos consideran el coste del tiempo junto con el del combustible. Por consiguiente, es una práctica habitual seleccionar velocidades mas rápidas que MRC. Así es posible volar mas lento que la velocidad de MRC manteniendo el mismo consumo que el inicialmente planificado. Este retraso realizable en el aire puede ser considerado en la fase pre-táctica para dividir el retraso asignado entre retraso en tierra y retraso durante el crucero. Con esta estrategia, el retraso es absorbido de manera gradual durante todo el vuelo utilizando el mismo combustible que el planificado inicialmente por la compañía. Esta estrategia presenta la ventaja de que los vuelos que están en el aire se encuentran en una situación mas favorable para recuperar parte del retraso que tenían asignado si la regulación se cancela. En primer lugar se ha realizado un estudio de la relación existente entre el combustible usado y el tiempo de vuelo cuando la velocidad de crucero es modificada. A continuación, se ha definido y analizado el retraso que se puede realizar sin repercutir en el consumo en la ausencia y en la presencia de viento. También se ha considerado la influencia de elegir un nivel de vuelo diferente al planificado y el uso de combustible extra para incrementar el retraso. Los resultados muestran que para vuelos de corto y medio alcance, la cantidad de retraso es de en torno a 5 minutos, esta cantidad aumenta a unos 25 minutos para vuelos de largo recorrido. El nivel de vuelo se ha identificado como uno de los parámetros principales que afectan a la cantidad de retraso que puede ser absorbido. Seguidamente se presenta la aplicación de esta técnica en regulaciones de ATFM realistas, y en particular de ground delay programs (GDP). Con el objetivo de mostrar resultados significativos, los GDPs definidos en 2006 en el espacio aéreo norteamericano han sido analizados. Han sido estudiados en detalle escenarios en los aeropuertos de San Francico, Newark y Chicago. Estos tres aeropuertos fueron los aeropuertos que implementaron m´as GDPs en 2006 y por su situación geográfica presentan tráficos con diferentes características. Para considerar el tráfico se han utilizado datos de la Federal Aviation Administration y características aerodinámicas y de consumo provenientes de Airbus. Finalmente, se presenta el efecto de usar radios de exención en los GDPs y el uso de políticas de priorización de vuelos diferentes a la utilizada actualmente (ration-by-schedule). Para concluir se ha realizado una breve discusión sobre el impacto de esta estrategia en la gestión del tráfico aéreo

Resource-Constrained Airline Ground Operations: Optimizing Schedule Recovery under Uncertainty

Die zentrale europäische Verkehrsflusssteuerung (englisch: ATFM) und Luftverkehrsgesellschaften (englisch: Airlines) verwenden unterschiedliche Paradigmen für die Priorisierung von Flügen. Während ATFM jeden Flug als individuelle Einheit betrachtet, um die Kapazitätsauslastung aller Sektoren zu steuern, bewerten Airlines jeden Flug als Teilabschnitt eines Flugzeugumlaufes, eines Crew-Einsatzplanes bzw. einer Passagierroute. Infolgedessen sind ATFM-Zeitfenster für Flüge in Kapazitätsengpässen oft schlecht auf die Ressourcenabhängigkeiten innerhalb eines Airline-Netzwerks abgestimmt, sodass die Luftfahrzeug-Bodenabfertigung – als Verbindungselement bzw. Bruchstelle zwischen einzelnen Flügen im Netzwerk – als Hauptverursacher primärer und reaktionärer Verspätungen in Europa gilt. Diese Dissertation schließt die Lücke zwischen beiden Paradigmen, indem sie ein integriertes Optimierungsmodell für die Flugplanwiederherstellung entwickelt. Das Modell ermöglicht Airlines die Priorisierung zwischen Flügen, die von einem ATFM-Kapazitätsengpass betroffen sind, und berücksichtigt dabei die begrenzte Verfügbarkeit von Abfertigungsressourcen am Flughafen. Weiterhin werden verschiedene Methoden untersucht, um die errechneten Flugprioritäten vertraulich innerhalb von kooperativen Lösungsverfahren mit externen Stakeholdern austauschen zu können. Das integrierte Optimierungsmodell ist eine Erweiterung des Resource-Constrained Project Scheduling Problems und integriert das Bodenprozessmanagement von Luftfahrzeugen mit bestehenden Ansätzen für die Steuerung von Flugzeugumläufen, Crew-Einsatzplänen und Passagierrouten. Das Modell soll der Verkehrsleitzentrale einer Airline als taktische Entscheidungsunterstützung dienen und arbeitet dabei mit einer Vorlaufzeit von mehr als zwei Stunden bis zur nächsten planmäßigen Verkehrsspitze. Systemimmanente Unsicherheiten über Prozessabweichungen und mögliche zukünftige Störungen werden in der Optimierung in Form von stochastischen Prozesszeiten und mittels des neu-entwickelten Konzeptes stochastischer Verspätungskostenfunktionen berücksichtigt. Diese Funktionen schätzen die Kosten der Verspätungsausbreitung im Airline-Netzwerk flugspezifisch auf der Basis historischer Betriebsdaten ab, sodass knappe Abfertigungsressourcen am Drehkreuz der Airline den kritischsten Flugzeugumläufen zugeordnet werden können. Das Modell wird innerhalb einer Fallstudie angewendet, um die taktischen Kosten einer Airline in Folge von verschiedenen Flugplanstörungen zu minimieren. Die Analyseergebnisse zeigen, dass die optimale Lösung sehr sensitiv in Bezug auf die Art, den Umfang und die Intensität einer Störung reagiert und es folglich keine allgemeingültige optimale Flugplanwiederherstellung für verschiedene Störungen gibt. Umso dringender wird der Einsatz eines flexiblen und effizienten Optimierungsverfahrens empfohlen, welches die komplexen Ressourcenabhängigkeiten innerhalb eines Airline-Netzwerks berücksichtigt und kontextspezifische Lösungen generiert. Um die Effizienz eines solchen Optimierungsverfahrens zu bestimmen, sollte das damit gewonnene Steuerungspotenzial im Vergleich zu aktuell genutzten Verfahren über einen längeren Zeitraum untersucht werden. Aus den in dieser Dissertation analysierten Störungsszenarien kann geschlussfolgert werden, dass die flexible Standplatzvergabe, Passagier-Direkttransporte, beschleunigte Abfertigungsverfahren und die gezielte Verspätung von Abflügen sehr gute Steuerungsoptionen sind und während 95 Prozent der Saison Anwendung finden könnten, um geringe bis mittlere Verspätungen von Einzelflügen effizient aufzulösen. Bei Störungen, die zu hohen Verspätungen im gesamten Airline-Netzwerk führen, ist eine vollständige Integration aller in Betracht gezogenen Steuerungsoptionen erforderlich, um eine erhebliche Reduzierung der taktischen Kosten zu erreichen. Dabei ist insbesondere die Möglichkeit, Ankunfts- und Abflugzeitfenster zu tauschen, von hoher Bedeutung für eine Airline, um die ihr zugewiesenen ATFM-Verspätungen auf die Flugzeugumläufe zu verteilen, welche die geringsten Einschränkungen im weiteren Tagesverlauf aufweisen. Die Berücksichtigung von Unsicherheiten im nachgelagerten Airline-Netzwerk zeigt, dass eine Optimierung auf Basis deterministischer Verspätungskosten die taktischen Kosten für eine Airline überschätzen kann. Die optimale Flugplanwiederherstellung auf Basis stochastischer Verspätungskosten unterscheidet sich deutlich von der deterministischen Lösung und führt zu weniger Passagierumbuchungen am Drehkreuz. Darüber hinaus ist das vorgeschlagene Modell in der Lage, Flugprioritäten und Airline-interne Kostenwerte für ein zugewiesenes ATFM-Zeitfenster zu bestimmen. Die errechneten Flugprioritäten können dabei vertraulich in Form von optimalen Verspätungszeitfenstern pro Flug an das ATFM übermittelt werden, während die Definition von internen Kostenwerten für ATFM-Zeitfenster die Entwicklung von künftigen Handelsmechanismen zwischen Airlines unterstützen kann.:1 Introduction 2 Status Quo on Airline Operations Management 3 Schedule Recovery Optimization Approach with Constrained Resources 4 Implementation and Application 5 Case Study Analysis 6 ConclusionsAir Traffic Flow Management (ATFM) and airlines use different paradigms for the prioritisation of flights. While ATFM regards each flight as individual entity when it controls sector capacity utilization, airlines evaluate each flight as part of an aircraft rotation, crew pairing and passenger itinerary. As a result, ATFM slot regulations during capacity constraints are poorly coordinated with the resource interdependencies within an airline network, such that the aircraft turnaround -- as the connecting element or breaking point between individual flights in an airline schedule -- is the major contributor to primary and reactionary delays in Europe. This dissertation bridges the gap between both paradigms by developing an integrated schedule recovery model that enables airlines to define their optimal flight priorities for schedule disturbances arising from ATFM capacity constraints. These priorities consider constrained airport resources and different methods are studied how to communicate them confidentially to external stakeholders for the usage in collaborative solutions, such as the assignment of reserve resources or ATFM slot swapping. The integrated schedule recovery model is an extension of the Resource-Constrained Project Scheduling Problem and integrates aircraft turnaround operations with existing approaches for aircraft, crew and passenger recovery. The model is supposed to provide tactical decision support for airline operations controllers at look-ahead times of more than two hours prior to a scheduled hub bank. System-inherent uncertainties about process deviations and potential future disruptions are incorporated into the optimization via stochastic turnaround process times and the novel concept of stochastic delay cost functions. These functions estimate the costs of delay propagation and derive flight-specific downstream recovery capacities from historical operations data, such that scarce resources at the hub airport can be allocated to the most critical turnarounds. The model is applied to the case study of a network carrier that aims at minimizing its tactical costs from several disturbance scenarios. The case study analysis reveals that optimal recovery solutions are very sensitive to the type, scope and intensity of a disturbance, such that there is neither a general optimal solution for different types of disturbance nor for disturbances of the same kind. Thus, airlines require a flexible and efficient optimization method, which considers the complex interdependencies among their constrained resources and generates context-specific solutions. To determine the efficiency of such an optimization method, its achieved network resilience should be studied in comparison to current procedures over longer periods of operation. For the sample of analysed scenarios in this dissertation, it can be concluded that stand reallocation, ramp direct services, quick-turnaround procedures and flight retiming are very efficient recovery options when only a few flights obtain low and medium delays, i.e., 95% of the season. For disturbances which induce high delay into the entire airline network, a full integration of all considered recovery options is required to achieve a substantial reduction of tactical costs. Thereby, especially arrival and departure slot swapping are valuable options for the airline to redistribute its assigned ATFM delays onto those aircraft that have the least critical constraints in their downstream rotations. The consideration of uncertainties in the downstream airline network reveals that an optimization based on deterministic delay costs may overestimate the tactical costs for the airline. Optimal recovery solutions based on stochastic delay costs differ significantly from the deterministic approach and are observed to result in less passenger rebooking at the hub airport. Furthermore, the proposed schedule recovery model is able to define flight priorities and internal slot values for the airline. Results show that the priorities can be communicated confidentially to ATFM by using the concept of 'Flight Delay Margins', while slot values may support future inter-airline slot trading mechanisms.:1 Introduction 2 Status Quo on Airline Operations Management 3 Schedule Recovery Optimization Approach with Constrained Resources 4 Implementation and Application 5 Case Study Analysis 6 Conclusion

Future regional transport aircraft market, constraints, and technology stimuli

This report provides updated information on the current market and operating environment and identifies interlinking technical possibilities for competitive future commuter-type transport aircraft. The conclusions on the market and operating environment indicate that the regional airlines are moving toward more modern and effective fleets with greater passenger capacity and comfort, reduced noise levels, increased speed, and longer range. This direction leads to a nearly 'seamless' service and continued code-sharing agreements with the major carriers. Whereas the benefits from individual technologies may be small, the overall integration in existing and new aircraft designs can produce improvements in direct operating cost and competitiveness. Production costs are identified as being equally important as pure technical advances

The challenge of managing airline delay costs

Estimates of airline delay costs as a function of delay magnitude are combined with fuel and (future) emissions charges to make cost-benefit trade-offs in the pre-departure and airborne phases. Hypothetical scenarios for the distribution of flow management slots are explored in terms of their cost and target-setting implications. The general superiority of passenger-centric metrics is of significance for delay measurement, although flight delays are still the only commonly-reported type of metric in both the US and Europe. There is a particular need for further research into reactionary (network) effects, especially with regard to passenger metrics and flow management delay