The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Xavier Prats - One of the best experts on this subject based on the ideXlab platform.
-
Linear Holding for Airspace Flow Programs: A Case Study on Delay Absorption and Recovery
IEEE Transactions on Intelligent Transportation Systems, 2019Co-Authors: Xavier PratsAbstract:This paper presents a method to introduce linear holding to flights affected by the airspace flow program (AFP) initiatives. Trajectories are optimized at their planning stage in such a way that the program performance is improved in terms of delay absorption before the congested area, and delay recovery at the destination airport. This recovery process is studied by comparing the case where the same Fuel consumption is fixed as the nominal flight, with several cases where some Extra Fuel allowances are considered at the flight planning stage. The effects for AFP delayed flights are thoroughly discussed in a case study followed by a sensitivity analysis on possible influential factors. Results suggest that using the proposed method could partially recover part of the AFP delay, even with no Extra Fuel allowances (e.g., reducing 3.3 min of ground delay and 1.7 min of arrival delay for a typical short-haul flight). When Extra Fuel is allowed, however, the maximum delay recovery increases up to 10 min for the studied case, which also proves to be more cost-efficient than current operations, when flight speed is increased after experiencing all delay on the ground.
-
Climb, cruise, and descent speed reduction for airborne delay without Extra Fuel
Journal of Aircraft, 2018Co-Authors: Ramon Dalmau, Xavier PratsAbstract:In the majority of situations, air traffic flow management (ATFM) regulations are issued due to weather-related capacity reductions. Considering the uncertainties in weather prediction and other unforeseen factors, ATFM decisions are typically conservative and the planned regulations may last longer than actually needed [1,2]. At present, ground delay is more preferable than airborne delay (holding) from safety, environmental, and operating cost points of view. However, when regulations are canceled before their initial planned ending time, as occur often [3,4], the already accomplished delay on ground cannot be recovered, or it can be partially recovered by increasing speed, leading to Extra Fuel consumption. To overcome this issue, a speed reduction (SR) strategy was proposed in [5], which aimed at partially absorbing ATFM delays airborne. Ground delayed aircraft were enabled to fly at the minimum Fuel-consumption speed (typically slower than the nominal cruise speed initially chosen by the airline), performing in this way some airborne delay. At the same time, part of the Fuel was saved with respect to the nominal flight. This strategy was further explored in [6], where aircraft were allowed to cruise at the lowest possible speed in such a way that the specific range (i.e., the distance flown per unit of Fuel consumption) remained the same as initially planned. In this situation, if regulations were canceled, aircraft already airborne and flying slower could increase their cruise speed to the initially planned speed and recover part of the delay without Extra Fuel consumption [2,6–8]. In this paper, the SR strategy presented in [6] is extended in such a way that not only the cruise phase is used to perform linear holding but also the climb and descent phases are subject of optimization to maximize the total amount of airborne delay that can be achieved without incurring Extra Fuel costs. Three cases are studied: SR only in cruise; SR in the whole flight but keeping the nominal cruise altitude; and SR for the whole flight while also optimizing the cruise altitude to maximize delay.
-
Effects of linear holding for reducing additional flight delays without Extra Fuel consumption
Transportation Research Part D: Transport and Environment, 2017Co-Authors: Xavier PratsAbstract:This paper presents an approach to implement linear holding (LH) for flights initially subject to ground holding, in the context of Trajectory Based Operations. The aim is to neutralize additional delays raised from the lack of coordination between various traffic management initiatives (TMIs) and without incurring Extra Fuel consumption. Firstly, motivated from previous works on the features of LH to absorb delays airborne, a potential applicability of LH to compensate part of the fixed ground holding is proposed. Then, the dynamic adjustment of LH in response to TMIs-associated tactical delays is formulated as a multi-stage aircraft trajectory optimization problem, addressing both pre- and post-departure additional delays. Results suggest that additional delays of 25 mins in a typical case study can be totally recovered at no Extra Fuel cost. A notable extent of delay reduction observed from the computational experiments further supports the benefits of LH for reducing different combinations of additional delays without consuming Extra Fuel.
-
Maximizing airborne delay at no Extra Fuel cost by means of linear holding
Transportation Research Part C: Emerging Technologies, 2017Co-Authors: Ramon Dalmau, Xavier PratsAbstract:This paper introduces a linear holding strategy based on prior works on cruise speed reduction, aimed at performing airborne delay at no Extra Fuel cost, as a complementary strategy to current ground and airborne holding strategies. Firstly, the equivalent speed concept is extended to climb and descent phases through an analysis of Fuel consumption and speed from aircraft performance data. This gives an insight of the feasibility to implement the concept, differentiating the case where the cruise flight level initially requested is kept and the case where it can be changed before departure in order to maximize the linear holding time. Illustrative examples are given, where typical flights are simulated using an optimal trajectory generation tool where linear holding is maximized while keeping constant the initially planned Fuel. Finally, the effects of linear holding are thoroughly assessed in terms of the vertical trajectory profiles, range of feasible speed intervals and trade-offs between Fuel and time. Results show that the airborne delay increases significantly with nearly 3-fold time for short-haul flights and 2-fold for mid-hauls to the cases in prior works.
-
Cruise speed reduction for ground delay programs: A case study for San Francisco International Airport arrivals
Transportation Research Part C: Emerging Technologies, 2013Co-Authors: Luis Delgado, Xavier Prats, Banavar SridharAbstract:Ground Delay Programs (GDP) are sometimes cancelled before their initial planned duration and for this reason aircraft are delayed when it is no longer needed. Recovering this delay usually leads to Extra Fuel consumption, since the aircraft will typically depart after having absorbed on ground their assigned delay and, therefore, they will need to cruise at more Fuel consuming speeds. Past research has proposed speed reduction strategy aiming at splitting the GDP-assigned delay between ground and airborne delay, while using the same Fuel as in nominal conditions. Being airborne earlier, an aircraft can speed up to nominal cruise speed and recover part of the GDP delay without incurring Extra Fuel consumption if the GDP is cancelled earlier than planned. In this paper, all GDP initiatives that occurred in San Francisco International Airport during 2006 are studied and characterised by a K-means algorithm into three different clusters. The centroids for these three clusters have been used to simulate three different GDPs at the airport by using a realistic set of inbound traffic and the Future Air Traffic Management Concepts Evaluation Tool (FACET). The amount of delay that can be recovered using this cruise speed reduction technique, as a function of the GDP cancellation time, has been computed and compared with the delay recovered with the current concept of operations. Simulations have been conducted in calm wind situation and without considering a radius of exemption. Results indicate that when aircraft depart early and fly at the slower speed they can recover additional delays, compared to current operations where all delays are absorbed prior to take-off, in the event the GDP cancels early. There is a variability of Extra delay recovered, being more significant, in relative terms, for those GDPs with a relatively low amount of demand exceeding the airport capacity.
Banavar Sridhar - One of the best experts on this subject based on the ideXlab platform.
-
Aircraft Trajectory Design Based on Reducing the Combined Effects of Carbon-Di-Oxide, Oxides of Nitrogen and Contrails
AIAA Modeling and Simulation Technologies Conference, 2014Co-Authors: Banavar Sridhar, Neil Y ChenAbstract:Aircraft operations need to meet the combined requirements of safety, efficiency, capacity and reduced environmental impact. Aircraft routes can be made efficient by flying wind optimal routes. However, the desire to reduce the impact of aviation emissions and contrails may result in trajectories, which deviate from wind optimal trajectories leading to Extra Fuel use. The lifetime associated with different emissions and contrails varies from a few hours to several hundred years. The impact of certain gases depends on the amount and location of the emission, and the decision-making horizon, in years, when the impact is estimated. The Absolute Global Temperature Potential (AGTP) is used as a metric to measure the combined effects of emissions and contrails. This paper extends earlier work by the authors to include the effect of oxides of nitrogen in the development of aircraft trajectories to reduce the combined effects of carbon dioxide, oxides of nitrogen (NOX) and contrails. The methodology is applied to air traffic in the continental US. The paper shows the trade-offs between reducing emissions and the cost of Extra Fuel using a Fuel sensitivity index, defined as the reduction in AGTP per kg of Fuel. The paper shows the performance of the optimization strategy for decision intervals of 10, 25 and 100 years. Based on the simplified models, the inclusion of NOX emissions has a slight influence on the minimal climate impact trajectories when the decision horizons are around 25 years.
-
Cruise speed reduction for ground delay programs: A case study for San Francisco International Airport arrivals
Transportation Research Part C: Emerging Technologies, 2013Co-Authors: Luis Delgado, Xavier Prats, Banavar SridharAbstract:Ground Delay Programs (GDP) are sometimes cancelled before their initial planned duration and for this reason aircraft are delayed when it is no longer needed. Recovering this delay usually leads to Extra Fuel consumption, since the aircraft will typically depart after having absorbed on ground their assigned delay and, therefore, they will need to cruise at more Fuel consuming speeds. Past research has proposed speed reduction strategy aiming at splitting the GDP-assigned delay between ground and airborne delay, while using the same Fuel as in nominal conditions. Being airborne earlier, an aircraft can speed up to nominal cruise speed and recover part of the GDP delay without incurring Extra Fuel consumption if the GDP is cancelled earlier than planned. In this paper, all GDP initiatives that occurred in San Francisco International Airport during 2006 are studied and characterised by a K-means algorithm into three different clusters. The centroids for these three clusters have been used to simulate three different GDPs at the airport by using a realistic set of inbound traffic and the Future Air Traffic Management Concepts Evaluation Tool (FACET). The amount of delay that can be recovered using this cruise speed reduction technique, as a function of the GDP cancellation time, has been computed and compared with the delay recovered with the current concept of operations. Simulations have been conducted in calm wind situation and without considering a radius of exemption. Results indicate that when aircraft depart early and fly at the slower speed they can recover additional delays, compared to current operations where all delays are absorbed prior to take-off, in the event the GDP cancels early. There is a variability of Extra delay recovered, being more significant, in relative terms, for those GDPs with a relatively low amount of demand exceeding the airport capacity.
-
Integration of Linear Dynamic Emission and Climate Models with Air Traffic Simulations
AIAA Guidance Navigation and Control Conference, 2012Co-Authors: Banavar Sridhar, Neil Y ChenAbstract:Future air traffic management systems are required to balance the conflicting objectives of maximizing safety and efficiency of traffic flows while minimizing the climate impact of aviation emissions and contrails. Integrating emission and climate models together with air traffic simulations improve the understanding of the complex interaction between the physical climate system, carbon and other greenhouse gas emissions and aviation activity. This paper integrates a national-level air traffic simulation and optimization capability with simple climate models and carbon cycle models, and climate metrics to assess the impact of aviation on climate. The capability can be used to make trade-offs between Extra Fuel cost and reduction in global surface temperature change. The parameters in the simulation can be used to evaluate the effect of various uncertainties in emission models and contrails and the impact of different decision horizons. Alternatively, the optimization results from the simulation can be used as inputs to other tools that monetize global climate impacts like the FAA’s Aviation Environmental Portfolio Management Tool for Impacts.
-
Fuel efficient strategies for reducing contrail formations in united states airspace
Document Analysis Systems, 2010Co-Authors: Banavar Sridhar, Neil Y ChenAbstract:This paper describes a class of strategies for reducing persistent contrail formation in the United States airspace. The primary objective is to minimize potential contrail formation regions by altering the aircraft's cruising altitude in a Fuel-efficient way. The results show that the contrail formations can be reduced significantly without Extra Fuel consumption and without adversely affecting congestion in the airspace. The contrail formations can be further reduced by using Extra Fuel. For the day tested, the maximal reduction strategy has a 53% contrail reduction rate. The most Fuel-efficient strategy has an 8% reduction rate with 2.86% less Fuel-burnt compared to the maximal reduction strategy. Using a cost function which penalizes Extra Fuel consumed while maximizing the amount of contrail reduction provides a flexible way to trade off between contrail reduction and Fuel consumption. It can achieve a 35% contrail reduction rate with only 0.23% Extra Fuel consumption. The proposed Fuel-efficient contrail reduction strategy provides a solution to reduce aviation-induced environmental impact on a daily basis.
-
Fuel Efficient Strategies for Reducing Contrail Formations in United States Air Space
2010Co-Authors: Banavar Sridhar, Neil Y ChenAbstract:This paper describes a class of strategies for reducing persistent contrail formation in the United States airspace. The primary objective is to minimize potential contrail formation regions by altering the aircraft's cruising altitude in a Fuel-efficient way. The results show that the contrail formations can be reduced significantly without Extra Fuel consumption and without adversely affecting congestion in the airspace. The contrail formations can be further reduced by using Extra Fuel. For the day tested, the maximal reduction strategy has a 53% contrail reduction rate. The most Fuel-efficient strategy has an 8% reduction rate with 2.86% less Fuel-burnt compared to the maximal reduction strategy. Using a cost function which penalizes Extra Fuel consumed while maximizing the amount of contrail reduction provides a flexible way to trade off between contrail reduction and Fuel consumption. It can achieve a 35% contrail reduction rate with only 0.23% Extra Fuel consumption. The proposed Fuel-efficient contrail reduction strategy provides a solution to reduce aviation-induced environmental impact on a daily basis.
Luis Delgado - One of the best experts on this subject based on the ideXlab platform.
-
Effect of Wind on Operating-Cost-Based Cruise Speed Reduction for Delay Absorption
IEEE Transactions on Intelligent Transportation Systems, 2013Co-Authors: Luis Delgado, Xavier PratsAbstract:En route speed reduction can be used for air traffic flow management (ATFM), e.g., delaying aircraft while airborne or realizing metering at an arrival fix. In previous publications, the authors identified the flight conditions that maximize the airborne delay without incurring Extra Fuel consumption with respect to the nominal (not delayed) flight. In this paper, the effect of wind on this strategy is studied, and the sensitivity to wind forecast errors is also assessed. A case study done in Chicago O'Hare airport (ORD) is presented, showing that wind has a significant effect on the airborne delay that can be realized and that, in some cases, even tailwinds might lead to an increase in the maximum amount of airborne delay. The values of airborne delay are representative enough to suggest that this speed reduction technique might be useful in a real operational scenario. Moreover, the speed reduction strategy is more robust than nominal operations against Fuel consumption in the presence of wind forecast uncertainties.
-
Cruise speed reduction for ground delay programs: A case study for San Francisco International Airport arrivals
Transportation Research Part C: Emerging Technologies, 2013Co-Authors: Luis Delgado, Xavier Prats, Banavar SridharAbstract:Ground Delay Programs (GDP) are sometimes cancelled before their initial planned duration and for this reason aircraft are delayed when it is no longer needed. Recovering this delay usually leads to Extra Fuel consumption, since the aircraft will typically depart after having absorbed on ground their assigned delay and, therefore, they will need to cruise at more Fuel consuming speeds. Past research has proposed speed reduction strategy aiming at splitting the GDP-assigned delay between ground and airborne delay, while using the same Fuel as in nominal conditions. Being airborne earlier, an aircraft can speed up to nominal cruise speed and recover part of the GDP delay without incurring Extra Fuel consumption if the GDP is cancelled earlier than planned. In this paper, all GDP initiatives that occurred in San Francisco International Airport during 2006 are studied and characterised by a K-means algorithm into three different clusters. The centroids for these three clusters have been used to simulate three different GDPs at the airport by using a realistic set of inbound traffic and the Future Air Traffic Management Concepts Evaluation Tool (FACET). The amount of delay that can be recovered using this cruise speed reduction technique, as a function of the GDP cancellation time, has been computed and compared with the delay recovered with the current concept of operations. Simulations have been conducted in calm wind situation and without considering a radius of exemption. Results indicate that when aircraft depart early and fly at the slower speed they can recover additional delays, compared to current operations where all delays are absorbed prior to take-off, in the event the GDP cancels early. There is a variability of Extra delay recovered, being more significant, in relative terms, for those GDPs with a relatively low amount of demand exceeding the airport capacity.
-
ATFM airborne delays without Extra Fuel consumption in wind conditions
2012Co-Authors: Luis Delgado, Xavier PratsAbstract:Air Traffic Flow Management (ATFM) regulations, such as ground holdings, are often canceled before their initially planned ending time. The ground delays impact on the cost of recovering part of the delay if the regulation is canceled, as aircraft are still at the origin airport. In previous publications, the authors have suggested a speed reduction strategy to split the assigned ATFM delay between ground delay and airborne delay. By flying at the the minimum speed that gives the same Fuel consumption as initially planned, the airline can maximize the airborne delay without any Extra Fuel consumption. In this paper, the effect of wind on the amount of airborne delay is assessed and a case study of Chicago O’hare airport is presented. Results show that wind has a great effect on the airborne delay that can be achieved and that, in some cases, even tail winds might lead to an increase of airborne delay.
François Brillet - One of the best experts on this subject based on the ideXlab platform.
-
The overall effects of road works on global warming gas emissions
Transportation Research Part D: Transport and Environment, 2009Co-Authors: Philippe Lepert, François BrilletAbstract:Road characteristics influence the amount of pollution generated by traffic. They govern the rolling resistance, which includes : the viscoelastic behaviour of the pavement structure, surface texture, and profile unevenness. Road works are performed on a periodic basis to maintain these characteristics at proper levels of service (e.g. safety, comfort, and noise). While such works produce additional pollution (due to congestion around worksites or Extra Fuel consumption along the detour route), they still result in less pollution over the long term. This article assesses the balance between an increase in gas emissions during road works and the reduction in emissions from traffic once the works are completed. It is demonstrated that when road works are introduced to correct longitudinal profiles, rather than texture, the emissions benefit is substantial.
Milan Janic - One of the best experts on this subject based on the ideXlab platform.
-
Modelling Extra aircraft Fuel consumption in an en‐route airspace environment
Transportation Planning and Technology, 1994Co-Authors: Milan JanicAbstract:This paper presents a model to quantify and minimise Extra Fuel consumed by aircraft flying at levels which are suboptimal in terms of Fuel consumption due to relatively crowded airways. It is based on a dynamic queueing system model. In analysing the sensitivity of the parameters influencing the consumption of Extra Fuel, the model allows for changes in the geometry of the airspace (the length and number of flight levels), the characteristics of the traffic (the intensity of the arriving traffic flow on the airway, the number, size and structure of various classes of aircraft requesting altitude changes (and the separation rules applied by Air Traffic Control in serving aircraft requesting altitude changes.
