Holger Pfaender

Fleet Assessment of Fuel Burn and NOx Emissions for NASA Environmentally Responsible Aviation (ERA) Technologies and Concepts

A system-wide model for fuel burn and NOx emissions is presented whereby the introduction of NASAs Environmentally Responsible Aviation aircraft technologies on future vehicles can be assessed with respect to fleet-level environmental impact. This model extends upon prior work in three ways: Improvements in operations balancing and allocation logic yield fuel burn estimates that more closely match empirical data for domestic and international operations; enhancements to vehicle environmental performance models offer a better representation of the updated ERA technology portfolio; parametric NOx emissions models for full-flight as well as departure and arrival segments are integrated into the existing system-wide model to offer fleet-level NOx estimates. Results for scenarios featuring varying levels of ERA technology introduction into the fleet are presented that characterize potential benefits achievable. Results suggest that significant reductions for local emissions can be attained, whereas total emissions closely follow favorable fuel burn improvements.

System-wide Fleet Assessment of NASA Environmentally Responsible Aviation (ERA) Technologies and Concepts for Fuel Burn and CO 2

A method for assessing the impact of vehicle technologies and new aircraft concepts at the fleet level is presented. Various aspects of the method constitute a departure from standard practice intended to address known shortcomings and advance the state of the art. In particular, an operational activity growth routine is implemented where operational sets are grown to match top-level and airport level forecasts that are fully balanced for all origindestination airport pairs. The proposed approach also features a novel fleet evolution scheme where replacements are devised on the basis of mission capabilities for aircraft types rather than on seat-classes, and the retirement of aircraft is applied to models introduced beyond the reference year. Surrogate models of fuel burn are regressed from gold-standard modeling tools, and are shown to be suitable for system-wide assessments on the basis of model representation accuracy. Fleet assessment results are shown for various technology

Effect of Fuel Price on Aviation Technology and Environmental Outcomes

This paper explores the effects of fuel prices on aviation technology and environmental outcomes. The concern is that significant efficiency improvements could potentially increase the environmental impact of aviation instead of reducing it by reducing costs and also increasing economic activity at the same time. Here we explore this effect known as Jevons’ Paradox, by exploring the dynamic interplay of efficiency, demand feedback, airline decision making, and aircraft technologies. The results produced through dynamic modeling show that it seems unlikely that this effect would altogether overwhelm efficiency gains. However, we find that the effect does reduce vehicle efficiency gains at the system level, not only due to extensive fleet turn-over times, but also due to demand bounce back effects.

Environmental Impact Analysis of Fleet and Policy Options of Aircraft Operators using System Dynamics

This paper proposes a novel approach to modeling the choices of aircraft operators in response to policies that have recently been proposed. The need for a comprehensive system level model involving numerous feedback loops is enabled by using a System Dynamics modeling approach. This will allow decision makers to move away from fixed long term forecast scenarios that are currently being used for environmental policy making and instead rely on a dynamic model that enables the evaluation of how aircraft operators might respond to proposed policies and the trade-offs between demand and efficiency improvements under constrained policy scenarios.

AN OBJECT ORIENTED APPROACH FOR CONCEPTUAL DESIGN EXPLORATION OF UAV-BASED SYSTEM-OF-SYSTEMS

The exploration of a integrated system of UAVs involves the concurrent design of systems (e.g. vehicles), networks, and operational plan. The complexity of the resulting design space even at the conceptual level can easily become unmanageable and finding preferred regions of the combined design space that are not simply a sub-optimal collection of individually optimized entities is a difficult task. Abstraction of the system, therefore, is required and achieved by using an object oriented approach for modelling the integrated system. Implementing this approach enhances the ability to efficiently search the combined system-of-systems design space. This approach is tested on a UAV-based package delivery architecture, examining tradeoffs between vehicle performance and the network topology for the economic viability of a notional service provider. The object oriented implementation is found to provide superior modeling flexibility compared to previous approaches.

Transportation System-of-Systems Simulator for Multimodal Demand and Emissions Forecasts

An accurate forecast for future transportation demand and emissions is important for all stakeholders in the National Airspace System. Due to uncertainties in future socio-economic variables and technologies, a scenario-based forecast and analysis is essential. In this sense an interactive simulation environment that provides capability to explore various future possibilities is desired. A Transportation System-of-Systems Simulator (TSS) was envisioned to answer the above challenges. This system-of-system level parametric tradeoff environment includes ground and aviation modes of transportation to capture dynamics in terms of mode choice, mode shift, and introduction of new modes for long distance travel within the continental United States. Parameters can be varied and their impacts on the time series of system level metrics can be interactively observed. Commonly used metrics Revenue Passenger Miles (RPM) and Vehicle Miles Traveled (VMT) are tracked. Resulting CO2 and NOx are quantified to measure environmental impact.

Technology Effects on Aircraft Fleet Decisions

This paper presents a net present value based decis ion making model of aircraft upgrade decisions that airlines are facing in an uncertain environment. The model introduces additional variables beyond an historic extrapolati on of aircraft age. These additional variables are based on relative cost improvements f or a particular replacement decision. This decision making model is then compared to established fleet forecasting methods. The model does compare well with the established methods while allowing for deviations to explore of fuel price sensitivities of these decisi ons. Finally, a comparison of the effect of this advanced decision making model on the environmental consequences is presented. I. Introduction HE aviation industry faces a number of criticisms a s to the environmental impact of aviation. The last decades, however, have seen a dramatic improvement in efficiency and environmental impacts while travel has inc reased equally dramatically. This was made possible by the constant improvement of aircraft and especially ai rcraft engine technologies. It is therefore necessary to maintain this pace of technology development or even try to accelerate it, because even though efficiency has improved, the ab solute system level environmental impact, especiall y for emissions and fuel burn has actually increased due to increase in travel volume in aviation. This is e specially necessary in the face of a number of policy goals t hat propose halting or actually decreasing the syst em level environmental impact. The airline industry faces itself pulled in opposin g directions by the traveling public, aircraft manu facturers, and environmental regulators while facing profitability challenges. The traveling public demands cheap, re liable, and safe transportation choices that are convenient and easy. This forces airlines to offer choices that m atch traveler’s demands, which can sometimes be counter to the demands of the other stakeholders. For example, passeng ers will typically favor flight frequency over aircraft size , since this allows airline customers to fly at a t ime convenient to them instead of forcing few flights with large airc raft. The result is that airlines can be forced by their customers to be pulled in directions of environmentally non opti mal solutions. The aircraft manufacturers will try to meet the dem ands of their customers, the airlines. However, the y have to match technology development schedules and engineering resource availability. This means realistically that the number of new aircraft design and improvement projects that can be under way at any given time is limi ted. Due to this constraint it becomes necessary to balance the frequency of technology updates with the amount of improvement available for the airline customers. Fo r example, it can be beneficial to delay a new airc raft design by a number of years to accommodate technology development schedules and engineering resources, in order to guarantee a certain minimum level of improvement that will be available. This is important because the investment of airlines in new technology aircraft requires a m inimum amortization of these investments. However, rapidly rising fuel costs can quickly cause demand for much better aircraft and leave airlines financially vul nerable. Environmental regulators worldwide are considering a number of policies that try to reduce the environ mental impact of aviation. This can encompass a variety of approaches and goals. The gamut runs from relative ly mild corrective actions or standards trying to force avi ation into a more environmentally friendly directio n to full Pagovian taxation that captures the entirety of the cost of externalities caused by aviation. However, fundamentally all of these proposals affect airlines directly. Th is happens through charges that airlines have to pa y that they might not be able to pass through to their customers, or indirectly through, for example a certification sta ndard for aircraft, that potentially limits the availability of aircraf t or forces design choices of manufacturers.

Scenario Exploration for Sustainability of the Multimodal Intercity Transportation System

As concern for environmental impact of various sectors grows, new methodologies and tools are needed to explore scenarios representing the wide variety of possible future socioeconomic environments and technologies. Sustainability of the transportation system is of paramount importance, as it is a driver of economic growth and a non negligible sector in terms of emissions. This study focuses on the two main modes of transportation for longdistance travel in the continental United States: commercial air transportation and automobiles. A parametric simulation environment, the Transportation Sytem-of-Systems simulator, has been developed and is used to assess the multimodal response of travelers to changes in prices and the impact on fuel use. The multimodal approach provides insight into potential mode shifts and tradeoffs in the transportation System-of-Systems. In high fuel price scenarios, both mode shifts and overall demand reduction occur. The introduction of more fuel efficient aircraft and automobiles is accelerated, which helps to maintain mobility while limiting CO2 emissions. With more fuel efficient vehicles, the effects of higher fuel prices is attenuated. Fuel price increase may be implemented separately on each mode at different times, and in most cases result in a decrease in CO2 emissions. The decrease in CO2 emissions resulting from increases in fuel price is limited (up to 2%) compared to the gain obtained through new technologies (of the order of 30%). Due to the multi-objective nature of this problem, multi-attribute decision making is used to identify the best scenario. High fuel price scenarios perform better if emphasis is on emissions reduction, but are penalized when mobility is weighted more strongly.

Parametric Assessment of Aviation Environmental Goals: Implications on R&D Decision Making

The prospects of the U.S. commercial aviation sector remain positive with a long-term outlook of growth, driven by the U.S. and world economies. The National Airspace System (NAS) is anticipated to become congested and flight delays are likely to propagate throughout the system. This will likely increase the consumption of aviation fuel, and consequently, nitrogen oxide (NOx) and carbon dioxide (CO2) emissions. Several U.S. research initiatives are addressing the sustainability needs of the future NAS. Meanwhile, the International Air Transport Association (IATA) has set system level goals to guide future research and development (R&D) programs. This paper proposes a quantitative approach that bridges the gap between R&D initiatives and IATA’s system level goals. The objective is to provide valuable insight into required contributions from technologies, operations, and bio-fuels to assess the applicability of IATA’s goals.

Framework Development for Performance Evaluation of the Future National Airspace System

Sustainability of the National Airspace System (NAS) continues to be a major concern to its governing body, the Federal Aviation Administration (FAA). Several research efforts are addressing the sustainability needs of the future NAS, including the Continuous Lower Emissions, Energy and Noise (CLEEN) program under the FAA, and the Environmentally Responsible Aviation (ERA) and Fixed Wing (FW) projects of the National Aeronautics and Space Administration (NASA). These initiatives are focused on developing and maturing technologies that would mitigate the environmental impacts of aviation. Alternatively, the Next Generation air transportation system (NextGen) is to provide substantial efficiency improvements from an operational perspective. Also, bio-fuels continue to be an attractive alternative to conventional jet fuels given their reduced life cycle emissions. This paper proposes an integrated framework that would evaluate the performance of the future NAS under different scenarios that consider varying technology, operation, and biofuel contributions. The objective is to assess whether or not the system level goals laid out by the International Air Transport Association (IATA) will be met.