Exploration of Designing Short-Range High-Capacity Aircraft

Airlines utilize single-aisle aircraft with ranges that are much greater than their operating ranges; a survey of trip length data from the Bureau of Transportation Statistics (BTS) T100 Segment database shows average trip distances of ~800mi for CONUS, but serviced with typically 150 passenger-capacity aircraft with a design range of greater than 2000mi. The difference between operating range and design range presents an opportunity for reducing fuel burn, and consequently, emissions and cost. This paper explores the potential impacts of designing short-range, single aisle aircraft on airline fuel consumption, and discusses other possible impacts – both positive and negative –on an airline that might use a short-range, single isle aircraft. I. Statement of Problem he operations of an airline are dictated by the different stages of airline planning that include aircraft acquisitions, route evaluation, aircraft allocation, scheduling of flights (and crew), maintenance and revenue management. These stages span the strategic and tactical decision horizons of airline planning. Airlines use numerous tools to streamline and improve tactical operations while the strategic decisions related to aircraft acquisitions and, longterm market outlook, center on the fuel efficiency of aircraft, their payload capacity, and expected network of operations. Estimations of future demand and market share dictate the type of aircraft that an airline will acquire; the choice of aircraft is normally based on acceptable cost and a longer design range. Aircraft manufacturer and airlines do not typically look at aircraft range as a possible venue for fuel (and cost) savings. The Boeing Current Market Outlook 2005 [1], for instance, appears to center on the description of airlines’ aircraft demand in terms of aircraft sizes (e.g. wide body vs. narrow body) to analyze the global forecast of commercial airplanes. From observation, there is no aircraft with a design range of 1000 nautical miles and payload capacity above 100 passengers. The highly uncertain nature of demand and associated airline operations required to support such demands, has prompted the need for longer range aircraft to ensure flexibility in servicing nearly any route on the network. The added range becomes an added cost in supporting such operations and has warranted further investigations. Work by Hahn [2] investigated the impact of short-range aircraft on fuel savings for trans-oceanic routes via staging (i.e. break the trip into smaller segments). Hahn concluded that savings of about 29% are possible considering the contribution from operations (17%) and the aircraft redesign (12%). However, given the considerable operational changes that enable staging, the fuel savings would have to be considerably larger to present a feasible business case. The assumption of the study was that the aircraft would be used to serve demand on long ranges. Work by Nangia [3] has examined the servicing of long-range tips using short hops (staging) based on historical design trends of Boeing and Airbus aircraft. The study predicts large fuel savings if high capacity aircraft can be designed more specifically for operations that support staging. Work by Tyagi and Crossley [4] utilized a multi-objective approach to examine the effects of designing an aircraft for staging on a single long-distance route and of designing an aircraft for staging on multiple long distance routes. Results of the study have suggested * Research Scientist, School of Aeronautics and Astronautics, Member AIAA † Graduate Student, School of Aeronautics and Astronautics, Student Member AIAA ‡ Postdoctoral Fellow, School of Aeronautics and Astronautics, Member AIAA § Professor, School of Aeronautics and Astronautics, Associate Fellow AIAA T 12th AIAA Aviation Technology, Integration, and Operations (ATIO) Conference and 14th AIAA/ISSM 17 19 September 2012, Indianapolis, Indiana AIAA 2012-5496 Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. 2 substantial fuel and cost savings; however the studies do not consider congestions delays and off-design routes which may reduce some of the observed benefits shown. The motivation for the aforementioned studies of staging long-range flights was to reduce fuel consumption and carbon emissions associated with the long flights. If the same motivation is turned to flights typically conducted in the continental US by single aisle aircraft, a hypothesis emerges that if the design range of single aisle aircraft was shorter than that of current aircraft, there is a potential to reduce fuel consumption. For most continental US routes, a shorter-range single aisle aircraft would not require staging; instead the design range of the aircraft would be much closer to the length of most short to medium range routes. Studies presented in Ref. [5, 6, 7] demonstrated how the design of a new aircraft could be directly coupled with an airline fleet allocation problem to identify aircraft requirements such as payload capacity, design range, and cruise velocity, that are substantially different from existing aircraft and result in reductions in predicted operating fuel burn.. This exemplifies a change in emphasis from designing the best performing aircraft to designing the aircraft that most improves operations. The best aircraft may be an aircraft not with the longest range, but an aircraft that optimizes operations. Figure 1 [8] shows the passenger–range diagram for different Airbus and Boeing aircraft with range under 6000mi; the shaded area shows the intended design space of exploration, and represents the short-range single aisle configuration that is being investigated. This paper presents a preliminary study of the potential reduction in fuel consumption associated with using single-aisle aircraft with shorter design ranges than currently available single-aisle aircraft. The study also makes an effort to consider entry-to-market feasibility and potential profitability of shorter design range aircraft. The work presented here considers the operations of an existing airline and compares the fuel consumption of serving passenger demand with existing aircraft to the fuel consumption of serving the same demand with aircraft with the same passenger capacity but shorter design range. The following text also discusses the implications of this change in aircraft utilization strategy on the financial and planning aspects of airline operations. II. Scope and Methods of Approach This work considers the potential entry into market of a short-range, single-aisle aircraft to serve routes in the continental US. This is just a segment of the global demand for air transportation and for aircraft; a fuller consideration of the success of a shorter-range, single-aisle aircraft would require consideration of the global market for new aircraft and operations in various regions of the world. The relative ease of accessing data from the US Department of Transportation’s Bureau of Transportation Statistics (BTS) for operations in the US made this market the focus of this work. This study considers the operations and demand served by Southwest Airlines for fiscal year 2010, as a representative airline, and investigates the impact that utilizing aircraft with smaller design range would have on the fuel consumption of the airline. The study does not exactly model and replicate Southwest operations but instead seeks to use its operations and business model for representative analysis – here the goal is to evaluate the impact that the use of a short-range, single-aisle design aircraft would have on an airline. T-100 Segment data from BTS [ 9 ] provides the operating environment – aircraft used, number of trips 0 50