Incorporating Green Design into Teaching Aircraft Preliminary Design

Abstract

Incorporating green design principles into a senior capstone aircraft design course may be an effective way to accomplish a number of objectives desired for ABET accreditation including the coverage of contemporary issues, global awareness, and ethics. The overwhelming environmental issues in designing an aircraft appear to be operating emissions either combustion by-products or noise but material selection and disposal are not insubstantial and should be considered. This paper is an initial look into what tools and guidelines exist for designing "green" aircraft as well as the policy and regulatory issues that will help motivate a culture shift to more environmentally fiiendly air transport. INTRODUCTION The senior capstone design course in engineering education is viewed by many faculty as a fit all course to include all of the ABET (Accreditation l3oard for Engineering and Technology) mandated material not yet covered by any other required course (ABET, 2001). Thus, a design instructor may be put upon to instill a knowledge of contemporary issues, global awareness, ethics, and project management; give the students the opportunity to employ communication and teamwork skills; and, by the way, teach the synthesis of design and while relaying practical methods for applying the knowledge and skills obtain in other courses. This combination of tasks can easily ovenihelrn the students and detract fiom the development of decision making skills very prized in industry. However, the introduction of "green design" principles presents an opportunity to cover three of these topics contemporary issues, global awareness and ethics with material closely related to the decision processes already b e i i developed as part of design. The goal of this paper is to examine the topics and instructional needs necessary to introduce green design principles into a particular senior design course, Aircraft Preliminary Design. In teaching students the basics of aircraft preliminary design, it is emphasized that 80% of the life cycle cost associated with an aircraft is determined during this initial phase of aircraft development. However, the traditional texts for aircraft design only emphasis the monetary cost, not the environmental. Fortunately in aviation, monetary costs and environmental costs often run in parallel. For example, the purchase price of an aircraft correlates very well with its gross weight as does its fuel consumption and thus overall emission. Thus, the industry has shown a steady trend in improved specific fuel consumptions (SFCs) engines, decreased structural weight, and higher aerodynamic efficiency. However, as will be discussed, this is not always the case and graduating students should be aware when the search for performance runs counter to environmental compatibility just as they should be aware when it runs counter to profit. The bulk of this paper is concerned with considerations most relevant to the commercial aircraft industry which has a much larger environmental impact that that of general aviation (GA). However, much as commercial aviation is growing rapidly, GA has been targeted for growth in the US with a NASA target of 10,000 aircraft sales by the year 2010 (NASA, 2000). Originally Presented at the 2001 Virginia Tech College of Engineering Green Engineering Conference JAAER, Winter 2002 Page 7 1 Gally: Incorporating Green Design into Teaching Aircraft Preliminary Des Published by ERAU Scholarly Commons, 2002 Incorporating Green Design Applying green design principles to GA aircraft will also be more challenging since there are fewer environmental regulatory restrictions in place. Thus, a culture of environmental consciousness is much weaker in the field. GREEN AIRCRAFT DESIGN The goals of lpeen design as put forward by Hendrickson, Conway-Schemph, Lave, and McMichael (200 1) are a good starting point in developing priorities in teaching environmental consciousness. These are: 1. Reduce or minimize the use of non-renewable resources 2. Manage renewable resources to insure sustainability; and 3. Reduce, with the ultimate god of eliminating, toxic and otherwise harmful emissions to the environment, including emissions contributing to global warming The current trend in transportation would support the reverse ordering of the goals, however, placing emissions on top ofthe list. While the aviation sector is not a large contributor to global emission with only 2-3.5% of the total impact on global warming, this transpcrbtion sector has received a disproportional amount ofinterest due to its large growth rate an increase of up to 300% is expected in total aviation miles flown by the year 2020. In addition, the bulk ofcommercial a i r d emissians occur in the 10-12 km altitude range where NOx and H20 emissions have an enhanced green house effect campared to equivalent bulk emissions fiom surEace transportation. The Intergovernmental Panel on Climate Change report on the impact of aviation (IPCC, 1999) on the global atmosphere is an excellent reference on the impact of aviation gaseous emissions. Some of the information presented in that report has a wide margin of error due to an inexact knowledge of atmospheric chemistry and the role of clouds in global warming. However, as agreed to in the 1992 Rio Declaration (UN, 1993), " lack of Ml scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation." This principle should be considered applicable to aviation due to the long life span of sircraft programs typically 30 years and the time delay associated with propagating design changes into the civil fleet (Guynn, 1998 and 2001). The Kyoto Protocol (UN, 1998) for reducing greenhouse gas emissions includes those fiom domestic aviation aperations and charges the signing parties to work through the International Civil Aviation Organization (ICAO) for establishing limitations or reductions in international aviation emissions. Similarly, the scope of research into environmentally friendly aircraft may be described succinctly as emissions, emissions and emissions whether considering noise, CO, or NOx. In setting their visions fw civil aviation, botb the European Commission (200 1) and NASA (2000) set gods far dramatic reduction in the noise and gaseous emissions in the 10 to 20 year fiamework. And significantly, neither plan supports the concept of sustained development since they project air traBc capacity increasing faster than emission reductions (for C 4 and noise). Finally, under the concepts of green engineering, an aircraft designer should also be l l ly aware of the impacts on reuse, recycle and disposal of their decisions. If a designer makes the choice of using composite materials to save weight he is buying into a material with a very low recyclability and a potential disposal problem. However, on a typical 150 passenger aircraft flying a block range of 1,000 nm, one pound weight savings will save approximately 0.18 pounds of fuel per flight. For a typical utilization of 1,200 flights a year over a 20 year life, this equates to a lifk cycle savings of 4,300 pounds of fuel for each pound of structural weight saved. Thus, current trades would push towards the use of more weight saving materials regardless of other considerations IMPACT OF AIRCRAFT PURPOSE AND MISSION The first opportunity an aircraft designer has to influence the environmental impact of a new concept is in deciding its appropriate purpose and mission. In general, there are three main reasons far a new commercial airplane program: 1. exploiting changing market opportunities, 2. responding to new regulatory action, or 3. exploiting new technologies Engineering students need no prodding to understand the last topic the application of new technologies but are much more reluctant to become involved in the two fbrmer which arguably play a much larger role in deciding the total environmental impact of the aviation industry. The current competition between W i g and Airbus about the m e of high capacity versus high-speed aircraft illustrates the market impact (Spmco, 2001). The