Securing the Future of U.S. Air Transportation A System in Peril (2003) / Chapter Skim
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4. Improving Aircraft Performance
4. Improving Aircraft Performance
Pages 27-41
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From page 27... ...
27 However aircraft productivity and efficiency are measured, they can be improved through advances in aircraft aerodynamics, materials, structures, and other disciplines that improve performance parameters such as lift-to-drag ratio (L/D) , ratio of empty weight to MTOW, and specific fuel consumption.
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From page 28... ...
The contribution of aircraft to regional emissions of NOX and particulate matter is currently on the order of 1 percent of all anthropogenic emissions. The aircraft contribution is increasing, however, as air traffic increases, while emissions from other sources are decreasing as a result of more stringent emissions standards and improved emissions reduction technologies.
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From page 29... ...
AIRFRAME CONCEPTS The Vehicle Systems Program of NASA's Aerospace Technology Enterprise has established five vehicle classes to facilitate trade studies of candidate technologies and assessments of technology integration issues. personal air vehicles uninhabited air vehicles (UAVs)
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From page 30... ...
For example, improved personal air vehicles could expand opportunities for air transportation to small communities, and UAVs are already fulfilling important military missions. The ability of supersonic aircraft to help meet increased demand is also problematic, especially in the case of supersonic business jets, which are likely to be the next class of supersonic aircraft to be developed.
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From page 31... ...
However, the ability to cruise at supersonic speeds is not without cost: Supersonic flight increases specific fuel consumption and requires a more robust airframe design. As a result, a supersonic aircraft has a higher fuel weight fraction and a shorter range and/or higher MTOW than a subsonic aircraft with a comparable payload capacity.
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From page 32... ...
The thick center section distinguishes the concept rather fundamentally from pure flying wing designs and leads to structural efficiencies that improve the overall performance of BWB aircraft.
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From page 33... ...
Technological advances would allow a modern cargo aircraft to have much better performance than multiple-use aircraft. Laminar flow over the wings would further increase the efficiency of BWB aircraft and of every other aircraft type discussed above.
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From page 34... ...
_ _ _ _ _________ -- Ideal Brayton Cycle Standard Sea-Level Conditions 0 20 40 60 80 100 1200 Pressure Ratio FIGURE 4-3 Thermal efficiency versus pressure ratio for conventional heat engine cycles assuming component efficiencies of 100 percent and maximum hydrocarbon fuel combustor temperatures. Source: Jeffrey M
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From page 35... ...
The efficiency of the Brayton cycle is governed by the maximum compressor exit temperature, which is determined by high temperature material limits. The propulsion taxonomy in Appendix D describes a broad range of propulsion concepts and substantiates the conclusion that the conventional gas turbine engine and its variants based on the Brayton cycle will continue to be the primary aircraft propulsion system of choice at least through 2025.
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From page 36... ...
Concepts such as BWB aircraft, supersonic business jets, and runway-independent aircraft dictate unique requirements and opportunities for advances in propulsion technology. Areas of interaction include extremes in engine size and fan bypass ratio, design for boundary layer ingestion, highly integrated engine-airframes, power extraction for boundary layer manipulation, variable cycle features, and architectures for integration of system controls.
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From page 37... ...
Avionics plays an increasingly critical role in the safe and efficient operation of commercial aircraft and now accounts for up to 40 percent of the capital cost of new aircraft. Onboard electronics perform or monitor virtually all critical functions in an aircraft, including engines, control surfaces, stability augmentation systems, active flow controls, flight path, collision avoidance, and interactions with the external air traffic control system.
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From page 38... ...
silicon and other materials, and the committee is hopeful that nanotechnology research might someday lead to material bonding methodologies for critical aviation applications. Nanotechnology may lead to the development of new structural materials with high strength-to-weight ratios and fracture toughness, durable coatings, greater resistance to corrosion, self-healing, and multifunctional characteristics.
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From page 39... ...
To better integrate research plans at a high level, the NRC has already recommended that the Office of Science and Technology Policy establish an independent standing committee to advise the federal interagency coordinating committee for nanotechnology on research investment policy, strategy, program goals, and management processes. Nanotechnology research and development in the United States would also benefit from the formation of a "crisp, compelling, overarching strategic plan" to articulate short-, medium-, and long-term goals and objectives (NRC, 2002d)
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From page 40... ...
. Nontraditional power and propulsion concepts and technologies, especially concepts and technologies that support the use of alternative fuels, such as fuel cells (which may have application as auxiliary power units in the foreseeable future)
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From page 41... ...
2001. Commercial Supersonic Technology: The Way Ahead.
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