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Aerospace Systems Efficiency Improvements for Legacy Aircraft


OBJECTIVE: Develop efficient analysis framework for airframe drag reduction and aeropropulsive efficiency improvement, and use this framework to demonstrate technologies"ability to reduce fuel consumption of Air Force legacy transport/tanker aircraft. DESCRIPTION: One critical aircraft efficiency enhancement is the reduction of the total fleet fuel burn, and one major avenue is improvement of airframe aerodynamics through minor alternations or retrofit, with minimal or zero adverse impact to mission readiness, maintainability, or other practical considerations. New ideas for drag reduction on near-term and legacy aircraft abound, as the field is old and concepts are easy to advocate. Examples include increase of laminar flow through passive or active means, more clever airframe-propulsion integration, deformable/deployable stall-control and high-lift devices, methods for gust load alleviation, and various flow-control devices. Considerable drag-reduction potential may be found through outer mold-line cleanup by removal of vortex generators and other protuberances that were affixed on legacy aircraft to address problems discovered in flight testing, or which were part of the original design intent. This solicitation aims at novel ways of applying existing concepts, or unique devices or material systems which enable improved aero performance. The intention is retrofit on existing aircraft, and specifically not the complete re-design of the aircraft itself. Accurate and fast simulation of aerodynamic drag and overall aircraft performance at the conceptual and preliminary design stages is essential for quantifying the effects of small design changes at the system level. The desired method is more advanced and more robust than statistical fits or generalization of classical textbook calculations automated in graphical user interface, and must be computationally more efficient than Navier-Stokes solvers. One possibility is modernization of classic panel methods, to include nonlinear panels, tolerance of non-watertight geometries, parametric geometry definition for rapid analysis of alternatives, and lumped-parameter models of flow control devices. The latter might include flow-through panels to simulate fluidic flow control, or time-dependent body forces to simulate plasma flow control. The method should obviate the need for defining the wake and should take advantage of modern three-dimensional geometry environments. While the focus is on analysis of technologies to improve energy efficiency of legacy configurations, the analysis method should be applicable to modern and future aeroconfiguration concepts, such as distributed propulsion. and modeling of high-lift systems. In summary, this solicitation is concerned with 1) aircraft drag reduction technologies, 2) quantification of how these technologies impact airplane performance/efficiency and overall fleet efficiency, and 3) an integrated tool set for assessing said quantification in a systematic way suitable for conceptual and preliminary design. PHASE I: Demonstrate the feasibility of the proposed analysis tool to easily and quickly evaluate drag reduction technologies and their impact on fleet system fuel costs. Initial system architecture and proposed interfaces will be defined. Define new drag reduction schemes and lumped-parameter models and provide the layout and software design of new prediction tools. PHASE II: Apply analytical framework to assess efficacy of proposed technology for drag reduction and aeropropulsive efficiency enhancement to 1) the entire aircraft and 2) fleet-wide assessment of aircraft. Perform detailed computational analysis of installed devices, validated with relevant wind tunnel data and/or higher-fidelity computations. Demonstrate analytical tool"s robustness and accuracy across the performance envelope. PHASE III: Applications include other DoD aircraft including Foreign Fleets using US equipments. NASA, or private companies, could consider commercial airliners or general aviation aircraft. REFERENCES: 1. NATO Science & Technology Organization Scientific Publications. A comparison of panel methods for subsonic flow computation, AGARD-AG-241, Jan 1979, AGARD. This report is available to all customers. AGARD flight test, & RestrictPanel. 2. NATO Science & Technology Organization Scientific Publications Special Course on Engineering Methods in Aerodynamic Analysis and Design of Aircraft, AGARD-R-783, Jan 1992, AGARD . This report is available to all, & RestrictPanel=9. 3. Joseph Katz and Allen Plotkin, Low Speed Aerodynamics (2nd Edition), Cambridge University Press, Cambridge, United Kingdom, 2010.
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