Active Tailoring of Lift Distribution to Enhance Cruise Performance

Summary During Phase I of this project, Raytheon Aircraft Company (RAC) has analytically and experimentally evaluated key components of a system that could be implemented for active tailoring of wing lift distribution using low-drag, trailing-edge modifications. Simple systems such as those studied by RAC could be used to enhance the cruise performance of a business jet configuration over a range of typical flight conditions. The trailing-edge modifications focus on simple, deployable mechanisms comprised of extendable small flap panels over portions of the span that could be used to subtly but positively optimize the lift and drag characteristics. Of key importance is that the proposed system implements the basic elements of “morphing” in a practical, first-order application to an existing aircraft configuration. This research is funded by the NASA Langley Research Center under NRA 03-LaRC-02, “Maturation of Advanced Aerodynamic and Structures Technologies for Subsonic Transport Air Vehicles.” The project directly addresses the reduced-emissions objectives of the NASA Twenty-First Century Technology Program (TCAT) through reduced cruise drag. Under contract NNL04AA34C, Raytheon Aircraft Company (RAC) completed the necessary analytical and experimental evaluation to demonstrate a technology readiness level (TRL) of 3 for a trailing-edge device to improve cruise characteristics by completing the following tasks: 1) Complete a literature review. Many reports from academia, industry and government agencies were reviewed during the process of generating design concepts. 2) Develop initial concepts. 4 concepts were identified for study based on the literature review as well as RAC experience. 3) Complete a first-order analytical study aimed at targeting an initial, optimal lift-distribution schedule. A preliminary analysis of several concepts was completed using computational fluid dynamics (CFD). 4) Down-Select concepts. Prior to wind tunnel testing, four concepts were selected for low speed aerodynamic testing. One configuration, the cruise tab, was later selected based on wind tunnel data and CFD analysis. 5) Develop a mechanization scheme. Concepts for mechanizing the trailing edge devices were created to determine the feasibility of each design under consideration. 6) Develop a set of trailing-edge lofts. Solid models of seven different configurations (4 concepts with multiple deflections and sizes) were generated. 7) Modify an existing wind-tunnel model of the Premier I and conduct a basic low-speed test. A low-speed model was modified and a successful test completed collecting data from 4 configurations with deflections. 8) Prepare a final report and briefing. This document serves as the final report for Phase I of this study and compliments the oral presentation given at NASA Langley Research Center in August of 2004. Several concepts such as the trailing-edge wedge and distributed wedges were eliminated from the study based on wind tunnel data. A slotted wing concept may be viable, possibly warranting further investigation beyond what the scope of this study allowed. The cruise tab concept yielded reduced aircraft drag and could be practically integrated in a marketable aircraft. Given the positive indications in aerodynamic performance of the cruise tab, technology benefits have been assessed for the cruise tab and are presented in this report.