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An inexpensive unmanned sub-scale aircraft was developed to conduct frequent flight test experiments for research and demonstration of advanced dynamic modeling and control design concepts. This paper describes the aircraft, flight systems, flight operations, and data compatibility including details of some practical problems encountered and the solutions found. The aircraft, named Free-flying Aircraft for Sub-scale Experimental Research, or FASER, was outfitted with high-quality instrumentation to measure aircraft inputs and states, as well as vehicle health parameters. Flight data are stored onboard, but can also be telemetered to a ground station in real time for analysis. Commercial-off-the-shelf hardware and software were used as often as possible. The flight computer is based on the PC104 platform, and runs xPC-Target software. Extensive wind tunnel testing was conducted with the same aircraft used for flight testing, and a six degree-of-freedom simulation with nonlinear aerodynamics was developed to support flight tests. = center of gravity I. IntroductionAeronautical research requires flight testing, both for validation of results obtained on the ground, and to guide the research. In general, the more complex the research issues, the more flight testing that must be done to get reliable answers. For some research, such as flight testing involving spins or other outof-control motion, or developing reconfigurable controls under failure conditions, it is impractical to use manned aircraft for flight research, because of the high cost and safety risks. Since sub-scale flying models are less expensive and unmanned, risks can be taken in research and development that could never be tolerated in a piloted flight test. There is also a need for an intermediate step between simulation and full-scale flight testing, particularly for nonlinear dynamic modeling and novel control designs. A subscale model aircraft can provide increased confidence in the methods and developments before risking the large investment ultimately necessary for a full-scale flight test demonstration. Subscale aircraft flight tests can be used early in the development phase to address these needs.In terms of funding, the trend in recent NASA spending for flight research and aeronautical research in general has been decreasing.To maintain a high degree of excellence in aeronautics research, this environment requires the development of low-cost flight research aircraft. NASA Langley Research Center (LaRC) has a long history of using sub-scale aircraft for flight research, and currently is heavily invested in using sub-scale aircraft for flight research

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