Browsing by Author "Dr. Charles E. Hall Jr., Committee Chair"

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Analysis and Parameter Estimation of the Aerodynamic and Handling Qualities of the C-130A Modified With Wing Tip Tanks
(2004-12-02) Phillips, David; Dr. Charles E. Hall Jr., Committee Chair; Dr. Ashok Gopalarathnam, Committee Member; Dr. James Selgrade, Committee Member
This work presents the background, flight testing, and resulting change in the aerodynamic and handling qualities of a C-130A Hercules modified with wing tip tanks. The data collected during the baseline and modified flight tests of this aircraft demonstrated the potential aerodynamic benefits of a tip tank design that incorporates a greater aspect ratio and end plating effects. Wing mounted pressure belts measured a 24% increase in local Cl near the tip tanks. This local increase in lift contributed to a 38% increase in CL max for the airplane. The pressure and dynamic data was gathered using a LIFT (Linux In Flight Testing) system, and it laid the foundation for finding the longitudinal and lateral directional stability coefficients of the airplane. Then using MATLAB® and the System IDentification Programs for AirCraft (SIDPAC) to reduce this data, it was possible to generate aerodynamic, lateral, and longitudinal parameters that clearly proved the overall benefits of the design change. The demonstrated lift benefits of these uniquely designed tip tanks for the C-130A cargo transport proved that by capitalizing on the benefits of a combination tip tank and end plate design it is possible to generate increased lift without adversely affecting the stability and dynamic parameters of the aircraft.
Development of a Wind Tunnel Test Cell for Small Propellers with Application to the Plank Unmanned Aerial Vehicle
(2009-11-30) Bishop, Jason Thomas; Dr. Ashok Gopalarathnam, Committee Member; Dr. Pierre A. Gremaud, Committee Member; Dr. Charles E. Hall Jr., Committee Chair
The Plank unmanned aerial vehicle has been designed to be a test platform for an experimental bias angular moment flywheel designed by the NASA Guidance and Controls Branch. The baseline configuration of the aircraft is a flying wing with zero quarter-chord sweep. The benefits of this type of configuration include low structural weight and complexity and reduced drag compared to a standard wing-tail configuration. However, this type of configuration is inherently sensitive to pitch disturbances due to low pitch damping and moment of inertia. In order to remedy this sensitivity, NASA has proposed the use of a bias angular momentum flywheel with its rotational axis aligned with the z-axis of the aircraft. This momentum wheel will effectively stiffen the pitch axis of the aircraft by coupling it with the high damping, high moment of inertia roll axis. The aircraft was designed to be re-configurable allowing for a variety of flying qualities ranging from a well-behaved wing and aft tail configuration to the much more sensitive flying wing configuration. This range of flying qualities will allow for a more comprehensive performance evaluation of the momentum wheel system as well as contribute to risk mitigation during initial flight tests. An electric propulsion system has been chosen for this aircraft due its simple operation and low vibration characteristics. The AXi 5330/18 motor was chosen along with a Castle Creations Phoenix HV-110 electronic speed control. The system is powered by three FlightPower 5000 mAh 10s Evo Lite battery packs connected in parallel. A four-bladed propeller configuration was used in order to absorb the necessary power from the motor while still fitting between the tail booms of the aircraft. In order to experimentally evaluate the performance of the Plank propulsion system in the NCSU Subsonic Wind Tunnel, the Propeller Test Cell (PTC) was developed. The PTC consists of a strain gage based load cell that measures the thrust and torque generated by the propulsion system along with system operating conditions such as current, voltage, RPM, motor temperature, and battery consumption. The PTC was used to characterize the performance of three candidate propellers for the Plank aircraft: 16x10, 17x8, and 17x10. With this data, certain propulsion specific performance parameters of the aircraft were calculated including thrust and power available, rate of climb and climb angle, range, endurance, and take off performance. After analyzing the performance for each of the three propellers, the 17x8 propeller produced the most desired aircraft performance and was chosen to be paired with the AXi motor and the Plank aircraft.
System Level Airworthiness Tool: A Comprehensive Approach to Small Unmanned Aircraft System Airworthiness.
(2010-04-30) Burke, David Alexander; Dr. Nelson Couch, Committee Member; Dr. Stephen Cook, Committee Member; Dr. Paul Ro, Committee Member; Dr. Ashok Gopalarathnam, Committee Member; Dr. Charles E. Hall Jr., Committee Chair
One of the pillars of aviation safety is assuring sound engineering practices through airworthiness certification. As Unmanned Aircraft Systems (UAS) grow in popularity, the need for airworthiness standards and verification methods tailored for UAS becomes critical. While airworthiness practices for large UAS may be similar to manned aircraft, it is clear that small UAS require a paradigm shift from the airworthiness practices of manned aircraft. Although small in comparison to manned aircraft these aircraft are not merely remote controlled toys. Small UAS may be complex aircraft flying in the National Airspace System (NAS) over populated areas for extended durations and beyond line of sight of the operators. A comprehensive systems engineering framework for certifying small UAS at the system level is needed. This work presents a point based tool that evaluates small UAS by rewarding good engineering practices in design, analysis, and testing. The airworthiness requirements scale with vehicle size and operational area, while allowing flexibility for new technologies and unique configurations.