| Summary: | The maturation of distributed electric propulsion (DEP) technologies for aircraft presents an opportunity to develop new aircraft configurations which take advantage of favorable aero-propulsive couplings. One such arrangement is the electrically blown wing, where the slipstream of distributed, electrically-driven propellers arranged along the wing lead edge is used to enhance the wing lifting capability, enabling reductions in required field length or improvements in cruise efficiency compared to aircraft with conventional high lift systems. DEP blown lift enables the development of a new class of electric super-short takeoff and landing (eSTOL) aircraft, which are fixed wing aircraft designed for sufficiently short runways to make them competitive with vertical flight aircraft. The objectives of this thesis is to examine where in the design space of potential aircraft the introduction of DEP blown lift technology offers a weight or fuel burn advantage compared to alternative configurations, and to examine the implications of flight in the low-speed, high-power envelope for vehicle stability and control. An approach is developed for modeling propeller-based distributed electric propulsion based on existing jet flap theory. The theory is advantageous for capturing the impact of propeller diameter on the lift augmentation. Corrections to the effective deflection angle of the jet based on the propeller size are developed. The modeling approach is incorporated into a conceptual design and optimization framework to examine the system-level impacts of distributed electric propulsion, focusing on hybrid-electric configurations. Hybrid DEP is shown to offer fuel burn benefits over conventional fixed-wing configurations for the cases where the design is constrained by takeoff and landing distance requirements. DEP blown lift is shown to enable fixed-wing eSTOL aircraft with takeoff and landing ground rolls of less than 150 ft. These aircraft can carry twice the payload for the same design mission and vehicle weight as a vertical takeoff and landing aircraft designed with the same underlying technology. This performance is achieved through a combination of lift augmentation and relatively low wing loading which results in takeoff and landing speeds of approximately 30 kts. On landing approach, gusts and atmospheric turbulence can be a large fraction of total vehicle airspeed. The ability of the aircraft and pilot to reject gusts and track a target trajectory directly effects the ground footprint required, because the expected lateral and longitudinal offset from the touchdown aiming point must be included in any estimate the total required runway size. The implications of flight in this low-speed, high-power regime on vehicle performance and stability are examined for a case study, the Electra EL-2 aircraft, a piloted hybridelectric DEP aircraft developed to demonstrate the feasibility of eSTOL operations. The thesis shows the need to use the electric motors as part of the attitude control system of the aircraft at slow speeds to increase the control power in the roll and yaw axes. Flight test results from this aircraft are shown to agree well with the jet flap modeling approach. Finally, a series of candidate flight control laws incorporating the electric motors into the EL-2 vehicle flight control system are presented. Exploratory tests of these control laws by ten pilots in the EL-2 simulator showed the inclusion of the motors in the flight control system improved the pilot handling qualities ratings and achievable landing precision of the aircraft, with the greatest improvements arising from the use of the motors to augment the longitudinal stability based on airspeed feedback.
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