Reviewing Group:Senior Aeronautical Design Review Committee / Experimental Unmanned Aircraft Systems (UAS) Research Group.
The following synthesis is conducted from the perspective of a Senior Aerospace Research Engineer specializing in V/STOL (Vertical/Short Take-Off and Landing) and Distributed Electric Propulsion (DEP).
Abstract:
This technical report documents the design, fabrication, and flight testing of an experimental amphibious UAS utilizing Distributed Electric Propulsion (DEP) to achieve enhanced Short Take-Off and Landing (STOL) performance through a "blown wing" effect. The project objective was to compare the efficiency and lift characteristics of a leading-edge propeller-driven DEP system against a previously developed internal-ducting blown wing design.
The airframe, featuring an S1210 high-lift airfoil and 1.5-meter wingspan, was constructed using a hybrid of 3D-printed polycarbonate (PC Blend) and CNC-milled Depron foam. Propulsion was achieved via 18 EMAC 1106 motors distributed along a 10mm carbon fiber spar, with an adjustable mounting system allowing for independent manipulation of the wing's angle of incidence and motor thrust vectors.
Flight testing successfully demonstrated the "blown wing" effect, enabling controlled flight at speeds as low as 3.4 m/s and supporting high wing loadings (up to 20.4 oz/sq ft) while maintaining slow-flight stability. Computational Fluid Dynamics (CFD) analysis via Air Shaper indicated a 25% increase in lift with propellers active, primarily due to increased local airspeed over the airfoil. However, the data revealed a significant trade-off in aerodynamic efficiency: the DEP system introduced turbulence that degraded the overall lift-to-drag (L/D) ratio compared to a clean wing. Final analysis highlights the critical role of differential thrust for yaw stability at high angles of incidence and suggests that further optimization of motor sizing and wing twist is required for operational efficiency.
Experimental Evaluation and Technical Summary:
0:00 DEP vs. Internal Ducting: Comparison of two blown wing methodologies. The current iteration replaces internal pneumatic ducting with 18 external electric motors to simulate distributed propulsion effects used in emerging commercial designs like Electra and Regent.
1:43 Design Specifications: Use of the S1210 airfoil for high-lift at low Reynolds numbers. CAD design utilized Onshape with a 10mm carbon fiber leading-edge spar to support the distributed motor array.
2:03 Advanced Fabrication Techniques: Integration of 3D-printed PC Blend for stiffness and CNC-milled 16mm depron foam. A unique V-groove relief technique was employed to facilitate the curvature of the fuselage nose section.
4:11 Power Plant Configuration: 18 EMAC 1106 4500KV motors with JSTXH connectors and TotalBoat epoxy waterproofing for amphibious operations.
6:14 Variable Geometry Spar System: Implementation of a laser-cut plywood clamping system allowing independent adjustment of the motor thrust angle relative to the wing's angle of incidence.
8:25 Initial Flight Performance: Maiden flights confirmed a high thrust-to-weight ratio, with the aircraft capable of hovering at approximately 25% throttle.
11:06 Amphibious Capability: Water testing demonstrated successful planing and take-off, though propeller proximity to the water surface necessitates precise taxiing.
12:18 Angle of Incidence (AoA) Sensitivity: Increasing the wing's angle of incidence relative to the fuselage significantly reduced stall speeds but increased pitch instability.
14:44 Operational Failure Mode: Total power loss due to battery exhaustion resulted in an unpowered drift; highlights the high current draw and potential for limited flight endurance in DEP configurations.
16:11 Quantified Speed Metrics: Data logging revealed mean airspeeds of 6 m/s at standard incidence, 5.5 m/s at medium incidence, and a minimum of 4.3 m/s at steep incidence.
18:27 Extreme STOL Envelope: Flight at extreme angles of incidence achieved 3.9 m/s. Results indicated high drag and a requirement for flight controller stabilization (ArduPilot) to prevent departure from controlled flight.
20:47 Power System Inefficiency: The aircraft cruises at only 12% throttle, leading to significant switching losses and current ripple. Excessive weight from oversized ESCs and motors contributed to suboptimal flight times.
22:31 High Wing Loading Slow Flight: Testing at an increased weight of 5.7 lbs (20.4 oz/sq ft wing loading) resulted in a surprisingly low stall speed of 6.5 m/s, demonstrating the efficacy of the blown wing in heavy-lift/slow-flight scenarios.