Unmanned Systems Technology 016 | Hydromea Vertex AUV | Power management systems | Unmanned Space Vehicles | Continental CD-155 turbodiesel | Swift 020 UAV | ECUs | DSEI 2017 Show report

66 These first three variants, in addition to testing and gathering critical data, were also intended to mature and ‘vet’ the technology being used. Streett says, “We’ve been designing UAVs for 30 years, for companies like Boeing and Northrop Grumman, and always with an eye on technical readiness. It’s absolutely critical to us that when a UAS enters the market it can consistently and certifiably perform exactly as required.” The company undertook various tests to analyse the flight and operation of the vehicle. CFD analysis was conducted to model the aerodynamics of the system from the design stages through to the testing phase. Also, rope assembly testing was conducted in fields and grassed areas near the company’s headquarters. Here, a rope was placed between two trees and tensioned, while a top-rope was tied between the tensioned rope and the UAV as it hovered, to determine its stability or gains for stability within the control loops. In the final stages of the trials, horizontal flight testing was conducted in CFD simulations, wind tunnels and airspace throughout California. “In addition to boat tests off the southern Californian coast, we also did a lot of structural analysis – dynamic simulations with finite element analysis, as well as different models – so we could simulate hazards like a bird strike and water landings, things you wouldn’t necessarily see or do on platforms of this size,” company president Rick Heise says. Control surfaces For flight control the system uses four ailerons that run along almost the entire trailing edge of the wingspan, with servo motors selected specifically for specific targets on controllability and feedback. Earlier designs of the 020 also featured wings that would fold upwards about structural or living hinges between the inboard and outboard ailerons, to limit drag during vertical flight by reducing the cross-sectional area of the UAV subject to wind loading. “When you’re looking at a minimum viable product for an aircraft, you want to lead with the options that are the least risky – and foldable wings add complexity, parts, cost and weight,” Heise says. “Anything’s open for future work, however, and adding in those foldable wings would significantly increase controllability during descent.” In addition to the ailerons, the propellers were carefully selected to execute the aerodynamic requirements of taking off vertically but flying horizontally. “Any of our UAVs that operate with the X-Blade design framework would have more than one propeller facing forward and more than one propeller facing back,” Streett explains. “By having all propellers facing forward, you would create a situation where the aerodynamics of that third and/or fourth propeller end up producing a larger projected area than if you had one facing back. From a technical standpoint, aerodynamics are better with the present configuration.” October/November 2017 | Unmanned Systems Technology The Swift 020’s wing-mounted propellers are crucial to both vertical and horizontal flight, so they do not fold in the way the central propellers do