Unmanned Systems Technology 017 | AAC HAMR UAV | Autopilots | Airborne surveillance | Primoco 500 two-stroke | Faro ScanBot UGV | Transponders | Intergeo, CUAV Expo and CUAV Show reports

29 Unmanned Systems Technology | December/January 2018 Thunder Power provides the 3300 mAh lithium-ion battery, which serves two purposes in the propulsion system. First it adds some capacitance that allows the engine to handle the base load while the battery handles the transients. Second, it serves as an emergency power source in case of an engine failure. The power goes to the HAMR’s six T-Motor U8 Pro brushless DC motors. Each one has a dedicated Edge Lite 50 electronic speed controller from Castle Creations, in this case chosen because of their data logging capability for flight testing. AAC might however use different controllers for production HAMR vehicles. The motors each drive a two- bladed 28.2 in diameter x 9.2 in pitch propeller, also supplied by T-Motor. For navigation, the prototypes rely solely on a GPS receiver integrated into the PixHawk 2 autopilot, which provides accuracy to about 2 m. However, the autopilot offers the option of a real-time kinematic system for much greater accuracy and precision. AAC intends to integrate that in the near future, and customers will be able to specify different autopilot/navigation systems. Although the propulsion system has a degree of redundancy thanks to the engine/battery combination, the flight control system is ‘single-string’ at the moment, although that could change. The current ground control station (GCS) is a laptop PC running MissionPlanner software, although AAC is flexible about that and will provide an alternative package if a customer asks for one. AAC also provides a remote piloting capability as standard, an important safety enhancement in case of a mistakenly placed waypoint, in which case the operator can take over the flying with the remote control transmitter, which is currently the FrSky Taranis. This can receive telemetry from the aircraft, providing the operator/pilot with essential status and health data if the GCS should fail or if the aircraft is being operated without it. The HAMR’s comms system is based on an off-the-shelf RDF 900 telemetry modem from jDrones, which is an Industrial, Scientific and Medical band device covering frequencies from 902 to 929 MHz and is designed for long-range serial comms applications. It is connected to antennas mounted at the bottom corners of the airframe at 90° to each other to maximise reception. Structurally, the HAMR is fairly conventional, with a carbon fibre reinforced plastic (CFRP) fuselage and aluminium beams to which the motors and fairings are attached. The fuselage is a monocoque made from multiple plies of high-modulus pre-preg CFRP fabric, although both the innermost and outermost plies are made from glass fibre reinforced plastic pre-preg to reduce the risk of galvanic corrosion. Cured in vacuum bags in an oven, the fuselage is moulded in two halves and then riveted and bonded together. The booms are tubes made of 6061 T6 aluminium alloy. Robustness and appropriate margins of safety, instead of redundant load paths, are applied to the structure to ensure that it won’t fail so long as it is operated within its designed flight envelope. The motors are attached to the booms using 3D-printed nylon mounts, which are formed by ShapeWays using selective laser sintering. The company also uses this process to make the structure of the fairings out of nylon. The fairing structure consists of ribs and spars made from 3D-printed plastic in a loose lattice structure, which are then covered with what is basically a vinyl sticker. This sticker is made from the same 3M vinyl that is used to wrap cars to give them dramatic custom colour schemes, although AAC buys the material in plain white. The material resists degradation by UV radiation from sunlight and is also waterproof. Rather than mounting the fairings on bearings, AAC chose the simpler solution of pivoting them directly on the polished aluminium of the booms, around which they rotate with negligible friction. Some key suppliers Engine: Desert Aircraft Electronic fuel injection: HFE International Fuel tanks: Dubro Electronic speed controllers: Castle Creations Hybrid propulsion system: LaunchPoint Technologies Battery: Thunder Power Motors: T-Motor Propellers: T-Motor Wiring: WireMasters Autopilot hardware: PixHawk Autopilot software: ArduCopter Comms: jDrones GCS software: MissionPlanner Remote controller: FrSky Composite materials and fuselage fabrication: Moore Brothers Metals: OnlineMetals 3D printing: ShapeWays Payloads: Customer-selected, initially Sony and Trillium Advanced Aircraft Company HAMR UAV | Dossier