Unmanned Systems Technology 002 | Scion SA-400 | Commercial UAV Show report | Vision sensors | Danielson Trident I Security and safety systems | MIRA MACE | Additive manufacturing | Marine UUVs

27 Scion UAS SA-400 optionally piloted helicopter | Dossier of gravity so that its dynamic behaviour is unaffected by diminishing fuel. “On the original Helicycle the primary tank fits within the main frame tower,” observes Lowry. “We had other things we also needed to fit in that space so we had to go to a completely new fuel tank set-up, with a new central tank that really hugs around the engine and the control system and landing gear, to maximise the use of space. That was a real design challenge.” Since Scion UAS couldn’t move the fuel load away from the centre of gravity, it had to expand the tank into every available adjacent nook and cranny. The consequently very complex design, which expands around the engine and control system and landing gear zones, was produced from carbon fibre composite (the simpler Helicycle tank is moulded plastic). It accepts 17 US gallons (64.4 litres), versus 16 for the standard item. The complex form of the main tank (evident from the exterior) helps dampen slosh, whereas the optional saddle tanks are fitted with internal baffles. There is an electric booster pump between the tanks and the mechanical fuel pump (with filtering of the fuel either side of it). The engine will run without that pump but it ensures positive head pressure to the engine-driven pump, Sampson explains. Ahead of the main tank the carbon fibre composite cabin floor and integral seat backrest tie into the spaceframe. The tank attaches to the back of the cabin floor and transfers weight through it to the spaceframe, but most of the fuel weight is transferred through the side payload mounts to the spaceframe, Lowry reports. The requirement from the NRL included that the electrical system would be 24 V (28 V), consistent with standard naval vessel power systems. Since the base Helicycle vehicle has a 12 V electrical system, a number of items had to be changed. The SA-400 power system has two alternators with separate control units. Each power system, one of which is dedicated to the payload, has its own set of batteries. Mogensen says, “With a separate payload power system, if anything electrical goes wrong on the payload side it will not affect the aircraft power system. Flying without a pilot on Unmanned Systems Technology | Spring 2015 The SA-400 has simple bodywork and leaves its tail unshrouded We had to go to a completely new fuel tank set-up, with a new central tank that really hugs around the engine and the control system and landing gear