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

26 The airframe The SA-400 is based on a straightforward tubular spaceframe, which does not have structural sheet bulkheads integrated into it. It is made from 4130 chromoly, the standard tubular steel for aircraft structures. A modification of the stock Helicycle frame, it has wall thickness increased where necessary and additional bracing in places. “There were a number of spots where we found we needed to reinforce the frame,” remarks Lowry. “We also had to make some significant changes to it to allow for payload integration and mounting, and to allow for the servos to be integrated into the aircraft. Our frame is a lot heavier than the original because there is a lot more to it.” The Scion UAS version of the frame is sandblasted, etched, primed and finished with an epoxy paint. Indeed, given that the initial SA-400 commission is specifically for use in a marine environment it was considered crucial that all bare metal in all parts of the craft should be covered. In places nickel plating is used – that is another in-house capability of Scion UAS. “As we go forward we will be building a custom spaceframe rather than modifying the Helicycle spaceframe,” confirms Sampson. “We are looking at making it out of titanium, for corrosion resistance in the marine environment as well as saving weight. And titanium works well with carbon fibre. “Carbon fibre is conductive, and when in direct contact with metal of any kind it creates a galvanic reaction, so you get galvanic corrosion – the metal, not the carbon, will corrode. Aluminium and steel will corrode quite rapidly, whereas titanium is electrically active enough that it and the carbon can be directly bonded together without any problem. “Also, titanium doesn’t corrode in salt water. A titanium frame means we will not have to add secondary operations such as anti-corrosion treatment. We can TIG weld titanium as well as chromoly in-house, and we figure titanium can save about 30 lb. We will make further refinements to the frame design when we bring manufacture in-house for the next- gen version of the SA-400.” Fuel system and electronics The SA-400’s fuel system, including the main tank, was re-engineered from the Helicycle base. Fuel is carried in the primary tank as well as optional side tanks. With or without the side tanks the fuel mass is centred on the craft’s centre Spring 2015 | Unmanned Systems Technology Now 20 years old, Scion Aviation moved to its current location near Fort Collins, about an hour north of Denver, Colorado, and almost in the shadow of the Rocky Mountains, in 2001. It carries out general aviation engineering, including r&d on behalf of a number of clients. Based close to the small Loveland-Fort Collins airport, Scion has its own helipad outside its main assembly hanger. Scion Aviation and Scion Unmanned Aerial Systems (UAS) are separate companies that share the same 22,000 sq ft building, which Aviation owns. UAS rents space and the use of plant and labour as necessary from Aviation. In total, 14 people work across the two companies. The facilities of Aviation include an aerospace-grade advanced composites construction capability, including complete airframes, which is exploited by some major players in the aerospace world. Aviation has design as well as manufacturing capabilities. It has CATIA and SolidWorks software and uses CAM as well as CAD. It also has an ISO 9 clean room for hand lay-up and the facility for vacuum bagging. It produces composites using pre-preg carbon fibre and small and large autoclaves, the latter being 8.5 ft in diameter and 50 ft long – large enough to accommodate a Learjet fuselage. Tooling is mostly MDF wood- or epoxy-based and is five-axis CNC machined using a 16 ft stroke water-cooled mill with 1 thou precision. It also offers CNC pattern-making using an infinite-length cutting table. Other capabilities include welding, finishing and assembly. It works with customers manufacturing both fixed- wing and rotor-based craft. Wind tunnel testing is not seen as being as critical for a rotorcraft as it would be for a fixed-wing design. For small rotor blade development Scion UAS has a whirl tower that runs a rotor in the open air and uses load sensors to measure its lifting capability. However, it isn’t feasible to simulate in any test cell the centrifugal forces to which the entire helicopter is subject during flight, so actual operation is the key to development. In addition though, Aviation has a CFD capability that can assist rotorcraft development. Scion Aviation Titanium doesn’t corrode in salt water, which means we will not have to carry out secondary treatments such as anti-corrosion