Unmanned Systems Technology 021 | Robot Aviation FX450 l Imaging Sensors focus l UAVs Insight l Liquid-Piston X-Mini l Riptide l Eurosatory 2018 show report l Zipline l Electric Motors focus l ASTS show report

30 vehicle, went out of business but was subsequently rescued. Between those events, Robot Aviation worked with Zanzottera to integrate an alternative two-cylinder unit, so there are now two engines available to power the FX450. The Hirth two-stroke is based on the F33 series but is equipped with fuel injection, weight and vibration-reduction measures and some added redundancy. The Zanzottera is the model 305Hs. In its standard form, the single-cylinder air-cooled F33 makes 28 hp (21 kW) at 6500 rpm, and is capable of running on gasoline, JP5 or JP8. Standard equipment includes a fuel pump, spark plugs, air filter, recoil starter, a complete exhaust system and dual capacitor discharge ignition. However, in the FX450 installation it features the optional electric starting system, which also includes a starter solenoid and a regulator/rectifier unit. The standard engine weighs 35 lb (15.8 kg), while the electric starting system adds 2 lb (0.9 kg). Hirth recommends a Time Between Overhauls (TBO) of 1000 hours. The Zanzottera 305Hs is a boxer engine, a horizontally opposed twin- cylinder, air-cooled two-stroke with a displacement of 312 cc and a power output of 25 hp (18.6 kW) at 7000 rpm. The fuel system uses a single throttle body injector to feed it with 95 octane petrol mixed with 2% synthetic two-stroke oil. Like the Hirth, it is also capable of running on Jet A1, JP5 or JP8. The manufacturer claims a specific fuel consumption of better than 330 g/hp/h and a weight complete with alternator of 26 lb (11.8 kg), recommending a TBO of 500 hours. Robot Aviation has not yet decided which engine will be offered as the standard power plant, and currently plans a fly-off between the two. It will install the Zanzottera in the next aircraft to be tested. Whichever engine is chosen, it will draw fuel from a pair of mid-body fuel bladders with slosh/explosion-proof foam inserts. The pusher configuration relegates the engine and propeller to the back, keeping their heat and vibration usefully distant from the two payload bays. Although final decisions still have to be made about the propeller, the aircraft we saw at Eggemoen was fitted with a three- blade, fixed-pitch CFRP unit from Helix. Each engine manufacturer also supplies a 2.8 kW generator that provides electrical power for the onboard systems and two payloads operating simultaneously. It also charges a lithium-ion battery sized to be capable of restarting the engine in flight in an emergency as well as providing back-up for the flight-critical systems in case of a generator failure. Mil-Spec modular wiring The FX450’s wiring conforms to military specifications for manned aircraft, and the company makes up its own harnesses for prototyping but is contracting that out for series production to local company Berget. Electrical engineer Knut Solberg is responsible for the wiring, and his goal was to create a standard modular harness onto which any sensor a customer wants, and which the airframe can accommodate, can be connected using its own small custom harness. Solberg chose large military-grade connectors that can handle the multiple power supply and signal wires connecting the payloads and other sensors, as well as the mission computer to the autopilot, which can be configured to suit whatever is connected to it. Solberg says he began thinking about the equipment that could go into the August/September 2018 | Unmanned Systems Technology The FX450 draws fuel from a pair of mid- body bladders that feature slosh-proof and explosion-suppressing foam inserts (Courtesy of Robot Aviation) This equipment bay towards the rear of the fuselage near the engine houses components that are less sensitive to heat and vibration. The electronics and sensors are up front (Courtesy of Robot Aviation)