Unmanned Systems Technology 020 | Alpha 800 I Additive Manufacturing focus I USVs insight I Pegasus GE70 I GuardBot I AUVSI Xponential 2018 show report I Solar Power focus I CUAV Expo Europe 2018 show report

Specification GE70 UAV hybrid system Horizontally opposed twin 37.2 x 32 mm = 69.56 cc Naturally aspirated Gasoline fuel All-aluminium structure Linerless Three main bearings, ball and roller Steel crankshaft, two pins Steel con rods Light alloy pistons; one ring One plug per cylinder Reed valve Electronic ignition Fuel injection Engine management system 9.0:1 compression ratio (minimum 6.0:1) Maximum rpm, 7500 Integrated AC starter/generator Integrated starter/generator management system Some key suppliers to this engine Cylinders: Desert Aircraft Crankcase: in-house Castings: DP Cast Crankshaft: in-house Pistons: Desert Aircraft Rings: Desert Aircraft Con rods: Desert Aircraft Big-end bearings: NSK Main bearings: NSK Ignition system: in-house Spark plugs: NGK Fuel injectors: undisclosed Electronic management system: in-house Data acquisition: in-house Wiring: in-house Throttle: CM Water pump: TCS Fuel pump: TCS Fluid lines: New Age Industries Generator: CM Exhaust: Desert Aircraft Air filter: K&N Oil: Redline Racing Design software: SolidWorks Design software: OrCAD 57 Pegasus GE70 | Dossier and crankpins are stock size and type – double sealed deep-groove ball bearings – we source our own bearings to our preferred material specifications [these are all-metal bearings] and impose our own clearances.” The crankshaft is 4130 chrome moly steel, hardened and ground, following DA70 practice. The crankcase is machined from billet 7075 T6 and is split transversally midway between the rear and centre bearings, again as per DA70 practice. The DA70 is rear-mounted, whereas the Pegasus version is bottom – or, depending on orientation, top – mounted. In other words, the four bolt attachments incorporated into the crankcase that mount it to an airframe are moved 90 º . Since the stock engine directly drives a propeller it has to be mounted rigidly to the airframe – the vehicle needs to react to the thrust to fly – “whereas”, notes McRoberts, “our EGU can be completely mechanically decoupled from the airframe, so very sophisticated isolation can be used; vibration damping can be much more effective. We have tried a number of commercially available damping systems, and all have worked extremely well.” The DA70’s cylinders are investment cast in aluminium alloy 356, and combine the barrel and the head. These are retained but with the cooling fins removed to be replaced by a suitable water jacket. As stock, each cylinder is attached to the crankcase by a lower flange using four short bolts. In the case of the Pegasus version, four longer bolts run from the top of the water jacket through to the crankcase, passing through the stock lower flange. McRoberts says, “That means the cylinder is loaded the same way, but having one long bolt to incorporate the jacket vastly assists assembly. The water jacket is 6061 aluminium alloy machined from billet – just one part each side, although there are spacers that allow the long bolts to preload the cylinder properly down to the crankcase.” Why water cooled? “The first Unmanned Systems Technology | June/July 2018 Data sheet The GE70 system – the engine/generator unit weighs 2.5 kg, the GCU 600 g, the fuel pump 185 g and the coolant pump 185 g