Unmanned Systems Technology 003 | UAV Solutions Talon 120 | Cable harnesses | Austro Engine AE50R and AE300 | Autonomous mining | AUVSI 2015 show report | Transponders | Space systems

47 Austro Engine AE50R rotary and AE300 I4 | Dossier Unmanned Systems Technology | Summer 2015 occupies 180 º of crankshaft revolution. In contrast, each of the three working chambers of the rotary engine runs through 1080 º (360 multiplied by three) through the four-stroke cycle, so each stroke is nominally 270 º (1080 divided by four). Since each firing stroke consequently lasts, in effect, one-and- a-half times longer, there is less torque fluctuation. At the same time, the longer induction stroke promises improved breathing at higher rpm. liquid cooling for the rotor housing. The lubricant is contained in the lower section of the rotor housing, around the combustion area. The impeller-type water pump is driven directly from the eccentric shaft, so it follows that pump speed is a function of engine speed. The pump delivers it into channels in the rotor housing, from which it exits to a water-to-air radiator. A radiator thermostat maintains an operating temperature of 70 C. Cooling air for the rotor is drawn in axially through a filter by a belt- driven fan, and is then immediately turned 90 º to be sent to the top of the adjacent side plate. It then travels down through that hollow plate and into the rotor cavity. The air passes through the centre of the rotor and the main bearing before travelling up through the other side plate and out through a duct. At that stage the flow is of air carrying oil splashed from the bearings, and this is discharged into the exhaust. Lietz remarks that the cooling discharge doesn’t significantly cool the exhaust flow. Mixing it with the exhaust does simplify things, while to extract the oil from the air ahead of that for a cleaner exhaust is possible, although at the cost of the additional weight and complexity of an air-oil separator, which is an optional extra. The AE50R has a mechanical oil pump driven by the eccentric shaft that creates very little pressure but does ensure a constant supply of lubricant to the shaft. Only the stationary pinion plain bearing is lubricated, not the roller main bearing. Another feed line from the pump goes to the injector housing, where the oil is added to the charge to lubricate the interface of the seals with the working surface. The oil pump runs at engine speed, so its rate of delivery is a function of that. The supply to the injector housing is constant rather than in any way modified in response to injector operation. It feeds into the charge flow through a port located beneath the injector. The AE50R is equipped with an electric starter and a 14 V, 18 A alternator. In a rotary engine, each of the three working chambers runs through 1080 º through the four- stroke cycle, so each stroke is nominally 270 º The AE50R propels this small unmanned helicopter