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

52 Summer 2015 | Unmanned Systems Technology AD of the AE300 though, the control system takes a note of readings from the exhaust gas temperature and lambda sensors, and calculates the precise quantity of fuel needed to obtain the requested power level, thus reducing fuel consumption. The link to the flight controller allows the engine’s operational parameters to be monitored in real time at a ground station. In addition, the data is logged and used to help assess the condition of the engine on an ongoing basis. Such monitoring not only assists with any necessary diagnosis, it can potentially allow an engine’s operating hours between rebuilds to be safely extended. Given that this engine control system incorporates twin ECUs, the control system clocks the number of operating hours of each and is programmed always to run on the one with fewer hours, unless a fault is detected. All sensors and actuators, aside from those that aren’t critical inputs to the ECU for engine operation, are also doubled up to obtain the required redundancy for in-flight use. There is consequently, for example, the introduction of a housing for a second camshaft speed sensor. Each set of sensors is connected to its own ECU, so if a sensor fails then the system will automatically switch over to the other ECU. If the corresponding sensor in that ECU should also fail, there is a control strategy that will account for the loss of that particular input, putting the engine into a ‘bring it home’ mode to keep the aircraft flying. In addition to the sensors for monitoring engine operation, the control system is fed data from an ambient pressure sensor so that it can compensate for altitude, and also a ‘weight on wheels’ sensor to indicate when the aircraft has taken off. In the automotive world, the engine has a driver-operated glow plug to assist cold starting, and Austro Engine has developed its own automatically controlled glow plug system, which is operated by the engine’s control system. Each ECU has its own power supply. Austro Engine produces its own engine harness to accommodate the doubling up of the sensors, and this optionally has MIL-SPEC connectors. Lietz notes that rival aero engines have a clutch between the engine and the gearbox, which can cause issues with that particular component. Since in normal circumstances the propeller does not need de-clutching, the AE300 does not have a clutch. It has instead a damper designed to absorb torque spikes. In effect, this consists of a pair of flywheels connected by springs. The damper assembly is bolted to the (integral) nose of the crankshaft, in place of the component that would be attached there in an automotive application. It is surrounded by a ring gear operated by the starter motor, which is modified from the 12 V operation of the automotive application to 28 V. The ring gear doubles as the target for the crank position sensor (of which there are of course two in this application). Lietz accepts that a clutch can be useful in the case of a prop strike, saying that the strategy with the AE300 is to log the impact of any such strike via the ECU for subsequent analysis. That will determine if any action such as inspecting the damper, inspecting the gearbox or perhaps even replacing the propeller is needed. Austro Engine supplies the AE300 complete with transmission, whereas the propeller is optionally supplied. The gearbox is of Austro Engine’s own design. It contains three gears – input, intermediate and output – and has a ratio of 1.69:1 to slow rotational speed, and in so doing multiply the torque from a maximum of 340 Nm at the crankshaft to 512 Nm at the propeller shaft. The gearbox contains an oil pump that supplies lubricant to the propeller shaft bearing, and also serves a hydraulic system that adjusts propeller pitch. than a one-third improvement over avgas for a given power level. Moreover, jet fuel is widely available across the globe, tends to be less expensive and is less flammable than avgas. The iron-block AE300 weighs 186 kg. Using 2.66 bar maximum absolute manifold pressure (1.66 bar gauge), maximum continuous power, for example for take-off, is 123.5 kW (166 bhp) at 3880 rpm. The engine is lifed for 1800 hours’ running time between overhauls. Lietz notes that competing aero engines typically have to be replaced at that point, whereas the AE300 is rebuilt “retaining 85% of its components” ready for another service interval of the same duration. Cruising at 60% engine load, the DA42NG consumes 5 US gallons per hour, per engine, while when loitering it will stay airborne with a consumption of less then 3 US gallons per hour, per engine. This means that in normal service an endurance of more than 12 Anatomy of the AE300 (continued)