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

50 Dossier | Austro Engine AE50R rotary and AE300 I4 Summer 2015 | Unmanned Systems Technology Specifications I4 83 x 92 mm = 1991 cc Turbodiesel Diesel or kerosene-based fuel Iron block, aluminium head Linerless Five main bearings Steel crankshaft, four pins Steel con rod Dohc, chain driven Four valves per cylinder 17.5:1 compression ratio Maximum rpm, 3880 The AE300 is based on a fully assembled I4 turbodiesel supplied from the manufacturer’s production line. Austro Engine retains only the core of the engine as manufactured for passenger car use (in that guise exploiting around 120 bhp). The engine was specifically designed to be tilted at 53 º from vertical in automotive applications, and Austro Engine maintains this. The biggest projects in converting it to aero use were the design and development of a suitable gearbox and a replacement sump. The exhaust system and turbocharger are also new, as is the intake manifold in this higher-boost application. The stock engine’s timing drive belt also powers a pulley that serves the air conditioning system pump. Since air conditioning isn’t required in this application, a different belt and belt tensioner are used: that is typical of the modifications made. As Lietz explains, “The original sump is a rather strange shape to suit car packaging, which isn’t suitable for our [aero] installations.” Moreover, the replacement enables the introduction of baffling, which reduces slosh from side to side in the wet sump. That helps to ensure the pipe feeding the (stock) oil pump always has sufficient pressure to draw on. The pipe is the standard version, modified in design only to meet the needs of the revised sump. The oil filter is of a different design from the stock item, and is considered superior for operation and maintenance. Consequently its housing is of a different shape, and it is in a different location for packaging reasons. An oil- air separator, filtering air from the oil returning to the sump, is incorporated into a bespoke injector cover, which protects the injectors from the heat of the overhead exhaust system. The exhaust system is reconfigured to put it and the turbo-supercharger over the engine, with the gas escaping over the wing. That makes it easier to remove surplus heat, reducing its impact on overall engine operation. It also reduces the craft’s infrared signature, which is important in some applications. The revised exhaust system is also beefier than standard, as appropriate to support the weight of a heavier turbo. Unlike the stock item, Austro Engine’s more powerful turbo does not have variable geometry; in this application the extra weight and complexity of that cannot be justified. Its wastegate is electro-pneumatic, with the pressure acting only on the side of the membrane that operates the valve. If pressure is lost, the default is for the valve to fall to maximum open to avoid overloading the turbine. The electronically operated valve controlling the pressure is under the direct command of the ECU. The intake manifold is more robust in recognition of the increase in plenum pressure – up from about 1.5 bar absolute in an automotive application. It is also designed to carry doubled-up charge pressure and temperature sensors. There are two versions of this manifold according to packaging requirement in respect of the location of the charge-air cooler. The AE300 maintains the original common rail direct injection system hardware. However, for automotive use the injection system provides five pulses for each cylinder on each cycle, whereas in this application, to save fuel, the last two pulses are omitted (via software reprogramming) since they are specifically for exhaust cleansing. The use of three pulses rather than only one avoids torque spikes, making for a smoother running engine, to the benefit of aero engine applications. Kerosene-based jet fuel provides less lubricity than diesel, in view of which the common rail fuel pump is replaced every 600 hours. The engine control system is bespoke to the AE300, with two ECUs (for redundancy) packaged in a single control box. Engine operational data is collected in this box, which interfaces with the flight control computer, and the system is protected from any potential outside interference by a robust firewall, Lietz notes. Lietz adds that in the case of rival aero engines, the control system normally reacts to instructions from the autopilot by obtaining the requested power level in straightforward fashion. In the case Anatomy of the AE300