Unmanned Systems Technology 009 | Ocean Aero Submaran S10 | Simulation and testing | Farnborough report | 3W-110xi b2 TS HFE FI | USVs | Data storage | Eurosatory/UGS 2016 report

50 Dossier | 3W-110xi b2 TS HFE FI ability is the result of 35 years of two- stroke development. And the multi-fuel capability isn’t a function of our fuel injection system – it works the same using a carburettor.” Heavy fuel innovations Since the 110xi is a premix lubricated two-stroke, no sump is required. However, underneath the main crankcase is a block through which each exhaust primary runs, travelling from its side of the engine to the other, to exit on the far side. Below those exhaust runs, within the block, are fuel passageways. The proximity of the exhaust is thus used to heat the incoming fuel and also to beneficially warm the crankcase above. Wintrich says, “It is important to keep the crankcase warm as well as the fuel, since with a two-stroke that is the first place the fuel-air mixture goes – not into the cylinder heads.” Clearly this patented fuel and crankcase heating system is part of the secret of making the 110xi a multi- fuel engine. A particular challenge with heavy fuel is cold starting, and here the 110xi has another innovation. At the top of the block, sandwiched between the crankcase floor and the exhaust primaries, are four glow-plug type cartridge heaters, which are switched on to warm the crankcase before the engine is started. The heat they generate travels through the crankcase into the adjacent twin cylinders. Schudt notes that such a small displacement engine does not require separate cylinder head heaters for cold starting. “The temperature of the cylinder head is controlled by this TCU – temperature control unit – and once we see 65 C on at least one of the cylinder head temperature sensors then we can start the engine.” The amount of time it takes to generate the 65 C required in at least one cylinder head for a successful start varies according to ambient temperature – typically it is about four minutes. Once the engine has fired then the external power supply for the cartridge heaters can be disconnected. That programmable power supply remains on the ground; it is not part of the UAV. Starting is also assisted by a pressure relief valve, which resembles a four- stroke engine poppet valve and opens into each combustion chamber through the head to connect it with ambient air. A spring holds it shut under normal running conditions and it is manually pressed down to open. Alternatively it can be operated automatically, in which case a tube links it to the crankcase, and it is arranged to open when there is no pressure in the crankcase to oppose its spring. August/September 2016 | Unmanned Systems Technology Components of 3W’s110xib2 TS HFE FI