Unmanned Systems Technology 002 | Scion SA-400 | Commercial UAV Show report | Vision sensors | Danielson Trident I Security and safety systems | MIRA MACE | Additive manufacturing | Marine UUVs

49 of the charge air are, on paper, the basis of efficiency higher than that of a comparable SI engine. The main inherent drawback of a CI engine though is lack of valve overlap to assist charging, but that is counteracted by the use of turbo-supercharging. The CI process does reduce the time available for injection, but that isn’t such an issue given a combination of forced induction and a correspondingly reduced engine speed. That in turn (due to the relatively low crankshaft speed) implies reduced frictional losses, while the relatively high compression ratio and the use of turbocharging imply high torque. The only real downside is the structural requirement caused by the associated elevated cylinder pressures, which can result in a weighty engine, but Danielson’s expertise with in-house aluminium and magnesium castings has paid dividends here. Although mechanically injected, the Trident family exploits direct injection into the combustion chamber, reflecting state-of-the-art CI practice. Also, CI lends itself to the use of heavy fuels: kerosene (paraffin) based fuels are widely used by armed forces. They are less flammable than gasoline, and so are better suited to CI rather than SI. The exhaust temperature of a CI engine is inherently lower than that of an SI one due to a higher expansion ratio. On top of that, the 100 TD2’s dual-stage turbocharging system further reduces the acoustic and thermal signatures of the exhaust – important considerations for many UAV operators. Most important of all though is flight time, and Hubschwerlen says the Tridents have been measured by DAS to be 40% more fuel-efficient than a UAV four-stroke SI engine of the same power level. He also reports that the Trident project was a response to specific issues encountered by the French military in operating its UAVs, identified as fuel injection problems, acoustic signature concerns, rapid wear, complexity of maintenance, high fuel consumption, high total ownership cost and operational risks. All of these were associated with the existing propulsion system the military used, which had not been designed for requirements such as high- altitude operation, extreme temperatures and high operational availability. Trident is designed to address those issues, exploiting proven Danielson technology in a package designed specifically for UAV requirements, in particular exploiting a range of fuel chemistries. In general terms, kerosene- based fuels ignite quicker than diesel, calling for appropriate adjustment Danielson Aircraft Systems Trident 100 TD2 turbodiesel | Dossier Unmanned Systems Technology | Spring 2015 Compact turbodiesel power – the Danielson Trident 100 TD2 The Trident project was a response to issues the French military had with operating its UAVs such as fuel injection problems and high total ownership costs