Unmanned Systems Technology 016 | Hydromea Vertex AUV | Power management systems | Unmanned Space Vehicles | Continental CD-155 turbodiesel | Swift 020 UAV | ECUs | DSEI 2017 Show report

51 in house resources for the manufacture of components, including crankshafts and con rods. His company ended up selling components to the likes of Porsche Motorsport and Evernham Engines. Thielert crankshafts were in Le Mans and NASCAR race-winning engines. Around the turn of the century, Thielert started investigating the aviation market. There, fuel efficiency was the name of the game rather than the search for power. Compared with a comparable spark ignition engine, the use of compression ignition – with its lack of throttling and much higher compression ratio – is a clear inherent advantage in respect of fuel consumption. The drawback of compression ignition though is that the greater structural requirement implies a heavier engine for a given power output. However, some contemporary turbodiesel automotive engines exploit a cleverly designed all-aluminium structure, minimising the weight penalty. One such was a 1.7 litre I4 from the undisclosed German motor manufacturer that Thielert identified as light enough to act as an aircraft engine. This liquid-cooled, wet-sump engine featured four valves per cylinder and common rail injection. A major benefit of adapting an engine from a major automotive manufacturer rather than designing from a clean sheet of paper is the huge amount of r&d that has gone into the existing engine. The manufacturer will have invested resources of a magnitude greater than anything an independent such as Thielert could hope to muster. Although a spark ignition specialist, Thielert Motoren had experience of turbo- supercharged race engine development in the late 1990s, and at that time it also developed its own engine control hardware and software. Both sets of expertise were very relevant to the new aviation project. Having adapted its chosen all- aluminium engine and integrated its own propeller reduction drive, in 2002 Thielert achieved certification of it for aviation use – the first diesel engine certification since the 1940s. Moreover, the certification included a full authority digital engine control (FADEC) system, a rarity among certified piston aircraft engines at the time. Indeed, the certifying authority had no existing requirements of such a system, so they had to be specially devised for this project. Impressively, Thielert had developed both the FADEC hardware and software in-house, based on its engine management system expertise. The certification it achieved applied to the vast majority of countries having an aviation authority, including Europe, the US and the Far East. In 2005, Thielert decided to switch to a more recent 2.0 litre version of the base engine. This had a heavier cast iron monobloc (combined crankcase and block) but the disadvantage of that was overcome by manufacturing an alternative aluminium item in-house. Continental Motors CD-155 I4 turbodiesel | Dossier Unmanned Systems Technology | October/November 2017 The CD-155’s in-house manufactured aluminium block Underside of the CD-155 cylinder head, showing the combustion faces