Unmanned Systems Technology 028 | ecoSUB Robotics AUVs I ECUs focus I Space vehicles insight I AMZ Driverless gotthard I InterDrone 2019 report I ATI WAM 167-BB I Video systems focus I Aerdron HL4 Herculift

64 A pple Tree Innovation (ATI) a company based in Cheshire, UK, oversees the development of the WAM series of engines, which were previously best known for the WAM- 120, a three-cylinder uniflow-scavenged two-stroke diesel engine for light recreational aircraft. Originally conceived by Mark Wilksch of Wilksch Airmotive (who has since left to pursue other engineering projects), ATI acquired the company in the mid-2000s, with an eye to developing a more commercial-grade (or potentially military-grade) version of the WAM-120. These efforts have resulted in the WAM-167BB, a 3.0 litre inline four- cylinder uniflow scavenged two-stroke diesel engine version for UAVs and light aircraft requiring multi-fuel capability. The engine incorporates several interesting design features that have remained consistent throughout all four WAM versions (including the WAM-100 LSA for light sport aircraft, and the WAM- 125BB as the first next-generation design). Most notably, the WAM engines are designed with an inverted engine block. This arrangement places the crankshaft at the top, and the cylinders and pistons underneath, although with the sump still at the base. A key advantage of the inverted Rory Jackson reports on the development of this two-stroke diesel and the advantages of its inverted engine block Top-down approach October/November 2019 | Unmanned Systems Technology The WAM-167BB is a four-cylinder two-stroke diesel engine with uniflow scavenging, indirect fuel injection, and an integrated turbocharger and supercharger (Images courtesy of Apple Tree Innovation)