32 June/July 2023 | Uncrewed Systems Technology The Hirth 4202HF (shown here with one of its early iteration) is an evolution (Courtesy of Hirth) Fuel efficiency and long life between TBOs were major factors driving Aergility’s choice of Turbotech’s recuperated turboprop engine (Courtesy of Aergility) mere compatibility with heavy fuels but optimised to run on them primarily or even exclusively. Hirth, for instance, welcomed us back for our 36th issue (February/March 2021) to show us its 3507-01M liquid-cooled, direct-injection heavy fuel engine, as well as its 4202, an architectural descendant of the S1218 designed with special features to prevent operational hazards such as heavy fuel ‘puddling’ and knocking. Similarly, we revisited Cobra Aero in issue 44 (June/July 2022), 5 years after covering its A33i single-cylinder, spark-ignited gasoline engine, to detail its new triple-inline cylinder A99H – in some ways a successor to the A33i, but again, optimised for using heavy fuels as its primary source of power. The A99H also incorporates some advances made during 2017-22, such as metal additive manufacturing and critical improvements in its ECU programming. Such is the importance of UAVs and other uncrewed systems to next-generation naval strategies and investments that we cannot imagine a future in which more companies do not come forward with robust and efficient heavy fuel engines. A few others have such solutions in development, although we have not featured them yet. Hybrid powertrains Both Hirth and Cobra Aero (among many others) have expressed to us a strong interest in hybridisation. Some of the reasons for this are similar to those in the automotive world. If electrical power output is more important than shaft power, then an engine can be run at its most fuel-efficient speed at intermittent points when a battery needs to be recharged, rather than having it ever idle or run near its redline. However, unlike road vehicles, UAVs face a dilemma regarding flight endurance. Users want more uptime in their autonomous systems, and the scale of their demand is now beyond that which batteries can deliver, or will feasibly deliver, unless recent trends
RkJQdWJsaXNoZXIy MjI2Mzk4