Unmanned Systems Technology 018 | CES show report | ASV Global C-Cat 3 USV | Test centres | UUVs insight | Limbach L 275 EF | Lidar systems | Heliceo DroneBox | Composites

57 in light aircraft. Peter Limbach Snr’s company did just that in 1968. Limbach’s first VW-based aviation engine had enlarged cylinders for a greater displacement, a revised intake system and other modifications appropriate to aircraft use. It powered an RF-5 motor-glider produced by Sportavia, a company based not far from the Limbach facility. Limbach’s flat-four aero engines have always been built from scratch, buying in little more than the crankcase from VW and sourcing other components from OEM suppliers or making them in-house. The current range includes four-cylinder boxers with displacements from 1680 to 2424 cc, and options including turbo- supercharging, liquid-cooled cylinder heads and port fuel injection. Currently under development is Limbach’s own dry-sump crankcase, which will break all connection with the original VW engine. Interestingly, the Limbach factory has an impressive test rig that mounts a running dry-sump engine on an articulated arm, permitting it to be evaluated for use in airships that require vectored thrust. Limbach’s original VW engine overhaul business ended in the 1980s, since when the company has been purely a manufacturer of two- and four-stroke aero engines. The two-stroke strand began in 1972, apparently inspired by the development of motor-gliders. These started to have an engine mounted on a pylon such that it could be pulled up into the fuselage to reduce drag in glide mode. A light and compact two-stroke, without the depth of a wet sump, was eminently suitable. Peter Limbach admits that he isn’t 100% sure if it was this particular application that prompted his father to design and develop a twin-cylinder boxer two-stroke. In fact, the majority of sales have been to the USA to power ultralight aircraft, often the single-seat, twin-engined Gemini Hummingbird, which was supplied in kit form. However, with the introduction of tougher operational rules this century the ultralight market has shrunk dramatically. The Limbach 275 cc two-stroke twin has had many other aviation applications, including powering a target drone produced by a French company. Lately there has also been a 550 cc four- cylinder version, the design of which came about as a thesis project by Peter Limbach (Jnr) at the Technical University of Aachen, which he completed in 1984. By 1990 there was a demand from the market for an engine with twice the power of the twin at the cost of a modest increase in size and weight. This is currently available as L 550 E and EF variants, while the twin is available as the L 275 E and EF. The L 275 EF under consideration Limbach L 275 EF | Dossier The current range includes four- cylinder boxers up to 2424 cc, and options such as liquid-cooled cylinder heads and port injection Unmanned Systems Technology | February/March 2018 The L 275 EF equipped with optional generator