Unmanned Systems Technology 004 | Delair-Tech DT18 | Autopilots | Rotron RT600 | Unmanned surface vehicles | AMRC | Motion control | Batteries

19 had to be capable of fully autonomous operation and be user-friendly – it was considered important that it didn’t need a specialist operator. Another central consideration was payload functionality. The primary task was visual imagery, and Delair-Tech’s CEO Michael de Lagarde points out that when it was designed, most commercial UAVs operating as flying cameras were in less demanding applications, such as use by the paparazzi. The DT18 was created from the outset for industrial applications however, and for series production. That all sounds straightforward but it had to be achieved in the context of a hugely demanding weight limit. Early in the design phase Delair-Tech learnt that the DGAC would consider licensing UAVs for BVLOS operation only where the total take-off weight did not exceed 2 kg, so that became the DT18’s target weight. Coming in at no more than 2 kg, the DT18 quickly gained DGAC certification for BVLOS operation. De Lagarde points out that this approval was based not only on the craft’s design and performance, including control strategies, but also on the techniques used to build it. Those techniques were in turn developed to allow cost-effective series production of a robust craft. Why was the DT18 a fixed-wing rather than a rotor craft? De Lagarde notes that a comparable rotor craft wouldn’t match its endurance, primarily because of inherently inferior aerodynamic efficiency. A rotor craft consumes more energy in flight. “The DT18 can fly for more than 100 km, which would be impossible for a 2 kg rotor craft,” he remarks, noting also that a fixed-wing craft offers inherently better stability and an overall higher margin of operational safety. De Lagarde points out that the 2 kg weight limit imposed by the DGAC ruled out the use of anything other than an electric motor. “A combustion engine wasn’t an option,” he says. “For our energy requirement it would have been heavier, and also noisier and polluting. Also, by using electric power, the motor’s rotor and its shaft with the propeller are the only rotating parts, which is good for durability and maintenance.” From the outset then there was no question that the DT18 was going to be anything other than a fixed-wing craft with electric propulsion. Throughout the design process, de Lagarde says, “A big focus was on how to extend flight time for a given amount of energy.” At the same time, he notes that while Delair-Tech keeps a keen eye on costs, he emphasises that the company’s top priority in the design of the DT18 has been to maximise its performance in the context of its operational criteria. Since cost was a consideration, Delair-Tech evaluated the use of off- the-shelf components. However, de Lagarde says that invariably the available component had unnecessary features, implying unnecessary weight, – a crucial consideration given the 2 kg target weight. Normally the only feasible option was to design a bespoke component. Even the autopilot is an in-house development, while the standard payload camera has little more than the sensor and lens outsourced. “We Delair-Tech DT18 | Dossier Unmanned Systems Technology | Autumn 2015 By using electric power, the motor’s rotor and its shaft with the propeller are the only rotating parts, which is good for durability and maintenance