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

20 Dossier | Delair-Tech DT18 had to learn a lot about cameras,” de Lagarde recalls. The telecoms system was also developed in-house. “There was no suitable off-the-shelf solution,” de Lagarde says. “We needed long- range communications with two-way data transfer. We needed a link that can transfer real-time data from the still and video cameras and which could be used for controlling the craft if necessary.” Design and development In respect of the DT18’s design, de Lagarde pays tribute to assistance from Supaero, otherwise known as the Institut Superior de l’Aeronautique et de l’Espace (ISAE) and part of Toulouse University. “We have always had a close relationship with Supaero, and a number of our engineers are graduates of it,” de Lagarde says. “We were able to use their resources, aided by finance provided by the [French government’s] ministry of science.” The DT18 was designed using CAD and associated CFD software, while development included testing of an early DT18 prototype in a wind tunnel at Supaero at wind speeds of up to 30 m/s. The tunnel testing programme lasted three weeks and embraced flow visualisation techniques. The DT18’s electronics are tightly packaged by its compact nature so it follows that there is a lot of electromagnetic radiation being generated in a very confined space. De Lagarde notes that at the design and development stages Delair- Tech was assisted by the French space agency in its quest to avoid potential interference. He also acknowledges valuable assistance from the ENAC, the Ecole Nationale de l’Aviation Civil, which is the academic institution that trains engineers for the DGAC. The first iteration of the DT18 prototype, the DT18 02, first flew on July 4, 2012, and this was the design that was put into production. There has been no fundamental design change since then – indeed, any such changes would have called for a re-certification of the design. However, a careful check has been kept for any fatigue cracks in the airframes, and over time this has led to minor reinforcement in certain areas. The DT18 has a straightforward autonomous control system, which is at once sophisticated and robust. “You must have good autopilot control,” notes de Lagarde, “and much of this is in the software. We use MEMS sensors, which are affordable if somewhat basic, but we have very sophisticated signal processing. The quality of our software is the key to the DT18’s performance.” The DT18 has an operational ceiling of 3000 m, although the DGAC’s BVLOS requirement is a maximum of just 150 m, with a maximum range of 15 km from the ground station. For optimum range, in still air the DT18 cruises at an airspeed of 17 m/s. Lowering that speed, by reducing the motor’s power requirement, increases the duration of a flight but decreases the distance that will be covered. The maximum endurance is about two hours’ flying time. Stall occurs at 11 m/s. The craft’s specification is for it to be operated Autumn 2015 | Unmanned Systems Technology Rearward view from a DT18 coming into land The DT18 fits into this case