Unmanned Systems Technology 038 l Skyeton Raybird-3 l Data storage l Sea-Kit X-Class USV l USVs insight l Spectronik PEM fuel cells l Blue White Robotics UVIO l Antennas l AUVSI Xponential Virtual 2021 report

27 Skyeton Raybird-3 | Dossier configuration right, we designed a novel and proprietary system for isolating the engine compartment and payload compartment in the fuselage. “That disrupts the vibrational frequencies from being transmitted from the combustion chamber to the gimbal. We developed it in-house, then added it to OS Engines’ own vibration isolation arrangement. It has come together as a great system overall.” Stepura adds that fuel efficiency is another major reason for choosing the GF40. In flight, the Raybird-3 consumes an average of 250 ml/hour from its 9 litre fuel tank. Although much of that is down to aerodynamic optimisation across the fuselage, Skyeton places great emphasis on the engine’s contribution. “To explain that figure a little further, the higher fuel weight at the start of a mission means maybe around 300 ml of fuel is consumed per hour, and towards the end it is around 200 ml/hour,” Stepura says. The engine block has largely been kept to the standard design, although some ancillary systems have been altered. For example, Skyeton has designed its own generator – effectively a transformer alternator, with field coils rather than permanent magnets. It is mounted directly onto the engine shaft behind the propeller for delivering 100 W for avionics and payload systems – or more, if the payload requires it – without using belts, which would add weight, parasitic losses and potential points of failure. Skyeton has found it to be sufficient across all its missions and sensor gimbals, including comparatively more powerful synthetic aperture radars (SARs). A battery pack sits between the generator and the electronics systems to regulate the AC voltage supply at 24 V DC. “The design and integration of the propeller has also been really important for getting our endurance and fuel consumption on target too,” Knyazhenko says. “Many UAVs use pusher propellers, because some developers hope to reduce vibration to the payload, or they want to mount the payload on the nose,” he observes. “But if you look at civil and general aviation, you see almost no manned aircraft being designed with pusher propellers. “Tractor propellers get so much more aerodynamic efficiency from being in direct contact with the air, compared with the downwash from the fuselage and potentially icing fragments that a pusher has to deal with.” Aerodynamic and durability optimisation of the carbon composite propeller was carried out by Mejzlik, which embedded the Raybird-3 and its flight data into its in-house design and performance simulation systems. Payload systems Skyeton has both developed and adopted a wide array of systems for sensing and photogrammetry. “It isn’t easy to predict exactly which sensor and level of accuracy each end-user will want – it can range from wildlife monitoring to 3D mapping, to oil & gas asset inspections,” Stepura says. “That said, from an altitude of 1 km, we’ve used consumer Nikon- or Canon-type cameras to capture resolutions of 5-6 mm per pixel. “The first time we did that was over a quarry, covering an area of Unmanned Systems Technology | June/July 2021 Skyeton performed aerodynamic optimisations across the hull design, while Mejzlik provided similar design work on the propeller