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78 Textron Systems has been testing an experimental VTOL-transition fixed- wing UAV, the X5-55, with a view to maturing future technologies for the company’s unmanned aerial capabilities. The system itself has been in flight tests since summer 2017. “It’s a blended-wing airframe with a distributed electric propulsion system that can scale up or down,” said Sean Baity. “We chose the present scale – a gross take-off weight of 34 kg – to deploy the payloads used on our Aerosonde and Shadow UASs.” The testbed aircraft uses Li-Po batteries but the intention is to be able to use hybrid power systems or smaller batteries in the scalable systems. Each of the four rotors has independent control and vectored thrust, a design aspect aimed at providing greater resistance to wind and improved manoeuvrability in VTOL mode. “It also allows us to transition between vertical and horizontal flight faster, and perform more aggressive tactical flight, without needing control surfaces,” Baity added. The autopilot developed for the X5-55 was derived and modified from Textron Systems’ existing library of VTOL- transition aircraft, to take into account the vectored thrust and absence of ailerons or flaps. Tomas Koutsky introduced us to PBS Aerospace, which makes turbojet, turboprop and turboshaft engines suitable for UAV applications, target drones and missiles. The newest model, just coming into production, is the PBS TJ80 turbojet running to 58,000 rpm and capable of producing 900 N of thrust. It has an outer diameter of 235 mm, a length of 514 mm and weighs 12 kg. An integrated starter/generator provides 750 W electrical power and offers in- flight restart. Specific fuel consumption is quoted as 0.123 kg/N/h. The engine is lubricated by a fuel-oil mixture and it can be started and operated in any position. Koutsky said the company is developing its most powerful turbojet, the PBS TJ150, which will run to 55,300 rpm and will be capable of producing 1500 N of thrust. Again with integrated starter/generator, this will have an outer diameter of 272 mm, length of 520 mm and a weight of 19.6 kg. Its starter/generator will provide 600 W, while specific fuel consumption is quoted as 0.119 kg/N/h. It will be ready for the market at the end of this year. “Both engines have excellent thrust- to-weight ratios,” Koutsky added. “They operate up to 10,000 m, 0.9 M, in a temperature range of -40 to +40 C, and they are controlled by FADEC.” Aveox discussed its electric powertrain solutions, designed to simplify system certification, at the show. “We use proprietary combinations of analogue and digital electronics in our DC motor controllers and power conversion electronics,” said John Nino. “Our products are classified as ‘simple items’ under RTCA/DO-254 requirements. “The lack of complicated electronics, and minimal use of software, significantly reduces the validation requirements under RTCA/DO-160 and DO-178 for commercial aircraft. “Our power conversion electronics are all analogue-based and meet DO- 160 power quality requirements. June/July 2018 | Unmanned Systems Technology Show report | AUVSI Xponential 2018 The new TJ80 from PBS The X5-55 from Textron features distributed electrical propulsion