Unmanned Systems Technology 033 l SubSeaSail Gen6 USSV l Servo actuators focus l UAVs insight l Farnborough 2020 update l Transforma XDBOT l Strange Development REVolution l Radio telemetry focus

48 Insight | UAVs Firefighting Parallel Flight Technologies is continuing to develop its quad-engine platform, thanks to funding from NASA and the National Science Foundation via SBIR grants from the US government, to produce a highly redundant (and therefore very safe) power architecture. The UAV was originally developed to provide an unmanned platform capable of carrying hoses, retardant or other critical logistics items for firefighters. “Each of the parallel-hybrid modules on the multi-copter’s four arms incorporates an internal combustion component and an electric motor component,” explains CEO Joshua Resnick. “That gives great potential for redundancy in and of itself, but a lot of data and programming rigour is needed to develop the right algorithms and hardware to leverage that. “So we developed some proprietary software for doing just that, which we trialled, with particular regard to the aircraft’s ability to remain stable and continue its flight path throughout a ton of different failure modes, and all at different altitudes.” As an example, through an interface with the flight computer, the operations team repeatedly inserted simulations of an engine flameout. They tested different ways a flameout could occur, such as by losing one cylinder, losing two, suffering oxygen deprivation or fuel starvation, and so on. They then tested the software’s ability to detect the flameout and respond to it by switching to the electric motor for thrust on the affected arm. “The aircraft was on a three-axis gimbal, and we recorded data from the flight controller on the degree of drift that the attitude, velocity and control experienced relative to their respective navigation targets, for the duration of the flameout and of the software dealing with it,” Resnick says. “Our test results found that, to all intents and purposes, an observer would not have been able to tell that the UAV was suffering a failure mode at all.” The company has also upgraded the UAV’s engines with electronic fuel injection systems from HFE International, following a number of customer requests to replace the engines’ carburettors and needle valves with ECU-timed injectors. “We’re keeping a close eye on the features and technologies our customers want, because we’re looking to move quickly towards flight trials of our beta-test prototype later this year,” Resnick adds. “The prototype used Desert Aircraft’s DA70 engines, but the beta-test version will use either DA100s or DA120s, depending on the customer,” he says. “Wildfires are an ongoing crisis in California, so we’re catering to a lot of demand there. In any case, with the new engines everyone will get at least 100 lb [45 kg] of payload capacity.” Humanitarian aid As featured in UST 30 (February/ March 2020), Wings For Aid is a Netherlands-based foundation dedicated to developing autonomous swarm distribution of charity aid and disaster relief supplies. Although its proof-of-concept flights so far have been conducted using a Pipistrel Sinus OPV, the flight team at Wings For Aid has recently taken delivery of its prototype UAV chassis (also manufactured by Pipistrel), which is to begin ground testing soon. The UAV has a 9.5 m wingspan, measures 2.9 m tall and 6.4 m from nose to tail, and has an empty weight of 390 kg. It has been designated the MiniFreighter 8/500FW, has a MTOW of 610 kg, and an expected cargo-carrying capacity of 160 kg. That capacity is enough for eight of the company’s patented 20 kg (or 70 litre) aid boxes, which will be dropped from an altitude of around 100 m. “We have also developed the flight control system with Pipistrel and one of its technology partners,” comments general manager Barry Koperberg. “In parallel with the introduction of this UAV, we’re working on radar- based detect & avoid systems with the Technical University of Delft and some commercial partners,” he says. “We’re also running range extension projects to cater for extended radio line-of-sight and interconnectivity for the cargo UAVs. Taken together, these projects will enable future swarming of UAVs over a wide airspace.” Each UAV will be capable of cruising at around 125 kph, with a maximum airspeed of 150 kph, the power coming from a Rotax 582UL and a tractor propeller drive integrated at the front of the airframe. This two-cylinder two-stroke uses liquid cooling and a rotary intake valve to produce a continuous 65 hp (48.5 kW) while running on premium unleaded gasoline. The maximum range is 500 km (or a 250 km return flight), and Koperberg estimates that with two UAVs his August/September 2020 | Unmanned Systems Technology Parallel Flight Technologies’ UAV has been trialled for its ability to remain airborne and stable throughout various potential failure modes (Courtesy of Parallel Flight Technologies)