Unmanned Systems Technology 036

92 T he Z1 is a fixed-wing VTOL UAV originating from the ideas of Rob Coatney, lead aerospace engineer at Zepher Flight Labs, who had previously worked on the tail-sitting flexrotor UAS from Aerovel and the tilt-wing Airbus Vahana project, among others. Its development began as a self-funded project by Zepher, a custom aerospace manufacturing and engineering company based in Washington state, in the US. Zepher Flight Labs, an independent organisation, was spun off from Zepher to develop the Z1 further. As the engineering team at Zepher worked to flesh out Coatney’s vision of this modular VTOL-transitioning UAV, others at Zepher, including vice-president of programmes and now president of Zepher Flight Labs Adam Stolz, talked with US government end-users to gauge their interest. This led to Zepher winning a US government contract in June 2020, directed at researching technologies for the Army Research Laboratory (ARL) that would support the efforts of the United States Army Special Operations Command (USASOC). More specifically, ARL and the USASOC were looking for a Group 2 UAS (weighing less than or equal to 55 lb, to eliminate the need for a qualified military pilot to be present during flight), with its design and specifications emphasising an optimised endurance and minimal acoustic signature for operations in ‘austere environments’, particularly deserts and oceans. At the time of writing, Zepher Flight was building the first prototype of the Z1 while flight-testing its subsystems on surrogate aircraft. The first flight tests of a fully integrated Z1 are expected this March. Zepher Flight’s work to achieve the USASOC’s endurance and acoustic requirements have led to the 25 kg UAV incorporating several key technologies, including a hydrogen fuel cell powertrain, a variable-pitch propeller (VPP), and a modular composite airframe with swappable and tool-free configurable components. The airframe also features a 4.4 m wingspan, with twin booms mounting four downward-facing e-motors for VTOL flight, as well as a payload bay with a 5 kg capacity and quick-release mounting locations on the nose and underbelly for ease of integration. “In addition to the initial military- government use, we feel this craft will be just as suitable for commercial and industry users,” Stolz adds. “We especially wanted to design towards five target areas, some in line with the USASOC’s requirements. Compared with a typical Group 2 UAS, these included increased endurance and efficiency, reduced acoustic signature, improved control during the VTOL phases of flight, and increased durability – particularly regarding the powertrain and its TBO figures. “We also wanted advanced manufacturability, including how easily we could scale the Z1’s architecture, to create newer or larger versions with the same core technologies and capabilities.” Rory Jackson explains how this VTOL- transitioning UAV has been designed for surveillance and other applications Quiet and persistent February/March 2021 | Unmanned Systems Technology The Z1 multi-role UAV is intended for use by the US Special Forces, and is being fitted with technologies including a hydrogen fuel cell (Images courtesy of Zepher Flight Labs unless specified otherwise)