79 The latest we know of comes from Unmanned Aerospace, whose GH4 – short for ‘Gyrocopter-Helicopter, 4th generation’ – features an overhead rotor that spins freely, as on an autogyro, but whose blades can also be pitched from the conventional zero-pitch angle to a ‘VTOL-pitch’ angle by way of a unique mechanism invented and patented (across 11 patents granted and 6 pending) by the company. “As you know, gyrocopters have no VTOL capability because the principle by which their overhead rotors generate lift requires that their blades maintain almost zero pitch. But we can transition between pitch regimes without using anything helicopters use,” Gad Shaanan, CEO of Unmanned Aerospace tells us. “Helicopters have been advanced greatly over the past several decades, but their mechanisms remain very complex and very maintenance-intensive. We have maybe 10% of their complexity and, on top of that, we’re hydrogenpowered, combining hydrogen fuel cells with booster batteries, giving us up to 30 minutes of green hovering power.” Total flight time potentially exceeds four hours, depending on hover time versus forward flight time, as well as payload, battery and fuel tank complements. An integrated rack system enables 15 lb (6.8 kg) of payload capacity, which can also be dropped as needed for quick delivery operations (Shaanan suggesting shore-to-ship work as one of several suitable niches for the GH4). The overhead rotor is powered to enable the rpm necessary for take-off, hovering and landing. The GH4 also integrates two electric tractor propellers on short wings for forward flight, during which the overhead rotor is depowered so that the craft can function as an autogyro (and hence the rotor moves passively at speeds of 350-500 rpm), including a conventional integrated teeter mechanism via which the advancing and retreating blades can be adjusted for optimal flight efficiency. At the time of writing, the GH4 has racked up around 50 hours of test flights (including a fail-fast approach to eliminate all significant points of failure, and to ensure fast and far-reaching improvements), with more planned. Tests thus far having included flights using aluminium frames to validate the transition mechanisms and various custom subsystems. “Everything is custom, or at least a heavily reconfigured off-the-shelf item, except for the fuel cell,” Shaanan says. “The autopilot comes from Embention, and we’ve been programming and programming it because there’s no offthe-shelf autopilot that fits the gyrohelicopter hybrid flight mechanisms we have; we’ve had to test the transitioning between VTOL mode and gyro mode a great deal to build software control from the ground up.” The fuel cell powertrain meanwhile has been supplied by Intelligent Energy, with three of that company’s 1.2 kW PEM fuel cells connected to enable up to 3.6 kW of power collectively, for recharging the battery and thereafter powering onboard subsystems. Unmanned Aerospace has additionally iterated the powertrain design heavily to ensure effective thermal management, extraction of hot air being more challenging inside the GH4’s sealed fairings than on the industrial multi-rotors typically integrating the fuel cells. “The GH4 ends up looking a bit like a shark because we now have gills on the sides behind the nose to let the air extract. Simultaneously, we have ducting inside to help get the hot air out, with an intake scoop on the bottom. Intelligent Energy have been a great help throughout the whole design and integration process,” Shaanan adds. “In addition to Intelligent Energy and Embention, we also work with multiple other European suppliers, including Plettenberg for the electric motors and Mejzlik for the propellers. For every part, we’ve really looked to start with the best of the best COTS products, and then afterwards look into what can be tuned back for closer efficiency through customisation.” The company aims to begin pilot production of commercial units of the GH4 by Q1 2026; it is also planning a GH5 and GH6, which will carry around 110 lb (49 kg) and 350 lb (158 kg), respectively. Earth observation Although the cost of launching cubesats and other orbital observation and mapping tools has dropped significantly in recent years, from millions of dollars to tens of thousands in some cases, so too have the costs of producing solar-powered HALE (high-altitude, long endurance) UAVs, capable of soaring through the stratosphere with theoretically limitless flight time. For many, the latter represents greater safety and reliability, not to mention far better affordability. Offering a more price-economic alternative to cubesats (as well as weather balloons and other methods of stratospheric and orbital surveying) motivated US-based company Windhover Labs to begin work on its Eterna HALE UAV around three years ago, the aircraft having sported a dual fuselage, tandem wing architecture since its inception. UAVs | Insight Uncrewed Systems Technology | August/September 2025 Helicopters have advanced greatly over past decades, but [they] remain complex and very maintenanceintensive
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