  A lot of UAV applications require vertical take-off and landing (VTOL)
combined with very long-range or endurance. Transitioning UAVs have been
proposed to combine the VTOL capabilities of helicopters with the efficient
long-range flight properties of fixed-wing aircraft. But energy is still a
bottleneck for many electric long endurance applications. While solar power
technology and battery technology have improved a lot, in rougher conditions
they still respectively lack the power or total amount of energy required for
many real-world situations. In this paper, we introduce the NederDrone, a
hybrid lift, hybrid energy hydrogen-powered UAV which can perform vertical
take-off and landings using 12 propellers while flying efficiently in forward
flight thanks to its fixed wings. The energy is supplied from a mix of
hydrogen-driven fuel-cells to store large amounts of energy and battery power
for high power situations. The hydrogen is stored in a pressurized cylinder
around which the UAV is optimized. This paper analyses the selection of the
concept, the implemented safety elements, the electronics and flight control
and shows flight data including a 3h38 flight at sea, starting and landing on a
small moving ship.
