Drone designs are usually a choice between flexibility and endurance. You can either go with a multirotor that’ll let you hover and make pinpoint landings, or you can go with a flying wing, which can handle bigger payloads and longer ranges. Finding a compromise is difficult, and usually, it’s also very messy. Amazon and Google, for example, are both working on delivery drones that have a whole bunch of frequently superfluous motors and propellers that help the drone to transition between hovering and efficient forward flight.
Delft University of Technology in the Netherlands has a history of managing to make successful drones that combine the best features of VTOL and fixed-wing flight. With their latest aircraft, they’re going old-school, with a biplane that can also take off and land vertically. The Delftacopter (get it?) is designed for outback delivery: not the steakhouse, sadly, but the mostly empty part of Australia, where the TU Delft team is testing its drone.
Historically, the reason to use a pair of wings in a biplane configuration like this was for reduced weight and strength. The wings in a biplane can be shorter than a monowing while still producing a given amount of lift, improving maneuverability, and the airframe as a whole can lift more weight for its size. The tradeoff is an enormous increase in drag resulting in a much lower top speed, but that’s not generally something that is as big of a deal for autonomous drones as it is for impatient humans. In the case of Delftacopter, the double wing also limits the influence of wind during take-offs and landings.
With that one big prop that it uses for both vertical takeoff and landing and horizontal flight, Delftacopter is efficient, compared to other hybrid platforms that rely on entirely separate systems for lift and thrust. Delftacopter does need to counteract the torque of that single enormous rotor, which is why it’s got those two little propellers out on the wings, but they’re tiny enough that they don’t have much of an effect besides preventing the drone from spinning out of control. Still, I wonder why they didn’t just make a much smaller version of the Convair XFY Pogo.
Photo: TU Delft
Anyway, Delftacopter is fully autonomous (with an Iridium satellite link for operation anywhere on the planet), and has a range of 60 kilometers with a top speed of 100 kilometers per hour. The autopilot takes care of horizontal flight, vertical landings, and the exceptionally tricky transition between the two.
The drone’s first job will be to pick up a blood sample from some poor shlub named Outback Joe who will be located in rough terrain somewhere in the Australian outback. While this is probably something that happens in Australia all the time, this particular scenario is part of the Medical Express UAV Challenge, which is taking place next week just outside of Brisbane.
[ Delftacopter ] via [ TU Delft MAVLab ]
Evan Ackerman is a senior editor at IEEE Spectrum. Since 2007, he has written over 6,000 articles on robotics and technology. He has a degree in Martian geology and is excellent at playing bagpipes.