Helicopter-plane hybrid drone takes to the skies

A hybrid unmanned aerial vehicle (UAV) developed by researchers at the National University of Singapore could pave the way to longer and safer drone missions in tricky operating environments.

Dubbed the U-Lion, it is capable of vertical take-off and landing like other helicopter UAVs, but can also transit to horizontal “cruise flight” like planes, even when switching to autonomous flight.

“This enables it to perform long range tasks,” said Wang Kangli, a UAV expert at the university and lead author of the study. The two flying modes also minimise dependency on take-off and landing facilities, making it useful for sea surveillance, disaster zone monitoring and forest mapping.

The U-Lion is designed in ‘tail-sitter’ configuration with adjustable wings to control the speed and direction of the device. When fully retracted, the wings reduce gust disturbance in vertical mode, and can be fully expended to provide sufficient lift in cruise mode, acting as a fixed-wing drone. The researchers developed advanced algorithms “to overcome the uncertainties in transition and achieve autonomous full envelope flight,” added Kangli.

However, creating a dual-mode drone isn’t an easy task. The structural differences in a vertical take-off and landing UAV and a fixed-wing UAV make it a challenge to combine and optimise the two functionalities in a single UAV. The unpredictability of aerodynamic forces also makes “the transition process difficult to automate,” said Kangli.

While the technology is still under development, hybrid drones could take off as soon as five years from now, say the scientists. They aren’t the only ones developing them: Google’s Project Wing is also working on hybrid UAVs.  

The research has been published in Science China Information Sciences.