Over the past several years, we've seen an increasing number of VTOL (vertical take-off and landing) aerial drones. True to their name, these take off and land vertically like helicopters, yet switch to faster and more efficient fixed-wing flight once airborne. One of the latest such aircraft, the U-Lion, has a couple of particularly interesting features.

The GPS-equipped autonomous drone was designed over a period of four years by PhD students Wang Kangli and Ke Yijie, working under the supervision of Prof. B.M. Chen at the National University of Singapore.

First of all, while most of the VTOL drones we've seen utilize four or more motor/propeller units, the U-Lion simplifies things by using just two motors powering a couple of stacked contra-rotating props. Those motors are mounted on a gimbal, allowing the angle of thrust to be changed as needed – this is how the aircraft is steered in vertical flight mode, and how it transitions between vertical and horizontal flight.

Additionally, the prototype drone's wings retract when it's in vertical flight, which apparently aids in stability. Once in fixed-wing flight, the angle of the wings can be adjusted according to the flying conditions and mission requirements, in order to deliver optimal performance. According to the university, this feature allows it to fly for longer distances than typical VTOL drones, while also being more maneuverable than regular fixed-wing models.

A paper on the research was recently published in the journal Science China Information Sciences.