Researchers at the German Aerospace Center (DLR) have demonstrated the ability to land an unmanned, autonomous aircraft travelling at 75 km per hour on the roof of a moving car. The feat may help make it possible to eliminate the landing gear, and increase the payload capacity and uses of, solar-powered and other ultralight aircraft.

Ultralight solar-powered aircraft can fly at altitudes in excess of 20 kilometers and stay airborne for several weeks; weight is crucial for long-duration flights. By omitting the landing gear, the weight of an unmanned aerial vehicle (UAV) can be reduced, thus allowing greater range and enhanced performance. Reinforcements to the aircraft structure that would typically be necessary also can be eliminated, contributing to a further reduction in weight.

Combining technologies from the fields of robotics and UAVs, researchers from the DLR Institute of Robotics and Mechatronics tested a system to land a three-meter, 20 kg, electrically powered fixed-wing UAV during flight trials at Mindelheim-Mattsies airfield in Bavaria. To do this, the researchers fitted a platform equipped with a number of optical markers to the roof of a car. The aircraft was able to navigate to a position—accurate to within 50 cm—above a 20-square-meter mobile platform. An optical multi-marker tracking system recognized the landing platform and performed a calculation of its position relative to the ground vehicle. The landing then was carried out under computer control.

The UAV navigated to a position within 50 cm above a mobile platform. Image credit: DLR.The advantage of this system is that the movement of the UAV and the ground vehicle are synchronized. With both vehicles traveling at the same velocity, the landing resembles a vertical helicopter landing when seen from the ground vehicle. The horizontal velocity components are thus close to zero, making the landing simpler and safer.

In experiments performed to date, flight operations safety rules required a driver to be present in the car. The driver received control commands via a graphical display, which instructed faster or slower driving. In the future, a robotic vehicle without a driver could be used.

The researchers envision the technology's payload-boosting potential as enhancing a number of civil applications, including the collecting climate and weather data, replacing failed communication networks or supporting crisis management.