Fraunhofer Researchers Assess Drone Strike Scenarios

Drone use is increasing globally and so have reports of their near misses with commercial aircraft. While bird strike testing is mandatory for aircraft, there is no equivalent standard test procedure for collisions with drones available currently. Over the last few years there have been numerous reports of rogue drone activity around major international airports and it appears to be only a matter of time before a major catastrophe occurs.

No drones allowed in the vicinity of helicopters. © Michael May

Cases of drones impacting air traffic have increased in the recent past. Almost 158 cases were reported at German airports in 2018. Germany’s federal police have warned of a massive threat posed by unmanned aerial vehicles. This year, at the beginning of May, flight operations at Frankfurt Airport had to be shut down completely for a short period following the sighting of a drone. Drones endanger aircraft coming into land and low-flying helicopters alike. Experts are of the opinion that a drone colliding with an aircraft would cause more damage to it than the impact of a bird strike!
Researchers from Fraunhofer EMI in Freiburg are researching on the subject. Dr. Sebastian Schopferer, one of the scientists working on this project explains, “From a mechanical point of view, drones behave differently to birds and also weigh considerably more. It is therefore uncertain, whether an aircraft that has been successfully tested against bird strike, would also survive a collision with a drone.”

Now, the Fraunhofer Institute for High-Speed Dynamics Ernst-Mach-Institute EMI is creating a test bench for recreating various collision scenarios with complete drones to study the consequences of a collision between an aircraft and a drone.

Typical lithium-ion battery (weighing approximately 700 grams), as installed in a drone. © Fraunhofer EMI

Safety

Initial impact tests with drone batteries and motors confirm catastrophic damage. Schopferer states, “Using compressed air, we accelerated these two components to speeds ranging from 115 to 255 meters per second and fired them at aluminium plates up to eight millimetres in thickness that were mounted in a test bench,” Schopferer further explains: “There was substantial deformation and indentation of the plates, and the drone battery and engine were completely destroyed.” The outcome of the tests was recorded with a high-speed video camera.

Researchers also conducted a number of quasi-static pressure tests side by side to determine the strength and rigidity of the drone components. These results will be significant for the derivation of numerically efficient, predictive simulation models to ascertain new and important findings about the impact behaviour of drones to be used by the industry. Use of such models during design phase will help assess the resistance of new aircraft components to the impact of a drone.

Fragments of a drone battery following impact with an aluminum plate on the test bench. © Fraunhofer EMI

Testing

Next, researchers plan to construct a new type of test bench for investigating the impact of complete drones with a maximum weight of three kilograms and flying at speeds of up to 150 meters per second to simulate realistic impact scenarios.

These investigations will benefit aircraft manufacturers and aviation authorities, providing them with important information for a more in-depth assessment of drone hits pose to aircrafts.