How do airplanes ensure safety from birds

Flight safety: test bench for drone collision tests

Reports of near-collisions between commercial aircraft and unmanned aerial vehicles are increasing. Tests against bird strikes are mandatory for aircraft, and there are no standardized test procedures for safety in the event of collisions with drones. That should change.

© depositphotos, I_g0rZh

© Michael May

Drones are increasingly affecting air traffic, and the Federal Police are even warning of a massive risk from unmanned aerial vehicles. In 2018, 158 incidents were reported at German airports. At the beginning of May of this year, flight operations at Frankfurt Airport had to be temporarily stopped completely due to the sighting of a drone. Drones not only endanger landing commercial aircraft, low-flying helicopters are also threatened. The impact on the cockpit windows, the wing leading edges and the engine is particularly feared by pilots. According to experts, a collision with a drone causes more serious damage to aerospace components than a collision with a bird. However, while the tolerance of an aircraft to bird strikes must be proven by standardized test procedures for approval, there are no corresponding regulations for safety in the event of collisions with drones. A research team at the Fraunhofer Ernst Mach Institute (EMI) in Freiburg sees a great need for action here. “Mechanically, drones don't behave like birds and they also weigh significantly more. It is therefore unclear whether the safety of a bird strike-proof aircraft is guaranteed in the event of a collision with a drone, ”says EMI scientist Sebastian Schopferer.

High risk potential

Initial impact tests with drone batteries and motors confirmed the potential risk. “We used a compressed air accelerator to bring these two components of a standard quadrocopter to different speeds - between 115 and 255 meters per second - and to impact them on flat aluminum plates up to eight millimeters thick that were clamped in a test stand. The plates were considerably deformed and dented, and the drone components were completely destroyed, ”says Schopferer, commenting on the test results, which were recorded by a high-speed video camera. Batteries and motors can cause particularly great damage due to their weight.

The primary aim of the test series with the components mentioned is to determine the momentum transfer on impact and to examine the damage pattern on aircraft materials such as aluminum alloys and fiber composites. In addition to these dynamic investigations, quasi-static compression tests are carried out in order to be able to determine parameters such as stiffness and strength of the components. These play an elementary role in the derivation of numerically efficient, predictive simulation models that the aviation industry can use to gain new, important insights into the impact behavior of drones. This allows statements to be made about the drone impact resistance of new types of aircraft components during the design phase.

Acceleration tests with complete drones

In the next step, the researchers at the Fraunhofer Institute for Short-Term Dynamics, EMI, plan to set up a new type of test stand (see picture below). The test stand enables entire drones weighing up to three kilograms to be accelerated to speeds of up to 150 meters per second. “We are using this to study the impact and fragmentation behavior of entire drones when impacting rigid and flexible targets in order to study the suspected catastrophic effect of a collision with aircraft. Tests in this weight class of drones are so far unique in the world, ”explains Schopferer. The experiments will be carried out with different variants, both hobby and semi-professional models with a mass of one to three kilograms will be used. Not only aircraft manufacturers should benefit from the tests, but also approval authorities will receive important information with the results in order to be able to assess the danger posed by drones to air traffic more comprehensively.

Text: Fraunhofer Institute for Short Term Dynamics, EMI

Fragments of the battery in the test bench after the impact test on an aluminum plate.
© Fraunhofer EMI


Switzerland adopts EU regulations on drones

Switzerland recently included the various provisions of the European Union on air safety and security as well as air traffic management in the annex to the aviation agreement. The most important legal act is the new European framework regulation for aviation safety. In particular, this also covers unmanned aerial vehicles (drones).

The new drone regulation requires that drone pilots are required to register from June 2020. The FOCA has started the implementation work for the introduction of the European regulation. This will allow drone pilots to fly according to the same rules in the entire European airspace in the future. More about the new regulation here