A recent report has found that drone collisions with large manned aircraft can cause more structural damage than birds of the same weight for a given impact speed.
The Alliance for System Safety of UAS (unmanned aerial systems) through Research Excellence (ASSURE) produced the report for the American Federal Aviation Administration (FAA) to try to quantify the dangers associated with drones sharing airspace with planes.
The research used computer modeling and physical validation testing to examine impacts with two different types of drones (weighing 1.2 kg and 3.6 kg) on two types of aircraft, a single-aisle commercial transport jet and a business jet.
They examined collisions with the wing leading edge, the windshield, and the vertical and horizontal stabilisers. The windshields generally sustained the least damage and the horizontal stabilisers suffered the most serious damage. The severity levels ranged from no damage to failure of the primary structure and penetration of the drone into the airframe.
Unlike the soft mass and tissue of birds, drones typically are made of more rigid materials. The testing showed that the stiffest components of the drone — such as the motor, battery and payload — can cause the most damage to the aircraft body and engine.
“Even small unmanned aircraft systems can do significant damage to engines,” said Kiran D’Souza, assistant professor of mechanical and aerospace engineering at Ohio State University, who led the engine ingestion portion of the study.
He conducted computer simulations to evaluate the potential damage of a drone entering a generic mid-sized business jet engine, including damage to fan blades, the nacelle and the nosecone.
The simulations revealed that the greatest damage and risk occurs during takeoff, since the fan is operating at the highest speed at this phase of flight. The location of the drone’s contact on the fan is a key parameter, with the most damage occurring when the impact is near the blade tip.
According to D’Souza, the next step is the development of a representative commercial jet engine model for ingestion simulations, as well as full-scale testing to verify and validate the simulations. The team is planning additional research on engine ingestion in collaboration with engine manufacturers, as well as additional airborne collision studies with helicopters and general aviation aircraft.
[Computer simulation of a drone-aircraft collision. Image: ASSURE]