Evidence That UAS And Airliners Don’t Mix

The idea that small UAS are too light and frail to damage a jet engine is being challenged by research conducted at Virginia Tech.
By Patrick C. Miller | November 05, 2015

One of the ideas I’ve seen put forth on social media regarding the potential consequences of a small unmanned aerial system (sUAS) being ingested by a jet engine is that they are too light and too frail to do any significant damage.

Research conducted at Virginia Tech’s Crashworthiness for Aerospace Structures and Hybrids (CRASH) Laboratory shows that this may not be true. A team led by Javid Bayandor, the lab’s director, and Michael O’Brien, professor of mechanical engineering, created a computer simulation showing what could happen.

While I had seen screen shots from the simulation, I wasn’t prepared for the video Bayandor emailed me which graphically animates the disintegration of a jet engine as it ingests an eight-pound quadcopter. It’s one of those moments that makes you sit up and say: “Whoa!”

While some might find it comforting to believe that their recreational drone poses no significant danger to something as massive as an airliner, Bayandor explained how it is that such a small, seemingly delicate aircraft can pose a potentially deadly threat.

Turbofan engines are purposely designed to have very tight tolerances that can be as small as a few millimeters. While Bayandor and O’Brien allow that some small recreational drones might pass through an engine with little or no effect, a drone with a battery pack and equipped with a camera would have enough mass to unbalance the turbine fan blades. If that happens, the engine can literally tear itself apart.

What impact this has on an airliner depends on at what point it is in flight and the pilot’s skill in handling the situation. An airliner just leaving the runway after takeoff would have a big problem if it suddenly lost an engine. In any event, unexpectedly losing an engine during takeoff or landing creates problems.

The Virginia Tech researchers are also looking at the effects of collisions between sUAS and helicopters and will likely have research results within the next month. While they don’t yet know how that simulation will look, they do know that helicopters are far less forgiving than fixed-wing aircraft when losing an engine or a rotor.

Whatever the case, such research will be valuable to regulators as they work to safely integrate UAS into the national airspace and to those who design aircraft, knowing that there are new potential threats they must consider.