As Drone Encounters Rise, Study Shows Visibility Concerns

OSU and ERAU researchers conclude motionless drones present the most danger.

plane and drone close encounter
A twin-engine airplane experiences a close encounter with a sUAS on final approach.Oklahoma State University

An airborne human-factors experiment conducted by researchers from Oklahoma State University and Embry-Riddle Aeronautical University concluded in a recent published study that certificated pilots failed to see a common type of quadcopter during approach to a runway, and in most cases, could never detect motionless drones.

In the testing, skilled pilots usually could see small unmanned aircraft systems (sUAS) encroaching on their airspace in 12 out of 40 encounters, or only about 30 percent of the time. And when the drones were motionless, only three out of 22 were spotted by the pilots. Drones were detected at distances of between 213 and 2,324 feet.

These findings, published in the International Journal of Aviation, Aeronautics, and Aerospace (IJAAA), illustrate a real and growing threat to aviation safety, said Dr. Ryan J. Wallace, assistant professor of Aeronautical Science at Embry-Riddle.

The research examined what happens as a pilot prepares to land and switches from instrument-guided flight to visual flight. Pilot participants were selected from a collegiate flight-training program. During the experiment, pilots conducted an approach to landing in a Cessna 172S while a DJI Phantom IV quadcopter-type drone flew a scripted series of maneuvers along the approach path. Pilots were told that they might or might not encounter a drone.

“Dangerous close encounters between aircraft and drones are becoming an increasingly common problem,” Wallace said. “Statistics on pilot sightings of drones continue to increase year over year, and what is being reported by pilots is probably just the tip of the iceberg. The vast majority of the time, unmanned aircraft are not being seen by pilots.”

The study concluded that if a drone was spotted at the study’s maximum detection range of 2,324 feet, the pilot would have only about 21 seconds to avoid a collision. “That might be enough time if the drone was hovering in one spot, but not nearly enough if it’s in flight, headed for the aircraft,” said Dr. Matt Vance, assistant professor of aviation and space at Oklahoma State. “The situation is far more dangerous when both aircraft are moving,” he said. “Our eyes are attuned to movement. When a drone is not moving, it becomes part of the background.”

An aircraft’s final approach for landing is an especially risky time for a drone encounter because “it can catch you unaware and you have little time to react,” explained Dr. Jon M. Loffi, associate professor of aviation and space at Oklahoma State. “You don’t have the altitude to maneuver safely, and if an engine ingests a drone, that could bring the aircraft down.”

The study stated that the number of pilot-reported encounters with unmanned aircraft has been on the rise since 2014 when the Federal Aviation Administration (FAA) first started recording UAS encounter data. In 2018, UAS sightings climbed to 2,308 nationwide, a 90.7% uptick from just three years earlier, with 526 of those sightings encountered during the final approach phase of flight.

A video of the testing posted by the study’s researchers shows test aircraft approaching a runway, and asks the viewer to see if they can spot the encroaching drones.