A report released on Friday paints a disturbing picture of how dangerous the skies can be when they are populated by both drones and manned aircraft.
The report from the Center for the Study of the Drone at Bard College identified 327 "close encounters" in U.S. airspace from December 2013 to September 2015 in which drones presented a hazard to manned aircraft. Of that total, at least 241 incidents met the Federal Aviation Administration's definition of a near-collision — two aircraft flying within 500 feet of each other. Ninety of the close encounters involved commercial jets.
Moreover, most of the incidents occurred in FAA-prohibited drone airspace — above 400 feet, and within five miles of an airport.
"This report adds a critical layer of detail and context to the conversation on the use of drones at home," said Dan Gettinger, co-director of the center and co-author of the report along with Arthur Holland Michel. "We are looking to furnish stakeholders and the public with a reliable, data-driven guide to the potential risks posed by drones to manned flight."
The study analyzed data from the FAA and the Department of Interior over the past two years. It defined "close encounters" as incidents where a drone comes within 500 feet of a manned aircraft, when a pilot declares a "near midair collision," when a pilot takes evasive action, or when the pilot uses descriptive language (such as "almost hit") that indicates the drone was way too close for comfort. There were no documented collisions.
In addition to the "close encounters," the researchers tallied another 594 "sightings," in which drones were spotted near or within manned aircraft flight paths but did not pose immediate danger.
The FAA did not immediately respond to a request for comment on the report. The agency has been working on coming up with regulations governing the operation of unmanned aircraft.
According to the study, New York City had the most "close encounters" — 83 (including nine incidents around Newark Airport, in New Jersey), followed by Los Angeles, with 39, and Miami, with 24.
The Bard College researchers said the incidence of close calls has surged in the past year as sales of consumer drones have taken off. And even more drones will be buzzing the skies next year — several hundred thousand to as many as 1 million drones are expected to be sold this holiday season.
As to how to prevent further close calls, the study suggests a variety of solutions. They include geo-fencing (using software to limit where unmanned aircraft can fly), "sense-and-avoid" systems that allow drones to autonomously detect a potential collision and take evasive action, registration of drones (something the FAA has already said it will implement) and education campaigns targeted at drone operators.
"Preventing the kinds of incidents that could potentially pose a threat to public safety will likely involve a combination of approaches, and will most definitely depend upon the collaboration of a multitude of stakeholders," the authors concluded.