As the number of drones in US national airspace continues to rise, with projections of as many as one million drones sold during this Christmas season, the number of close encounters between unmanned and manned aircraft is increasing as well, according to a new study.
Although there has yet to be a collision between a drone and a manned aircraft, a new study, Drone Sightings and Close Encounters, released Friday by The Center for the Study of the Drone at Bard College identified 327 close encounters involving drones flying dangerously closed to manned aircraft.
Using data from the Federal Aviation Administration (FAA) and Department of Interior, the report explored 921 incidents in the national airspace from December 2013 to September 2015. Of these incidents, 594 involved drone sightings near manned aircraft flight paths, but not close enough to pose immediate danger of collision.
In 28 instances, pilots “maneuvered to avoid a collision with a drone.”
The report defined “close encounters" as incidents where a drone comes within 500 feet of a manned aircraft, when a pilot declares a “near midair collision.” A sighting, on the other hand, is when “a drone is spotted above its legal ceiling or in the vicinity of an airport or aircraft, but does not pose a clear potential for a collision.”
The majority of all incidents occurred above 400 feet, the maximum altitude at which drones are allowed to fly, according to FAA regulations, and within five miles of an airport, which is prohibited airspace for all drones.
“This report adds a critical layer of detail and context to the conversation on the use of drones at home,” said Dan Gettinger, codirector of the Center for the Study of the Drone, and coauthor of the report. “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 proliferation of drones has spurred serious safety concerns. Homeland Security Today recently reported that with the surge in drone popularity, pilots have reported an increase in close calls between planes and drones, with nearly 700 incidents reported in this year alone. In 2014, the number of close calls was only at 238.
According to the report, eight times as many incidents were reported in the first seven months of 2015 than in the same period in 2014.
An FAA spokesperson told the report’s authors that there were 137 reports in October 2015 alone. Explaining the reason for the uptick, the spokesperson said, “You are hearing about more incidents due to a combination of factors: There are more drone users and there is also more awareness by the pilot and air traffic controller communitieswho report incidents.”
One of the most significant challenges to integration of UAS into national airspace is the potential that one could hit a passenger plane. Just this summer, two passenger airplanes narrowly avoided collision with a drone while approaching one of the nation’s busiest airports, John F. Kennedy International Airport in New York.
Last year, Homeland Security Today reported that a small drone nearly collided with an NYPD helicopter over the George Washington Bridge.
Although it is impossible to predict the actual impact of a major collision, the possible consequences are significant. A team of engineers at the Crashworthiness for Aerospace Structures and Hybrids (CRASH) Lab at Virginia Tech conducted simulations of a small unmanned aircraft being ingested into a turbofan engine.
They found that a 3-foot diameter drone, if ingested into a 9-foot diameter turbofan engine, could potentially cause up to three of the engine blades to fail, and might result in loose debris moving around the engine chamber at speeds of up to 700 miles per hours. These factors, the team concludes, could cause engine failure.
“Once an engine has ingested a drone, it will suffer from a minimum of operational stability issues, to a maximum of thrust loss due to catastrophic failure,” the CRASH team stated.
The study notes that as the number of incidents grows, the need for solutions becomes more urgent. The report proposed a number of solutions, including geo-fencing—a system that uses software to limit where unmanned aircraft can fly—and sense-and-avoid systems which allow unmanned aircraft to autonomously detect a potential collision with another aircraft and take evasive action.
Other solutions include implementing a traffic management platform that keeps drones and aircraft separate, registration of drones, and education campaigns targeted at drone operators.
“With more and more drones entering our airspace, ‘Drone Sightings and Close Encounters’ will serve as a reliable resource for policymakers and the industry as they work to develop strategies and solutions to address the growing number of potentially dangerous incidents between manned and unmanned aircraft,” said Gettinger. “Our hope is that this study can help engender a collaborative dialogue among stakeholders working on this issue.”
