A new study by researchers at Embry-Riddle Aeronautical University of flights by DJI-manufactured small unmanned aircraft systems (sUAS) over Daytona Beach in Florida over a 13-day period suggests many more sUAS flights are taking place than previously thought, according to the paper’s lead author.

Additionally, by far the bulk of the 192 DJI drone flights analyzed operated over built-up areas—often very near aerodromes—rather than near unimproved land; and 21.5 percent flew at altitudes above the maximums imposed by the FAA for the FAA UAS Facility Map (UASFM) areas in which they were being flown. “The data gathered suggests that more than one in five of these drone flights presented an unmitigated risk to nearby manned aviation operations,” the study found.

Ryan Wallace, the lead author of the study, told AIN, “In my personal opinion, [the study’s findings] would suggest that helicopter operations and aerial application would be the most vulnerable” manned-aviation activities as regards potential collisions with sUAS drones, “because they tend to share the same lower altitudes as drones. This is why we’re seeing reports of lots of helicopters in very close proximity” to drones in flight.

The 192 sUAS operations detected by the researchers using a DJI AeroScope were flown by 73 different sUAS vehicles, and 177 or 93.7 percent of the flights operated in designated UASFM areas. Of those flights, 126 flew in the Daytona Beach International Airport Class C Surface Area. Additionally, 184 (nearly 97 percent) of the 190 drone-flights the researchers analyzed in total flew within 5 statute miles of an aerodrome.

Altogether 48.7 percent of the flights operated over residential neighborhoods and 21.5 percent over commercial, industrial, or public properties—including the Daytona International Speedway. “This was an unexpected finding,” said Wallace. “We thought most drone operators would choose relatively open areas offering a safety buffer from hazards, but that wasn’t the case.”

In “perhaps the most egregious finding among the dataset,” one sUAS flew at an altitude of 90 feet above mean sea level (msl) within 0.25 nm of the approach path to Daytona Beach International Airport’s Runway 7L just seconds after a manned aircraft had flown past, the study reported. “Assuming the pilot was performing the published ILS approach, the aircraft would have crossed the Runway 7L threshold crossing at a height of 58 feet agl (88 feet msl). It is highly probable that the aircraft descended through the UAS altitude while on approach.”

Another drone flew only 475 feet away from and at “nearly co-altitude” with a manned aircraft flying just offshore and parallel to the Daytona Beach shoreline. The manned aircraft probably was towing a banner and so would not have been able to perform an evasive maneuver easily, according to the researchers.

Wallace told AIN the researchers have subsequently performed as-yet-unpublished studies of drone operations near other U.S. airports surrounded by Class B or Class D airspace. This has shown them that Daytona Beach “may or may not be representative” of all other US urban areas for numbers of drone flights, “but the amount of drone activity [overall] is likely to be much higher than we had anticipated,” he said. Drone activity in the Class B and Class D airspace areas studied was at levels “equal to or even greater” than at Daytona Beach.