Near-miss crash study leads ERAU researchers to recommend drones fly further from airports

An Army helicopter was crossing New York Harbor six years ago when it was struck by a drone weighing just over 3 pounds, the first such crash between an uncrewed aerial system and a piloted aircraft in the United States.

While only a bit more than 1 foot in diameter, the DJI Phantom 4 drone was no apparition. It damaged the Black Hawk's rotor blade, window frame and transmission deck.

The helicopter pilot was able to safely land, but the crash reverberated across the aviation community, echoing the potential dangers posed by the rapidly growing use of drones.

Since 2017, there have been a handful of other collisions. While none were catastrophic, a research project headed by Embry-Riddle Aeronautical University faculty has found that eight near misses occurred annually at one Texas airport over a three-year period. The same study included a recommended change to Federal Aviation Administration rules. governing the use of drones near the corridors where aircraft take off and land.

A few months later, Ryan Wallace joined Embry-Riddle Aeronautical University as an assistant professor of aeronautical science with an eye on continuing his research into how to keep airspace safe from the proliferation of drones.

Assessing the problem for researchers was a problem in itself. The only data available to assess near-crashes were reports filed to the FAA by pilots who might have seen a drone during a flight and estimated its distance.

Wallace assembled a team, including ERAU professors Scott Winter and Stephen Rice plus research assistant Sang-A Lee and David Kovar, the founder and CEO of URSA Inc., an unmanned and robotics systems analysis company. They found a more objective and accurate way to fill gaps of knowledge in how common near-crashes are and where they are most likely.

How to replay more than 2 million flights

The researchers worked with data from the Dallas-Fort Worth International Airport, which had partnered with a company to use a drone-detection device on an antenna above one of its concourses. The device captured signals from every drone within a 30-mile radius.

"We can use those signals and interpret those signals so that we can tell what the drone is doing: the altitude and telemetry," Wallace said in an interview with The News-Journal. "And we can fuse that data with another source of FAA data from the ADS-B (Automatic Dependent Surveillance-Broadcast), signals that most aircraft have that allow us to see what they are doing. Their telemetry and altitude ran together like a movie to tell in time where drones are in relation to the aircraft."

In addition to ADS-B, the FAA's upgrade from radar technology, the researchers also used Mode S messages transmitted by aircraft. They were able to access that data from the OpenSky Network, a Switzerland-based nonprofit that makes real-time air traffic control data available to the public.

URSA’s Airspace Awareness Platform helped the researchers visualize the interactions between drones and aircraft. It helped them to identify instances where a drone came within 500 feet of an aircraft. That was the standard Wallace and the researchers used to define near-miss crashes.

Near-miss crashes rare, but noteworthy

In all, the ERAU team considered more than 1.8 million piloted aircraft operations and nearly 460,000 drone flights between August 2018 and July 2021.

In that time, it found 24 near misses, according to the team's research paper, which was peer-reviewed and published by the Society of Automotive Engineers in the SAE International Journal of Aerospace.

"In all of these cases, one of them had been recognized by the crew of the aircraft and reported to the FAA," Wallace said.

Rice, one of the researchers and an ERAU professor of human factors, said the same three small drones were responsible for 13 of the 24 near-miss encounters, according to a university news release. In all but one of the near misses, the drone was operating at an altitude higher than 400 feet.

That is typically the FAA's maximum, although it is lower for drones operating within five miles of an airport.

The mean distance between the drones and aircraft in the 24 near misses was 215 feet, while commercial airliners were involved in nearly half of the near misses.

If the ratio of FAA-reported near-miss sightings to actual near misses at DFW held true nationwide in 2021, the number of actual near misses would top 62,000.

Wallace said he's not surprised at the number of near misses because reliance on human observation is guaranteed to lead to underreported encounters.

"You have aircraft going at a high rate of speed, and it may only be a flash for them," he said. "In many cases, where the drone is at, relative to their (peripheral vision), they may not see anything."

Growing number of drones in sky

The number of small drones operating in U.S. airspace was expected to grow from nearly 1.5 million in 2020 to nearly 2.4 million in 2025, according to the FAA.

Flights of larger drones, those greater than 55 pounds, are also forecast to nearly double between 2021 and 2026, according to an FAA report.

“The proliferation of drones, particularly ones available to the general public, poses obvious risks,” Rice said, according to a university news release. “Unfortunately, not all drone operators are responsible, knowledgeable or safety-minded. Many of them are not even aware of the rules they must follow.”

Recommendation to FAA

The researchers found that most near misses occur within 1.5 miles of a corridor for arrivals and departures. They are recommending extending the runway exclusion zones for drones from about 1 mile to 3.5 miles, providing more protection for aircraft when they are flying below 500 feet, Wallace said.

Of the 24 near misses detected by the researchers at DFW, seven involved helicopters. All seven were within 1.25 miles of a heliport. So Wallace and his team recommended extending heliport geofencing zones − areas that trigger warnings to drone users − from 500 meters to 1.5 miles.

In a statement, the FAA told The News-Journal it continuously evaluates risk in the National Airspace System.

"This includes input from our air traffic professionals and pilots as well as from reports from educational institutions such as Embry-Riddle Aeronautical University," the FAA statement said.

In addition to an array of existing policies and programs aimed at drone safety, the FAA is working with five airports to "evaluate technologies and systems that could detect and mitigate potential safety risks posed by drones." Testing at airports in Atlantic City, New Jersey; Columbus, Ohio; Syracuse, New York; Huntsville, Alabama; and Seattle, Washington, continues through Sept. 30, 2023.

Wallace said he has not heard directly from the FAA about his study's recommendations.

"We're very pleased to contribute to the conversation about safety," he said. "We believe (our work) provides additional data points to make informed decisions about the protection of aircraft."

This article originally appeared on The Daytona Beach News-Journal: ERAU researchers uncover 24 near-miss drone-aircraft crashes near DFW