Drone Risk to Airplanes “Minimal”, Mercatus Study Says

In a scathing response to the FAA’s exaggerated reports of drone sightings at airports, drone law researchers at the Mercatus Center of George Mason University have produced a new study about drone risk to airplanes.  The study uses bird strike data to estimate the risk of collision with an airplane.  While other studies have similarly used bird strike data, but then manipulated a mathematical assumption of how much more damage a dense material drone could cause, this study estimates first the likelihood of any collision actually taking place at all – and then calculates the likelihood of that collision being fatal to passengers.

Their answer: Once every 187 million years.

Researchers Eli Dourado and Samuel Hammond have published studies on drone regulation before, most recently publishing a paper concerning the benefits of the drone registration program.  Now they’ve taken on the premise that most regulation is based on: drones pose an extreme risk to passenger planes.

The report also takes issue with the FAA’s definition of “near misses” when it comes to airplanes sighting drones while in flight.  Pointing out that the overblown risk estimate served to garner support for heavy regulation,  researchers side with the Academy of Model Aircraft (AMA) in calling the FAA’s rhetoric “sensationalized.”

The FAA has based its rationale for a consumer UAS registry on a growing incidence of UAS sightings and “near misses.” As its docket argued, “Pilot reports of UAS sightings in 2015 are double the rate of 2014. Pilots have reported seeing drones at altitudes up to 10,000 feet, or as close as half-a-mile from the approach end of a runway. . . . The risk of unsafe operations will only increase as more UAS enter the national airspace.”

In a 2015 investigation, the Academy of Model Aeronautics (AMA) called the validity of these near miss reports into question. Of the 764 near miss incidents recorded by the FAA, the AMA found only 27, or 3.5 percent, were genuine UAS near misses. Instead, the FAA had been counting simple sightings as near misses—even when the operators were fully compliant with current UAS regulation. The FAA has also counted several cases where the pilot had explicitly reported that it was not a near miss, and more than a dozen cases where the flying object was officially unidentified. The AMA therefore accused the FAA of creating fuel for sensationalized and inaccurate media reports which, with the benefit of hindsight, helped build momentum for its rulemaking.

Calculating the probability of collisions based on a comparison of the bird population to the drone population, and then further calculating a damage probability based on the actual damage caused by birds, the researchers say that the risk that small drones pose to passenger aircraft is negligible.  Not only negligible, but meeting the FAA’s own definition of “acceptable risk.”

Given the tiny risk levels that recreational drones pose, the paper concludes with a recommendation for regulators: that they raise the regulation threshold from the current 2 kg to more reasonable weight limits as adopted in other regions:

Since the probability of any collision with any UAS is around 3.06×10−5 per 100,000 flight hours, countries that have even higher cutoffs for regulation than 2kg can be said to be acting responsibly. For example, the United Kingdom and Denmark have a 7kg threshold above which recreational UAS operators must inform their nearest air traffic controller or fly in an approved flying site. For registration, France recently moved to a 2kg threshold, while Canada still has a generous 35kg threshold.

Although UAS at the above thresholds are more likely to cause damage and injury than the 250g cutoff adopted by the FAA, we still estimate that the probability of a collision remains at an acceptable level.