Part 107, the rule broadly authorizing commercial UAS (drone) operations, was an important step forward for the commercial UAS industry.  However, Part 107 limited operations in important ways.  One significant limitation surrounds flights over people.  Under current FAA regulations, flights over people other than the UAS flightcrew are prohibited.  This prohibition creates significant obstacles for commercial UAS operators, especially those that typically need to occur in more urban and suburban environments, such as media and newsgathering activities, real estate, infrastructure inspection and, someday, package delivery, will require the flexibility to operate over people.

Over the last several months, the FAA has drafted a flights over people rule, yet to be released.  The agency has approved only one company thus far – CNN – to fly a drone over people.  In the background, there has been an ongoing technical discussion:   What actually happens if a small drone falls out of the sky and hits a person on the ground?

A new report published by a consortium of universities through the Alliance for System Safety of UAS through Research Excellence (ASSURE) has studied the issue, and its findings – released just a few days ago — suggest there is less risk to people than the FAA had previously considered.  ASSURE’s research findings are significant because they appear to support broader regulatory approvals for flights over people.

ASSURE researchers conducted a wide range of UAS crash tests and reviewed over 300 publications from the automotive industry, consumer battery market, toy standards, and other fields.  To better understand how being struck by a UAS could cause injury, the research team dropped UAS on  automotive crash test dummies to measure impact forces and the amount of kinetic energy (KE) transferred to a person during a collision.  The potential for blunt force trauma, penetration and laceration injuries for specific impact KEs and impact angles was evaluated using injury metrics established by the National Highway Traffic Safety Administration (NHTSA).

Crash test dummies
Source: Final Report for the FAA UAS Center of Excellence Task A4: UAS Ground Collision Severity Evaluation, Revision 2

The research and crash test data showed that multi-rotor UAS fall more slowly than the same mass of metal due to higher drag coefficients and because UAS have unique features that reduce KE transfer during a collision and therefore the likelihood of injury.  To illustrate the effect, researchers compared the probability of sustaining a serious neck injury from being struck with a DJI Phantom 3 versus pieces of steel and wood weighing the same amount and traveling at similar impact speeds.  The tests showed that an average probability of sustaining a serious neck injury for both steel and wood was 67% and 66%, respectively, whereas the Phantom 3 only presented a 12.5% chance of a serious neck injury.  Researchers found that several key features of UAS, including construction with plastic materials that flex, deform and sometimes break, act to absorb energy and dissipate impact forces.  These findings suggest that there may be less risk to people on the ground from a falling UAS than what prior studies considered by the FAA found.

While the FAA’s Notice of Proposed Rule Making (NPRM) for UAS operations over people has been delayed over agency security concerns, the ASSURE research findings should influence future rulemaking efforts for UAS flights over people.

In the near term, companies applying for Part 107 waivers to allow flights over people should closely review the ASSURE report, as some of its findings may be helpful in building a safety case necessary to grant a waiver for flights over people.  The ASSURE report also contains a wealth of information that UAS manufacturers may want to consider, from a vehicle design and safety standpoint.  This is particularly true for manufacturers of UAS intended to be operated near and around people in urban and suburban environments.