Micro UAS

Micro UAS Rules. Big Impact?

Are drones allowed to fly over crowds of people?


A potential answer to this question was recently presented by the Micro Unmanned Aircraft Systems (“UAS”) Aviation Rulemaking Committee (“ARC”) convened by the Federal Aviation Administration (“FAA”).

By way of background, on February 23, 2015, the FAA issued a Notice of Proposed Rulemaking (“NPRM”) detailing proposed rules for the operation and Certification of Small Unmanned Aircraft. (The final rules are likely to be issued in June or July of 2016 in 14 C.F.R. Pt. 107.)  The Small UAS NPRM contemplated a micro UAS classification, and to further evaluate a separate regulatory framework for these micro gadgets, the FAA tasked the ARC with considering “recommendations for a performance-based standard that would allow for micro UAS to be operated over people who are not directly participating int he operation of the UAS or under a covered structure.”

On April 6, 2016, the ARC, composed of UAS industry stakeholders, released its final report and recommendations (dated April 1, 2016). In a consensus – not unanimous – report, the ARC identified four small UAS categories (for the moment referred to as Category 1, 2, 3, and 4). What separates each category is the “risk threshold that correlates to either a weight or an impact energy equivalent and, to the extent necessary to minimize the risks associated with that category, additional performance standards and operational restrictions.”

Header Micro Rules FAA

In a nutshell: The proposed micro UAS rules envision a risk-based analysis where the decision to allow a drone to fly depends on the weight of the drone and the probability that the drone would cause an injury if it directly impacted (read fell on) a person on the ground.

In this framework, micro drones weighing 250 grams or less (Category 1) may operate “directly above” one or more persons. The ARC “believes that the level of risk of injury posed by this category of UAS is so low that no performance standards and no operational restrictions beyond those imposed by the proposed Part 107 are necessary.” In contrast,    “[u]nder Categories 2, 3, and 4, a small UAS may operate over people if it does not exceed the impact energy threshold specified for each category, as certified by the manufacturer using industry-consensus methods, and if its operator complies with operations restrictions specified for each category.”

The idea of risk in this framework borrows from the “Abbreviated Injury Scale” (“AIS”) developed by the Association for the Advancement of Automotive Medicine (“AAAM”). In this scheme, an AIS level of 3 on a scale would correspond to a “serious” injury (where 1=minor and 6=maximal).

Importantly, the ARC recommendations are in addition to the forthcoming Pt. 107 rule.  As such, the ARC micro UAS report deals with drones that “fall down, impacting a person. Risk posed to people on the ground by lateral impacts, such as a forward-speed loss-of-control scenario, are already addressed by proposed part 107.”

In differentiating injuries from falling drones as opposed to forward moving drones, the ARC was presented with a study showing that the kinetic energy-based injury calculation was overstated as it relates to UAS.  That is, drones generally tumble and fall on impact, resulting in only an average 38% kinetic energy transfer.  Compare that to a streamlined, aerodynamic baseball that falls on a fan in foul territory – 100% transfer.


Bottom line: The ARC has set out a considered framework that looks to industry to fill in the blanks through self-certification and industry custom and practice:

“For a particular model of small UAS to qualify for operations over people, the manufacturer of that model will therefore have to certify that the product’s impact energy, as measured by a test established by industry consensus standards body, does not, in the most probable failure modes, exceed a specified threshold. The intent of the test should be to establish the typical or likely impact energy of the most probable failure mode, and not simply the worst case condition.”

A summary of the recommendations: