UAS Ground Collision Severity Evaluation Revision 2
Conclusions That Could Result in Revisions to Part 107
A major contention between the regulators and the drone community has been the threat posed to innocent bystanders to a collision with a sUAS. The above very visible incidents were cited by the pro-regulator proponents. The FAA’s own Center of Excellence has issued conclusions which may/should result in revisions to Part 107.
Final Report for the FAA UAS Center of Excellence Task A4: UAS Ground Collision Severity Evaluation Revision 2 was issued by the University of Alabama in Huntsville (UAH), the University of Kansas (KU), Mississippi State University (MSU) and Embry-Riddle Aeronautical University (ERAU). The CoE Task A4 concluded:
The A4 team has reviewed the available research and techniques used to address blunt force trauma, penetration injuries and laceration injuries that present the most significant threats to the non-participating public and crews operating sUAS platforms. The most significant of these characteristics related to ground collision severity are:
1) The impact KE and impact orientation based upon a specific vehicle is the most significant metric for evaluating blunt force trauma injuries. Blunt force trauma is the most likely cause of fatalities due to UAS collisions for mUAS and sUAS with the exception of single rotor helicopters whose blade mass and blade speed present a lethal impact threat. Impact KE can be easily estimated and measured, based on vehicle velocity, during testing.
2) The energy density parameter is the best metric for evaluating the possibility of penetration injuries caused by sharp edges or small impact areas in the vehicle design. This parameter is very challenging to measure during testing.
3) Rotor diameter is the metric for severity of injury from rotors and propellers to define when blade guards or other protective measures are required to prevent laceration injuries (which is the most likely type of injury to occur). Single rotor helicopter configurations present a potentially lethal threat to the throat and head area due to the blade mass and speed of larger single rotor helicopters. Rotor diameter is easily measured.
Or as explained in the executive summary—
“Collision dynamics of [sUASs] is not the same as being hit by a rock…Multi-rotor UAS fall slower than metal debris of the same mass due to higher drag on the drone. UAS are flexible during collision and retain significant energy during impact. Wood and metal debris do not deform and transfer most of their energy.”
The CoE study does not address the regulatory implication of their more sophisticated analysis. The comparison of a drone’s impact versus suggests that the threat of injury, as estimated by the four universities, is less than the risk assessment which was the basis of the safety parameters of the final Part 107.
Almost a year ago (June 21, 2016) after much research, drafting, policy palpitations and internal/external reviews, the FAA issued Operation and Certification of Small Unmanned Aircraft Systems. In order to authorize a new form of aviation, the FAA was mandated to assess the risk of these aircraft operating in the NAS and near people and property.
Years before the final promulgation, the FAA chartered an Aviation Rulemaking Committee to advise on Small Unmanned Aerial Systems. That 74 page report analyzed risks and their conclusions were included in the final rule. The ARC indicated that its judgments were subject to an A internal Safety Risk Analysis. Thus, the safety parameters relied upon in the final NPRM may have been too restrictive. The CoE work product should trigger a review of the Part 107 limitations.
There was a lot of analytical work done to assess the consequences of a sUAS being ingested by an airline turbine. Perhaps the CoE parameters should be inserted into those studies?
There may be some technical reason why the CoE report neither mentioned nor recommended changes to Part 107. It would seem that such a review should be started forthwith. The reassessment of the drone-turbine interaction may not be as compelling.