Final Report for the FAA UAS Center of Excellence Task A4: UAS Ground Collision Severity Evaluation Revision 2 Mr. David Arterburn, Principal Investigator – [email protected] Director, Rotorcraft Systems Engineering and Simulation Center The University of Alabama in Huntsville Dr. Mark Ewing – [email protected] Associate Professor and Director of the Flight Research Laboratory The University of Kansas Dr. Raj Prabhu – [email protected] Professor, Department of Agricultural and Biological Engineering Mississippi State University Dr. Feng Zhu – [email protected] Assistant Professor, Mechanical Engineering Department Embry-Riddle Aeronautical University Dr. David Francis – [email protected] Post-Doctoral Researcher, Center for Advanced Vehicular Systems Mississippi State University SECURITY STATEMENT: There is no classified or proprietary information in this report. DISTRIBUTION A: Distribution is unlimited 1 Legal Disclaimer The information provided herein may include content supplied by third parties. Although the data and information contained herein has been produced or processed from sources believed to be reliable, the Federal Aviation Administration makes no warranty, expressed or implied, regarding the accuracy, adequacy, completeness, legality, reliability or usefulness of any information, conclusions or recommendations provided herein. Distribution of the information contained herein does not constitute an endorsement or warranty of the data or information provided herein by the Federal Aviation Administration or the U.S. Department of Transportation. Neither the Federal Aviation Administration or the U.S. Department of Transportation shall be held liable for any improper or incorrect use of the information contained herein and assumes no responsibility for anyone’s use of the information. The Federal Aviation Administration and U.S. Department of Transportation shall not be liable for any claim for any loss, harm, or other damages arising from access to or use of data or information, including without limitation any direct, indirect, incidental, exemplary, special or consequential damages, even if advised of the possibility of such damages. The Federal Aviation Administration shall not be liable to anyone for any decision made or action taken, or not taken, in reliance on the information contained herein. 2 Revision History Revision Description of Change Release Date - Initial Release as required by Contract 27 Oct 2016 - Changed footnotes to first citing only unless second reference is included in Figures or Tables throughout document - page 12 – changed eighteen knowledge gaps to twenty three knowledge gaps in the overview. - page 15 changed "but where pre-approved." to "but were pre- approved." In the first paragraph of section 1.2.2 - page 20 changed “to combined” to “to be combined” at the end of the second paragraph of 2.4.6 - page 22 changed “it important” to “It is important” on the second paragraph of section 2.5.1 - page 23 Table 5 change “should” to “Shoulder” in the first row of the Upper Limbs section - page 27 reference 41 was changed from http://www.faa.gov/uas/publications/media/Micro-UAS-ARC-FINAL- Report.pdf to 1 8 Mar 2017 https://www.faa.gov/uas/resources/uas_regulations_policy/media/Micro- UAS-ARC-FINAL-Report.pdf due to the FAA changing the location of the document. - page 28, section 2.7 changed rate of "3.57x10-3 fatalities per flight hour" to rate of "3.57x10-8 fatalities per flight hour" - page 46,47 Figure 6,7 and 8 updated with complete legends - page 84, section 4.9 changed "most baseball fatalities (25 (58 percent) were" to “He was able to confirm 104 deaths with baseball accounting for 43 (41 percent) of them. .…. Of the 43 total baseball fatalities, 25 (58 percent) were due to blows to the head.” - page 85, Section 4.9.1 changed “where” to “were” in the paragraph below Table 32 - page 86, section 4.10.1 deleted rotational energy equation and moment of inertia equation since these equation were already introduced in Equation 5 and 6. Updated all follow-on numbering for equations including those in the text. - page 87, paragraph below Figure 24 “k3” was changed to k3 Added a new Figure and Table based upon comments from the FAA following Peer Review and Public Release preparation. Figures 23 and Table 29 were added to show the results of steel and wood impact studies 2 28 Apr 2017 that were conducted after completion of the A4 Task. Edits to the paragraphs were made to discuss the results shown in Figure 23 and Table 29. Added legal disclaimer per FAA request. 3 Acknowledgements: The following researchers in addition to the respective university Principal Investigators shown on the title page made fundamental contributions to the content of this UAS Characteristics White Paper, the Ground Collision Final Report and the dialogue with the FAA A4 Project Management Office, Micro-Air Advisory Rulemaking Committee, and UAS Science and Research Panel during the first half of this project – Dr. Brian Landrum (UAH), Mr. Christopher Duling (UAH), Mr. Nishanth Goli (UAH), Mr. Drew Darrah (KU), and Mr. Eric Bodlak (KU). The A4 team would like thank the following Program Managers and subject matter experts from the FAA – Mr. William Oehlschlager, Mr. Wes Ryan, Mr. Christopher Swider, Mr. Paul Campbell, Mr. Ben Walsh, Mr. Paul Albuquerque and Mr. Paul Rumberger. The A4 team also recognizes the vital importance of the exchange of ideas with the A3 Air Collision Severity Evaluation team members including Mr. Tom Aldag, Task A3 Principal Investigator, and Dr. Robert Huculak, Wichita State University, and Dr. Doug Cairns, Montana State University, as well as the continued dialogue with the ASSURE Leadership throughout this project. 4 Executive Summary The UAS Ground Collision Severity Evaluation Final Report documents the UAS platform characteristics related to the severity of UAS ground collision based upon the literature search of over 300 publications from the automotive industry, consumer battery market, toy standards, and other fields. The literature search included existing standards from a variety of industries and applications as well as methods of analysis and criteria currently in use by other civil and federal agencies. Space debris casualty models were evaluated and extended for proposed use with UAS to determine their viability for ground collision severity assessments and metrics. Parametric analysis, summary data and modified methods are presented to provide insight on the most significant UAS characteristics and how such characteristics are related to the ground collision severity problem. Qualitative characteristics as well as quantitative metrics are presented. Data and Analysis developed during the Task A11 research is also included to update data collected in the early phases of Task A4. Where needed, knowledge gaps are identified for topics outside the scope of the current research. The literature search included the evaluation of various criteria developed for human blunt force trauma injuries, penetration injuries and laceration injuries. These injury types represent the most significant threats to the non-participating public and crews operating mUAS and sUAS platforms. The kinetic energy for the worst case terminal velocity or maximum cruise airspeed, energy density, and rotor diameter are the most significant UAS characteristics contributing to blunt force trauma penetration and laceration injuries, respectively. Two impact kinetic energy methodologies are presented to provide a risk and scenario based approach to determining kinetic energy thresholds for safe UAS operations. Parachute mitigations and the application of area weighted kinetic energy methodology for two scenarios are presented to outline thresholds for a broader range of vehicle weights to conduct flight over people than is currently possible with the unmitigated vehicle designs currently available. An initial investigation of energy transfer based on crash testing and dynamic modeling was conducted along with finite element analysis for human head and torso impacts. The crash test results and subsequent analysis strongly suggest that RCC-based thresholds are overly conservative because they do not accurately represent the collision dynamics of elastically-deformable sUAS with larger contact areas in comparison to the metallic debris analysis methods for high speed missiles on the national test ranges. Dynamic modeling is necessary to improve the assessment of UAS failure modes and associated impact energy, to establish appropriate standoff distances, to model impact footprints for severity analysis and to conduct probability assessments as part of an applicant’s submission for waiver or certification. Lithium Polymer batteries dominate the mUAS and sUAS market as the principle energy source for these platforms. While many of the manufacturers state they test their batteries in accordance with Lithium Ion battery testing methods for consumer electronics, the batteries are rarely marked to show compliance with these standards and many of the test methods are not consistent with the forces and energy levels associated with ground collision impact energy. More research is required to address the fire hazard and impact hazard presented by the broad spectrum of batteries and battery chemistries used in mUAS and sUAS platforms. Twenty-three knowledge gaps were identified during the execution of the literature search and are recommended for future research efforts. 5 Table of Contents Executive Summary ................................................................................................................................