SAFETY CONSIDERATIONS FOR OPERATION OF UNMANNED AERIAL VEHICLES IN THE NATIONAL AIRSPACE SYSTEM Roland E. Weibel and R. John Hansman Report No. ICAT-2005-1 March 2005 MIT International Center for Air Transportation Department of Aeronautics & Astronautics Massachusetts Institute of Technology Cambridge, MA 02139 USA 2 SAFETY CONSIDERATIONS FOR OPERATION OF UNMANNED AERIAL VEHICLES IN THE NATIONAL AIRSPACE SYSTEM by Roland E. Weibel and R. John Hansman Abstract There is currently a broad effort underway in the United States and internationally by several organizations to craft regulations enabling the safe operation of UAVs in the NAS. Current federal regulations governing unmanned aircraft are limited in scope, and the lack of regulations is a barrier to achieving the full potential benefit of UAV operations. To inform future FAA regulations, an investigation of the safety considerations for UAV operation in the NAS was performed. Key issues relevant to operations in the NAS, including performance and operating architecture were examined, as well as current rules and regulations governing unmanned aircraft. In integrating UAV operations in the NAS, it will be important to consider the implications of different levels of vehicle control and autonomous capability and the source of traffic surveillance in the system. A system safety analysis was performed according to FAA system safety guidelines for two critical hazards in UAV operation: midair collision and ground impact. Event-based models were developed describing the likelihood of ground fatalities and midair collisions under several assumptions. From the models, a risk analysis was performed calculating the expected level of safety for each hazard without mitigation. The variation of expected level of safety was determined based on vehicle characteristics and population density for the ground impact hazard, and traffic density for midair collisions. The results of the safety analysis indicate that it may be possible to operate small UAVs with few operational and size restrictions over the majority of the United States. As UAV mass increases, mitigation measures must be utilized to further reduce both ground impact and midair collision risks to target levels from FAA guidance. It is in the public interest to achieve the full benefits of UAV operations, while still preserving safety through effective mitigation of risks with the least possible restrictions. Therefore, a framework was presented under which several potential mitigation measures were introduced and could be evaluated. It is likely that UAVs will be significant users of the future NAS, and this report provides an analytical basis for evaluating future regulatory decisions. This document is based on the thesis of Roland E. Weibel submitted to the Department of Aeronautics and Astronautics at the Massachusetts Institute of Technology in partial fulfillment of the requirements for the degree of Master of Science in Aeronautics and Astronautics. 3 4 Acknowledgements This work was supported by the Presidential Fellows program at MIT, and the National Aeronautics and Space Administration/ Federal Aviation Administration Joint University Program under grant number SAA-95-G-017. The authors wish to thank the participants in the program for providing valuable feedback and advice. The authors would also like to thank Dr. Jim Kuchar at MIT Lincoln Labs, Phil Potter of the FAA, Matt DeGarmo at MITRE, Ryan Schaeffer at SRA International, and Dr. John Appleby of Aurora Flight Sciences for providing guidance and insight from within the UAV field. Thanks to Alex Mozdzanowska, Philippe Bonnefoy, Laura Major Forest, Helen Jiang, Tom & Hayley Reynolds, and Jonathan Histon of MIT’s International Center for Air Transportation for technical insight and support. 5 6 Table of Contents 1 Introduction 15 1.1 Objective..........................................................................................................15 1.2 Motivation........................................................................................................15 1.3 Approach..........................................................................................................18 2 Background 19 2.1 Expanding Role of Military UAV Operations.................................................19 2.2 Effort Toward Civil UAV Operations .............................................................21 3 Key Issues in UAV Operations in the NAS 23 3.1 NAS Overview.................................................................................................23 3.1.1 Visual and Instrument Flight Rules .....................................................24 3.1.2 Airspace Classifications.......................................................................24 3.2 Air Traffic Management System .....................................................................26 3.2.1 Current System.....................................................................................26 3.2.2 General UAV System ..........................................................................27 3.2.3 Potential UAV Architectures ...............................................................28 3.2.4 Architectures of Example UAV Operations ........................................32 3.3 UAV Performance Capabilities .......................................................................35 3.3.1 Potential Classifications.......................................................................36 3.3.2 Performance Analysis..........................................................................37 3.4 Representative Aircraft for Classification .......................................................40 4 Regulatory Bases for Civil Operation of Unmanned Aircraft 43 4.1 Legal Basis for FAA Regulation of Aircraft....................................................44 4.2 Mechanisms for Safety Regulation..................................................................46 4.3 Current Unmanned Aircraft Rules...................................................................47 4.3.1 Model Aircraft.....................................................................................47 4.3.2 Moored Balloons, Kites, Unmanned Rockets, and Unmanned Free Balloons ...........................................................................................................49 4.3.3 Certificate of Authorization .................................................................51 4.4 Conclusions......................................................................................................52 7 5 System Safety Analysis 53 5.1 Risk Assessment Methodology........................................................................53 5.1.1 Severity Classifications........................................................................55 5.1.2 Likelihood of Occurrence....................................................................57 5.2 Empirical Levels of Risk .................................................................................58 5.2.1 Ground Fatalities..................................................................................58 5.2.2 Midair Collisions.................................................................................61 5.3 UAV Risk Analysis Approach.........................................................................62 6 Ground Impact Hazard Analysis 65 6.1 Ground Impact Model......................................................................................65 6.2 Model Limitations............................................................................................67 6.3 Model Application ...........................................................................................68 6.4 Results..............................................................................................................69 6.5 Conclusions......................................................................................................74 7 Midair Collision Hazard Analysis 77 7.1 Collision Rate Formulation..............................................................................77 7.2 Data Source......................................................................................................79 7.3 Average Midair Collision Risk over the United States....................................79 7.4 Airway Structure..............................................................................................80 7.4.1 Regions Investigated............................................................................81 7.4.2 Data Transformation ............................................................................82 7.5 Midair Collision Risk in the Vicinity Airways................................................82 7.5.1 Jet Routes.............................................................................................82 7.5.2 Victor Airways.....................................................................................85 7.6 Conclusions......................................................................................................87 8 Ground Impact and Midair Collision Risk Mitigation 89 8.1 Need for Mitigation..........................................................................................89 8.2 Risk Mitigation Strategies................................................................................89 8.2.1 Possible Mitigation Measures of Ground Impact Risk........................89 8.2.2 Possible Mitigation Measures of Midair Collision Risk......................91