Date of Award


Document Type


Degree Name

Master of Science in Aviation - Applied Aviation Safety



First Advisor

Deborah Carstens

Second Advisor

Stephen Cusick

Third Advisor

Heidi Hatfield Edwards


Over the last few years, the use of unmanned aerial systems (UAS) has significantly increased. With an increase in the use of UASs, the number of UAS sightings near manned aircraft and airports have also increased, as shown by the Federal Aviation Administration (FAA)(FAA, 2019a). Although not every near sighting had a severe consequence associated with it, the risks were still present. As UASs are becoming more readily available to the general public, the risks present due to UASs flying in the National Airspace System (NAS) and near airports is also increasing. For the study, incident and accident reports were obtained from the National Transportation Safety Board (NTSB) and the Aviation Safety Report System (ASRS) databases. After the reports were downloaded, reports that did not have information regarding UASs were discarded. Two instrument forms were developed, one for NTSB reports and one for ASRS reports. Next, qualitative content analysis was used to identify the most frequently occurring Human Factors Analysis and Classification System (HFACS) of the contributing factors and probable cause(s) of the reported incident or accident. After the HFACS categories were identified for the NTSB and ASRS reports, all the incidents that had a similar chain of events were grouped for representation in the Bow-tieXP software. After the analysis, a total of seven bow-tie diagrams were created with each representing the identified event identified from the content analysis. The bow-tie diagrams helped identify the threats that could lead to the occurrence of the top event. If the top event occurred, the consequences arising from them were documented. The bow-tie diagram also helped identify barriers that could be used so that the risks associated with each threat and consequence were mitigated. After the bow-tie diagrams were completed, recommendations were made for safe operations of UASs in the NAS and airports.


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