Many beneficial civilian applications of commercial and public small unmanned aircraft systems (sUAS) in low-altitude uncontrolled airspace have been proposed and are being developed. Associated with the proliferation of civil applications for sUAS is a paradigm shift from single-UAS visual operations in restricted airspace to multi-UAS beyond visual line of sight operations with increasing use of autonomous systems and operations under increasing levels of urban development and airspace usage. Ensuring the safety of sUAS operations requires an understanding of associated current and future hazards. This is challenging for sUAS operations due to insufficient mishap (accident and incident) reporting for sUAS and the rapid growth of new sUAS applications (or use cases) that have not yet been implemented. These applications include imaging, construction, photography and video, precision agriculture, security, public safety, mapping and surveying, inspections, environmental conservation, communications, parcel delivery, and humanitarian efforts such as delivery of medical supplies in developing nations. This paper will summarize research results in the identification of: 1.) Current hazards through the analysis of sUAS mishaps; and 2.) Future hazards through the analysis of a collection of sUAS use cases. The mishaps analysis will include the identification of mishap precursors and an analysis of their individual contributions to the mishaps as well as an analysis of worst-case hazards combinations and sequences. The future hazards are identified through an assessment and categorization of use cases for sUAS, the identification of associated paradigm shifts in terms of operations and new vehicle systems (both cross-cutting and for specific use case categories), the determination of future potential hazards (relative to the vehicle, ground control station, operations, and UTM system) arising from these paradigm shifts, and future potential impacts and outcomes (relative to the vehicle, other vehicles, people, ground infrastructure, and the environment). Key findings from these analyses are also summarized. The analysis results are then used to develop a set of combined (current and future) hazards for assessing risk.

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(anteroposterior view) showing small uterine arteries (arrowed).escape of about 2 litres of infected liquor amnii and a volume of gas. A subtotal hysterectomy and excision of the sac was performed. The patient was maintained on intravenous fluids and antibiotics and she made a good recovery. She was discharged frI hospital after six weeks, and six weeks later she was welL Cases 3, 4, and 5 These three cases were identical in presentation and were all extrauterine pregnancies complicated by a pyogaseous infec The pregnancies were all postmature, with subsequent fetal death and failed induction of labour. The radiological findings (Fig. 3) confirmed pyogaseous infections similar to that in Case 2. CommentIn early cases of gas gangrene or pyogaseous infection of the uterus the features are those of septicaemia, which may lead to circulatory failure and death, as in Case 1. Extension of gas gangrene from the uterus to the peritoneum leads to peritonitis. Other complications are emphysematous vaginitis, thrombophlebitis, lymphangitis, and renal failure (Adams and Adams, 1931; Holly et al., 1960). The principles of treatment are early diagnosis, prompt prophylaxis, early elimination of the focus of infection, massive antisera administration, and systemic antibiotic therapy.The prognosis depends mainly on the extent and duration of the infection, early diagnosis and treatment, and the degree of kidney damage. Hill (1936) reported a mortality of 63% in 30 cases of postabortal and puerperal gas gangrene. Russel and Roach (1939) were the first to report the use of x-ray examination in the diagnosis of gas gangrene of the uterus. The presence of air and fluid in large amounts, as in the present cases, indicates sepsis by gas-forming organisms, since the gas is more than would be seen in cases of uncomplicated fetal death. Radiography is the diagnostic method of choice. It 1S quick and reliable, and thus ensures early and prompt surgical intervention to eliminate the focus of infection. Bacteriological examination of vaginal discharge or of a vaginal swab and blood cultures, though useful, may prove negative. Moreover, the results are usually delayed.We are grateful to Professors J. P. Hendrickse and 0. A. Ojo for permission to report these cases, and to Professor S. P. Bohrer for the use of the radiological museum and for his helpful criticisms.