Studies for drone regulations accelerated the pace for the assessment of risk for drone operations. A recently published ‘Annual Safety Review 2017′ discusses the aviation accidents in detail containing a chapter specialized for drones. This report by EASA, involves the data from European Central Repository (ECR) experienced by EASA member states.
With the increase in the number of drones and possibly raising consciousness on reporting occurrences, the numbers of non-fatal accidents raised by 470% in 2016 relative to 2011-2015 average, luckily maintaining zero fatalities. Most of the times, it is commercial airliner pilots to report the occurrences, and rarely the UAS pilot.
The prior key risk areas has been investigated and aircraft upsets is by far the most common cause of the occurrences and set as the first key risk to address for safe integration of drones into airspace. 50% of RPAS accidents falls in this case which often results in a damage or destruction of UAS following loss of the control of the drone by the pilot.
Second key risk area is airborne collision although it is rarely encountered due to probable frequency with exponential increase in the number of drones. Obstacle collision is the 3rd risk area which will tend to increase with integration of drones especially in urban areas.
Ref : https://www.easa.europa.eu/system/files/dfu/209735_EASA_ASR_MAIN_REPORT_2017.pdf