Being hit in the head by a drone won't necessarily end in decapitation. Thanks to aeronautical boffins, we know now that there is a range of possible outcomes.
Not content to let the US Federal Aviation Administration ponder drone drubbings – something the agency did in April – researchers from Virginia Tech and State University have come to some very unsurprising conclusions about drone injury scenarios, albeit under the imprimatur of a peer-reviewed journal.
The research, titled "Ranges of Injury Risk Associated with Impact from Unmanned Aircraft Systems," published this month in the Annals of Biomedical Engineering, examines what happens when drones of varying weights – DJI Phantom 3, DJI Inspire 1, and DJI S1000+, ranging from 1.2kg (2.6lb) to 11kg (24.3lb) – fly into and are dropped on people's heads.
Incidents of this sort have been reported and presumably will continue. The US domestic drones accident database mostly documents property damage, but it also contains accounts of injuries. Last year, for example, a drone documenting a wedding in Windham, New Hampshire, crashed into the crowd, resulting in concussion, stitches and lawsuit.
The flying impact test was conducted on a Hybrid III test dummy at speeds ranging from 16 metres per second (36 miles per hour) to 22 metres per second (49 miles per hour). The drop impact test was conducted from a height of 5.5 metres (18 feet), using a powered-down drone (no rotating propellers).
The researchers – led by Steven Rowson, an assistant professor of biomedical engineering and mechanics, and Stefan Duma, professor of engineering and interim director of the Institute for Critical Technology and Applied Science – concluded that the consequences of being hit by a drone vary.
But a drone dropping on your head looks more likely to do harm than a drone delivered horizontally.
"The maximum risk of AIS 3+ injury associated with live flight tests was 11.6 per cent, while several falling impact tests estimated risks exceeding 50 per cent," the paper says. "Risk of injury was observed to increase with increasing UAS mass, and the larger models tested are not safe for operations over people in their current form."
Got that? Heavier drones can be expected to do more damage.
AIS here refers to the Abbreviated Injury Scale, which grades injury severity on a scale of 1 to 6, with 3 being serious and 6 being unsurvivable.
Live flight tests were unlikely – less than 5 per cent – to produce a concussion. Having a drone drop atop one's head however offers a more certain path to that outcome: The estimated risk of concussion for being beneath a 24-lb DJI S1000+ when it plummets was 100 per cent.
Despite the obviousness of the sentiment, the researchers rather coyly conclude that having heavy objects hovering overhead might be ill-advised.
"Given that many of the falling impact tests resulted in estimated risk of injury over 50 per cent, further consideration to the maximum mass threshold should be taken if UAS are to be permitted to operate over people," the paper says.
The researchers intend their data, like car crash tests, to help define what represents an acceptable level of risk for drones. A safety standard, they observe, "does not imply that products are injury-proof. People still die in car crashes and football players still occasionally die due to head injury."
So too will they die from drone collisions – to say nothing of drone strikes – just not very often, if the rules that emerge from this process end up being both effective and observed. ®