With the amount of battery power required to keep them in the air for a reasonable length of time, I've often heard them described as "flying cinder blocks". O

With the amount of battery power required to keep them in the air for a reasonable length of time, I've often heard them described as "flying cinder blocks". Often the injury concerns come not from propeller blade cuts, but a lithium battery getting dropped on someone's head from 200ft when it loses charge unexpectedly.