Great points Rick.
What it will come down to is a set of numbers for probability-of-failure by category of severity. FAA will set forth the figures, and when the systems are able to achieve them reliably, passenger UAVs will be certified safe by the FAA. Standard failure analysis in engineering involves quantifying failure possibilities in gory detail, nothing new, and all the possibilities will be considered. No pilot-less airplane flies until everything is considered and assigned risk numbers per likelihood of occurring. It is closed- loop, exact science for the most part.
Human flight is more risky as far as unresolvable unknowns are concerned, and we do see quite a few human failures every year. Mechanized flight is pretty wild when it fails, but again it is easier to know how it will fail. It is only machinery programmed to move around using known principles of Newtonian physics, which is not out of the realm of present scientific knowledge. Cost, and need are the larger unknowns.
Last edited by Cubdriver; 11-30-2012 at 04:16 PM.