>The fully autonomous Elroy is and designed for densely populated areas
Where do they expect something like this to land? Densely populated areas are not known for having plenty of open/empty spaces for something with spinning blades to land. Existing heliports? Those are not typically near anything convenient, except maybe the pads on top of buildings. However, this has a max altitude of 60 feet, so it can't reach those.
I don't think this could be a winning design: it's inefficient because it's really like a helicopter.
IMHO, the ones with some sort of small wings and horizontal propellers have way more chance to succeed. Efficiency during horizontal travel is much better - and this is position where you spend most time - as well as increased max speed and lower noise during travel.
The pitch of the blades is fixed (if I believe the photos from their website), so the variations in lift is simply controlled by the variation in speed of the given rotor. This is just like any hobby quad/hex/octo/younameit-copters out there.
That means you can't reverse the pitch to gain angular momentum from a fall, and therefore, implement autorotation like a "traditional heli" can.
You do have multiple rotors for redundancy (in case one of them fails), but that's not going to protect you from a complete power failure of course if that power source is global.
You can increase safety by providing each rotor with its own independent power source.
Where do they expect something like this to land? Densely populated areas are not known for having plenty of open/empty spaces for something with spinning blades to land. Existing heliports? Those are not typically near anything convenient, except maybe the pads on top of buildings. However, this has a max altitude of 60 feet, so it can't reach those.