This one can fly with just one rotor running: https://youtu.be/gfkRCzgHGq8 https://youtu.be/gfkRCzgHGq8 Admittedly it would be a pretty terrifying ride to the

This one can fly with just one rotor running: https://youtu.be/gfkRCzgHGq8 https://youtu.be/gfkRCzgHGq8 Admittedly it would be a pretty terrifying ride to the ground, but preferable to plummeting. There’s a lot of rotational energy in the aircraft though. I think there’s probably significant scope for improvement in redundancy of these systems.