[aannoonn]

In regards to turning on the z-axis to be able to land with engine failure, I believe User is referring to Autorotation: http://en.wikipedia.org/wiki/Autorotation

[gcr]

I thought autorotation was only useful if you're moving ahead very fast (high ground speed) while also falling. Is that right? Most drones are essentially hovering much of the time.

[robotresearcher]

No, it's not autorotation. Here's a lovely demo:

https://www.youtube.com/watch?v=ek0FrCaogcs&feature=youtu.be