An incident at or near hover is close to the ground, and so has much better chances of survival. The issue with multiple rotors is that if one rotor fails the

An incident at or near hover is close to the ground, and so has much better chances of survival. The issue with multiple rotors is that if one rotor fails the craft immediately pitches over and crashes. The Chinook solves this because the two rotors have a linked shaft. Definitely a quadrocopter becomes unstable with only 3/4 rotors. Maybe the octocopter posted elsewhere in this thread can sustain one failure and still land.