Multi-copters with fixed-pitch, variable-RPM rotors are unable to auto-rotate in the event of motor failure. However, when the aircraft has more than four rotors there exists a level of control redundancy that may allow the aircraft to tolerate the failure of one or more control effectors. This redundancy can be exploited in the control system design such that the aircraft can be recovered or complete the mission after the failure of a control effector. Provided sufficient redundancy, control systems may be designed that require no reconfiguration post-failure, making use of multirotor coordinate control inputs. In the event that failure causes the aircraft to go unstable or uncontrollable, more advanced control design techniques can be used to return the aircraft to the desired trajectory for recovery or completion of the mission task.
