A rotorcraft having multiple rotors, and wings that provide lift in forward flight, has mechanical coupling between rotors that can be disengaged and optionally reengaged, during flight. The coupling can, which can prevent a failure of one rotor from interfering with rotation of the other rotor(s), can be accomplished using many different types of devices, including for example, dog clutches and friction clutches, and collapsible clutches. Disengagement can range from being completely under control of an operator, to partially under operator control, to completely automatic. Among many other benefits, designing, manufacturing, fitting, retrofitting or in some other manner providing an aircraft with a device that can disengage rotation of one of the rotors from that of another one of the rotors during flight can be used to improving survivability in an emergency situation.