Abstract: A mounting arrangement for the fan rotor of a ducted fan engine includes a first drive which supports and rotates the fan under normal operating conditions but which includes a frangible connection which breaks when an excessive out-of-balance force is applied to the fan rotor for example after loss of one or more blades. A second supporting and driving structure is provided which has built-in transverse flexibility but which can transmit torque. This structure is redundant during normal operation of the engine but comes into use when the frangible connection is broken and allows the fan rotor to rotate eccentrically around a new axis in an inverted condition.