Abstract: A rotor assembly comprising a drive shaft 13 mounted in a first bearing means 22 at a location spaced from a first end of the shaft 13 and supported at the first end by a support means 23 which is more flexible in bending and in torsion than the drive shaft 13. The support means 23 is mounted for rotation in a second bearing 24 which is co-axial with the first bearing 22. A rotor 10 is connected to the first end of the drive shaft 13 to be driven thereby, and is also supported directly in the second bearing means 24 through a frangible coupling 33. The frangible coupling 33 is designed to break the connection between the rotor 10 and the second bearing means 24 only when the rotor 10 is subjected to a predetermined out-of-balance load to allow the rotor 10 and drive shaft 13 to run inverted.

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.