Recently, Cessna released Mandatory Service Bulletin SB560XL-27-34, which calls for the inspection or replacement of the aft elevator trim cables. Many Cessna aircraft have already replaced these cables during normal maintenance with the newest cables available, due to cable fraying. Although this new cable is an improved design, there is an additional item that can be accomplished to improve the Flight Control system.
Cessna now also has a new pulley available for the aft location where the cables make the 90 degree turn out to the trim actuators. This pulley is a larger diameter which makes it necessary to also replace the mounting brackets. This larger pulley will relieve the bend radius of the cable which, when combined with the new cable, can improve the longevity of the cable. Installing the larger diameter pulleys is an optional item and currently it is found only as a note in the IPC and can be easily overlooked.
Although this adds some labor and parts to the job, in the end we feel that installing the larger pulleys with the new cable ensures that the system is improved to the best possible design.
If you have any questions about this Service Bulletin, contact your Duncan Aviation Citation Tech Rep.