E. DESCRIPTION
Following an in service event, this Service Bulletin requires an urgent check of the proper installation and functionality of the Tail Rotor servo-actuator feedback lever installation and interface on the back end of the component.
Incorrect installation may lead to loss of Tail Rotor control which, depending on the flight condition, could lead to loss of control of the aircraft.
Feedback on the compliance to this Service Bulletin is required
3. Perform a visual inspection of the input lever of the TR servo-actuator:
3.1 With reference to Figure 1 and Figure 2 perform an in situ inspection of the nut (60), the cotter pin (50), the lock-wire and the hinge bracket element (90) connected to the lever feedback link (110) for condition and absence of damage.
3.2 Check the connection elements of the input lever (110) of the TR servo-actuator taking particular care on the lever feedback link.
Murphy, there are possibilities as you suggest. The wording of the SD is perhaps not ideal and certainly doesn't detail any specific potential fault or assembly mistake, and maybe that is for a reason; the intention being to ensure that all ships have the components in place and correctly installed in good condition, not to support speculation about actual cause of the accident. However the SD also doesn't mention that washer with the other components.
Nothing to do but wait...