Courtesy of Aircontactgruppen
An FAA Emergency Airworthy Directive has been issued for some Sikorsky S-92As. It is limited to all models with tail rotor pitch change shafts that have less than 80 hours time in service. The AD also requires that any such shaft assembly with less than five hours time in service since new or overhaul be removed from service.
The Nov. 18 issuance follows a report of an operator losing tail rotor control while hovering. Signs of excessive heat were found in a preliminary investigation, which helped determine that binding in the tail rotor pitch change shaft assembly’s double row angular contact bearing was the cause. As required by the emergency AD, all tail rotor pitch change shaft assemblies that have five or more hours time in service receive a one-time borescope and visual inspection of the area in question to determine the condition of the bearings.
Such inspections should for items like damaged bearings and seals, purged grease with any metallic particles from the bearings and radial play in the bearings. Correct installation of the white Teflon seals, snap rings, and cotter pin should also be checked, as well as determination of whether there is free rotation in the angular contact bearing.
These inspections are required within 20 hours time in service or before reaching 80 hours (whichever comes first) for pitch change shaft assemblies with more than 15 hours time in service. All defective tail rotor pitch change shafts should then be removed before aircraft are put back into service. Alternate methods of compliance may be proposed.