The report of a Sikorsky S-92A operator losing tail rotor authority while in a hover has prompted the FAA to issue Emergency Airworthiness Directive 2016-24-51, which calls for inspecting helicopters with recently installed tail rotor pitch change shaft (TRPCS) assemblies before further or significant flight, dependent on the flight hours since the assembly was installed.
Preliminary investigation of the incident helicopter found that binding in the assembly's double-row angular contact bearing reduced tail rotor control. It also found evidence of excessive heat, an indicator of a binding bearing.
Because bearings fail rapidly under these conditions, the emergency AD is limited to assemblies with less than 80 hours' time in service. It requires removal of all new or rebuilt assemblies with five or fewer hours' time in service; boroscoping assemblies with five to 15 hours; and inspecting all assemblies with between 15 and 80 hours within the next 20 flight hours before reaching 80 hours' time in service (whichever comes first).
Assemblies with evidence of damage must be replaced. Alternative methods of compliance can be approved by the FAA’s Boston Aircraft Certification Office.