Follows Multiple Reports Of Issues With Tail Rotors

The FAA has issued an emergency AD (2016-24-51) following three reports of operators losing tail rotor (TR) control caused by a failed tail rotor pitch change shaft (TRPCS) assembly bearing.

Following the first two reports, the FAA issued and subsequently published as a final rule Emergency AD 2016-24-51 (81 FR 95425, December 28, 2016). That AD applies to Sikorsky Model S-92A helicopters with a TRPCS assembly that has less than 80 hours time-in-service (TIS) with bearings that were manufactured prior to November 3, 2016. Emergency AD 2016-24-51 is intended to address an unsafe condition with low-time bearings by requiring removal of TRPCS assemblies that have less than 5 hours TIS and one-time inspections for certain conditions.

Since Emergency AD 2016-24-51 was issued, a third report of an S-92A helicopter losing TR control was reported, and a preliminary investigation determined that the bearing failed despite having more than 80 hours TIS. The FAA has determined that the unsafe condition can exist on TRPCS bearings regardless of hours TIS. Therefore, this Emergency AD applies to all TRPCS assemblies.

This Emergency AD requires a one-time visual inspection and a repetitive borescope inspection of the TRPCS assembly bearing. The repetitive inspection is intended to detect bearing deterioration. The actions in this Emergency AD are intended to detect a binding bearing, prevent loss of TR control, and possible loss of control of the helicopter.

The Emergency AD requires, before further flight, removing the TRPCS assembly and inspecting the bearing. If the bearing does not rotate freely; the bearing sounds rough or chatters; there is any purged grease with metal particles; a nick or dent; or if there is a cut, tear, or distortion in the bearing seal, before further flight, replacing the TRPCS assembly is required. It also requires, within 10 hours TIS, and thereafter at intervals not to exceed 10 hours TIS, inspecting the TRPCS assembly with a borescope. If the white Teflon seal or snap ring is missing, or if there is a rip, tear, or heat damage on the seal or if there is no gap in the snap ring, replacing the TRPCS assembly is required before further flight.

The FAA considers this Emergency AD to be an interim action. If final action is later identified, it might consider further rulemaking at that time.

(Image from file)

FMI: Emergency AD