The December 28 hard landing of a Sikorsky S-92A on a North Sea oil platform has prompted yesterday's Alert Service Bulletin (ASB 92-64-011) from the manufacturer that calls for a special one-time inspection of the tail rotor and bearing assemblies and a data check of the aircraft's health usage and monitoring system (HUMS).
It mandates an off-the-aircraft check of the tail-rotor pitch-change-shaft (PCS) bearing. Inspections are to be carried out immediately as aircraft are returned to base, and Sikorsky said it expected that the majority of inspections would be finished this week.
The new ASB comes after the December 28 incident, in which a CHC S-92A operating from Aberdeen spun upon landing on the Total West Franklin rig, damaging the helideck and the aircraft's landing gear. The operator CHC said the flight crew reported “unexpected control responses” on final approach and executed an emergency landing.
Additionally, the ASB follows an FAA emergency Airworthiness Directive on November 18 after a report of another S-92A losing tail-rotor authority. That AD called for inspecting helicopters with recently installed tail-rotor PCS assemblies before further or significant flight. Preliminary investigation of the incident helicopter that triggered the Emergency AD 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.