The global Sikorsky S-92 fleet is again subject to mandatory inspections after the Lockheed Martin-owned manufacturer issued an Alert Service Bulletin (ASB) on January 10 requiring all operators of the type to undertake one-off inspections.
The off-aircraft inspections of the tail rotor pitch change shaft and bearing assemblies, required to be performed before the next flight, and a specific check of the Health and Usage Monitoring System (HUMS) data are in response to an incident involving an S-92A on December 28 2016 when the helicopter lost tail rotor authority and spun while landing on an offshore platform in the UK’s North Sea.
The helicopter, operated by CHC, landed safely and shut down with no injuries to the passengers or crew.
While stressing that the S-92s were not grounded, Sikorsky said it estimated that the mandatory inspections would take approximately 11 hours to complete and that the majority of operators would complete their inspections within 24-48 hours depending on their operational tempo.
“Safety is our number one priority and Sikorsky is working closely with our customer and investigative authorities to determine the root cause of the loss of tail rotor authority,” said Sikorsky in a statement.
“We have communicated additional guidance to S-92 operators regarding HUMS usage and will continue to provide information as it becomes available.”
In late November 2016, the US Federal Aviation Administration (FAA) issued an emergency airworthiness directive (AD) for all Sikorsky S-92A tail rotor pitch change shaft assemblies to help prevent loss of tail rotor control and possible loss of control of the helicopter.
This directive was prompted after an S-92 operator reported losing tail rotor control while the helicopter was in a hover.
In August 2007, the FAA also issued an AD for inspecting S-92A tail rotor pitch change shaft and bearing assembles.