North Sea S-92 Accident Report Released by AAIB

by Matthew Beres, Airborne Retrofit & Modernization Analyst, Forecast International.

The United Kingdom’s Air Accidents Investigation Branch (AAIB) has released a Special Bulletin regarding an S-92 accident on December 28, 2016, at the North Sea’s West Franklin wellhead platform.

The initial investigation focused on the tail rotor and its components. Immediately, it became apparent that the tail rotor servo piston was damaged. Removing  the servo revealed  the tail rotor pitch change shaft (TRPCS) double row angular contact bearing to be in a severely distressed condition.

Here’s a breakdown of what happened:

Here’s a breakdown of what’s being done:

The Operator will:

  • Review all HUMS data to ensure no anomalies
  • Provide fleet-wide borescope inspections
  • Require  HUMS to be serviceable before flight
  • Reduce time between HUMS download/analysis to a five-hour maximum

Sikorsky will:

  • Provide a one-time inspection of the TRPCS and bearing assembly for ratcheting, binding, and rough turning
  • Compliance is essential and is to be accomplished prior to the next flight from a maintenance facility
  • Enforce a three flight-hour limit before return to a maintenance facility
  • Require operators  under Temporary Revision 45-03 to use S-92 HUMS ground station software to review Tail Rotor Gearbox energy analysis Condition Indicators for alert conditions on a reduced flight-hour interval
  • Records in excess of published alert levels will require inspection of the pitch change shaft and bearing

Both the AAIB and Sikorsky are continuing to examine the accident, including the relevant helicopter components. More details will be provided as information becomes available.

Please feel free to use this content with Forecast International and analyst attributions, along with a link to the article. Contact Ray Peterson at +1 (203) 426-0800 or via email at for additional analysis.

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About Richard Pettibone

A military history enthusiast, Richard began at Forecast International as editor of the World Weapons Weekly newsletter. As the Internet grew in importance as a research tool, he helped design the company's Forecast Intelligence Center and currently coordinates the EMarket Alert newsletters for clients. Richard also manages social media efforts, including two new blogs: Defense & Security Monitor, covering defense systems and international issues, and Flight Plan, which focuses on commercial aviation and space systems. For over 30 years, Richard has authored the Defense & Aerospace Companies, Volume I (North America) and Volume II (International) services. The two books provide detailed data on major aerospace and defense contractors. He also edits the International Contractors service, a database that tracks all the contractors involved in the programs covered in the FI library. More recently he was appointed Manager, Information Services Group (ISG), a new unit that encompasses developing outbound content for both Forecast International and Military Periscope.

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