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Main Gearbox Malfunction/Collision with Water Cougar Helicopters Inc. Sikorsky S-92, C-GZCH

Main Gearbox Malfunction/Collision with Water Cougar Helicopters Inc. Sikorsky S-92, C-GZCH St. John’s, NL - March 12, 2009 Wendy A. Tadros, Chair Mark Clitsome, Director of Air Investigations Mike Cunningham, Investigator-in-Charge Jean-Marc Ledoux, Regional Manager Quebec.

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Main Gearbox Malfunction/Collision with Water Cougar Helicopters Inc. Sikorsky S-92, C-GZCH

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  1. Main Gearbox Malfunction/Collision with Water Cougar Helicopters Inc. Sikorsky S-92, C-GZCH St. John’s, NL - March 12, 2009 Wendy A. Tadros, Chair Mark Clitsome, Director of Air Investigations Mike Cunningham, Investigator-in-Charge Jean-Marc Ledoux, Regional Manager Quebec

  2. Photo of C-GZCH (occurrence aircraft). Source: Mark Stares 2008

  3. Wreckage Recovery and Examination

  4. Wreckage Recovery and Examination

  5. A complex equation of16 causes and contributing factors.

  6. TSB Safety Advisories • October 2009 Helicopter pilot helmets • December 2009Survival suits • December 2009Automatic oil bypass system • March 2010Emergency flotation systems

  7. Flight Path

  8. Contributing Factors • Ambiguous Emergency Procedure • Knowledge of Helicopter System • Crew Simulator Training • Ditching in a Hostile Environment

  9. Photo of C-GZCH (occurrence aircraft). Source: Mark Stares 2008

  10. S-92 OccurrenceAustralia, July 2008 • S-92 loses oil from main gearbox. • Cockpit warnings, crew reaction very similar to Flight 91 accident. • Safe landing 7 minutes later.

  11. Galling • Damaged titanium studsfound. • Thread galling from repeatedremoval/re-installation. • Titanium does not withstand wear from metal on metal contact very well. • More frequent oil filter changes than expected. Damaged titanium stud from another Cougar Helicopters S-92

  12. After Australia S-92 Occurrence Fall 2008 • Mandatory enhanced inspection of titanium studs. January 2009 • Alert Service Bulletin to replace titanium studs with steel within 1250 flight hours or 1 year. Cougar Helicopters • Ordered steel studs. • Did not perform enhanced inspections of titanium studs from Fall 2008.

  13. Helicopter Certification • Main gearbox must be able to run without oil for at least 30 minutes. • To enhance landing opportunities. • Sikorsky was confident S-92 could meet this requirement.

  14. Helicopter Certification • Main gearbox failed after 11 minutes during test. • Rule includes clause that test not required if failure shown to be extremely remote. • Oil cooler most likely failure route. Bypass valve added. • Oil filter bowl and its fasteners not assessed.

  15. Four Recommendations • All S-92 helicopters to meet a 30-minuterun dry • The FAA to decide if even 30 minutesis enough time • Transport Canada to restrict flights wherethe helicopter’s flotation system is not up to the task for the sea conditions that day; and • Emergency breathing equipment on flights where survival suits are required

  16. 16 factors were at play that day.

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