Main Gearbox Malfunction/Collision with Water Cougar Helicopters Inc. Sikorsky S-92, C-GZCH
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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
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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. - PowerPoint PPT Presentation
Transcript of Main Gearbox Malfunction/Collision with Water Cougar Helicopters Inc. Sikorsky S-92, C-GZCH
Main Gearbox Malfunction/Collision with WaterCougar Helicopters Inc. Sikorsky S-92, C-GZCH
St. John’s, NL - March 12, 2009
Wendy A. Tadros, ChairMark Clitsome, Director of Air Investigations
Mike Cunningham, Investigator-in-ChargeJean-Marc Ledoux, Regional Manager Quebec
Photo of C-GZCH (occurrence aircraft). Source: Mark Stares 2008
Wreckage Recovery and Examination
Wreckage Recovery and Examination
A complex equation of16 causes and contributing factors.
TSB Safety Advisories• October 2009
Helicopter pilot helmets
• December 2009Survival suits
• December 2009Automatic oil bypass system
• March 2010Emergency flotation systems
Flight Path
Contributing Factors
• Ambiguous Emergency Procedure
• Knowledge of Helicopter System
• Crew Simulator Training
• Ditching in a Hostile Environment
Photo of C-GZCH (occurrence aircraft). Source: Mark Stares 2008
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.
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
After Australia S-92 OccurrenceFall 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.
• 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.
Helicopter Certification
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.
Four Recommendations1. All S-92 helicopters to meet a 30-minute
run dry
2. The FAA to decide if even 30 minutesis enough time
3. Transport Canada to restrict flights wherethe helicopter’s flotation system is not up to the task for the sea conditions that day; and
4. Emergency breathing equipment on flights where survival suits are required
16 factors were at play that day.
