April 2, 2008 | Mark Paradies

Safety Alert Passed on From OGP

OGP SAFETY ALERT

SAFETY ALERT NO. 189:
SIKORSKY S76A+ AND S76A++ HELICOPTERS


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Time incident occurred: 

Type of Activity: 
Transport – Air
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Applicabale Filter Categories: 
Air transport

Applies to BHP Billiton contracted Sikorsky S76A+ and S76A++ helicopters fitted with Turbomeca Ariel 1S or 1S1 engines.

Sikorsky S76 twin engine helicopters equipped with Turbomeca Ariel 1S or 1S1 engines are fitted with engine overspeed sensors designed to shutdown an engine to prevent catastrophic damage in the event of an engine overspeed. Once an engine has been shutdown by this protection system it cannot be restarted in flight as the overspeed protection system is inaccessible to the flight crew and can only be reset on the ground. The overspeed protection is incorporated into a component known as the Tachometer Box with two installed on each helicopter, one for each engine.

What Went Wrong?:

BHP Billiton has experienced two separate over water in flight engine shutdowns resulting from false overspeed indications. In both events the helicopter was flown back to an onshore location and landed safely with the one remaining operative engine. Investigation by the engine manufacturer, Turbomeca, revealed that failures of the overspeed protection system resulted from ingress of moisture and internal corrosion.


Corrective Actions and Recommendations:

In response to the failures on BHP Billiton contracted aircraft and other known events, Turbomeca has developed a replacement Tachometer Box with improved sealing to address the issue of moisture ingress and internal corrosion. The replacement of existing Tachometer Boxes with the improved part is recommended by Turbomeca in Service Bulletin 292 77 0330 for helicopters operating in humidity saturated environments which is typical of BHP Billiton offshore petroleum operations.

Sikorsky S76A+ and S76A++ helicopters that are not compliant with Service Bulletin 292 77 0330 Incorporation of Modification TU 330) by 10 July 2008 shall not be used by BHP Billiton.

BHP Billiton assets using or are likely to use Sikorsky S76A+ or S76A++ helicopters are to verify helicopter operators have incorporated Modification TU 330 before using these helicopters beyond 10 July 2008.

Click here to download entire alert including Turbomeca service bulletins (pdf 155kb).

Source Contact:

Stan Medved
Aviation Safety Manager
BHP Billiton
+61 3 9609 3018

Joe Gross
Aviation Adviser
BHP Billiton Petroleum
+1 713 499 5452

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