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What happened

On the morning of 11 July 2013, a Sikorsky S-76C helicopter, registered VH-EXU, departed the heliport at Longford, Victoria on the first of a series of passenger ferry flights to a number of offshore platforms that were located throughout the Bass Strait oil and gas fields.

On departure from the Snapper platform for a return to Longford, the right engine failed. The helicopter descended rapidly toward the surface of the water.

The crew controlled the helicopter and secured the failed engine. In addition, in response to a right engine fire warning, the crew discharged fire extinguisher agent into the right engine compartment. A positive rate of climb was established and the helicopter was flown away before being escorted back to Longford by other company helicopters for a single-engine landing.

What the ATSB found

The engine failure was attributed to the fracture of a second-stage, high-pressure turbine blade. The liberated blade impacted and damaged adjacent blades with the resulting loss of power and associated increased vibration.

The engine and failed blade structure were inspected by the engine manufacturer. The manufacturer concluded that the failure was due to a combination of metal fatigue, blade creep and oxidation deposits. While a definitive cause for the blade fracture has yet to be determined, blade material, dimensional and quality assurance checks have ruled out any deficiencies.

In the absence of published data from the helicopter manufacturer, the operator had established helideck flight departure and approach profiles consistent with the performance capabilities of the helicopter. In this case, the lift-off from the helideck followed the operator’s standard departure profile. Given this profile, the helicopter descended to within 30 ft (9 m) of the sea surface during the recovery to stabilised flight.

What's been done as a result

In the absence of a conclusive cause of the blade fracture and remedial information, the operator imposed a service life limitation on their helicopters’ engine turbine assemblies that were fitted with the same blades. In addition, the engine manufacturer issued notifications to operators and introduced specific inspection requirements relevant to potentially affected turbine assemblies.

At the time of writing, the engine manufacturer was continuing its investigation into the cause of the blade fracture.

Safety message

This occurrence highlights how a situation can quickly change from normal operations to one where the flight crew have to deal with an in-flight emergency. In this respect, effective crew interaction, thorough pre-briefing and anticipation of what can go wrong has been shown to increase the likelihood of a successful outcome. Recovery from the engine failure and potential ditching, and return of the helicopter to Longford, reaffirms the benefits of those preparatory actions.

 

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The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

 
 
 

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General details
Date: 11 July 2013 Investigation status: Completed 
Time: 8:35 EST Investigation type: Occurrence Investigation 
Location   (show map):74 km east of Longford Occurrence type:Engine failure or malfunction 
State: Victoria Occurrence class: Technical 
Release date: 20 October 2016 Occurrence category: Incident 
Report status: Final Highest injury level: None 
 
Aircraft details
Aircraft manufacturer: Sikorsky Aircraft 
Aircraft model: S-76C 
Aircraft registration: VH-EXU 
Serial number: 760432 
Type of operation: Private 
Sector: Helicopter 
Damage to aircraft: Nil 
Departure point:Snapper Platform, Vic.
Destination:Longford, Vic.
 
 
 
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Last update 20 October 2016