Aviation safety investigations & reports

In-flight engine failure involving Sikorsky S-76C helicopter, VH-EXU, Snapper Platform, Bass Strait (74 km east of Longford, Victoria), on 11 July 2013

Investigation number:
AO-2013-124
Status: Completed
Investigation completed

Final Report

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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.

 

Download Final Report
[Download  PDF: 2.58MB]
 
 
 

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 level: Defined - click for an explanation of investigation levels  
Location   (show map): 74 km east of Longford    
State: Victoria   Occurrence type: Engine failure or malfunction  
Release date: 20 October 2016   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

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.  
Last update 14 November 2018