Aviation safety investigations & reports

Engine failure during take-off involving Bombardier Dash 8, VH-ZZE, at Darwin Airport, Northern Territory, on 11 November 2019

Investigation number:
AO-2019-060
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

Download Final report
[Download  PDF: 814KB]
 

What happened

On 11 November 2019, at about 1510 Central Standard Time, a Bombardier DHC-8-315 aircraft, registered VH-ZZE and operated by Surveillance Australia, was about to start the take-off roll from Darwin Airport, Northern Territory, on a surveillance flight. There were four crew on board.

The aircraft was on the departure runway with the brakes on. Power was applied to both engines, but when take-off power was reached, and prior to the release of the brakes, the crew heard a loud bang. The take-off was aborted, and air traffic control advised the crew of smoke from the right engine. After reviewing the engine instrumentation, the crew shut down the engine and returned the aircraft to the maintenance hangar.

A subsequent inspection of the runway identified metal fragments behind the aircraft’s take‑off position. An external inspection of the right engine revealed significant damage to the power turbine (PT) assembly.

What the ATSB found

The PT shaft of the aircraft's right engine fractured due to fatigue cracking, resulting in secondary damage and engine failure. The fatigue cracking initiated at corrosion pitting, which was probably associated with prolonged low‑altitude operation in a marine environment.

The PT shaft originally installed in the engine was replaced during its first overhaul in 2011 due to excessive corrosion pitting. However, the finding of corrosion was not escalated by the maintenance organisation to Pratt & Whitney Canada (P&WC), possibly due to the informal reporting process at the time (this process was replaced in 2018 with formal guidance and criteria for reporting such findings).

The ATSB investigation also identified that the PT shaft in Pratt & Whitney Canada PW100 series engines operating in certain marine environments is susceptible to corrosion pitting, which can grow undetected between scheduled inspections, increasing the risk of shaft fracture and engine failure.

What has been done as a result

Pratt & Whitney Canada advised the ATSB that it had commenced a review of historical overhaul experience of the PT shaft in an effort to identify which engines and operators are potentially exposed to an increased risk of PT shaft corrosion.

In addition, P&WC has proposed a range of safety action to address the safety issue concerning corrosion-related fracture of PT shafts in PW100 series engines that should complement its formalised reporting. This includes considering a borescope inspection of the PT shaft between overhauls during hot section inspections (HSI) with defined corrosion inspection criteria. A method to remove contaminants from inside the shaft during service is also being investigated. Additional mitigating action for engines within the PW100 engine fleet that have completed an HSI, but are potentially exposed to the risk of PT shaft corrosion, is also being assessed.

While the proposed actions should address the safety issue, no timeline for their implementation was provided. As such, the ATSB has issued a safety recommendation to P&WC to support the proposed action.

Safety message

The corrosion-related fracture of the power turbine shaft of the aircraft’s engine in this occurrence highlights that corrosion pitting that exceeds repair limits on safety‑critical components should be a warning sign to manufacturers, maintainers, and operators that the existing maintenance strategy may not be effective.

Additionally, manufacturers should provide guidance and criteria to maintenance organisations for assessing and reporting corrosion on safety‑critical components. This enables identification of whether the maintenance strategy is effective or if changes are required to reduce the risk of in‑service failures.

Download Final report
[Download  PDF: 814KB]
 
 
 

The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

Safety Issue

Go to AO-2019-060-SI-01 -

Power turbine shaft corrosion

The power turbine shaft in Pratt & Whitney Canada PW100 series engines operating in certain marine environments is susceptible to corrosion pitting, which can grow undetected between scheduled inspections. This increases the risk of shaft fracture resulting in engine failure.

Safety issue details
Issue number: AO-2019-060-SI-01
Status: Open – Safety action pending
General details
Date: 11 November 2019   Investigation status: Completed  
  Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): Darwin Airport   Investigation phase: Final report: Dissemination  
State: Northern Territory   Occurrence type: Engine failure or malfunction  
Release date: 10 March 2021   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Bombardier Inc  
Aircraft model DHC-8-315  
Aircraft registration VH-ZZE  
Serial number 640  
Operator Surveillance Australia  
Type of operation Aerial Work  
Sector Turboprop  
Damage to aircraft Nil  
Departure point Darwin, Northern Territory  
Destination Darwin, Northern Territory  
Last update 10 March 2021