Aviation safety investigations & reports

Uncommanded engine shutdown involving De Havilland Aircraft of Canada DHC-8, VH-LQD, 77 km north-north-west of Brisbane Airport, Queensland, on 26 June 2018

Investigation number:
AO-2018-049
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

Download final report
[Download  PDF: 859KB]
 

What happened

On the 26 June 2018, QantasLink was operating a De Havilland Aircraft of Canada DHC-8-400 aircraft, registered VH-LQD, on a scheduled passenger service from Mackay to Brisbane, Queensland. As the aircraft approached the top of descent, the right engine shut down uncommanded. The crew were unable to feather the propeller and it continued to rotate at low speed, in a coarse pitch condition. The crew actioned the ‘Non-Normal’ checklist and continued to Brisbane Airport where the aircraft landed safely.

What the ATSB found

The ATSB found that a bearing within the engine’s intercompressor case fractured, leading to an automated in-flight engine shutdown. Despite detailed technical examination, the reason the propeller did not feather could not be established. However, the operator identified that the one engine inoperative performance reduction between a counter‑weight coarsened propeller and a fully feathered propeller was only 0.5–0.9 per cent.

The ATSB also found that aircraft maintainers missed an opportunity to ground the aircraft when, on the day before the flight, metal debris was detected on the turbomachinery chip detector. It was identified that the procedures in the aircraft maintenance manual were confusing and ambiguous. This probably led to a misunderstanding by the personnel within the approved maintenance organisation and the continuing airworthiness maintenance organisation, which allowed the aircraft to be released to service.

The ATSB also found that the approved maintenance organisation personnel were not recording all the work performed during regular inspections. This meant that the maintenance information system was incomplete and an opportunity to identify the developing bearing degradation was missed.

What's been done as a result

As a result of this occurrence, QantasLink released a technical advisory bulletin to pilots advising of the incident and warning that the propeller may not always feather as practiced in the simulator.

They have also introduced a system to monitor metallic debris found on chip detectors. This will assist trend identification and ensure analysis results can be accessed quickly in the event of a reoccurrence of debris. Additionally, the organisation contracted to assist with engine monitoring now has a function, which allows monitoring and alerting of fault messages within recorded engine and flight data.

In addition, QantasLink have issued an airworthiness standing order to all certifiers within the approved maintenance organisation to introduce a single certification statement standard for all maintenance. They have also introduced a documentation check to be completed by supervisors after maintenance is completed. A recurrent course is also under development for all certifiers to ensure they remain current with all aircraft maintenance documentation recording requirements.  

The engine manufacturer Pratt & Whitney Canada advised they have standardised the wording relating to debris analysis guidance in the next revision of the aircraft maintenance manual. The ATSB acknowledges the improvement this will make, but considers that there is still ambiguity and the potential for the confusion in the procedure.

As such, the ATSB has issued a recommendation to Pratt and Whitney Canada to improve the clarity of procedures within the chip detector debris analysis section of the aircraft maintenance manual.

Safety message

When performing safety‑critical tasks like aircraft maintenance, it is very important that procedures are clear and unambiguous in order to avoid misinterpretation and error such as those that occurred in this incident.

The occurrence also illustrates that the high reliability of modern aircraft maintenance depends on accurate record keeping of all performed tasks to both communicate what has been done and assist in trend identification.

Download final report
[Download  PDF: 859KB]
 
 
 

The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

Safety Issue

Go to AO-2018-049-SI-01 -

Unclear procedures in Aircraft Maintenance Manual

The procedures in the aircraft maintenance manual relating to chip detector debris analysis were written in a way that could cause confusion and error. This probably influenced the actions of the maintenance personnel to release the aircraft to service with a deteriorating bearing.

Safety issue details
Issue number: AO-2018-049-SI-01
Status: Open – Safety action pending
General details
Date: 26 June 2018   Investigation status: Completed  
Time: 1749 EST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): near Brisbane Airport   Investigation phase: Final report: Dissemination  
State: Queensland   Occurrence type: Engine failure or malfunction  
Release date: 16 September 2020   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer De Havilland Canada  
Aircraft model DHC-8-402  
Aircraft registration VH-LQD  
Serial number 4371  
Operator Sunstate Airlines (Qld), operating as QantasLink  
Type of operation Air Transport High Capacity  
Sector Turboprop  
Damage to aircraft Minor  
Departure point Mackay, Queensland  
Destination Brisbane, Queensland  
Last update 16 September 2020