Aviation safety investigations & reports

Hydraulic system failure involving Boeing 757, VH-TCA, Auckland International Airport, New Zealand, on 5 February 2018

Investigation number:
AO-2018-014
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

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What happened

On 5 February 2018, a Boeing 757 freighter aircraft, registered VH-TCA, operated by Tasman Cargo Airlines Pty. Ltd., departed from Auckland International Airport, New Zealand for Sydney International Airport, Australia.

Passing through an altitude of 6,000 ft, the left hydraulic system quantity warning message displayed. The crew actioned the Quick Reference Handbook (QRH) checklist and obtained clearance from Air Traffic control (ATC) to level out at 8,000 ft, in a holding pattern to the north‑west of Auckland Airport.

Shortly after commencing the holding pattern, the crew received further warning messages regarding both the left and right hydraulic systems. Following the appropriate actions in the QRH checklists, the crew shut down both systems. The crew made a PAN call to ATC with a request for an immediate return to Auckland. The flaps and landing gear were extended using the alternative systems and the aircraft landed without further incident.

What the ATSB found

The ATSB identified that the dual hydraulic failure was the result of a number of sequential failures in the hydraulic system. The initial failure was a ruptured left main landing gear flex hose, which resulted in a loss of the left hydraulic system pressure. Subsequently, the power transfer unit (PTU) pressure switch did not operate as intended, following depletion of the hydraulic fluid from the left system. This resulted in overheating and failure of the right hydraulic system. The pressure switch was the subject of a 2010 non-mandatory service bulletin which, if implemented, would likely have prevented the failure of the right system.

What's been done as a result

Following the occurrence, the operator conducted preventative maintenance on the aircraft, replacing all of the main landing gear flex hoses as well as updating the PTU pressure switch to conform to the published service bulletin. In addition, the operator revised the aircraft maintenance plan to introduce improved inspections and a time‑limited life on the flex hoses.

Safety message

This occurrence highlights that although some service bulletins are not deemed to be safety critical, they can still have an impact on aircraft reliability. While operators are required to implement all airworthiness directives, the ATSB recommended that operators familiarise themselves with non-mandatory service bulletins and consider the potential impacts of delaying implementation.

Boeing recommends that operators perform periodic inspection of hose assemblies paying particular attention to the high-risk areas of the landing gear area, the engine/pylon areas and the tail/empennage area. Hose assemblies can be difficult to inspect in-situ due to access constraints and the limitations of visual inspection of the multi-layered construction of the hose. As a result, some operators have chosen to introduce a hose replacement schedule, based on flight time in service or a calendar period, in addition to periodic in-situ inspections.

Picture of the ruptured hydraulic flex hose

Picture of the ruptured hydraulic flex hose. Source:  ATSB

Source: ATSB

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The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

General details
Date: 05 February 2018   Investigation status: Completed  
Time: 0820 UTC   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): Auckland International Airport, New Zealand   Investigation phase: Final report: Dissemination  
State: International   Occurrence type: Hydraulic  
Release date: 01 May 2019   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer The Boeing Company  
Aircraft model 757-236  
Aircraft registration VH-TCA  
Serial number 25620  
Operator Tasman Cargo Airlines  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Nil  
Departure point Auckland, NZ  
Destination Sydney, NSW  
Last update 01 May 2019