Aviation safety investigations & reports

Nose landing gear axle fracture - VH-VBA, Boeing 737-7Q8, Melbourne Aerodrome, Victoria, 25 July 2009

Investigation number:
Status: Completed
Investigation completed


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On 25 July 2009, a Boeing 737-7Q8 aircraft, registered VH-VBA, was taxiing toward the runway for departure at Melbourne aerodrome, Victoria, when the crew reported hearing a loud thud from the airframe. The crew of a passing company aircraft advised the crew of VH-VBA that they had lost a nose wheel tyre. It was subsequently discovered that the right wheel had detached from the nose landing gear (NLG) as a result of a fracture of the axle.

An Australian Transport Safety Bureau investigation of the NLG failure determined that the nose wheel had separated as a result of the initiation and propagation of a fatigue crack through the right, inboard bearing journal. The fatigue crack had originated under the influence of residual stresses in the steel surface associated with grinding damage during manufacture, and its initiation was probably hydrogen-assisted from plating processes applied to the journal bearing surfaces.

As a result of the occurrence, the aircraft operator conducted an immediate, fleet-wide inspection of axles with similar service history. To reduce the likelihood of future possible axle failures, the aircraft manufacturer conducted an audit of the landing gear supplier's processes and production records, in an attempt to establish the extent of the grinding problem. The aircraft manufacturer also released a communication to 737 operators and maintenance providers, detailing enhanced inspection recommendations for the identification of grinding damage.

Download Final Report
[Download  PDF: 1.44MB]

Safety Issue

Go to AO-2009-047-SI-01 -

Nose landing gear residual stress and hydrogen embrittlement

Fatigue cracking originated within the aircraft nose landing gear (NLG) right axle as the result of surface damage associated with grinding during manufacture, and was probably assisted in its initiation by hydrogen evolved during plating processes.

Safety issue details
Issue number: AO-2009-047-SI-01
Who it affects: Operators of Boeing 737 aircraft
Status: Adequately addressed
General details
Date: 25 July 2009   Investigation status: Completed  
Time: 0826 EST   Investigation level: Systemic - click for an explanation of investigation levels  
Location   (show map): Melbourne Aerodrome    
State: Victoria   Occurrence type: Landing gear/indication  
Release date: 30 July 2010   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer The Boeing Company  
Aircraft model 737  
Aircraft registration VH-VBA  
Serial number 28238  
Type of operation Air Transport High Capacity  
Damage to aircraft Minor  
Departure point Melbourne, Vic.  
Destination Sydney, NSW  
Last update 03 April 2020