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Following landing at Melbourne Aerodrome on 20 October 2009, the crew of a Boeing 737-8FE aircraft, registered VH-VUI, reported that the aircraft was difficult to taxi, requiring more power and steering input than usual. A subsequent visual inspection revealed the number-4 wheel to be oriented at an angle with respect to the axle and, following disassembly, it was discovered that the inner wheel hub and bearing mount had broken away from the wheel assembly.

Examination of the wheel revealed that the inner hub had failed from fatigue cracking that had initiated in the area adjacent to the bearing cup.

Fatigue cracking of the inboard bearing cup bore was an emerging issue for the 737 wheel type at the time of the failure. In May 2009, the wheel manufacturer issued a temporary revision to the Standard Practices Manual, with an updated inspection method for the susceptible area, and the aircraft manufacturer had issued a service letter in August 2009 with a periodic inspection requirement. The operator was in the process of reviewing and incorporating the changes into their own maintenance schedules at the time of the incident.

Immediately following the occurrence, the operator performed a fleet-wide examination, identifying those wheels potentially at risk of a similar failure. Subsequently, ten wheels were removed from service for immediate inspection. The operator also implemented an ultrasonic inspection program for wheels with over 4,000 cycles at every tyre change.

The manufacturers of both the aircraft and the wheel released updated information to operators and maintainers in early 2010, which included a revision to the recommended inspection interval.

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Safety issues

AO-2009-062-SI-01 - AO-2009-062-SI-02 -  

Landing gear wheel design

The post-2005 main landing gear wheel design had shown a susceptibility to fatigue cracking at the inner hub bearing bore shoulder radius.

Safety issue details
Issue number:AO-2009-062-SI-01
Who it affects:Boeing 737 landing gear wheel manufacturer, operators and maintainers of Boeing 737 aircraft
Status:Adequately addressed


Inadequate inspection procedures

At the time of the last tyre change, crack initiation at the bearing bore shoulder radius was an emerging issue with no requirement for mandatory inspection of this area during a tyre change.

Safety issue details
Issue number:AO-2009-062-SI-02
Who it affects:Boeing 737 landing gear wheel manufacturer, operators and maintainers of Boeing 737 aircraft
Status:Adequately addressed

General details
Date: 20 October 2009 Investigation status: Completed 
Time: 0841 ESuT  
Location   (show map):Melbourne aerodrome Investigation type: Occurrence Investigation 
State: Victoria Occurrence type: Landing gear/indication 
Release date: 20 January 2011 Occurrence class: Technical 
Report status: Final Occurrence category: Incident 
 Highest injury level: None 
Aircraft details
Aircraft manufacturer: The Boeing Company 
Aircraft model: 737 
Aircraft registration: VH-VUI 
Serial number: 34441 
Type of operation: Air Transport High Capacity 
Damage to aircraft: Minor 
Departure point:Adelaide, SA
Destination:Melbourne, Vic.
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Last update 14 November 2018