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.
Procedures updated by the manufacturer and incorporated into australian operators of B737 aircraft and inspections carried out on suspect wheels.
Immediately following the occurrence, the operator reviewed the information supplied by the wheel and aircraft manufacturers and assessed the wheels on their fleet. Subsequently, the operator elected to remove ten wheels from service that fell within an identified risk profile The operator has further reported to the ATSB that since this occurrence, it has altered its non-destructive wheel inspection procedure to include an ultrasonic inspection in accordance with Honeywell Standard Practices Manual, ATS Number 32-49, Temporary Revision No 32-1, dated 1 May 2009.
Initially, the operator performed the inspection at each tyre change after the 11th change. However, following the results of a number of inspections, and in conjunction with the Honeywell Service Bulletin (2612311-32-003), the operator has since altered the inspection in line with the Service Bulletin and performs an ultrasonic inspection of the bearing bore at every fifth tyre change. As a result of the occurrence, the operator also performed a review of its engineering change evaluation procedure which resulted in changes to the process flow chart to include additional steps and a more structured risk assessment
The ATSB is satisfied that the action taken by the aircraft operator adequately addresses the safety issue.
Following the occurrence, the wheel manufacturer released Service Bulletin 2612311-32-003 in February 2010, which provided specific non-destructive inspection requirements for wheel part number 2615480.
The Service Bulletin required mandatory non-destructive inspection of wheel halves SN B7900-B15418 to be performed on a yearly basis or every fifth tyre change.
The ATSB is satisfied that the action taken by the wheel assembly manufacturer adequately addresses the safety issue.
In November 2009, the aircraft manufacturer updated the inboard hub fracture issue to a safety service related problem (safety-SRP) and advised operators to incorporate the recommended inspections and inspection intervals as soon as practical. The aircraft manufacturer released a further Service Bulletin (SB-737-32-1444, issued 8 April 2010) and an update to its previous Service Letter (737-SL-32-162-A, issued 4 May 2010) that summarised the issue, and contained the recommended non-destructive checks and intervals.
The service bulletin urged operators to perform inspections as per the Honeywell Service Bulletin and standard practices manual mentioned previously.
The ATSB is satisfied that the action taken by the aircraft manufacturer adequately addresses the safety issue.
