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Interim Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: IR19990049
Date issued: 27 May 1999
Safety action status:
Background: Why this Interim Recommendation was developed

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority note the above safety deficiency and interim recommendations and initiate appropriate action to ensure the integrity of Australian Boeing 737 main landing gear trunnion pin assemblies.

As a result of the investigation of this safety deficiency, the Bureau simultaneously issues the following interim recommendations:

IR990046

The Bureau of Air Safety Investigation recommends that Boeing Commercial Airplane Group alert Boeing 737 operators to this safety deficiency and implement an appropriate inspection program.

IR990047

The Bureau of Air Safety Investigation recommends that Boeing Commercial Airplane Group review the effectiveness of Service Bulletin 737-32A1198 revision 2.

IR990048

The Bureau of Air Safety Investigation recommends that the Federal Aviation Administration note the above safety deficiency and interim recommendations and take appropriate action as considered necessary to ensure the integrity of Boeing 737 main landing gear trunnion pin assemblies.

IR990050

The Bureau of Air Safety Investigation recommends that Australian operators of Boeing 737 note the above safety deficiency and interim recommendations and take appropriate action as considered necessary to ensure the integrity of Boeing 737 main landing gear trunnion pin assemblies.

Initial response
Date issued: 12 July 1999
Response from: Civil Aviation Safety Authority
Action status: Closed - Accepted
Response text:

I refer to BASI Occurrence 9901455, relating to the in-flight failure of a main landing gear trunnion pin in a Boeing 737-376 on 4 April 1999, which generated Interim Recommendation IR990049. The recommendation was for the Civil Aviation Safety Authority (CASA) to note the deficiency and initiate appropriate action to ensure the integrity of Australian 737 main landing gear trunnion pins.

This incident showed that the undercarriage is generally fail safe in this area, by lowering safely when the problem occurred. However, more extensive corrosion may have had a different outcome.

CASA has discussed the occurrence with both Australian operators of the aircraft, and Boeing has also been advised of the problem. Boeing is currently reviewing the entire undercarriage system for corrosion problems and is shortly expected to address this, and other faults, via service bulletin or similar document.

Pending issue of such data by the manufacturer, both operators have developed inspections to check the trunnion pin lugs for corrosion. CASA believes that this action is appropriate under our existing regulatory framework, and the inspections implemented are suitable to prevent further problems. Issue of an Airworthiness Directive is considered to be unnecessary because of the operators' actions and the impending issue of improved manufacturer's data. CASA will continue to monitor the manufacturer's response to this problem.

 
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Last update 01 April 2011