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Output Number
IR19990049
Approval Date
Published Date Time
Recommendation type
Interim recommendation
Mode
Aviation
Date released

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.

Organisation Response
Date Received
Organisation
Civil Aviation Safety Authority
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.