Output Number
Approval Date
Published Date Time
Recommendation type
Mode
Date released

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 actuator beam arm assemblies.



As a result of investigation into this occurrence, the Bureau
simultaneously issues the following interim recommendations:



IR990019



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.



IR990020



The Bureau of Air Safety Investigation recommends that Boeing
Commercial Airplane Group review the effectiveness of Service
Bulletin 737-32A1224.





IR990022



The Bureau of Air Safety Investigation recommends that the Civil
Aviation Safety Authority initiate appropriate action to ensure
that Australian operators of Boeing 737 aircraft immediately
inspect all main landing gear actuator beam arm assemblies for
evidence of cracking.



IR990023



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
actuator beam arm assemblies.

Organisation Response
Date Received
Organisation
Federal Aviation Administration (FAA)
Response Text

The US Federal Aviation Administration issued an Airworthiness
Directive (AD 99-10-12) as Amendment 39-11165 to all B737
operators, effective 27 May 99:



SUMMARY: This amendment supersedes all existing airworthiness
directive (AD), applicable to certain Boeing Model 737-100, -200,
-300, -400, and -500 series airplanes, that currently requires
repetitive inspections to detect cracking, plating degradation, and
corrosion of the main landing gear (MLG) actuator beam arms and
actuator beam attach bolts; and rework or replacement, if
necessary. The existing AD also provides for optional terminating
action for the repetitive inspections. This amendment removes the
requirement to inspect the actuator beam attach bolts, expands the
applicability of the existing AD to include additional airplanes,
and removes the optional terminating action. This amendment is
prompted by reports of cracked MLG actuator beam arms. The actions
specified in this AD are intended to detect and correct corrosion
and cracking of the MLG actuator beam arm, which could result in
damage to the control cables for the aileron and spoiler and
consequent reduced controllability of the airplane.