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Interim Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: IR19990022
Date issued: 19 March 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 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.

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

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.

IR990021

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.

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.

Initial response
Date issued: 08 June 1999
Response from: Civil Aviation Safety Authority
Action status: Closed - Accepted
Response text:

I refer to your interim recommendation IR990022 in regard to the Actuator Beam Arm failure on B737 VH-CZL on 12th Mar 1999. The incident resulted in substantial secondary damage to the wing structure and flight control cables, and it was this damage, rather than the undercarriage failure, which was of major concern (the undercarriage is designed to fail safe).

CASA has investigated the incident, and found that this failure was previously covered by inspections mandated by AD/B737/57. Those inspections ceased after a modified actuator beam arm was installed, as nominated by the AD as closing action. VH-CZL had a modified actuator arm beam, and inspections for cracking were therefore not required.

The significance of the secondary damage suffered by VH-CZL was such that CASA decided to reintroduce initial and repetitive inspections by reissue of AD/B737/57 Amendment 1. This amended AD was issued on 29 March 1999 and requires visual and ultrasonic inspections even if the actuator arm had been replaced. Boeing was advised of the action and requested to advise us when suitable terminating action is developed.

The US FAA was also advised of our action. The FAA has subsequently issued AD 99-10-12 effective 27 May 99 to perform almost identical work as required by the CASA AD. The FAA AD was issued as a final form without industry consultation.

The action initiated is considered adequate to correct the unsafe condition revealed by the incident involving VH-CZL. This action will be reviewed when further information is received from Boeing or the FAA.

Receipt of IR990022 enabled urgent corrective action to be initiated by CASA, and subsequently by Boeing and the FAA. Expeditious issue of IR990022 by BASI is therefore much appreciated.

 
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Last update 01 April 2011