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Safety Action

Summary

As a result of the investigation into this occurrence, the Bureau of Air Safety Investigation issued the following Interim Recommendation on 16 September 1997:

"IR970138
The Bureau of Air Safety Investigation recommends that Boeing Commercial Airplane Group issue service information and appropriate corrective action to applicable B747 operators requiring fleet checks for:

  1. correct placement of aileron control cables on the cable drum located at WS776.98; and
  2. correct installation of aileron control position decals at WS767 and WS780".

Boeing response
The Boeing Commercial Airplane Group response, dated 13 November 1997 stated:

"The reference cover letter provided a copy of your report of an incident involving a 747-300 airplane, Serial Number 23029. The report indicates that one of the left aileron cables was broken during taxi prior to departure. The report stated that the aileron cable failures may be due to misrouting which may occur as a result of incorrectly installed markers. A check by the Australian Bureau of Air Safety Investigation found eight airplanes with incorrectly installed markers.

Your report recommended that Boeing initiate a fleet check for proper placement of the aileron control cables at Wing Station (WS) 776.98 and correct installation of aileron cable markers at WS767 and 780.

It has not been determined whether the incorrect marker installations occurred during or after manufacture. As a result of these findings, we plan to issue a service bulletin to 747 operators recommending fleet checks of all 747 airplanes prior to Line Position 1130, except Line Position 1122, for

  1. Correct routing of aileron control cables on the aileron cable drum located at wing station 777
  2. Correct installation and replacement as required, of aileron cable position markers at wing station 767 and wing station 780

Airplane Line Position 1130 was delivered in September 1997. Airplane Line Position 1122 was checked at Boeing. A review of the applicable engineering drawings shows that the marker installation and cable installation drawings are correct, and have always been correct. In addition, a check of airplanes in the factory and on the flight line indicates that both the markers and cables are currently being installed per drawing".

BASI response status: Closed - Accepted

Subsequent safety action

Boeing issued Service Bulletin 747-27-2367 (Flight controls - aileron - aileron control cable inspection and control cable marker inspection, replacement) on 25 June 1998.

As a result of the Bureau's interim recommendation, the US National Transportation Safety Board (NTSB) conducted an independent review of the circumstances of this occurrence and subsequently issued recommendation A-98-6 to the US Federal Aviation Administration (FAA) on 3 February 1998. This recommendation stated:

"The National Transportation Safety Board recommends that the Federal Aviation Administration:

Issue an airworthiness directive to require operators of Boeing 747 airplanes, produced before production line number 1130, to conduct a one-time inspection of the aileron control system to ensure correct routing of the aileron control cables on the aileron cable drum located at wing station (WS) 776.98 and correct installation of aileron cable decals at WS767 and WS780 at the earliest possible inspection interval".

 
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