Boeing Co 747-312, VH-INJ

Investigation number

199702693

Occurrence date

20/08/1997

Location

Brisbane, Aero.

Report release date

01/02/1999

Report status

Final

Investigation type

Occurrence Investigation

Investigation status

Completed

Aviation occurrence type

Flight control systems

Occurrence category

Incident

Highest injury level

None

Safety Action Significant Factors Analysis 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:

correct placement of aileron control cables on the cable drum
located at WS776.98; and
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

Correct routing of aileron control cables on the aileron cable
drum located at wing station 777

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".

While taxiing for departure, the crew of the Boeing 747 selected
the flaps to the take-off position. As the flaps extended, the left
outboard aileron deflected to the full down position. The aircraft
returned to the gate for rectification.

Investigation revealed that the left aileron cable (AA-11),
which connected the inboard aileron quadrant to the aileron cable
drum at wing station (WS) 776.98, had failed immediately outboard
of the cable drum. The adjacent cable (AB-13), which connected the
outboard aileron quadrant to the aileron control drum, was frayed
at a location consistent with having been in contact with the other
cable. The aileron cable drum had four grooves to accommodate the
four separate aileron cables which ran inboard and outboard from
the drum and connected to the inboard and outboard aileron
quadrants. Markers were installed at the WS767 and WS780 locations
to provide visual guidance for the routing and attachment of the
aileron cables to specific grooves on the cable drum.

The aileron control drum forward guide pin was bent and
displayed evidence of abrasion from interference by the cables.
There was also abrasion to the top two grooves of the cable drum.
Further examination revealed that the two aileron cable markers
(decals) attached to the aileron drum's inboard and outboard
mounting brackets at WS767 and WS780 were installed incorrectly.
The marker for WS767 was fitted at WS780 and vice versa.

The aircraft had been manufactured in 1983 and had operated
62,399 hours to the time of the incident. Since 2 June 1997, when
both cables were changed due to wear, the aircraft had operated
1,022 hours. The appropriate dual certifications, for the aileron
control system, had been carried out at that time.

The investigation determined that another aircraft in the
operator's fleet had had the same aileron cables changed, due to
fraying and wear, about 12 months prior to the incident. This
aircraft was inspected and it was found that the aileron cable
markers at WS767 and WS780 were also transposed.

The investigation also found that eight other aircraft, from
various operators, had aileron cable markers incorrectly installed
at the WS767 and WS780 locations. However, it was not possible to
determine if the markers had been transposed during, or after,
aircraft manufacture.

Aircraft Details

Manufacturer

The Boeing Company

Model

747

Registration

VH-INJ

Serial number

23029

Operation type

Air Transport High Capacity

Damage

Minor