Yahoo! is not affiliated with the authors of this page or responsible for its content.
Aviation Mechanics Bulletin SEPTEMBEROCTOBER 2004
F L I G H T S A F E T Y F O U N D A T I O N
Aviation Mechanics Bulletin
Aircraft Wiring
Incidents Persist in
Aging Systems F L I G H T S A F E T Y F O U N D A T I O N
Aviation Mechanics Bulletin
Dedicated to the aviation mechanic whose knowledge,
craftsmanship and integrity form the core of air safety.
Robert A. Feeler, editorial coordinator
Aircraft Wiring Incidents Persist in Aging Systems ....................................... 1
Maintenance Alerts ........................................................................................ 10
News & Tips .................................................................................................. 17
SeptemberOctober 2004
Vol. 52 No. 5
We Encourage Reprints
Articles in this pub li ca tion, in the interest of aviation safety, may be re print ed, in whole or in part,
but may not be offered for sale, used commercially or distributed electronically on the Internet or
on any other electronic media with out the ex press writ ten per mis sion of Flight Safety Foun da tions
di rec tor of pub li ca tions. All uses must credit Flight Safe ty Foun da tion, Avi a tion Mechanics Bul le tin,
the spe ci c article(s) and the author(s). Please send two cop ies of the re print ed material to the director
of pub li ca tions. These restrictions apply to all Flight Safe ty Foundation publications. Reprints must
be purchased from the Foundation.
Whats Your Input?
In keeping with FSFs independent and non par ti san mission to disseminate objective safe ty in for ma tion,
Foundation publications solicit credible con tri bu tions that foster thought-pro vok ing dis cus sion of
aviation safety issues. If you have an article proposal, a com plet ed manu script or a technical paper
that may be ap pro pri ate for Aviation Mechanics Bulletin, please contact the di rec tor of pub li ca tions.
Rea son able care will be tak en in handling a manu script, but Flight Safety Foun da tion assumes no
responsibility for material sub mit ted. The publications staff re serves the right to edit all pub lished
sub mis sions. The Foundation buys all rights to manu scripts and payment is made to authors upon
publication. Contact the Publications De part ment for more in for ma tion.
Aviation Mechanics Bulletin
Copyright © 2004 Flight Safety Foundation Inc. All Rights Reserved. ISSN 0005-2140
Suggestions and opinions expressed in FSF pub li ca tions be long to the author(s) and are not
nec es sar i ly endorsed by Flight Safety Foundation. This information is not intended to supersede
operators/manufacturers policies, practices or requirements, or to supersede government
reg u la tions.
Staff: Roger Rozelle, director of publications; Mark Lacagnina, senior editor; Wayne Rosenkrans, se nior
ed i tor; Linda Werfelman, senior editor; Rick Darby, associate editor; Karen K. Ehrlich, web and print
production coordinator; Ann L. Mullikin, pro duc tion designer; Susan D. Reed, production specialist;
and Patricia Setze, li brar i an, Jerry Lederer Aviation Safety Library.
Subscriptions: One year subscription for six issues in cludes postage and handling: US$240. In clude old
and new ad dress es when requesting address change. Attention: Ahlam Wahdan, membership services
coordinator, Flight Safety Foundation, Suite 300, 601 Madison Street, Al ex an dria, VA 22314 U.S.
Tele phone: +1 (703) 739-6700 Fax: +1 (703) 739-6708
Cover photo: © Copyright 2004 Getty images Inc. Aircraft Wiring Incidents
Persist in Aging Systems
The U.K. Air Accidents Investigation Branch cited four
recent incidents in which wiring problems were associated with
aging aircraft electrical systems and/or maintenance issues.
FSF Editorial Staff
The U.K. Air Accidents Investigation
Branch (AAIB), citing several recent
accidents and incidents involving
electrical arcing and damaged air-
craft wiring, has recommended that
the U.S. Federal Aviation Administra-
tion (FAA) and the European Aviation
Safety Agency (EASA) accelerate the
distribution of guidance material for
development of electrical systems
standard wiring practices manuals.
Aging[-related] and maintenance-
related wiring incidents continue to
occur despite, generally, an enhanced
awareness of the problems associated
with aircraft wiring systems, AAIB
said in its Overview: Incidents Re-
sulting From Damage to Electrical
Wiring. The overview was published
along with AAIB reports on four inci-
dents involving wiring problems that
occurred between Nov. 8, 2002, and
July 30, 2003.
All these incidents show how prone
electrical wiring is to damage occur-
ring over time or being introduced
during maintenance or modi cation
action, the overview said. 2
FLIGHT SAFETY FOUNDATION AVIATION MECHANICS BULLETIN SEPTEMBEROCTOBER 2004
Electrical Fire Disables
Interphone, Cabin Lights
In the rst incident, the ight crew of a
Boeing 737-400 observed smoke and
detected the odor of electrical burning
soon after departure on Nov. 8, 2002,
from London (England) Heathrow
Airport for a ight to Kiev, Ukraine.
Six crewmembers and 68 passengers
were in the airplane. The cabin-call
aural warning sounded, indicating
that cabin crewmembers were call-
ing the ight crew on the interphone,
but the captain and rst of cer were
unable to contact the cabin crew on
the interphone. They donned oxygen
masks and conducted the electrical
smoke/fumes or re checklist.
Both pilots were aware of continued
banging on the locked cockpit door,
which had commenced after their
failed attempts to reply to the cabin
crew on the interphone, the incident
report said. This heightened the pi-
lots concerns about what was happen-
ing since they were unable to either
communicate with the cabin crew or
establish the cause of the smoke.
After the smoke dissipated, the cap-
tain briefed the rst of cer and cau-
tiously removed his [oxygen] mask
so that he could reach the ight deck
door unencumbered by the masks
hose.
He checked through a peephole
for signs of re or possible intruders,
the report said. Seeing neither, he
opened the door and was met by a ow
of water coming from a panel in the
roof between the forward toilet and
the galley. The cabin services direc-
tor (CSD), who had been the person
banging on the door, explained that
about 15 minutes after takeoff, he had
seen sparks and ames coming from
the panel, followed shortly thereafter
by a continuous stream of water.
A cabin crewmember had turned
off the water-isolation valve but had
been unable to stop the water from
pouring off the roof panel. Concerned
that the water might ow into the
avionics bay, the crewmember then
stuffed towels into the gap beneath
the ight deck door. Another cabin
crewmember working in the rear of
the airplane said that the rear galley
and some cabin lights had stopped
functioning.
The ight crew ew the airplane back
to Heathrow where they conducted
a precautionary landing, stopped
the airplane on the runway and shut
down the engines to allow an inspec-
tion of the airplane by aircraft rescue
and re ghting (ARFF) personnel.
The visual inspection revealed no
re or damage, and thermal imaging
revealed no hot areas in the airplanes
ceiling; nevertheless, the report said,
on pulling down the damaged ceil-
ing panel [just outside the flight
deck door], a [burned] wiring loom
[bundle of wires] could be seen. Next FLIGHT SAFETY FOUNDATION AVIATION MECHANICS BULLETIN SEPTEMBEROCTOBER 2004 3
to this was the water-supply hose to
the forward galley, from which water
was still pouring.
The investigation found that damage
had occurred in an area inside the ceil-
ing panel where a braided-steel hose
(a water hose that delivered water
from the crown of the fuselage to the
galley on the right side of the forward
cabin) had been secured with a nylon
electrical tie-wrap strap.
The report said, It appeared that
there had been abrasion and arcing
between the wires and the hose,
resulting in the severing and short-
ing of a number of the wires. The
braided-steel hose was lying against
the frame of the ceiling panel, and
it appeared that there had also been
electrical shorting to this portion of
the airframe.
In one section of the hose, the steel
braid had melted, and at least two
holes had formed in the inner hose,
resulting in the water leak.
Comparison with a sister aircraft
indicated that the hose was too long
for this application and that the extra
length had been looped through
this overhead area and then only se-
cured by a tie-wrap to adjacent wire
bundles, the report said. Part of the
hose was protected by plastic spiral
wrap, but this did not extend to the
portion of the hose in contact with the
wire bundles.
Twenty- ve circuit breakers were ac-
tivated (tripped) during the incident,
including those that provided the
cabin interphone and cabin lighting