The NTSB has found a new focus for its investigation into TWA Flight
800 -
lavatory waste.
There is no longer any doubt that the NTSB determination of probable
cause
for TWA 800's explosion is going to be faulty wiring. Exacerbated
by
"galley fluids" and leaky toilets perhaps.
Two Reuters articles follow:
Focus of TWA 800 crash
on wiring - NTSB
WASHINGTON, Sept 14 (Reuters) - National Transportation Safety
Board (NTSB)
investigators are focusing on possible sparking from aging wires
as the
cause of the 1996 TWA Flight 800 crash off Long Island that killed
all 230
people on board.
James Hall, chairman of the NTSB, told NBC's Today Show that testing
of
wiring bundles in 25 different planes has focused U.S. aviation
officials'
attention on Boeing 747's electrical system as a possible cause
of the
accident.
"We are now looking very closely at possible electrical discharges
that may
have come off of some of that wiring that could have caused the
accident
itself,'' Hall said.
NTSB investigators have long suspected that fumes in the plane's
center fuel
tank were ignited by some sort of electrical fault.
Hall was speaking from Calverton, Long Island, where the reconstructed
wreckage of TWA 800 was being moved to a smaller hangar Tuesday.
On Monday, USA Today reported that the private laboratory hired
by the NTSB
to test Poly-X wiring -- the same type used in the destroyed
TWA 747
aircraft -- found that it sparked more than expected when bundles
of it were
wet-tested.
Wet-testing simulates what might happen when cracked insulation
on
electrical wires is exposed to salt water or waste water from
an airplane's
galley or restrooms.
For his part, NTSB chairman Hall refused to confirm those results
during his
NBC News interview, deferring any comment until the safety board's
final
report is released.
That report is expected early next year.
U.S. panel told all aircraft
wiring ages, cracks
By Tim Dobbyn
WASHINGTON, Sept 15 (Reuters) - All aircraft wiring ages, and
it is not
uncommon to find five to 10 insulation cracks per 1,000 feet
of wire in
active aircraft, a congressional subcommittee heard Wednesday.
Armin Bruning, an engineer who heads a company that has done testing
for the
National Transportation Safety Board, said the plastics insulating
wire all
aged, leading to problems ranging from minor troubles with instruments
to
fires and sometimes deaths.
Wiring is becoming one of aviation's hottest safety topics, with
a suspected
role in two high-profile crashes in the last four years. There
has also been
increased research into the problem.
A Federal Aviation Administration official told a hearing of the
House
Transportation subcommittee that the so-called aging aircraft
fleet would
soon include heavily electronics-reliant aircraft of the 1980s
such as the
Boeing 757 and 767 and the Airbus A-300.
"The FAA and, indeed, the entire aviation industry are only now
beginning to
have a greater appreciation and understanding about the need
to examine
nonstructural aspects of our aircraft,'' FAA Associate Administrator
Tom
McSweeny said.
Bruning, president of Lectromechanical Design Co., a Dulles, Virginia,
concern that has worked with the U.S. Navy, said humidity, high
temperatures
and strain all contributed to wire aging.
Although not all insulation breaks lead to sparks or accidents,
it is best
to minimize the problem, he said.
TWA, SWISSAIR CRASHES
NTSB aviation safety director Bernard Loeb said the board's attention
had
been focused by two major crashes: the 1996 explosion of a TWA
jumbo jet off
Long Island, which killed all 230 people on board, and last year's
Swissair
MD-11 crash off Canada's Nova Scotia coast, which killed the
229 people it
carried.
Safety investigators suspect that an electrical fault, possibly
in the fuel
measuring system, ignited fumes in the center fuel tank of TWA
Flight 800.
In the Canadian crash, attention has focused on damaged wires
in the ceiling
of the cockpit.
Loeb said inspections of more than 25 other aircraft after TWA
800 found
wiring problems in all cases, ranging from lint and metal shavings
on wire
bundles to cracks in insulation.
The NTSB is following up with tests in which wire bundles contaminated
with
metal drill shavings are vibrated.
It was recently reported that another series of tests documenting
the arcing
potential of TWA 800-type wire when contaminated with galley
fluids and
lavatory waste showed surprisingly violent reactions.
Loeb said outside the hearing that the NTSB was also planning
to use an
operating Boeing 747 to check the effect of turning powerful
electrical
circuits on and off and the induction of strong currents into
adjacent
low-voltage wires.
Under one scenario, excessive electrical energy may have entered
TWA 800's
fuel tank through the normally low-voltage fuel measuring system.
"The safety board is concerned that industry and regulatory efforts
have
been relatively ineffective in preventing the types of wiring
hazards seen
during the TWA Flight 800 investigation,'' Loeb testified.
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