Oxygen Fed Electrical Fires

Art
A reasonable indication that the Smoke and Fumes of Unknown Origin was started was the flame-out of the #2 (tail) engine. This occurs at one of the final stages of that checklist and is an expected (not abnormal) occurrence due to the power coming off the fuel pumps (and #2 engine, being high set, not being able to gravity feed its fuel). Of course the main wire-bundle that goes over the top of the cockpit/cabin bulkhead would also contain many of the engine systems controller's related wiring harnesses. If its integrity was compromised by the electrical fire (known to have been in that vicinity) then power to that fuel pump could have been cut (causing a Number two engine flame-out). This latter theory is supported by the investigator's finding that the ADG was still stowed and never deployed.

At this stage, due to a number of things that have recently come to my attention, I am inclined to believe that the electrical fire in the aft cockpit ceiling area burnt through, ruptured (or exploded) the high-pressure oxygen tubing to the jump-seat oxy regulator (or melted the regulator itself). The resultant blow-torch would've caused the simultaneous transmission by both pilots (requesting an immediate landing) that occurred just before all comms were lost. At the same time, of course, much of the wiring would have had its insulation incinerated off it causing multiple systems failures (including the #2 tail engine failure and bus outages). Because all the oxygen would've been lost in a very short time, both the pilots would have then been easily overcome by fumes and toxic-smoke. Indeed they would have had to have ripped off their oxy masks once the 100% oxygen flow to them was cut off. Much should be learnt from the toxicological analysis of the pilots - but nothing has been released to date. The oxygen blow-torch effect would explain away the globules of molten aluminium found in that area. The RAAF lost A9-300 (P3B Orion) in 1980 due to a cockpit oxygen fire on the ground during elec maintenance at 492 Sqn (92Wing) RAAF Edinburgh. It's a very conclusive sort of emergency.

"Gerden said there is no evidence so far of frayed, chafed, or
nicked wiring in the forward section. But there is evidence of
electrical arcing and wiring with insulation missing. But he said
investigators aren't sure yet why insulation might be stripped
from some wires."

"Some material from the ceiling area just aft of the cockpit
includes a few small pieces of melted aluminum, melted copper
wiring, arcing damage, and charred or missing wire insulation."

"A fire onboard doomed Swissair Flight 111 was so intense it
melted aluminum in the ceiling near the flight crews' heads, the
Transportation Safety Board reported yesterday.

"This gives us an indication that the heat was high, and it gives
us an indication there most likely was a localized fire in an area
up above,'' said board spokesman Jim Harris."

"Tiny pieces of metal - some the size of a quarter - were taken
from an area near wiring that programmed the plane's
entertainment system.

The sheepskin fabric on the observer seat, located in the
cockpit behind the pilots' seats, has a few drops of melted
plastic imbedded in it."

This is very speculative but it accords with the hardware in the area of the elec fire and would be a tenable explanation of whatever sudden happenstance rapidly alarmed both pilots into making coincident transmissions. If this was the case, then the investigators would need to locate the regulator, a pin-holed oxy tube or a section of wiring whose loss of insulation was related to a more focussed heat source than just the charring of an arc-tracking flash-over. The many miles of bundled wiring in our modern electric jets make them vulnerable to a very localised failure. It's like saying that a thousand miles of oil pipe-line is so strategically liable to terrorist interdiction that a foot wide hole anywhere along it can negate its function. For the same reason, once a wiring failure occurs in a modern airliner, later locating and pinpointing the failure point (and the cause) is real "needle-in-a-haystack" stuff. "Wire is wire" until its insulation is compromised. Once it is, you've got a toxic haemorrhage of fire that can carry over to insulation batts, oxy systems, fuel, hydraulics, adjacent wiring - and pilot's physiologies. System failures stemming from the original failure's arc-tracking can be rapid-fire and very disabling. This is why electric jets need better real-time wiring integrity monitoring and a fall-back system with real (not illusory) electrical redundancy.

regards

John Sampson
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Ader wrote:

John,

How sure can we be that Zimmermann was on the smoke/elec/air checklisting?
He could still have been working on the first [very long] checklist when
full loss of communications occured.

If you are right, Pat could also be right [A Kapton Electrical Fire Example].

So far I didn't see FACTS to support it. Did you? Did I overlook / miss something?

Regards
Art

PAPCECST@aol.com wrote:

John et al,

Stephen Thorne of Canadian press has been asking the Canadian TSB for a
toxicology report concerning the cockpit crew and they haven't released their
findings yet. You might e-mail him at: bushky@hotmail.com and see what the
latest info that he has been able to find. You might want to e-mail him your
latest evaluations on what you believe might happened. Isn't buss #2 the
essential buss that the IFES was hooked up to and isn't this buss connected to
#2 engine?

I'm going to e-mail a cc of this msg to Res also. I think he will be most
interested and with his contacts, he might be able to get some more
information of this possibility.

Patrick

REPLY:

Patrick

Yes I will contact Stephen Thorne and see what he's heard about the toxicology. I was fascinated by the disconnected link on the Halifax News page that mentioned the possibility of the pilots' oxygen system being possibly involved. I brought this up some many months ago now. I was thinking that the Halifax News report link at
http://www.hfxnews.southam.ca/Crash/index.html
may have been disconnected after criticisms by the TSB (as unfounded speculation). I received a 105 minute phone call yesterday from Tim Van Beveren (German TV documentary maker) yesterday morning our time (from Florida). He told me he'd just had a most difficult interview with Vic Gerden. Gerden has obviously been reamed out about the continuing leaks and is now reportedly taking a very formal uncooperative stance. This may well be a desired result orchestrated by those South of the Border who made those disclosures about the CVR.

Gen #2 is located on Eng #2 but AC Bus 2's power source is determined by the bus-tie sensing relay on a prioritising basis. i.e. when #2 engine (and it's associated #2 GEN) dropped out, the bus-tie sensing relay simply switches the bus loads between remaining generators (and/or the ADG). However the ADG was found stowed. Bus 2 was the IFE Bus.

Unfortunately, from the toxicological point of view, I'm not sure that the pathologists can distinguish between the trace elements of toxic gases that would naturally be there as a result of the fire and a disabling amount of these toxins ingested by pilots robbed of their 100% oxy supplies. Time and sea-water and fuel would mask and dilute much of it also. I'd be surprised if anything conclusive could be determined - but I might be wrong. If there was an oxygen fed blowtorch, that is the best bet for "the golden nugget" they keep talking about. I would imagine that there would be clear evidence of that having taken place. When you look for a sudden occurrence that simultaneously alarmed both pilots, didn't need discussion (i.e. no clues on CVR), and motivated them into simultaneous transmissions and leaps in inspiratory rates ..... it seems to fit that bill. Please look at my new
page at:
OXYFED.html
It has a few supportive quotes that might justify such a conclusion (about an oxy-fed fire).

Friday, February 5, 1999

Oxygen may have fed fire

Emergency supply to Swissair pilots likely made
blaze worse - report

By RICHARD DOOLEY -- The Daily News

Investigators probing the crash of Swissair Flight 111 are
looking at the possibility oxygen from the pilot's and co-pilot's
emergency air supply might have fed the cockpit fire suspected
of bringing the jetliner down.

Canadian Transportation Safety Board investigators have found
heat-damaged wiring from two overhead cockpit circuit breakers.

Some of the wires display tell-tale markings of electrical arcing,
lightening-like flashes of electricity released along the wire.

Found in the same overhead area, was stainless steel tubes
carrying the flight crew's emergency oxygen supply which was
in use at the time of the crash.

The Sept. 2 crash killed all 229 passengers and crew aboard.
Wreckage is still being recovered from the ocean floor about 10
kilometres southwest of Peggy's Cove.

Investigators have said localized areas of the cockpit were
subject to intense heat, sometimes hot enough to melt the aircraft's aluminum.

Aviation Week, the top aviation industry magazine in the U.S.,
speculates in a recent edition leaks from the emergency oxygen
supply, caused by electrical arcing, could have intensified the fire.

Investigators are reconstructing the forward section of the jet to
trace the source and spread of the fire. Investigators are also
experimenting with sections of the aircraft to determine what
kind of temperatures were found in the cockpit's overhead section.

Test panels from undamaged areas of the plane are being
subjected to varying degrees of heat for comparison with the
heat-damaged cockpit sections.

Transportation Safety Board spokesman Jim Harris said the
oxygen-supply theory is just one scenario investigators are considering.

"We just don't know, at this point, if there were problems with
the oxygen supply," he said.

Part of the problem is differentiating between damage to the
oxygen carrying tubes done by the impact or exposure to electrical arcing.

"We don't have all the information yet," said Harris. He said
tests have begun to determine how the oxygen-supply tubing was damaged.

Investigators have found several wiring problems in the
Swissair jet and other MD-11s still in service around the world.

Two Federal Aviation Administration air-worthiness directives
concerning wiring have been issued since December as a result
of the Canadian investigation.

Investigators reported finding loose terminal connections,
chafed wiring, wires bent at too small a radius, improperly
sealed wire conduits, and incorrectly routed wiring bundles in
some of the dozen MD-11s they inspected.