Re: Swissair MD-11 (SR 111, JFK-GVA) crash off Nova Scotia

Date:         26 Oct 98 02:59:41 
From:         JF Mezei <jfmezei.spamnot@videotron.ca>
References:   1 2 3 4 5 6
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Alan Browne wrote:
> This is confirmed by the report in AW&ST where as part of the SMOKE
> drill, the electrical buses are switched to isolate the source of smoke.
> During some configurations of electrical power in the drill, the CVR in
> one case and the FDR in another are disconnected.  They are simply not
> critical to keeping the aircraft in flight.  It is frustrating that
> their data is not available.  The AW&ST report implied that the various
> configurations were not the same accross all MD-11's.

You'll note that in the case of Valujet's burning DC-9, the FDR and CVR showed
erratic behaviour during the descent. I beleive that they were missing a
couple of minutes of CVR not at the end but during the descent (it restarted).
I do not beleive that the pilots there were doing the checklist
(the fire was well beyond that point).

It was confirmed that for SR111, that the pilots turned off a lot of non
essential systems (such as cabin lights, requiring the FAs to conduct their
cleanup/prep with flashlights). And they stayed off. Also there was no
indication that either the CVR or FDR were turned off while the pilots were
doing their checklist. Shouldn't both show some time "off" while the pilots
were rotating the switch which isolates the buses etc ?

I find it hard to beleive that when electrical fire is suspected, that one
would cycle through a list of devices, turn them off and then back on to find
out whoch is the culprit. In the case of SR111, it took over 3 minutes between
the time smell was detected and smoke was seen. How long would pilots have to
leave a unit off before being able to confirm that it is or is not the culprit
(unit=circuit=bus). Is it not more accurate to state that when an electrical
fire is detected, pilots would shut off all non-essential systems period ?.

Also, during the 3 minutes between initial smell and sight of smoke, could the
pilots not visually identify the source of such smoke ? Or is there so much
wind in the cockpit that any smoke coming out of a device would quickly be
diffused ?

Furthermore, considering that the ventilation system (especially in the
cockpit) pushes "fresh" air in the cockpit and waste air goes down to the
cargo hold and/or back to the passenger cabin, is it not logical to conclude
that the presence of a small amount of smoke in the cockpit could either come
from the ventilation system or from the cockpit itself ?

And considering that the smoke/smell were not detected in the cabin, would it
be logical to conclude that it could not have come from the ventilation system
and that as such, the smoke would have had to have been generated inside the
cockpit ?