Re: Silk Air and SR 111

Date:         07 Oct 98 02:49:07 
From:         "Jim" <jmueksch@earthlink.net>
Organization: EarthLink Network, Inc.
References:   1
Followups:    1
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In the case of the Silk Air flight, the speculation is that the recorders
may have been intentionally shut off (breakers pulled).

In the case of the MD-11, there is some speculation that the pilots may have
moved a switch in the cockpit as part of the "Smoke From the Air
Conditioning System" checklist.  This switch removes power from a bus in
order to help the pilot determine which bus/air conditioner is causing the
smoke problem.  This is a four position rotary switch, with the twelve
o'clock position being the "Normal" position.  The checklist calls for the
pilots to start rotating the switch in a clockwise fashion in order to
isolate the problem.  The 3 o'clock position removes power from one of the
busses and air conditioners, if the problem persists, the pilots are to move
it to the 6 o'clock position which restores the first bus and removes power
from a second bus...etc...etc...etc until the problem is isolated and the
pilots can tell which bus is causing the problem.  It turns out that the FDR
and CVR are connected to the bus that is powered off at the 3 o'clock
position.

The big question is:  Did the FDR and CVR go off-line because the pilots
moved the switch (as they were supposed to) or did they go off line because
of a massive electrical failure on-board the aircraft?  You can bet the the
Canadian NTSB is searching for the answer to that one.

A recent news report said that they have recovered the FADEC (digital engine
controller - a computer) from one of the engines.  The FADEC contains a
memory chip.  They are sending it to a laboratory where they will try to
read the memory chip to glean information about what was going on with the
engines during the last six minutes of flight.  This may help fill in some
of the void left by the absence of data from the FDR during that time
period.

Jim