Re: B 737-500 Depressurization Incident

Date:         30 Mar 99 01:54:03 
From:         nw1@gte.net (Neil Wagner)
Organization: gte.net
References:   1 2 3
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On 17 Mar 99 01:25:01 , gfoley@gcfn.org (Gerard Foley) wrote:

>: Is it an urban myth that oxygen masks automatically deploy ?  How come they
>: required manual intervention to be deployed when just about every safety
>: briefing to pax mention "will automatically deploy in the unlikely event of a
>: de-pressurisation" ? ?
>
>In the cited case, the pressure was increasing.  The automatic deployment
>would presumably be for decreasing pressure.

In the cited case, the pressure was initially decreasing.  The
emergency checklist in use be the crew probably required them to
deploy masks manually at 14000' cabin altitude.  The automatic
aneroid is for those situations where the pressure loss is sudden
or the crew is too busy to notice or take action about the loss of
cabin pressure.

In this incident, after the outflow valve was manually closed and
the packs began operating again, the cabin altitude would have
descended pretty quickly, maybe on the order of three or four thousand
feet per minute (an educated guess, maybe more quickly).  It was
probably the fast cabin descent that did the damage to the passenger's
ears.
__________________
Neil - nw1@gte.net