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

Date:         26 Oct 98 02:59:44 
From:         Becky Dillon <bdillon1@mindspring.com>
Organization: MindSpring Enterprises
References:   1 2 3 4 5 6 7
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JF Mezei wrote:
>
> Anonymous lo14 wrote:
> > Some *cargo* compartments depend on a lack of oxygen to snuff out a
> > fire, but no passenger compartment can do that.  That's because those
> > cargo compartments are inaccessible in flight.  You fight passenger
> > cabin fires with fire extinguishers.
>
> In the case of the DC-9 (Valuejet), it was considered a Class-D cargo
> compartment which, if I remember correctly, assumes air starvation as
> method of extinguishing, right ?
>
> But the DC-9 also vents cabin air through holes in the cabin floor
> alongside the walls, and that air goes to the cargo hold (one of which
> is heated).  So I wonder how it can starve a cago fire of air unless it
> stops pumping air in the cabin.

The air which exits the cabin flows around the outside of the cargo
compartment walls.  These are made of fire retardant material.  The heat
in the forward cargo compartment comes from, IIRC, avionics rack cooling
air exhaust, which also flows around the outside of the compartment.  I
believe though that there are pressure equalizing valves between the
compartment and the space outside of it.

The system of extinguishing is marginal at best, and would allow keep a
fire to smoulder but not become a full inferno, unless an oxidizing
agent was present as well, like activated O2 generators.

I think the best design is that found on the 767ER and similar systems.
Cargo fire detection and extinguishing.  This system has two halon
bottles installed.  One bottle dumps the entire contents into the
compartment immediatly, the other bottle then meters its contents out
over a period of time to ensure continued suppression (180 minutes in
the case of the ER).

-Seth