Re: Engine fire extinguishers... do they exist?

From:         qj09@dial.pipex.com (Mike Pye)
Organization: UUNet PIPEX server (post doesn't reflect views of UUNet PIPEX)
Date:         07 Sep 96 17:09:04 
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Erico Oller Westerberg <ew@appelberg.se> wrote:

>Re: Engine fire extinguishers...do they exist?


>Could anyone tell me if there are any fire extinguishers mounted
>inside or close to the engines in modern airliners? If there are
>any - how do they work? Any special gas, different to those used
>in regular fire extinguishers?

I used to be involved with aero engine fire safety issues, but I am now
a little out of touch, so check anything I say if you intend to use it
for other than personal information.

There are Airworthiness Regulations governing the provision and
performance of aero engine fire extinguishing.  As far as I am aware
all 'modern' airliners will be equipped with fire extinguishing.  In
some rare cases fire extinguisher bottles are mounted on the engine,
but, in general, the normal procedure is to mount them on the
airframe, from where the extinguishant  is 'piped' to the relevant
engine nacelle fire zones.  Core engine fires are not usually a
problem and tail pipe fires, when they occur, are normally
extinguished by 'motoring' the engine to expel unburnt fuel.

The fire extinguishing agent in common use currently is known as
Halon, (I can't recall the full chemical name without looking it up !)
However, the problem with Halon is that it does attack the ozone layer
and its use is currently being phased out (under the Monteal Protocol
?).  My recollection is that the discharge of Halon is now banned in
many countries and it may only be used for 'essential services', such
as aero engine applications.  The manufacture of Halon is, I belive,
now banned and existing use is based on 'banked' stocks, generally
recovered from ground based applications.  Recovery and banking is
expensive and fire extinguisher manufactures are currntly evaluating
alternatives, although, in general, these are either heavier or more
expensive than Halon.

When used, fire extinguishing agent is expelled under pressure and is
required to produce adequate concentrations (typically 5% by mass) in
all nacelle fire zones simultaneously for about 0.5seconds (?).  As
far as I am aware, the 'legal' requirement is for a two shot system.

I hope this goes at least some way towards answering you question.

Rgards

Mike Pye

E:  mike_pye@dial.pipex.com