02 systems

[forget]

The item Cabin Smoke in Tech Log needs some input from engineers ( and I is one ). The point I’m trying to pin down is this. I accept that 02 cabin masks are there for de-pressurisation. However, there have been fatal cabin fires where the deployment of cabin masks would, I believe, have produced more walking wounded and fewer bodies. The argument that 02 would feed the flames is, I think, wrong as where you have flames you won’t have live passengers - generally. One question is, using a cabin mask and taking a lung-full of air, what’s the mix of cabin air to 02.

[JET SET SPARKY]

FORGET......are you having a laugh or have i got the wrong end of the stick about your post?????
a few flaws in your cunning plan mate,
1)have you ever seen a fire fuelled by pure 02? it burns reeeaaaal gooooood!
2)the rubber jungle becomes another obstacle to sight and movement in the event of evacuation
3)would you sit there supping good old 02 or would you ,like me be trampling over the heads of bewildered pax trying to get the **** out of there(should we be on the ground )?????

my father and grandfather are/were airport crash crew members,and i've seen the piccys/videos of melting flesh in aicraft cabin fires..anything that fuels a fire (heat oxygen fuel) SHOULD be absent(as far as possible) in the event of such an occurance...ask the manchester firemen!!!
the ONLY things that would help pax ,you and me included,in the event of cabin fire are
1)SMOKE HOODS...maybe the accountants of airlines could work weight penalties/cost off against the increase in safety margin?.......nah let em choke
2)IN-BUILT RETARDENT SPRINKLER SYSTEMS.....again weight/cost against safety
two v. simple life savers
too expensive for airlines

sorry if i've read it wrong, but 02 and fire don't mix ,if you like your skin attached to your bones

[Genghis the Engineer]

Airline emergency oxygen masks (at least the pax variety) supply pure O2, which then mixes with the cabin air. So, the wearer will get the same amount of smoke, just supplemented by Oxygen. The proportion will be a function of cabin pressure, starting at 0 at around 6,000 ft cabin pressure to about 100% O2 at 25,000 ft cabin pressure.

Given in a fire / smoke environment most people die of CO / CO2 poisoning, not O2 starvation, the masks would be irrelevant. They are also tied to the aircraft, which might cause a bit of a problem during evacuation.

Best thing by far from what I've seen of reports & courses is cabin water mist which damps fire and smoke, whilst retaining a breathable cabin atmosphere. The beancounters love it too because it's a lot lighter than a normal firefighting system so they can cram a few more SLC in. That said, the trials on smokehoods are pretty promising as well.

G

[forget]

Jet Set Sparky, You have indeed got it wrong. I was careful to say smoke in the cabin - not fire - although, obviously, one may lead to the other.

You say - ‘would you sit there supping good old 02 or would you ,like me be trampling over the heads of bewildered pax trying to get the **** out of there’. The trouble is, Manchester proved that people do tend to sit until told what to do. As I recall, people died from smoke inhalation which may, just may, have been prevented if they’d been on oxygen until the fire-fighters got in there. Your point about 02 fuelling a fire is obvious - but what I’m saying is that if there are already flames in the area then the pax have already gone - one way or the other.

Now let’s put you in the cabin of an aircraft that’s making an emergency landing with smoke in the cabin. You know all about aircraft plastics and you‘ll be dead from smoke inhalation in less than a minute. Above your head is a chance of survival - but you won’t touch it. Get my drift. Think this through again. Remember I used examples such as Air Canada where the aircraft landed with more live pax than eventually walked off. I’m simply asking the question - if some of the fatalities had been on oxygen would they have survived?

[JET SET SPARKY]

....forget my old mate,did you FORGET what you wrote?...."..there have been fatal cabin FIRES where the deployment of cabin masks would,i believe have produced more walking wounded...."
sorry if i got THAT wrong ,but regardless of whether there's flames ,smoke,sparks whatever,oxygen is a fuel for FIRE !
if ,for instance ,you deploy oxy automatically (as you may be suggesting we should do)in the event of SMOKE(swissair MD11 to give an example of a real instance) if that smoke becomes a FIRE you've just added to the medium by dangling hundred of nice little fire makers in front of the pax!!!!! No seriously ,the safe way to extend your survival time on a smoke filled aircraft (hypothetically speaking IF airlines supplied proper survival kit to pax)is by donning a smoke hood which prevents the smoke stinging the eyes and filters a percentage of poisons from the air hopefully this ficticious airline will also have a retardent sprinkler aswell that will reduce a potential fire risk ,NOT INCREASE IT TENFOLD AS OXYGEN WOULD DO(see how the valujet 9 burned as result of chemical oxygen generators chain reacting HEAT+FUEL+OXYGEN+HEAT+FUEL+OXYGEN etc. etc. i think it took 6 MINUTES from initial reports of SMOKE to loss of control).
Your point;you MAY breath longer if you have the 02 mask(BUT see genghis'point about you will still breath in the toxins if using a dropdown mask)
my point;the aircraft WILL burn away quicker if pure 02 is fed to the fire

HEAT+OXYGEN+FUEL= FIRE ,simple basic physics innit?

[This message has been edited by JET SET SPARKY (edited 20 December 1999).]

[forget]

JSS, Curses - you’ve sussed why I use the handle forget! The thought which started this was; are there circumstances where pax 02 masks would assist in smoke filled cabins? It seems not, particularly as Genghis has pointed out that the proportion of 02 to the masks is a function of cabin pressure, starting at 0 at around 6,000 ft cabin pressure to about 100% O2 at 25,000 ft cabin pressure. ( That can’t apply to 02 generators - can it? ) However, if Genghis wasn’t referring to 02 generators then my gut feel tells me there will be such circumstances. The difficulty is - who’s going to make the decision and drop the masks. No one - so the whole thing is academic. You mention Valujet and use burning 02 generators as an example of why 02 shouldn’t be used in the cabin. What happens when the onboard generators are catching fire? Seems to me that this would have been preceded by smoke and, if on the ground, 02 masks may give the pax a few extra minutes.

Incidentally, is everyone totally convinced, and I mean totally, without any doubt at all, that 02 generators were the initial cause of Valujet’s problem?

Enough of this - how do you feel about resurrecting flying boats?


[This message has been edited by forget (edited 21 December 1999).]

[JET SET SPARKY]

yeah flying boats would be cool!

and how about putting VC-10s and 707's back into production...modern jets are too quiet/clean/economical very very sensible but very boring....convair cv-990 coronado anybody??

..from the not very economical engineer :)

[Genghis the Engineer]

As it happens I had the old BCAR Section D out last week considering certification of flying boats for training.

A wonderful idea aesthetically, but there's an awful lot of expertise that's been lost since we last built them in a big way in the 1950s (for example I can only find two practicing test pilots in the entire UK with seaplane ratings!)

I'm sure that there are a fair number of sites around the world where flying boats could be operated happily (the unpronouncable new HK airport for example) or the Solent is still there.

Probably a topic for another thread, which I'll gladly leave somebody else to start.

G

[JET SET SPARKY]

..Genghis...i went to the bombardier factory in montreal about two years ago,they are still producing cl-415(i think thats right?) water bombing flying boats! They would probably have the expertise.....dunno if they'd build us a shorts sunderland to keep us happy though! :)

more piston 'liners like the super connie is what we need,sod the money