Inspired by Romney:
Wouldn’t it just feed the fire? I mean, planes do have supplemental oxygen.
Consider as an example Air Canada Flight 797. This flight had a slow smouldering fire that started under the rear lavatory. The cabin filled with smoke. The pilots managed to make an emergency landing despite the smoke and losing electrical power and most of their flight instruments. When the doors were opened to let the passengers out, the sudden influx of oxygen caused a flashover that turned the cabin into an inferno.
Had it been possible to open the windows in flight, the plane would probably have burst into flames and crashed with a loss of all lives. As it was, about half the people onboard managed to make it out before the flashover.
If you want to help prevent deaths from fires on airplanes, work on controlling ignition sources and making airplane contents less flammable. If the plane is so full of smoke that people can’t breathe, it’s probably already to late to save them.
I suppose there have to be some circumstances where it could blow out the fire.
After all, people blow out candles all the time.
Not that there aren’t more circumstances where strong winds that would do more to spread the fire.
Wouldn’t be worth the testing to really find out.
But it’s got to make more sense then, for instance, trying to gain speed by running past fat people to get some sort of sling shot effect.
I wonder why halon suppression systems aren’t more widely used. Halons are gases that can be flooded into a confined area. They are (mostly) non-toxic, and are effective at low concentrations; that is to say, they don’t require displacing enough oxygen to suffocate the passengers (they work by chemically disrupting the fire).
I understand they have severe environmental concerns, but given the infrequency of use and otherwise vast superiority to the alternatives, I’m curious what I’m missing (maybe just the cost).
I suspect that cost is the main factor: not the cost of installing it, but the cost of carrying the extra weight on every flight.
Fortunately fires are rare on commercial flights, but in my (non-expert) view the easiest way to respond to help the passengers and suppress the fire would be:
(1) drop the oxygen masks and make sure every passenger is using one; then
(2) lower the pressure in the aircraft so that there is less oxygen available to feed the fire.
The oxygen masks won’t deploy automatically because of smoke in the way that they will if the cabin loses pressure, but I’m assuming that there’s a non-automatic way to deploy them.
I hope that’s in the manual then 
But then after you’ve landed you need to wait until it’s all out before you can open the doors, otherwise…vooom! Right? Imagine sitting on a plane that’s on fire and not being able to get out :eek:
I don’t think it’s possible to deliberately lower the cabin pressure below the outside pressure. For one thing, the seals and such are designed to keep pressure in, not out. Also, there’s no mechanism on the plane to pump air out of the cabin. Cabin pressure is maintained by taking some high-pressure air from the engine compressors and directing it into the cabin. To lower the cabin pressure, you’d need a vacuum pump to draw the air out.
Airliners do have Halon extinguishers. The type I fly has fixed extinguishers in the cargo hold, the engines, the toilets and portable extinguishers distributed through the cabin plus one in the flight deck.
The passenger oxygen masks are worse than useless in a fire. They work by mixing oxygen from an oxygen generator with ambient air from the cabin as you breath. They don’t do anything to prevent smoke inhalation and they might give passengers the false impression that they don’t need to get down out of the smoke because they are wearing a mask.
The sources of a fire is either going to be from something in the cargo bay, an item in the passenger cabin, something in the airconditioning system, or an electrical fault.
The cargo bay is taken care of by the fixed fire extinguishers, if they don’t put it out then you’re in lots of trouble. The passenger cabin is taken care of by cabin crew with a PBE and a portable fire extinguisher. The airconditioning and electrics are taken care of by flight crew procedures.
The way to fight a fire is to get the protective breathing equipment on, grab an extinguisher, find the source and put it out. Up the front, the pilots would have put oxygen mask and goggles on and will be trying to trouble shoot the location of fire while they also get back on the ground.
If there is enough smoke to make breathing difficult for the passengers, it is probably too late anyway.
I think he meant to lower the pressure compared to normal cabin pressure, not below ambient pressure.
But it is not the procedure to do that. There is a procedure to depressurise the cabin in case of smoke/fire but that seems to be for the purpose of turning the airconditioning packs off in case they are the source of the fire.
Halon is stored in pressurized cylinders so a ‘whole-cabin’ system would require a large tank that was both heavy and highly pressurized (which statistically could actually make the plane *less *safe).
Yes, oxygen generators generate O[sub]2[/sub] thru an exothermic chemical reaction. IOW they get really really hot (upwards of 500°F). Boxes of improperly stowed ones in the luggage bay are what brought down that ValuJet flight in the Florida everglades.
Again, before that ValuJet crash most airliners had no active fire suppression system for the cargo hold because, since they’re not pressurized, lack of oxygen made it difficult to impossible for a fire to start or spread there. It’s also why it was gross, criminal negligence for them to have been shipped on that ValuJet flight like that (i.e. putting something that generates high heat & it’s own oxygen supply in the cargo hold). It’s been reported that that fire got so hot the floor in the passenger cabin began to melt before it crashed.
Twenty or so years ago PBS’ NOVA did an episode about how in an on-board fire people are more often killed by smoke inhalation than by the actual fire. Many in the airline safety world were pushing for requiring, along with oxygen masks & life vests, having thin, lightweight, foldable passenger ‘smoke hoods’ as well. Seems as though nothing became of it.
Yeah, like a Halon tank, having an emergency depress valve to clear smoke from the cabin would probably be outweighed by the extreme danger of it accidentally triggering at altitude (you’d literally only have seconds to get a mask on before passing out and asphyxiating.
Ok. Maybe I wasn’t clear. Our cargo bay has fixed Halon extinguishes for the entire underfloor cargo area. Therefore, I don’t know that weight and safety is the reason it’s not present in the passenger cabin. I think it’s more likely that it is not necessary because the passenger cabin has people in it who can locate a fire and use one of the portable Halon extinguishers on it. Much better to use a small amount of Halon in a controlled fashion if you can rather than flooding the cabin with the stuff.
Cargo holds are pressurised. If they weren’t they wouldn’t carry people’s pets in them and depressurisation accidents like the Turkish Airlines DC10, caused by the cargo door blowing out, wouldn’t have happened.
Except that we do have a way to dump the cabin pressure and you’d have a lot longer than a few seconds because the dump isn’t that quick. Whether it would clear smoke or not would depend on where the smoke was coming from.
I read the cite. So was there anyway to sit still–psychologically doubtful, but anyway–for smoke to be cleared?
I think if they’d stayed in there with the doors closed they probably would have all died of smoke inhalation. Not a good situation to be in.
All commercial aircraft have both manual and automatic oxygen deployment systems. I test this everyday on the Boeing 737 in the Renton factory.
Halon is not used as a fire suppressant on airplanes anymore, it is highly corrosive to aluminum. Halon was at one time used in the Boeing factories as part of a fire control system. After a couple accidental halon discharges and the cost and mess that required very extensive cleanup, it was removed. In my 30+ years working for Boeing, I have never seen it installed or used for in flight fire suppression.
Opening a window on a pressurized airplane at altitude would result in what is called rapid decompression. Anything within 10 feet of that window would be sucked out, whether it fit through the opening or not.
Boeing airplane can release cabin pressure at altitude if necessary. All have outflow valves that can be slowing opened to relieve pressure while at the same time reduce the bleed air that is used to pressurize the cabin. There is a functional test in the factories that test this.
Halon has been banned for ages.
There are substitutes, but keep this in mind when asking about “Halon.”
There is an aviation exception, halon is still allowed and often the only choice.
Yes, however the passenger oxygen systems are of no use in a fire situation because they mix ambient air with the O2, so you still suffer from smoke inhalation and there is no point using them.
Halon 1211 is used for portable extinguishers and this cite from Boeing.com claims they use Halon 1301 for the cargo hold.
This is the summary from this fairly in-depth article on finding a replacement for Halon extinguishers in aircraft. Given that the article was published in the 4th quarter of 2011, I think it is safe to assume that Halon is still the only option on current production aircraft.