Can cabin decompression fight fires?

Pi1otguy

Pi1otguy

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I was watching Seconds to Disaster when they covered Air Canada flight 797 in which a there was a fire in or around the lavatory within the walls with smoke but no visible flames. It appears that the attempt to use an extinguisher failed because the fire could not be seen or directly accessed.

The pilot appeared to have taken the right actions, but watching from outside the event this question came to mind.

Even though a flash fire occured upon opening the door, would a pilot induced depreesurization of the cabin have helped by starving the fire for the 10 or so minutes the O2 generators last? There would probably still be a fire, but wouldn't it lay down quite a bit and take longer to flare up upon opening the door?

Unrelated: Do airlines continue to use flight numbers of accident flights?
 
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I'm pretty sure the 9/11 flt #'s will never be used again by thier respective airlines. And as far as the firefighting thing goes, never thought about it before. Our policy for an inflight fire that is more structural than a known component is to find the nearest landing spot 'cause the clock is ticking. We are told in training that once a structural fire starts, we have somewhere around 15 minutes to put it out or land before the airframe starts to come apart. If we had a situation of visible smoke but no fire, I belive I'd have the fire fighters start removing panels to find the source. Another solution for our aircraft (E-3/707) is to kill all electrical power. When the smoke stops, if it stops, bring each electrical bus back online one at a time with a fair amount of time between each one to see if the smoke starts again. We would use this procedure over water or if we were a fair amount of time away from an emergency airfield. Either way, a fire on the aircraft is my biggest fear as an engineer because of how elusive it can be.
 
A very good friend of mine from the bank died on that Air Canada flight.

In addition, my brother in law was a member of the RCMP group tasked with recovering body parts from that Swissair flight that went down outside of Halifax. He still talks of finding a running shoe with a foot still inside of it!
 
AWACSEng said:
Our policy for an inflight fire that is more structural than a known component is to find the nearest landing spot 'cause the clock is ticking.
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I'd hope a similar policy is in effect for any fire that isn't quickly put down in military or civil aviation.

If we had a situation of visible smoke but no fire, I belive I'd have the fire fighters start removing panels to find the source.
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I was under the impression that interior panels required specialized tools to remove, and don't come off easily.
 
Pi1otguy said:
I'd hope a similar policy is in effect for any fire that isn't quickly put down in military or civil aviation.



I was under the impression that interior panels required specialized tools to remove, and don't come off easily.
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Military aircraft many times just has a foil coated insulator along the cabin and ceilings. This is radiation and heating insulations. The panels that hold on equipment generally use phillips head screws.
 
Pi1otguy said:
I was under the impression that interior panels required specialized tools to remove, and don't come off easily.
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The panels open up real nice with the special tool we call a crash axe. And as far as any other fire goes, for us they are somewhat easier to deal with 'cause most of our equipment is exposed and fairly easy to identify and isolate. As far as interior panels go, most heavy mil aircraft have the foil insulater blankets but we have good old fashioned airline interior panels, but like I said, they open up nicely with a little "help".
 
The air at 30,000 feet has the same O2% as air at sea level. The PO2 is lower, but fire is about fuel/air mass ratio, not densities.
 
We've never been taught anything about depressurizing for fire...just blowing the extinguishers as much as we can as we hustle to the nearest airport. Lowering the pressure can, however, help pull smoke or bad smells out of the cabin. Someone lets one rip at 16,000 feet? You better believe we're going to bring the cabin up to 9,500 feet pretty quick...it works, too; those outflow valves open and whoever is in row 9 will be able to feel the air moving backwards.
 
Teller1900 said:
Someone lets one rip at 16,000 feet? You better believe we're going to bring the cabin up to 9,500 feet pretty quick...it works, too; those outflow valves open and whoever is in row 9 will be able to feel the air moving backwards.
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You are lucky your outflow valves are in the back. :rolleyes:
 
Matt, you bring up another good point about cabin ventilation. Step 4 of our Fire Smoke or Fumes checklist is Cabin Alt: 9500'. The only reason it is so deep in the checklist is cause O2 on/100%, smoke goggles on as req., and crew report preceed raising the cabin. Ron, you are absolutly correct. There is the same level of O2 at altitude as there is at SL, it is just less dense. Fire can live on any O2 regardless of pressure.
 
Everskyward said:
You are lucky your outflow valves are in the back. :rolleyes:
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We have 2 outflow valves. One in the foward and one in the aft lower compartment. I fly with the foward one closed so when I let one go, the rest of the crew knows it.:D:D:yes:
 
The "fix" for Air Canada flight 797 was to add an automatic fire extinguisher under each lav sink. They improved the latch and seal on the under lav sink access door. The last fix was the addition of the smoke detector. The smoke detectors and the extinguishers work well.
Ron
 
Ron Levy said:
The air at 30,000 feet has the same O2% as air at sea level. The PO2 is lower, but fire is about fuel/air mass ratio, not densities.
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Good point. I guess I assumed less O2 available (per volume of air) = lower fire. I suppose I watch too much Star Trek TNG. (Crusher & LeForge decompressed a cargo bay to put out an uncontrolled fire and held their breath in the vacuum of space for ~30 sec.)
 
Pi1otguy said:
Good point. I guess I assumed less O2 available (per volume of air) = lower fire. I suppose I watch too much Star Trek TNG. (Crusher & LeForge decompressed a cargo bay to put out an uncontrolled fire and held their breath in the vacuum of space for ~30 sec.)
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Well that is hard vacuum! But where is the line or demarcation? How low a pressure do you need to extinguish flame?
 
Pi1otguy said:
Even though a flash fire occured upon opening the door, would a pilot induced depreesurization of the cabin have helped by starving the fire for the 10 or so minutes the O2 generators last? There would probably still be a fire, but wouldn't it lay down quite a bit and take longer to flare up upon opening the door?
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I don't think activating a whole plane-load of O2 generators would be a great tactic for fire supression.

Regards,
Joe
 
Pi1otguy said:
Good point. I guess I assumed less O2 available (per volume of air) = lower fire. I suppose I watch too much Star Trek TNG. (Crusher & LeForge decompressed a cargo bay to put out an uncontrolled fire and held their breath in the vacuum of space for ~30 sec.)[emphasis added]
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Dump to zero air, and the fire goes out, but even at 30,000 feet, there's still enough air to support combustion under the right circumstances. In addition, it's a lot easier to sustain a fire than to get one going; converserly, it's harder to extinguish a fire than to prevent one from starting.
 
Teller1900 said:
I'd rather do that than pump pure oxygen into an open fire! They'll wake when you get down low enough.
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Just for clarity, you do know I'm talking about the lil plastic O2 masks that pop down from above, right? And that the O2 generator is in reference to the O2 generators (possibly just an O2 tank) that supplies the mask for the pax, not the cabin.
 
Pi1otguy said:
Just for clarity, you do know I'm talking about the lil plastic O2 masks that pop down from above, right? And that the O2 generator is in reference to the O2 generators (possibly just an O2 tank) that supplies the mask for the pax, not the cabin.
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Yup, I know. Ours feed off of two 1800psi O2 tanks that are in the nose under the avionics bay. Those little masks are usually either continuous supply or diluter demand, so they'll just pump pure O2 into the cabin...something that is highly flammable. An ember or a spark would love to find one of those masks as it's streaming oxygen out. Even if it's an a/c that uses oxygen generators, you wouldn't want those being introduced to open flame. We'll use our pressure demand system in the cockpit in the event of a fire because it's pretty well sealed against leaks, but the masks in the back are going to be worthless in a smoky cabin - they mix the O2 with ambient air before it's delivered to you, so you'll still be sucking down smoke while putting pure O2 into a fire. Our memory items for cabin fire/smoke are pretty simple - 1. Crew don O2 masks; select 100%. 2 Raise cabin alt as high as practical (sucks the smoke out the outflow valves). 3 land as soon as practicable.

Compare to memory items for rapid depressurization: 1. Crew don 02 masks; select "emergency" if needed. 2. Cabin 02, select on. 3 Descend to 10,000 feet or less. 4. Land as soon as practicable.

Those little masks may only introduce a small amount of oxygen, but any amount of pure oxygen is too much in a fire.
 
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