posted
Here's another one from Mythbusters: A pilot uses too much hairspray, and while flying, there's a short in his communication system. The flammable hairspray, the spark, and the pure oxygen in his mask combine to create an explosion that blow his head clean off. They put it to the test with a ballistics-gel head covered with real hair. It didn't explode, but it did start burning like a campfire.
-------------------- I like to go down to the playground and watch the kids run and jump and scream, because they don't know I'm only using blanks. Posts: 942 | From: Illinois | Registered: Jan 2004
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Joe Bentley
Ding Dong! Merrily on High Definition TV
posted
Makes some sense. Many flight cabins have an extremely oxygen rich atmosphere and a lot of hair products have an alcohol base to them which is very flammable.
-------------------- "Existence has no pattern save what we imagine after staring at it for too long." - Rorschach, The Watchmen Posts: 8929 | From: Norfolk, Virginia | Registered: Jun 2002
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posted
The alcahol would evaportate within minutes at most - yesterday I spilled a lot of isopropyl alcahol and it was gone after a minute or two. The larger surface area provided by the droplets from a spray would allow the alcahol to evaporate almost instantly.
-------------------- Fools! You've over-estimated me! Posts: 3745 | From: New York City | Registered: Jan 2004
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posted
Somehow I doubt hair spray will lead to an inflight fire or explosion.
However of a real danger is something I read in Flying magazine and then had happen to me which would most certainly cause an explosion. Flying has a section in their magazine called "and I learned about flying from that" in which pilots recall how they overcame tryig situations while piloting their aircraft.
I read this probably about 5 years ago so don't count on me for 100% accuracy I would rather you try and find the article for yourself, but it was a tale about a pilot flying (i think) a Cessna 172. What happened is on older 172's there is a com switch on the left windshiled pillar of the airplane. Also running down that pillar is the line for the fuel valve. Anyway what happened is he flipped the switch for the com to talk to ground and the jack shorted out and the spark burned throug the fuel selector line and began leaking gasoline into the cabin. now this is a difficult situation because he cannot talk to anybody, he is losing fuel and the cabin of the airplane is filling with gasoline and noxious fumes (what would really ignite in a fire). Anyway he handled the situation and all was fine but the potential to become a huge fireball was there. If anybody wants to look up the article it he was some correctional officer transfering a prisoner by air (and that is about all I hazily remember).
the reason I remember it is while I was taking my own flight lessons about 6 months after reading that article the same thing happend to me (while we were on the gorund fortunatly) in a rental Cessna 172. We had the master on and I was checking the radios switiching the jacks when I heard a pop and started to smell gasoline. the instructor and I got out of the airplane fast and had the only available local A&P check it out. When he pulled off that cover the line has a small leak and there was a burn mark around the switch. That is prbably the only reason I still remember that article.
Anyway, for those interested in flying, (not the morbid facination of accidents) Flying magazine's "and I learned about flying from that" is a wonderful column to read. It is interesting to see how resourceful pilots can be in tense situations.
Posts: 163 | From: NYC | Registered: Aug 2004
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posted
A hairspray-induced fire was suggested as the probable cause for a 1950s airliner accident. The story is told in one of the Robert Serling books; Probable Cause I think.
quote:Makes some sense. Many flight cabins have an extremely oxygen rich atmosphere and a lot of hair products have an alcohol base to them which is very flammable.
Umm, no. The cabin atmosphere in the vast majority of commercial aircraft is the same 80% nitrogen, 20% oxygen mix as you find throughout the atmosphere. It is pressurized slightly so that the partial pressure of oxygen stays at a healthy level, but that pressurization is such that the cabin altitude is generally not higher than about 10,000 feet even when the aircraft is as high as 41,000 feet. So the partial pressure of oxygen is probably less than at sea level.
About the only place you'll commonly find oxygen-enrichment is in the masks and cannulas of a supplemental oxygen system.
Yes, there are some specialty applications where you have a cabin atmosphere of pure oxygen, but I don't consider them to be what you'd call "common."
The utility of pure oxygen atmospheres is that you can have a greatly reduced total pressure and still provide an adequate partial pressure of oxygen to sustain healthy blood oxygen levels. For example, the sea level atmosphere is about 15 psi and composed of 20% oxygen and 80% nitrogen. The partial pressures are 15*.2 = 3 psi oxygen, 15*.8 = 12 psi nitrogen. So if you strip out all that useless nitrogen you can get by with a cabin pressure of only 3 psi. And the utility there is that it lets you get away with build a lighter containment vessel (cockpit, cabin, capsule, canopy, whatever).
And, of course, the major downside of pure oxygen is flammability. "Apollo One" pretty much says it all.
Going off on a tangent, several research aircraft have used an interesting pressurization system that uses both oxygen and nitrogen to best advantage. In these aircraft, the pilot wears a pressure suit serviced with pure oxygen at about 3 psi for breathing. The cabin around the pilot's suit is pressurized with pure nitrogen at 3 psi. The two pressures cancel each other out, so there is no pressure differential across the membrane of the suit. That keeps the suit limp, so it doesn't interfere with the pilot's movements. The pure nitrogen in the cabin is good for fire supression, and the low cabin pressure keeps the cabin structure light because it doesn't have to be very strong to hold in 3 psi. And if the cabin pressure is lost, the suit will still maintain the 3 psi of oxygen inside, though the suit will puff up and make movement a lot harder. We'll probably see a system like that in Steve Fossett's Perlan phase II stratospheric sailplane, if he maintains his interest in the program that far...
Bob "Al Veoli" K.
Posts: 2079 | From: California | Registered: Feb 2000
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quote:Makes some sense. Many flight cabins have an extremely oxygen rich atmosphere and a lot of hair products have an alcohol base to them which is very flammable.
Umm, no. The cabin atmosphere in the vast majority of commercial aircraft is the same 80% nitrogen, 20% oxygen mix as you find throughout the atmosphere. It is pressurized slightly so that the partial pressure of oxygen stays at a healthy level, but that pressurization is such that the cabin altitude is generally not higher than about 10,000 feet even when the aircraft is as high as 41,000 feet. So the partial pressure of oxygen is probably less than at sea level.
The myth(s) cited on the show dealt with Canadian fighter jets, I believe they said "A 104's". The rig they built was a crude mock-up of a fighter jet cockpit, not a commercial aircraft, pressurized cockpit with flight helmet, mask, communication headset (short-circuited to provide ignition), etc.
Posts: 121 | From: Illinois | Registered: Jul 2005
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quote:Originally posted by react2distract: The myth(s) cited on the show dealt with Canadian fighter jets, I believe they said "A 104's". The rig they built was a crude mock-up of a fighter jet cockpit, not a commercial aircraft, pressurized cockpit with flight helmet, mask, communication headset (short-circuited to provide ignition), etc.
I think the F-104 has a cockpit that is pressurized with bleed air from the compressor section of the J-57 engine. The pilot generally wears a face mask supplied with oxygen from a diluter/demand pressure-breathing regulator; (probably from an MD-1 or CRU-79 regulator). So, yeah, there is potential for there to be an oxygen-rich atmosphere in the cockpit, but it wouldn't be pure oxygen except inside the mask.
Posts: 2079 | From: California | Registered: Feb 2000
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quote:Originally posted by TB Tabby: Here's another one from Mythbusters: A pilot uses too much hairspray, and while flying, there's a short in his communication system. The flammable hairspray, the spark, and the pure oxygen in his mask combine to create an explosion that blow his head clean off.
Further investigation proved that actually his head was eaten by a fox.
Posts: 1651 | From: Columbus, Ohio | Registered: Aug 2004
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quote:Originally posted by TB Tabby: ...The flammable hairspray, the spark, and the pure oxygen in his mask combine to create an explosion that blow his head clean off. They put it to the test with a ballistics-gel head covered with real hair. It didn't explode, but it did start burning like a campfire.
The burning part stands to reason.
The only hard part is that aviation headsets and microphones operate on millivolts. I guess if there were a short between one of the microphone wires and a 28 volt bus, you might coax a spark out of the in-mask microphone. But that's a long, long shot. I'd guess that the most likely outcome there is that one of the 30 ga or so wires in the mic would just melt through without achieving flash temperature of any of the nearby microphone components. Remember, the oxygen itself doesn't burn, it just helps other stuff burn, and that other stuff is what you need to raise to ignition temperature. I suppose that lingering propellant and aerosol components from the hairspray might be a candidate, but a very weak one - the mask only covers your mouth and nose. I'd worry more about after-shave and cologne, but only by a very tiny increment.
Going off on a slightly different tangent, for many years, there was a myth in the glider world that if you wore lip balm under your oxygen mask, the greasy balm would oxidize and burn your lips. I made a point of testing it with several balms (including Carmex and Chapstick) and achieved no such result.
The reaon I'm careful about greasy stuff around oxygen systems is that if you get them smeared on surfaces that end up pressurized to the 2000 psi of the oxygen tank, they will spontaneously combust. So when I'm installing a bottle or regulator or such I will keep my hands scrupulously clean.
Bob "O2 be young again" K.
Posts: 2079 | From: California | Registered: Feb 2000
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posted
If it didn't ignite to kill, it would probably sufficate them in the enclosed cockpit. Which is why your not allowed to smoke (not just the fire ignitable but also because the plane is enclosed tight).
-------------------- Joseph Z Posts: 1356 | From: Woodbridge, VA | Registered: Jul 2004
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you are not allowed to smoke because of the possibility of fire and the FAA's position on the effects of second hand smoke. I don't think it has much to do with the sealing of the aircraft because the aircraft has a ventilation system.
I remember going to Italy in 1998 and having to take a domestic flight from Amsterdam to Rome. That plane was pressurized (I think it was a dc-10) and all the europeans on it were smoking. They even had a specific smoking section (which I imagine is pretty novel for something in europe, where just about everybody smokes).
Usually if there is a fire in an aircraft the smoke builds faster than it can be vented. Even a fire in an unpressurized aircraft, such as a cessna 172, with the doors open and in flight, the smoke can still get pretty thick. don't ask me how I know this.
Posts: 163 | From: NYC | Registered: Aug 2004
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