Been watching some re-runs of Air crash Investigations and in some episodes the pilots put on their emergency oxygen masks.
The normal masks for passengers are the basic drop down yellow type but these ones pilots wear look like they are out of Star Wars or something Hannibal Lector would wear.
I realize the pilots masks would be more complicated than passengers, not to slip off and have radio communication capability, but why are they so large and cumbersome?
The masks for the passengers need only ensure that the passenger does not end up with brain damage from a lack of oxygen before the airplane can return to a safe altitude. The pilots have to receive enough oxygen to remain alert enough to continue operating the airplane and deal with whatever emergency resulted in the loss of pressurization.
It used to be an FAA requirement that whenever the pilot or co-pilot left the cockpit, the remaining one had to wear the oxygen mask as long as there was only one pilot there. It might still be a requirement.
And a pilot friend told me that though those masks are large (and heavy), they are actually more comfortable than the passenger drop-down ones held on with elastic.
The pilot and co-pilot get their oxygen from bottled oxygen and the masks have built in microphones. Passenger oxygen, in most cases, comes from chemical generators. I test the passenger oxygen systems daily on the 737 assembly line.
Smoke is a common threat in aviation accident incidents. My guess is that the face mask is a mitigation against cockpit smoke.
This is part of the answer. The O2 masks double, with the addition of smoke goggles, as smoke masks. The passenger masks mix O2 with ambient air and are of no use as protection against smoke inhalation, they are only to keep you alive in case of depressurisation. The pilot masks have a mic, the ability to provide either diluted O2 or 100% O2 on demand or 100% O2 at positive pressure. They also have vents that send a stream of O2 into the smoke goggles to help keep them clear.
To ensure adequate blood oxygenation, the masks & regulators have a feature called “positive pressure breathing.”
At high altitude, simply inhaling even pure oxygen won’t get enough into the bloodstream to keep the brain & body working well enough. So the regulator has a device to detect ambient altitude (cabin air pressure really) and force oxygen at fairly high pressure into the mask.
That will only be effective at ramming oxygen into the lungs if none of it leaks around where the mask fits the face. So the head harness is a pretty stout thing which is adjusted to fit uncomfortably tightly. The face-sucker is clamped tightly over your nose/mouth & when it’s in positive pressure mode it’s a real PITA to breath. Unlike normal everyday life it takes positive effort to exhale & with just a slight relaxation of that effort the mask will inflate your chest like a balloon. Normal breathing is pull gently, relax, pull gently, relax, … . Pressure breathing is relax, push HARD, relax, push HARD, … It’s difficult to talk intelligibly while pressure breathing.
The mask is designed to be able to be put on using one hand in just a couple seconds. At very high altitude and with a very rapid loss of pressure (= big hole in the airplane), you may only be conscious for 5-10 seconds total. Gotta be quick. Or be dead. And it has to fit over headsets and / or eyeglasses.
Older designs were a rigid plastic frame with some hinges & springs; you’d hook the frame benind your head & then pull the facemask forward against spring pressure & down over your forehead to place it over your nose / mouth. Then release it back to let the springs relax a bit but still smash it into your face. Ideally you didn’t sweep your glasses off onto the floor with the same motion.
More modern designs dispense with the plastic frame and instead have a harness of flexible rubber (surgical) tubing. When you grab it to put it on, you squeeze a lever which inflates the tubing making the harness rigid & much bigger than your head. It’s easy to push the mask directly onto your face & the harness ends up around & behind your head. When you let go, the tubing deflates & shrinks down to tightly conform to your head, securing the mask in place for for pressure breathing.
As **Richard Pearse **explained, older set ups include separate smoke goggles which are sorta like snorkelling masks. Deep enough to have room for eyegalsses & with a fairly large opening to provide some semblance of peripheral vision. They too are held onto the head by heavy elastic straps to ensure a smoke-proof fit against a face. Those go over the oxygen mask harness & are uncomfortable & unwieldy as hell.
Some of the lastest designs incorporate the smoke mask & oxygen feed in one unit; these look a lot like the gear you see modern firefighters wear.
Here are some thumbnail pix of various models. http://www.aviationoxygen.com/delivery_above_25000.html
The one at upper right demonstrates a mask plus separate smoke goggles. The rightmost 3 in the bottom row are typical latest-and-greatest airline units both with & without smoke masks and using the inflating tube harness. The one at bottom left is standard military gear; not relevant for airline use.
I really have to say - if the company can’t be bothered to make the clickable thumbnails of their products link to a full-sized image, it doesn’t fill me with confidence at their abilities to produce life-saving safety equipment.
Really, guys - is it that fuck’n hard to do?
That was an online retailer, not the manufacturer. But I had the same thought you did when I stumbled on that page. It proved harder than I expected to find any decent pix at all.
Thank you all for comprehensive replies.
The masks I was referring too were like this
http://i656.photobucket.com/albums/uu281/wetpaint/OxygenMask.jpg
With some additional Googling I see there are various types of mask some not as complicated as the this one so maybe I was looking at old versions.
Thank y’all
Why could they not design the air delivery system to work like the CPAP mochines that people with sleep apnea use? The air pump apparatus is sensitive to the back-pressure coming from you, and positively pumps air into you when you inhale, but backs off the pressure when you exhale. This makes breathing much easier. They can’t/don’t do that for pilots’ emergency air masks?
I’m speculating, but here are some ideas:
It’s probably a matter of the pressure supply being much stronger.
There’s no way you could sleep with this thing ram-filling your lungs. CPAP machines have to be gentle enough to let you sleep through wearing them. Also they have to let you breathe while unconscious.
This stuff is requried to be very reliable even when used only once in its lifetime.
Simplicity is good. There are no electronics which could fail if power was interrupted; the whole thing is mechanical.
The bit at the back of the head on that picture is the smoke goggles. The masks are also designed to be quick donning so you can put them on with one hand over the top of whatever headset you’re wearing. The big U shaped metal harness going around the ears is to make room for the headset. The masks have to have controls so you can change the modes. Although they can provide O2 at positive pressure, it’s wasteful, so you need to be able to change it to diluted O2. Same with the O2 that clears the goggles, if you’re not wearing the goggles then you don’t want that O2 escaping so you need to be able to turn it on and off. All of this complicates the mask significantly.
I think they are used much more often than that – probably on nearly every single flight. For example, if the pilot leaves the cockpit to go to the restroom, the co-pilot must wear his oxygen mask until the pilot returns. That probably happens on a regular basis.
We clean, fit, & test the masks, regulators, and the override mode of the emergency pressure breathing function at every crew change. So that’s a couple times per day per aircraft.
The actual functioning of the altitude-sensitive pressure breathing system can’t be exercised except by actually using it during a decompression at altitude. That was the feature I was thinking specifically of when I wrote the above. Not that the reader could have known that. 
So we don’t necessarily know it’ll work automatically when needed. We do know we can manually override pressure breathing to full on because we tested it. And going immediately to override is part of the reaction to high altitude decompression. Just in case.
I recall an incident many years ago wherein the regulators’ automatic pressure breathing feature malfunctioned for 2 of the 3 folks in the cockpit who needed it during a decompression. It turned out that those devices weren’t being removed & refurbished at the periodic aircraft overhaul. They were just sitting there since new. And after 20 years the lube had dried out on some aneroid which stuck in the closed position. There was a mad flail to remove, test, & refurbish all the regulators on the fleet. I couldn’t tell you whether or not they’re any better maintained today.
Pre-9/11 we used to do a lot of pilot-leaving-the-cockpit enroute for coffee, potty breaks, etc. It also was always more prevalent on 3-man vs. 2-man cockpits and hence more prevalent in the past vs. now.
Nowadays, at least at my carrier, we really work pretty hard to avoid opening the door inflight. I can go a couple *months *between inflight pee breaks. Of course the necessity of pee breaks goes up dramatically as the flight gets longer than about 4 hours. My personal boredom-o-meter gets too high much past 4 hours, so I prefer to fly the 2 to 4 hour hops. The guys on long-haul would have a different experience.
And yes, you’re right that the regulations require the single pilot to wear the mask when the other pilot is out of the cockpit at cruise altitudes. Which does exercise at least some parts of the oxygen system.
I thought that too…Well, not so much that I fear for my life because of their website design so much as I just thought the design was bad. Then I realized that they weren’t thumbnails, they were just pictures in a grid format. I also figured it was the type of thing that the people who wanted/needed those things probably already sort of know what they’re looking for. That was further confirmed by scrolling down and seeing that those masks are about $8000 each :eek:. In other words, when you’re ready to make that purchase you’re probably either going to want to talk to someone or you already know exactly what you want and don’t need any more details. It seems as though you can buy some of the more generic stuff (O2 tanks, meters etc) right off the site though.
