Oxygen Mask - how does it work?

I read here that the system is working as designed, that, if, while on ground, you black out if OBOGS is turned off or the oxygen flow is turned to 0.

But how does the oxygen mask work? Does it not just enrich the environmental air with additional oxygen when enabled? Or does the oxygen flow valve completely control the air flow as whole - like, if turned down, you can't breathe at all?

What exectly causes the lack of oxygen, if the system to provide additional oxygen is not working?

Flagrum,

The mask is supposed to “seal” the pilot face (nose and mouth) and if obogs is off, there is no oxygen and the pilot kind of suffocates. It becomes real hard to breath in real life. I can say that because I tested that myself. I could breath but it was almost and Yoga exercice.

OBOGS - On Board Oxygen Generator System - basically filters oxygen molecules from engine bled air and feeds the system. This way there is no need to have an reservoir do be filled once bellow a certain level like the majority of commercial planes has.

I hope the explanation helps.

All the best,

Sydy

No actually when you start cold and dark OBOGS switch is already off. Only turning down the flow knob makes you pass out.

Somewhat curious about this myself.

So the mask forms an airtight seal with the face? No external air can get in?

But the cabin is pressurised? I suppose the mask is worn as a precaution in case pressurisation is lost?

Are pilots obliged to wear the mask at all times (in the air)?

Are pilots obliged to wear the mask at all times (in the air)?

They don't. I think you're right, the mask is worn more as a precaution than anything else. You can see videos on youtube with people flying in military jets (Prowlers, Hornets) with their mask taken off.

I dont think the blue angels use them.

the cockpit is pressurized, so the mask is for that moment when bullets smash your canopy or some leakage at high altitude

Reading the literature it seems that the mask requires the oxygen flow switch on regardless if OBOGS or O2 bottle type lot aircraft. In procedures switching on oxygen flow and donning mask or switch off and doffing mask are simultaneous.

Breathing ECS or cabin air without the enriching system should be done with the mask off. From what Sydy says perhaps you can breathe with difficulty because you are drinking through a long straw, all the uncooperative plumbing of the system.

The mask is better air than cabin air. Mask is positive pressure relative to cabin. ECS does not get enriched air, only temperature-conditioned bleed. Only masks get enriched air.

If flow is shutoff, the mask is sealed and will not allow outside (cabin) air. Sadly happened to a backseater in a Viper in 2006. He started to breathing rapidly causing onset of hypoxia. Pilot instructed him to gang load his O2. At some point he turned off flow, instead of going 100% oxygen. :(

In any “high performance” military aircraft O2 mask is to be worn at all times

In regards to the perpose of presurizstion of the cockpit, below curtain barometric pressures your body processies the available oxygen differently. So if you didn’t have your mask on and lost pressure suddenly, you’d pass out pretty quickly. With the mask you’d be ‘fine’ below crazy high altitudes. And the cockpit itself isn’t receiving the oxygen, your mask is.

Pet peeve, In the movies you often see pilots take their mask off and gasp for air like they aren’t getting enough oxygen...totally BS, you never even need to take a deep breath when on O2, you’re never breathing easier. Try Scuba diving sometime.

A stab at TOPGUN, I see. You’re a liar. TOPGUN is 100% authentic and real!

In any “high performance” military aircraft O2 mask is to be worn at all times

 

In regards to the perpose of presurizstion of the cockpit, below curtain barometric pressures your body processies the available oxygen differently. So if you didn’t have your mask on and lost pressure suddenly, you’d pass out pretty quickly. With the mask you’d be ‘fine’ below crazy high altitudes. And the cockpit itself isn’t receiving the oxygen, your mask is.

 

Pet peeve, In the movies you often see pilots take their mask off and gasp for air like they aren’t getting enough oxygen...totally BS, you never even need to take a deep breath when on O2, you’re never breathing easier. Try Scuba diving sometime.

"Oxygen Mask - how does it work?"

It doesn't, it's a game!

:megalol:

I have problems with it getting tangled up with the flight stick...

Oxy mask apart from the risk of loss of cabin pressure also help with G tolerance by providing positive pressure. I.e the mask is trying to force oxygen into your lungs. Some info on history of it can be found http://medind.nic.in/iab/t00/i2/iabt00i2p51o.pdf

A stab at TOPGUN, I see. You’re a liar. TOPGUN is 100% authentic and real!

ABSOLUTELY. Smoking hot civvy with zero stick time instructing aviators about ACM? Of course that happens.

LOLOLOL That was good!:D

In any “high performance” military aircraft O2 mask is to be worn at all times

 

In regards to the perpose of presurizstion of the cockpit, below curtain barometric pressures your body processies the available oxygen differently. So if you didn’t have your mask on and lost pressure suddenly, you’d pass out pretty quickly. With the mask you’d be ‘fine’ below crazy high altitudes. And the cockpit itself isn’t receiving the oxygen, your mask is.

 

Pet peeve, In the movies you often see pilots take their mask off and gasp for air like they aren’t getting enough oxygen...totally BS, you never even need to take a deep breath when on O2, you’re never breathing easier. Try Scuba diving sometime.

Reminds me of the scene in Independence Day when Jimmy takes off his mask trying to shake off

the aliens.. "Put your mask back on! That's an order marine!"

What I’ve understood if not in combat, it is to be worn at higher altitudes as there is low level of oxygen. At low altitude it is a pilot’s decision to make. In combat, I think you are correct.

What I’ve understood if not in combat, it is to be worn at higher altitudes as there is low level of oxygen. At low altitude it is a pilot’s decision to make. In combat, I think you are correct.

Nah, in any high performance aircraft exygen shall be worn at all times. Whether pilots actually follow the regs is a different story.

the cockpit is pressurized, so the mask is for that moment when bullets smash your canopy or some leakage at high altitude

Just to follow up on this as I don't think this was addressed:

The cockpit is pressurised, but not to the same level as say, an airliner.

An airliner will keep cabin altitude below 10,000ft throughout the flight, regardless of aircraft altitude.

The F/A-18 (like many other combat aircraft) does not. Cabin altitude climbs above 10,000ft at a real altitude of 28,000ft, reaching 16,000ft at a real altitude of 40,000ft. No enough to keep you brain ticking over, if at all.

Although I'm no authority, I suspect the reason for this is to strike a balance between low pressure (minimising the damage caused by explosive decompression), and high pressure (providing some pressurisation, probably more to prevent decompression sickness, as much as air to breathe).

Just to follow up on this as I don't think this was addressed:

 

 

The cockpit is pressurised, but not to the same level as say, an airliner.

 

 

An airliner will keep cabin altitude below 10,000ft throughout the flight, regardless of aircraft altitude.

 

 

The F/A-18 (like many other combat aircraft) does not. Cabin altitude climbs above 10,000ft at a real altitude of 28,000ft, reaching 16,000ft at a real altitude of 40,000ft. No enough to keep you brain ticking over, if at all.

 

 

Although I'm no authority, I suspect the reason for this is to strike a balance between low pressure (minimising the damage caused by explosive decompression), and high pressure (providing some pressurisation, probably more to prevent decompression sickness, as much as air to breathe).

Even at 18k cabin alt, it's not a big deal. I've done it more than once weather flying a skydive aircraft or skydiving in general. You probably wouldn't want to be up there for 30 min or so, but you aren't going to pass out either.

Even at 18k cabin alt, it's not a big deal. I've done it more than once weather flying a skydive aircraft or skydiving in general. You probably wouldn't want to be up there for 30 min or so, but you aren't going to pass out either.

Fair enough! Might depend on the person? It guess it wouldn't do much for mental function even if you remain conscious!

Fair enough! Might depend on the person? It guess it wouldn't do much for mental function even if you remain conscious!

It's not even noticeably at 18k. Maybe after 30 min or so you may get a headache or something, but that's about it. Technically speaking, you're required to wear oxygen at all times flying above 14,500 cabin alt, but...

There are many reasons why fighter pilots wear the mask from to to td. The obvious reason is to survive. You brain really gets slow the further you go up, and that is obviously dangerous if you are in a plane fast like a bullet.

I had the chance to do hypoxia training back in flight school in the swiss af and never will forget the lesson learned. Already above 10`000ft your (brain-) work is slowing down rapidly and doing your math or pilot tasks is getting difficult. But you feel good and you do not realise that you are in trouble, (unless you got the proper awareness training). Your lethargy grows with the altitude, the flight-medics in the chamber had to push me all the time so that I did, or better tried to do my tasks. At 25`000ft I finally past out. As soon as I got oxygen, my brain recovered extremely quickly and my skin changed color back from pale blue to standard.

It is called oxygen system but actually what you normally get thru the mask is breathable air. If your suffer from air sickness or you need to recover quickly, we could switch to 100% oxygen. That smells a bit strange but it may help.

There is also the intercom and radio mic in the mask..., and it may help to survive an ejection... For all those reasons it was mandatory to wear the mask in fighter jets during the whole flight.

Watch this link....

Also pulling g's ..you want as much oxygen as possible.

F-22 fleet was grounded due to faulty oxygen system.

https://abcnews.go.com/Blotter/22-raptor-grounded-oxygen-scare/story?id=14802706