Higher Altitudes and O2

[Baradium]

Communications wouldn't really be a problem, you'd just have to use a throat mic.  They're used with many hands free phone systems, and were used by WWII bomber crews because of the oxygen mask.  I am curious how that would work with the ear drums though.  With higher pressure in the respiritory tract than ambient.  I'd think it'd be like doing a fast decent, except you couldn't pop your ears.   

Phil

I believe the system he is thinking of is just a steady stream of air, not pressurizing your lungs.  And therein lies the problem, you wouldn't fix the reason for the oxygen requirement.  Seems the only way to make it work would be a pressure suit... which is decidedly invonvenient.  Diluter demand masks mix ambient air with the oxygen flow at a variable rate depending on altitude so that you use less oxygen at the lower altitudes (since you don't need it all).   

In our case, we have two settings, we have a pressure demand setting and a continuous flow setting.   The first setting only flows oxygen when you breath in (so when you breath out it allows outflow into the cabin.  The second setting always flows oxygen to eliminate the possibility of outside air seeping into the mask in cases such as smoke in the cockpit etc.  The disadvantage to that setting is that now to breath out you have to overcome more pressure to force air outside the mask.

The passenger emergency masks in our case are deployed by a valve, when oxygen flows to them it pulls a pin from the pressure which pops the cover and deploys the mask.  Pulling the mask to your face further pulls another pin to start oxygen flowing to that mask.

In the big jets, the deployment is automatic based on cabin pressure altitude and each mask has its own oxygen generator that is activated by pulling a pin when you pull the mask to your face.

[fireflyr]

Oh, hehe.  Yes, pressurized cabins are definitely pressurized ambient air, but that's not what I had meant.

My curiosity was for aircraft that can make it to those altitudes that might not have a pressurized cabin.  Let me try again.

I work as a sleep lab technician.  Most of the time, I am treating Sleep Apnea.  For patients who have sleep apnea, they are prescribed a mask that fits over the nose, or the nose and the mouth.  This creates pressurized ambient air in the nasal passages, or nasal and oral passages locally on the person.  The rest of the body doesn't experience any kind of pressurized air.

What I was thinking is how useful it would be to develop a similar system as a way to provide an air supply to a pilot in flight who might not have a pressurized cabin, and might not have an easy time of finding a supplier of compressed O2, or would rather pay a higher cost upfront than have to always pay for the service to recharge his O2 tank.

As I think about it more and more, I'm beginning to doubt it's viability as a replacement for O2 for pilots.  O2 can be delivered via a simple cannula.  The pressurized air is delivered via a mask, or at best, by bigger tubing that fits in the nasal passages, called "Nasal pillows".  While you wouldn't have to recharge your O2 canister, you would likely have to recharge a battery.  This battery would likely have to be somewhat bulky to carry sufficient charge over a sustainable amount of time.  Weight would likely be at least as much as an O2 canister, if not heavier.

Getting back to the mask, this could be problematic.  I know pilots without perfect vision who opt out of wearing glasses because of limited visibility where the frames of the glasses lie in their field of view.  The mask does sit somewhat in front of the eyes.  Nasal Pillows don't, but I'm about to touch on the disadvantage with those.

Nasal masks or pillows might create a problem with communications.  The pilot's microphone normally sits immediately in front of their lips.  Everytime I've seen a pilot with a headset, that's where the microphone has been.  With pressurized air in the nasal passageway, that means there will be a gust of air each time the pilot opens his mouth to speak into the microphone, and it could create unwanted interference, unless there was a dampener on the microphone.  Still, if someone isn't used to the mask, it is unusual to try and speak with air rushing out of one's mouth.

Further considerations are the effects of the pressure on a person's ears.  This is especially important in flight, and at higher altitudes.  It could cause more problems than it fixes.

I guess I answered my own question.   

Isn't that sort of like talking to yourself---had that problem and the nice people at Shady Rest took care of me for a while, but   I'm- f i n e  n o o o w !

[spacer]

You don't need to increase the actual pressure, just bring the oxygen percentage up until it supplies the same relative
gas pressure from a more 'friendly' altitude. That's the beauty of cannulae.
My grandpa preferred a cannula to a mask, as it was easier to smoke with it on. He had emphysema... but not for long. 

[TheSoccerMom]

I learned a surprising lesson once when I planned a flight with enough oxygen for 7 people, with extra for a few unforeseen changes in altitudes at the hands of ATC, etc., and then threw in "extra" in case our mission took us further than we'd planned.  I thought I had every angle covered.  I briefed everyone, and we had agreed-upon altitude call-outs over the intercom, which everyone was on.  Buddy checks were a must;  we all agreed to the plan, and we headed out.

Imagine my surprise when we were still in the midst of mapping targets when one of the guys in the rear said the gauge on one of their tanks "was getting low kinda fast".  Well, it sure was, and it resulted in having to cancel the remainder of our flight, to RTB.

It turned out a nice young man, who was with an unnamed branch of the military known as the U.S.AIR FORCE, decided, on his own, without telling anyone, that HE "needed" to be on oxygen above 6,000 MSL!!!!  He had been briefed, along with the rest of the crew, but back on the ground, he argued that he "was going to be on the safe side", so just cranked it up.  He never mentioned a word to anyone, until after we landed prematurely, without having finished the targets.

I was so irked at his attitude that I was standing there, jaw hanging down, trying to figure out how to rip into him and yet sound semi-diplomatic, when I was saved the whole exercise, because the head of the mission jumped in and did it for me.  We had flown around at 6500 feet for almost 2 hours, before we climbed up to FL200, so he had really wasted a big chunk of our oxygen.

Anyway -- it was a lesson for me, that briefing is only as good as the brains receiving the information.  He was sure he'd be hypoxic at 6,000, and I just wish he would have SAID something.  He wasn't even 30, and he was a non-smoker, so it's not like he had a special need.

I found it especially surprising, because it came after flying on fires in the western U.S., where ground elevations range from 8,000 - 12,000 feet EASY.  My own perceptions, and habits, prevented me from seeing this one coming!

So....  monitor your O2 and always double-check....  I was so thankful I had a sharp scientist in back, to catch the imminent shortage.

huff, puff...   

[undatc]

I know here at UND, we have many regs that we have to fly by, in addition to regular FAA regs.  Most of them are from accidents we have had, and generally are good practice.

Any flight here that spends more than 30min above 10,000' and is a day flight, must have oxygen on board, and all passengers on.  It less than reg's but its safe.  Night flights  our regs give us 7,000' and above.

And smoking does effect hypoxia, quoted from the Jepp book, "There are 4 types of hypoxia, Stagnant Hypoxia, Hypoxic Hypoxia, Hypemic Hypoxia, and Histotoxic Hypoxia."  Smoking would fall under Hypemic Hypoxia as one of the main byproducts of smoking is CO2 which is easier to connect to the cell receptors in your hemoglobin then O2.  Because the CO2 molecule is attached, the oxygen cant, which results in a lack of ability of your cells to carry oxygen.  From the Jepp book again, "...smokers who smoke an average of 3 cigarettes a day experience a simulated altitude of 4,000msl while still on the ground."

UND has a pressure chamber, and I've taken the course that uses it.  It is definately worth doing, if you get the oppurtunity to take a 'flight' in one, do it.

[Gulfstream Driver]

And smoking does effect hypoxia, quoted from the Jepp book, "There are 4 types of hypoxia, Stagnant Hypoxia, Hypoxic Hypoxia, Hypemic Hypoxia, and Histotoxic Hypoxia."  Smoking would fall under Hypemic Hypoxia as one of the main byproducts of smoking is CO2 which is easier to connect to the cell receptors in your hemoglobin then O2.  Because the CO2 molecule is attached, the oxygen cant, which results in a lack of ability of your cells to carry oxygen.  From the Jepp book again, "...smokers who smoke an average of 3 cigarettes a day experience a simulated altitude of 4,000msl while still on the ground."

Or CO.  Just a little different.   

[fireflyr]

WOW, Thanks for that----settles several issues I've wondered about---Thanks

[Baradium]

Part 121 requires O2 for the flight crew at any time above 10,000 ft. 

Part 135 requires O2 for any time over 30 minutes above 10,000 ft.

In both these cases PAX have different rules as welll, but it's pretty close to the 12,500 rule (has to do with percentages).


undatc, personally I'd refer to those as additional "rules" not regs, since they aren't required by the FARs.  Helps stop confusion.


Is there any more news on this recent UND crash (in a non UND aircraft)?


MTSU requires you to wear jeans or other long pants while flying, for the same reasons.

[Gulfstream Driver]

UND Policies and Procedures.  Know them.  Love them.

No new real news out of Crookston on that crash.  The airport manager for Crookston told the paper it was definitely the weather, but you know how official that is.  The NTSB should have a preliminary report by Friday, so look for that on their web site.  I've been trying to keep up with it, but the Grand Forks Herald doesn't seem that interested anymore.

From the pictures, it looks like a stall/spin accident.  I was thinking it might be CO poisoning that caused it.  The state Medical Examiner in St. Paul is doing autopsies on the bodies, which were both found inside the plane.

Is that MTSU rule only for winter flying?  What's the reasoning behind it?

[undatc]

Sorry for the misquote there, but for us here, the policies and procedures are basicly just an extension of regs.

And I dont believe the crash in Crookston was a UND plane, at least I havent heard anything about on campus, and I have several CFI friends.

[Gulfstream Driver]

It was a Crookston Flight Service 172.

[Baradium]

Is that MTSU rule only for winter flying?  What's the reasoning behind it?

The rule is year round.  MTSU has never had a fatality involving a flight school airplane.  Years ago a flight school 152 crashed and the fuel caught fire.  The student and instructor maintained that if they hadn't been wearing long pants they wouldn't have been able to get through the flames to get out of the aircraft, or would have been injured much worse if they had.  They received only minor injuries and watched the plane burn from a safe distance.  Since that point it was flight school policy.

It's important to differentiate from FAA regulations and flight school rules, once you get out of the "flight school world" and into the "real world" you need to know


Here is the preliminary report for that crash:

IDENTIFICATION
  Regis#: 9850G        Make/Model: C172      Description: 172, P172, R172, Skyhawk, Hawk XP, Cutla
  Date: 12/02/2006     Time: 0030

  Event Type: Accident   Highest Injury: Fatal     Mid Air: N    Missing: N
  Damage: Destroyed

LOCATION
  City: CROOKSTON   State: MN   Country: US

DESCRIPTION
  A/C WAS FOUND BY POLK COUNTY SHERIFF 1 MILE SW OF CROOKSTON, MN

INJURY DATA      Total Fatal:   2
                 # Crew:   1     Fat:   1     Ser:   0     Min:   0     Unk:   
                 # Pass:   1     Fat:   1     Ser:   0     Min:   0     Unk:   
                 # Grnd:         Fat:   0     Ser:   0     Min:   0     Unk:   

WEATHER: KCKN 020035Z 32011G16KT 1SM SN OVC002 M07/M08 A2990

Winds out of 320 degrees at 11 kts gusting to 16,   1sm vis with snow.... overcast at 200 ft...  not good weather at all...

[Africaspotter]

I was at 9,500ft recently and LA Center asked for my altitude. I was looking at my altimeter and I could see the arrow indicating the 10ft steps, but for some reason I could not find the other arrow... 

I think it really depends on the person and health state, but I personally think that you should stay well below 10,000ft in an unpressurized aircraft. If you think about it, you only get 70% oxygen compared to sea level at 10,000ft... Can't be too healthy.

Cheers,

Felix

[Gulfstream Driver]

I was at 9,500ft recently and LA Center asked for my altitude. I was looking at my altimeter and I could see the arrow indicating the 10ft steps, but for some reason I could not find the other arrow... 

I think it really depends on the person and health state, but I personally think that you should stay well below 10,000ft in an unpressurized aircraft. If you think about it, you only get 70% oxygen compared to sea level at 10,000ft... Can't be too healthy.

Cheers,

Felix

Excellent point.  Altitude affects everyone differently.  That's why it's good to know your limitations.

[TheSoccerMom]

Ditto, Gulf...  there are really big differences between people of similar appearance, age, etc.  It can be a surprise sometimes!  I flew a scientist who informed me she had gotten woozy on an earlier flight, at only 6,000 feet MSL!  She didn't smoke, either.  And she is quite young.  Not the person I would have thought of! 

Another reminder not to "assume"....