Is flight at 12,500 actually flight above 12,500?

[SkyHog]

If I plan a flight at 12,500ft, and fly it there, am I required to use oxygen after 30 minutes, or does that start at 12,501ft?

 

[Larry in TN]

14 CFR 91.211 Supplemental oxygen.

(a) General. No person may operate a civil aircraft of U.S. registry—

(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

 

[SkyHog]

14 CFR 91.211 Supplemental oxygen.

(a) General. No person may operate a civil aircraft of U.S. registry—

(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

Right - maybe I'm overthinking it.

Thank you.

 

[dmspilot]

At cabin pressure altitudes

If pressure is lower than standard, then you may end up having to use it after 30 minutes, even if you are at 12,499.

 

[SkyHog]

If pressure is lower than standard, then you may end up having to use it after 30 minutes, even if you are at 12,499.

I'm pretty sure that pressure altitude is corrected for atmospheric pressure, and therefore provided the altimeter is set correctly, the altitude read off the altimeter would be the actual limit here, no?

 

[dmspilot]

I'm pretty sure that pressure altitude is corrected for atmospheric pressure, and therefore provided the altimeter is set correctly, the altitude read off the altimeter would be the actual limit here, no?

When set to the local altimeter setting, the altimeter reads indicated altitude. Pressure altitude can be determined by setting the altimeter to 29.92"Hg. If and only if the local altimeter setting is 29.92"Hg would indicated and pressure altitude be equal.

 

[Larry in TN]

I'm pretty sure that pressure altitude is corrected for atmospheric pressure, and therefore provided the altimeter is set correctly, the altitude read off the altimeter would be the actual limit here, no?

No. The altimeter only reads pressure altitude when it is set to 29.92. If the pressure is lower than standard, i.e. altimeter setting below 29.92, then your cabin pressure altitude will be above your indicated altitude.

 

[DesertNomad]

14 CFR 91.211 Supplemental oxygen.

(a) General. No person may operate a civil aircraft of U.S. registry—

(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

Is it cumulative? What if one flies at 12500 for 25 minutes, then descends to 12490 for a few minutes, then back up to 12500 for 25 minutes?

 

[N747JB]

Is it cumulative? What if one flies at 12500 for 25 minutes, then descends to 12490 for a few minutes, then back up to 12500 for 25 minutes?

Only if the plane departed from a treadmill and had an AOA indicator!

 

[Maciej]

For the record, I'd try going up to that altitude and feeling it out, I was able to sit at 11,500' no problem in my Diamond for most of my cross country (literally) flights, but anything above 12,500' I'd get hypoxic pretty quickly.

 

[steingar]

If you plan to fly that high routinely you should get some oxygen whether or not you go past 12.5K. It'll make the experience far more enjoyable, especially for you Nick.

 

[tawood]

I routinely fly at altitudes above 10k...and I have to use O2 for anytime above 10k, or else I start gasping. I'm a big tub of goo.

 

[Ravioli]

Go to Walgreen' and get one of the finger Pulse Oximeters (like $30). Do some readings on the land and then fly and check it after about 10 mins at 5k, 10k, and 12k.

Then you'll have some data for your personal oxygen rules.

 

[Ted]

It's worth noting that for Part 135 the limit is set to 10,000 ft, with no 30 minute rule. Cabin altitudes must be kept at or below 10,000 ft. Above 10,000 ft, passengers and crew are required to have oxygen.

It's been a while since I've had to know the exact wording so I can't recall if the pax are required to use O2 or if they're just required to be offered O2. Someone who still flies 135 I'm sure can remember. But, I think that's a relevant point. Remember Part 91 tends to give you enough room to hang yourself, Part 135 is more restrictive based off of "This has killed enough people in the past." So while under 91 we aren't required to adhere to 135 regs, it makes sense to take them into consideration.

 

[Larry in TN]

It's worth noting that for Part 135 the limit is set to 10,000 ft, with no 30 minute rule. Cabin altitudes must be kept at or below 10,000 ft. Above 10,000 ft, passengers and crew are required to have oxygen.

There is a 30-minute rule under part 135 (and part 121).

135.89 -- Pilot requirements: Use of oxygen.

(a) Unpressurized aircraft. Each pilot of an unpressurized aircraft shall use oxygen continuously when flying—

(1) At altitudes above 10,000 feet through 12,000 feet MSL for that part of the flight at those altitudes that is of more than 30 minutes duration; and
(2) Above 12,000 feet MSL.​

As far as passenger oxygen, it has different requirements than the pilots.

135.157 -- Oxygen equipment requirements.

(a) Unpressurized aircraft. No person may operate an unpressurized aircraft at altitudes prescribed in this section unless it is equipped with enough oxygen dispensers and oxygen to supply the pilots under §135.89(a) and to supply, when flying—

(1) At altitudes above 10,000 feet through 15,000 feet MSL, oxygen to at least 10 percent of the occupants of the aircraft, other than the pilots, for that part of the flight at those altitudes that is of more than 30 minutes duration; and
(2) Above 15,000 feet MSL, oxygen to each occupant of the aircraft other than the pilots.​

 

[Ted]

Thanks for the clarification, Larry. Point being, it's more restrictive than 91 by a good margin.

 

[midwestpa24]

Legal or not, spending a lot of time at altitude without O2 can lead to a hangover style headache and fatigue. Even spending 8 hours at 7,000 in a day can do it for me.

 

[luvflyin]

If I plan a flight at 12,500ft, and fly it there, am I required to use oxygen after 30 minutes, or does that start at 12,501ft?

Depends on your 'cabin' altitude. Turning the heater on and off, opening and closing vents, leaky door gaskets etc all affect this. Not by a lot, but we are talkin about the 1 foot difference between 12500 and 12501.

 

[Hank S]

Legal or not, spending a lot of time at altitude without O2 can lead to a hangover style headache and fatigue. Even spending 8 hours at 7,000 in a day can do it for me.

Used to happen to me if I spent a couple of hours at 9500 msl. Then I bought a set of Halos and moved my clamp-o-matic headset to backseat passenger use, and I don't have after-flying headaches anymore . . . .

 

[MauleSkinner]

Thanks for the clarification, Larry. Point being, it's more restrictive than 91 by a good margin.

Good point, but I think it's more important to identify how and when I personally become hypoxic than to try to apply regs that are based on everybody but directly apply to nobody's physiology.

 

[Zeldman]

One advantage to flying medevac is there is plenty of oxygen onboard in case we lose pressurization.

 

[Ted]

One advantage to flying medevac is there is plenty of oxygen onboard in case we lose pressurization.

True, but in a MedEvac situation isn't it often a concern of how the patient's body (not just SpO2) will react to the pressure change? Obviously it depends on the condition, but things like brain bleeds (and lots of other conditions) I understand require keeping a cabin pressure at a low altitude to prevent them getting worse or causing more damage.

At the relatively low altitudes that I fly in the 414, I don't worry about it a ton. But I do think I'll get my O2 bottle refilled and start carrying it along for these longer trips, especially if night flying is involved.

 

[Zeldman]

True, but in a MedEvac situation isn't it often a concern of how the patient's body (not just SpO2) will react to the pressure change? Obviously it depends on the condition, but things like brain bleeds (and lots of other conditions) I understand require keeping a cabin pressure at a low altitude to prevent them getting worse or causing more damage.

At the relatively low altitudes that I fly in the 414, I don't worry about it a ton. But I do think I'll get my O2 bottle refilled and start carrying it along for these longer trips, especially if night flying is involved.

Yes, that is correct. There were times the med crew would request to keep the cabin pressure altitude as low as possible, especially for head injuries for other conditions. Although I usually did not want to know the condition of the patient until after the flight, so I would do as requested without any further explanation.

 

[Tantalum]

my Diamond for most of my cross country

Slightly OT, but I noticed your vacuum gauge was a hair below 5. I've noticed this too in the Archer I fly.. on the ground it reads typically reads just a hair over 5, but once I get up over 9K it starts to dip to just below 5. I thought maybe it was coincidental with the altitudes, but seeing yours makes me think that the lower overall pressure does have some impact on the vac pump?

 

[Ted]

Yes, that is correct. There were times the med crew would request to keep the cabin pressure altitude as low as possible, especially for head injuries for other conditions. Although I usually did not want to know the condition of the patient until after the flight, so I would do as requested without any further explanation.

Agreed. Best thing is to pretend your cargo is a box of rocks, and follow orders from the med crew without further questioning. To do your job safely you can't let emotion get in the way - a hazard for med crews/air ambulance pilots.

 

[Zeldman]

Agreed. Best thing is to pretend your cargo is a box of rocks, and follow orders from the med crew without further questioning. To do your job safely you can't let emotion get in the way - a hazard for med crews/air ambulance pilots.

I agree. Never thought about the box of rocks thought.....

But sometimes hard to put the emotions away when the patients are kids. Hardest part of the job.

 

[SkyHog]

So I brought along a pulse oximeter. Got strange results:

At 10,500 i dropped to about 89. At 12,500 I went up to 94. When I landed at 6200ft or so, I was at 96.

I’ll have to play with this some more, but that seems illogical

 

[LongRoadBob]

Go to Walgreen' and get one of the finger Pulse Oximeters (like $30). Do some readings on the land and then fly and check it after about 10 mins at 5k, 10k, and 12k.

Then you'll have some data for your personal oxygen rules.

Thanks for that! Damn, as often happens, this came along at the right time. I posted in October in the hangar about being subjected to Anyhdrous ammonia from a minibar in Milano. (Hmm...good song title) and haven't yet flown since the accident but feel as if I am having a harder time breathing still.

So I got to wondering about how one would find out about their personal oxygen altitude limits.

Thanks for that! I'm in Norway and suspect I might have to go online to find these but that will work.

 

[BigBadLou]

Thanks for that! Damn, as often happens, this came along at the right time. I posted in October in the hangar about being subjected to Anyhdrous ammonia from a minibar in Milano. (Hmm...good song title) and haven't yet flown since the accident but feel as if I am having a harder time breathing still.

So I got to wondering about how one would find out about their personal oxygen altitude limits.

Thanks for that! I'm in Norway and suspect I might have to go online to find these but that will work.

I agree with Ravioli, a pulse oximeter is a good investment.
However, if you plan on keeping it for actual flights above 10k, I would recommend a slightly more advance (and thus slightly more expensive) oximeter with an alarm. If you become hypoxic up there, you might stop looking at the oximeter anyway. So an audible alarm would be a good way to wake you up from the hypoxic haze to notice the number and start an immediate descent. (or huff some O2)

 

[SkyHog]

I agree with Ravioli, a pulse oximeter is a good investment.
However, if you plan on keeping it for actual flights above 10k, I would recommend a slightly more advance (and thus slightly more expensive) oximeter with an alarm. If you become hypoxic up there, you might stop looking at the oximeter anyway. So an audible alarm would be a good way to wake you up from the hypoxic haze to notice the number and start an immediate descent. (or huff some O2)

Lol. No one loses consciousness at 10k ft.

 

[Clark1961]

Lol. No one loses consciousness at 10k ft.

I’ve lost consciousness at much lower altitudes...

 

[ElPaso Pilot]

So I brought along a pulse oximeter. Got strange results:

At 10,500 i dropped to about 89. At 12,500 I went up to 94. When I landed at 6200ft or so, I was at 96.

I’ll have to play with this some more, but that seems illogical

Breathing rate and depth will affect your readings as well.

When you see a lower reading at altitude, deep and slow breaths will bring it back up.

 

[SkyHog]

I’ve lost consciousness at much lower altitudes...

Fair enough.

No one loses consciousness from hypoxic hypoxia at 10,000ft.

 

[nauga]

However, if you plan on keeping it for actual flights above 10k...[emphasis added]

No one loses consciousness from hypoxic hypoxia at 10,000ft.

Is flight at 12,500 10,000 actually flight above 12,500 10,000?

Nauga,
unmasked

 

[Checkout_my_Six]

I’ve lost consciousness at much lower altitudes...

well....ya.