doug_or
Topic Author
Posts: 3188
Joined: Sat Mar 18, 2000 9:55 am

### O2 For 10% Of Pax- Why?

I've been studying for the ATP written, and some of the part 121 FARs strike me as a little strange. they make refrence to aircraft being required to have O2 for 10% of the passengers in certain situations. Am i correctly reading this to mean that O2 only needs to provided to 1 in 10 passengers?!? if so, why bother?

thanks,
Doug
PDX/LAF/IND
When in doubt, one B pump off

mjzair
Posts: 369
Joined: Tue Nov 30, 1999 12:10 pm

### RE: O2 For 10% Of Pax- Why?

I am studying for the JAA ATPL, and the text refers to a 10% rule, this states that the total number of oxygen dispensers has to exceed the number of cabin attendent and passanger seats by 10%.
Could this be what you are refering to?

doug_or
Topic Author
Posts: 3188
Joined: Sat Mar 18, 2000 9:55 am

### RE: O2 For 10% Of Pax- Why?

from FAR 121.327

(1) For flights of more than 30 minutes duration at cabin pressure altitudes above 8,000 feet up to and including 14,000 feet, enough oxygen for 30 minutes for 10 percent of the passengers.

(2) For flights at cabin pressure altitudes above 14,000 feet up to and including 15,000 feet, enough oxygen for that part of the flight at those altitudes for 30 percent of the passengers
When in doubt, one B pump off

Minuteman
Posts: 260
Joined: Sat Aug 05, 2000 1:01 am

### RE: O2 For 10% Of Pax- Why?

Weird...

121.327 is in reference to reciprocating engine aircraft, but 121.329 has the same requirements for turbine engine aircraft.

The third part of the both rules states:

(3) For flights at cabin pressure altitudes above 15,000 feet, enough oxygen for each passenger carried during the entire flight at those altitudes.

I wouldn't have believed the 10% and 30% rules without the third, 100% part.

flyf15
Posts: 6633
Joined: Tue May 18, 1999 11:10 am

### RE: O2 For 10% Of Pax- Why?

I can't say I've read deeply into this, but I'd assume they mean for planned flights at these cabin pressure altitudes -- ie: not emergency oxygen. Makes sense, below 14000ft I could see about 10% of the pax needing to breathe oxygen. Below 15000ft, I could see about 30% needing it. And above 15000, I could see enough needing it that it should be carried for all.

Guest

### RE: O2 For 10% Of Pax- Why?

When the US FAR 121 mentions 10% or 30%... it means the amount of oxygen required for the physiological requirements of the total amount of passengers... at low cabin altitude, 10% of the physiological needs for the total amount of passengers would be sufficient... at higher altitudes, it is based on 30%, and above FL 150, it is for everyone...
xxx
Just for your information, do not think that "passenger oxygen masks" are of much help at high flight levels in case of loss of pressurization... it is doubtful that such masks could sustain physiological human requirements above say some 25,000 feet... These flimsy masks are just good enough to give oxygen for passengers in an emergency descent, most emergency descents procedures mention descents to 14,000 feet...
xxx
We have charts with flight time and number of passengers for minimum oxygen requirements in the aircraft operating manual...
xxx
Happy contrails -
(s) Skipper

doug_or
Topic Author
Posts: 3188
Joined: Sat Mar 18, 2000 9:55 am

### RE: O2 For 10% Of Pax- Why?

Skipper to the rescue agian!

thanks
When in doubt, one B pump off

Guest

### RE: O2 For 10% Of Pax- Why?

Dear Doug...
Read your 121 regulations, for oxygen, it deals (fine print) "Oxygen for SUSTENANCE" or "Oxygen for emergency descent" (if I remember well), quite different requirement... excuse this old fart, I am in a hotel, dont have my 121 regs handy...
Happy contrails
(s) Skipper

MxCtrlr
Posts: 2312
Joined: Tue Nov 13, 2001 11:22 am

### RE: O2 For 10% Of Pax- Why?

Also remember, if your aircraft has gotten into a situation where O2 is required, there is also most likely, an emergency descent in play. The likelihood that you will require oxygen for a full 30 minutes is remote at best. More like 10 minutes (and, in some of the emergency descents I've been on, more like 5 minutes). Plus, some of the passengers just sit and stare at the mask when they drop. The F/A's have to put them on the pax for them!

MxCtrlr
Freight Dogs Anonymous - O.O.T.S.K.
DAMN! This SUCKS! I just had to go to the next higher age bracket in my profile! :-(

VIflyer
Posts: 454
Joined: Wed May 26, 1999 2:29 pm

### RE: O2 For 10% Of Pax- Why?

just my 2 cent
I reject your reality and subsitute my own

Guest

### RE: O2 For 10% Of Pax- Why?

Airplanes flying below FL250 (or so certificated) do not require oxygen system. Further, on ANY flight under US FAR 121, a briefing to passengers about oxygen is NOT required if flying below FL 250...
xxx
Most air carriers make an oxygen briefing no matter what altitude, because the cabin attendants have a "standardized" briefing for all flights... sometimes they include an "overwater" briefing, even if flying only in the Sahara...
xxx
The more the briefings, the less the interest of passengers... unfortunately. Briefings should be short and clear to keep their interest...
xxx
(s) Skipper

FrequentFlyKid
Posts: 1097
Joined: Thu Nov 22, 2001 5:04 am

### RE: O2 For 10% Of Pax- Why?

Correct me if I am wrong, but my understand of the oxygen masks was to sustain the life of a passenger, not to necessarily keep them conscious. I know that's a little off-topic, but I've always wondered that.

Guest

### RE: O2 For 10% Of Pax- Why?

You are quite correct, the passengers O2 masks are basically worthless, they just will help keep them "alive" (and scared) during the 2 to 3 minutes emergency descent to 14 or 15,000 feet... be aware also that transport category airplane are certificated to their maximum flight level so that they can maintain a cabin altitude equal to or better than 8,000 feet.
xxx
Pilots masks, although a little more efficient, can do OK to about 30 to 32,000 feet (they are not "pressure systems" like you have in fighters), higher than that, again, they will assist pilots for the emergency descent... just that... a lot of pilots flying high altitude airplanes should be reminded of that fact...
xxx
With USA airlines (121) when a pilot leaves his station, the other pilot is required to wear his mask... good point... not many foreign airlines do require this... However many foreign countries require actual "pressure chamber O2" physiological training, for pilots operating aircraft above FL 250... in the USA, "just watching a video" about it, is... sufficient...
xxx
It is considered that "unpressurized airplanes" can be flown without oxygen to about 10 to 12,000 feet (USA insists for lightplane pilots not to fly higher than 10,000 feet without oxygen)... I have a Bolivian pilot friend who lives in LaPaz, and flies a Cessna 185... he does not wear oxygen unless exceeding 15 or 16,000 feet - but is body is accustomed to that altitude. La Paz airport is 13,500 feet high...
xxx
I go to the pressure chamber every 2 years for recurrent training... one thing I have learned, if I have to get the death penalty, this would be my choice for execution... you feel good, very good, and then... nothing...
xxx
(s) Skipper

b727
Posts: 464
Joined: Sun Oct 24, 1999 3:19 am

### RE: O2 For 10% Of Pax- Why?

When the airmasks drop, how would you find a mask for an infant or child that is sitting on your lap? Is their an extra mask every other seat etc...

Thanks
B727

Glenn

doug_or
Topic Author
Posts: 3188
Joined: Sat Mar 18, 2000 9:55 am

### RE: O2 For 10% Of Pax- Why?

Well Glenn, I know at least on you namesake there are 4 masks per row, to allow for seated infants and O2 for FAs that may need to assist pax
When in doubt, one B pump off

Guest

### RE: O2 For 10% Of Pax- Why?

Dear Glenn -
xxx
Like Doug mentioned, per row of "3 seat units" there are 4 masks... the larger "center aisle units" (wide bodies) of 4 or 5 seats have 5 or 6 masks...
xxx
No matter what - as a parent, how much you love your child, take YOUR mask first THEN give the child the mask... if you do the opposite, you may faint, his mask will fall, he will faint too... so, first SAVE YOURSELF (in ANY emergency) so you can help others...
xxx
(s) Skipper

Guest

### RE: O2 For 10% Of Pax- Why?

This thread reminds me of the famous Southwest Airlines cabin safety briefing...

"Welcome aboard Southwest Flight 124 to Orlando. To operate your seatbelt, insert the metal tab into the buckle, and pull tight. It works just like every other seatbelt and if you don't know how to operate one, you probably shouldn't be out in public unsupervised. In the event of a sudden loss of cabin pressure, oxygen masks will descend from the ceiling. Stop screaming, grab the mask, and pull it over your face. If you have a small child traveling with you, secure your mask before assisting with theirs. If you are traveling with two small children, decide now which one you love more...

b727
Posts: 464
Joined: Sun Oct 24, 1999 3:19 am

### RE: O2 For 10% Of Pax- Why?

Thanks B747Skipper.

I was wondering how that works, and I will be traveling with my daughter soon,

B727
glenn

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