Minimum OXYGEN for CREW B737-200

[Zenj]

Hi,

Its becoming a disputed issue of late, some airlines say 1300psi , some say in 2 hours with max of 3 crew its 900psi, whats the real limit ?

Flying at FL370, whats the limit ? I see the charts showing FL140 as the basis of operating with masks, does that mean calculations based from TOC to FL140 ? sometimes seem confusing !

Lets hear from the expert ...

Zenj

[NSEU]

Unfortunately, bottles are never fitted with temperature gauges, so it's mostly down to guesswork.
Recently, our 744 flight crews have been insisting that pax/crew pressures be at 1800psi or more for certain flights (irrespective of the temperatures) because their manuals tell them it should be this (apparently no temperatures are mentioned). Maintenance manuals/checksheets have the values (with temperatures), so conflict between the two is inevitable. Engineers bow down to flight crew requests, simply because no one really knows what the bottle temperatures are anyway.... especially when you have bottles in multiple locations (at different temperatures).
On a 744, pressure indications can go up 80 psi in a few hours on a warm day (after a long cold flight). Most of the bottles on a 744 are close to the external skin, so get pretty cold.
Pressure/temperature "guesswork" is based on length of flight, location of bottles, ambient ground temperature, length of ground stop, etc.... You'd have to be a rocket scientist to figure out correct values :} Also, crew requests at the last minute means the oxygen bottles will be refilled fairly quickly (within safety limits)... This induces a temperature rise in the bottles... and the pressures will drop down after we have finished topping up the bottles.

Unfortunately, it's all very "hit and miss".

Rgds.
NSEU

[I-2021]

Hello,

On the 732 you can have 3 kinds of oxygen bottles. 39 cubic feet , 76 or 114. As far as i know these are the ones used, but there might be other ones also. According to the number of crew using oxygen and the temperature of the bottle you get the required amount of PSI. Ask your operator technical department if they issued a service bulletin regarding these requirements according to the kind of oxygen bottles fitted in your airplanes. Check also the requirements for the passenger oxygen bottle, that is normally a 114 cubic feet one with a minimum dispatch pressure of 1400 PSI.

[HAWK21M]

Depends on the Capacity of the Bottle in use.
On our Freighters We use the extra volume 114cuft.Hence requirements is min 1800psi from Main base,min 1200psi from terminal station,min 1000psi during transit with 3 crew & min 900psi during transit with four crew.
regds
MEL