Originally Posted by
ElNull
I have 2 questions regarding crew oxygen:
Since during a preflight we put Normal/100% switch to 100%. Under what circumstances we use the Normal (air-oxygen mixture)?
In the "EMER DESCENT" Abnormal Procedure PRO-ABN-MISC, it says go to "Normal" to preserve O2 supplies.
If you are over high ground, European Alps, Mongolian Plateau etc the time to 10,000ft may be longer than normal so preserving O2 is a factor.