Airsupport,
I'm not trying to pick an argument or put you down. I AM saying that different jurisdictions have different interpretations and standards.
Under JAR or the UAE GCAA (Which is JAR complient) you must be able to supply passengers with oxygen for the entire time above 140 in the event of a depressurisation, no matter how unlikely that depressurisation is.
You stated that you could not fly a paricular route on one pack because of the increased likelyhood of a depressurisation. I simply telling you that under some sets of rules it makes no difference how many packs are operating.
You then state-
EXCEPT the trip we didn't go, BECAUSE WE COULDN'T GUARANTEE THAT FOR THAT TRIP.
Does this mean you CAN guarentee not to have a depressurisation if you have two packs operating? What about if you have a windoow or door blow out, or an outflow valve failure? Under the rules I fly under, you must be able to cope with a depressurisation at all times.