Originally Posted by yotty
If a particular aircraft has significantly more oxygen servicing it becomes "common knowledge" among the engineers.
Perhaps I'm trying to compare apples with oranges. Different fleet, different rules, different routes. If one of our aircraft flew away from main base and did a 4 sector flight, it would be
unlikely that the same engineers would see the aircraft the next day. Also, it wouldn't raise any eyebrows if the aircraft required another O2 service on the return to main base. Thanks to the lack of dilligence by some (outsourced) engineers who didn't reopen the bottles after servicing them, our flight crews were subsequently required to suck on the O2 during their preflights until the levels made a noticeable drop . If you do this for 4 sectors, the O2 is, of course, going to drop 10 psi or so. If you only top up the O2 to just over 1850, the aircraft will most likely need a service when it returns. Because of safety concerns, you can't fill up the bottles quickly, and because of time constraints, you may only have the time to fill up the bottles to just over 1850. The requirement for engineers to check the O2 levels everytime an aircraft returns to main base (which may also be on the line as you say) may have been removed since I left my old airline, but I know old habits die hard. Dedicated engineers will still check and service the system because they know the aircraft will be delayed if there is a last minute call to a departing aircraft... especially if some of the sectors involve routing over the Himalayas.
Perhaps the official report mentioned above has some typographical errors and omissions. Wouldn't 310psi generate some kind of EICAS message for crew O2?