Now, subparagraph (ii) — Page 275, Lesson 356

I want to walk you through the supplemental oxygen requirements for pressurised aeroplanes, and then we'll move into the non-pressurised rules. This is dense regulatory material, so let's take it piece by piece. First, a key principle that frames everything: cabin crew members carried in addition to the minimum number required, and any additional crew members, are treated as passengers for the purpose of oxygen supply. So the regulation counts only your minimum required cabin crew as crew — everyone else on top of that is a passenger in the oxygen calculation. Now, subparagraph (ii). For aeroplanes intended to operate at pressure altitudes above 25,000 feet, you must provide sufficient spare outlets and masks, and/or sufficient portable oxygen units with masks, for use by all required cabin crew members. The critical design point is that these spare outlets and portable units must be distributed evenly throughout the cabin. The reason is immediate availability — each required cabin crew member must have oxygen available no matter where they happen to be located at the moment of a cabin pressurisation failure. Subparagraph (iii) — again for aeroplanes operating above 25,000 feet — requires an oxygen dispensing unit connected to oxygen supply terminals, immediately available to each occupant, wherever seated. Here's the key number: the total number of dispensing units and outlets must exceed the number of seats by at least 10 percent. And again, those extra units are to be evenly distributed throughout the cabin. Subparagraph (iv) introduces a stricter requirement with two triggers. It applies to aeroplanes intended to operate above 25,000 feet, OR aeroplanes which, if operated at or below 25,000 feet, cannot descend safely within four minutes to 13,000 feet. And there's a date condition: the individual certificate of airworthiness must have been first issued on or after 9 November 1998. For these aeroplanes, you need automatically deployable oxygen equipment, immediately available to each occupant, wherever seated. Same 10 percent rule: total dispensing units and outlets exceed seats by at least 10 percent, extra units evenly distributed. Subparagraph (v) gives a reduction. For aeroplanes not certificated to fly above 25,000 feet, the oxygen supply requirements from Appendix 1 may be reduced to the entire flight time between 10,000 feet and 13,000 feet cabin pressure altitude — for all required cabin crew members and for at least 10 percent of passengers. But there's a safety condition: at all points along the route to be flown, the aeroplane must be able to descend safely within four minutes to a cabin pressure altitude of 13,000 feet. So the four-minute descent capability is what buys you the reduced oxygen supply. Now we move to OPS 1.775 — supplemental oxygen for non-pressurised aeroplanes. The general rule is simple and absolute: an operator shall not operate a non-pressurised aeroplane at altitudes above 10,000 feet unless supplemental oxygen equipment is provided, capable of storing and dispensing the oxygen supplies required. So 10,000 feet is the hard ceiling for non-pressurised operation without that oxygen capability. Let me make sure you've got the key numbers locked in: 25,000 feet is the threshold that triggers the spare outlets and the 10 percent excess rule; four minutes to descend to 13,000 feet is the safety criterion; 9 November 1998 is the certification date that triggers the automatically deployable requirement; and 10,000 feet is the ceiling for non-pressurised aeroplanes without supplemental oxygen.