ABSTRACT
National military and civil aviation authorities usually set out under various regulations the minimum acceptable provision of oxygen to be carried on board aircra registered in that state or country. In aircra with low-dierential pressure cabins (i.e. with a cabin altitude greater than 8000 feet in normal ight, such as small military combat aircra), personal oxygen equipment is worn routinely and used by the aircrew throughout ight. e denition and performance of such systems in military aircra are addressed in relevant military documentation, e.g. Defence Standards and Military Specications. For commercial aircra registered in the USA, the Federal Aviation Administration (FAA) sets out the requirement for oxygen in various classes of aircra under FAA Regulations (FARs parts 25, 121 and 135). In the UK, Schedule 4 of the CAP 393 Air Navigation Order (2014) requires that equipment that will deliver oxygen-enriched air or 100 per cent oxygen to the crew be installed in all commercial (i.e. public transport) aircra that y above an altitude of 10 000 feet. Furthermore, if the aircra is capable of maintaining its cabin altitude below 10 000 feet, then oxygen must be available in sucient quantity to supply all crew members and passengers in the event of a failure of pressurization above 15 000 feet for a specied interval, and to supply all crew members and ten per cent of the passengers if pressurization fails below 13 000 feet. In all other aircra, i.e. in those that y unpressurized, sucient oxygen must be carried for continuous use by all occupants whenever the aircra is ying above 12 000 feet and for continuous use by the crew and ten per cent of the passengers for any period in excess of 30 minutes during which the aircra ies between 10 000 and 12 000 feet. In aircra with high-dierential pressure cabins, i.e. with a cabin altitude below about 8000 feet at all times during routine ight, such as passenger aircra and large military transport or bomber aircra, such equipment is used only if the cabin altitude exceeds safe limits, although emergency therapeutic oxygen may be required by ill passengers at normal cabin altitudes.
