Why are aircraft required to have oxygen systems?
To supply oxygen to crew and passengers in emergencies such as cabin depressurisation, as required by EU-OPS 1.760.
What does EU-OPS 1.760 require regarding passenger oxygen?
Pressurised aircraft above 25,000 ft must carry undiluted oxygen for passengers who may require it after depressurisation.
Why does hypoxia occur at altitude?
Air pressure and density decrease, reducing oxygen molecules per breath and lowering blood oxygen levels.
What is cabin altitude typically pressurised to?
Approximately 2,500 m (8,000 ft).
What type of oxygen is used in aircraft systems?
Aviator’s Breathing Oxygen – very dry, pure gaseous oxygen.
Why is medical oxygen unsuitable for aircraft use?
It contains moisture that can freeze at altitude.
Why is oxygen considered hazardous?
Although non-flammable, it reacts violently with oils, grease, and many substances.
Name key oxygen safety precautions.
No petroleum products, no smoking/open flames, clean tools, AMM compliance, slow valve opening.
Where are flight crew oxygen bottles usually located?
Remotely mounted, typically in avionics bays or cargo compartments.
What pressure are flight crew oxygen bottles typically charged to?
Approximately 1,800–1,850 psi.
What does a pressure reducing valve (PRV) do?
Reduces high bottle pressure to a usable system pressure.
What triggers passenger oxygen mask deployment?
Cabin altitude rising above approximately 14,000 ft.
Where are passenger oxygen masks stored?
In Passenger Service Units (PSUs) or Emergency Oxygen Containers (EOCs).
What materials are modern oxygen bottles made from?
Aluminium, Kevlar™-wrapped composites, or all-aluminium designs.
What is the function of an oxygen bottle burst disc?
To release pressure safely if bottle pressure becomes excessive.
What indicates an oxygen bottle discharge externally?
A ruptured green blowout disc on the fuselage.
Why is a thermal compensator used during oxygen servicing?
To dissipate heat generated during refilling and prevent overheating.
What materials are used for oxygen system tubing?
Stainless steel (high-pressure), aluminium (low-pressure), plastic hoses (masks).
How is oxygen tubing identified?
Green tape marked ‘BREATHING OXYGEN’ at intervals.
What is portable oxygen used for?
Emergency, first aid, and smoke protection.
What components are found on a portable oxygen cylinder head?
Shut-off valve, pressure gauge, regulator, relief valve, frangible disc, filling valve.
What are smoke hoods used for?
Protection from smoke and toxic gases during fires or emergencies.
How long must cabin crew smoke hoods provide oxygen?
At least 20 minutes during active use.
What is continuous-flow oxygen?
Oxygen flows constantly regardless of inhalation or exhalation.
