11.15 - Oxygen Flashcards
What is the percentage of oxygen contained in the atmosphere at sea level?
21% Oxygen
What is the normal way to prevent hypoxia in an aircraft cabin?
Pressurising the cabin so that the oxygen is forced into the bloodstream as it passes through the lungs under normal cabin pressure.
Chemical oxygen generator systems are normally provided for?
Chemical oxygen generator systems are normally provided for passengers.
What is the function of the LP supply valve in the crew oxygen system?
The LP supply valve can be set to allow or isolate the gaseous oxygen supply from the oxygen cylinder to the distribution manifold.
What pressure is oxygen normally stored at on aircraft?
Oxygen on aircraft is stored normally at a pressure of 1800 psi
How is the crew oxygen cylinder protected against overpressure?
the pressure relief valve protects the system in case of overpressure (>175 psi) and the crew oxygen cylinder’s internal pressure (usually 1800 psi) is protected against overpressure by the frangible disk which ruptures releasing oxygen if internal cylinder pressure exceeds 2600 psi
The oxygen flows overboard through the disk and through the green disk on the outside of aircaft.
What happens when the cabin altitude reaches 14000 FT?
A pressure switch closes to complete a circuit, energising the solenoid which opens the passenger oxygen container doors. The ‘‘SYS ON’’ warning light in the cockpit will be illuminated to alert the flight crew.
List the safety precautions when working with oxygen? (5)
- Keep Oxygen away from fire
- Keep oil and grease away from oxygen hoses and fittings
- Wear clean overalls
- Use clean spark-proof tools
- Never mix oxygen with other gases
What are the different ways that the cabin oxygen system can be activated?
- Automatically if the cabin altitude reaches 14000 ft.
- Manually by the flight crew by actuating the guarded switch on the oxygen control panel in the cockpit.
Both methods energise the door latch solenoids opening oxygen container doors
How do you know an oxygen generator has been activated?
A heat sensitive tape on the generator turns black due to the surface temperature increase (can be up to 260^C) once the oxygen generator has been activated.
How do chemical oxygen generators work?
Multiple hoses are fitted to the generator and oxygen masks are connected at the other end of the hose. If a mask is pulled to face level, the activation pin is pulled out by a lanyard which releases the firing pin.
The firing pin strikes the primer which starts a chemical reaction of sodium chlorate and iron in the generator which generates oxygen.
(a) 21%
(c) To pressurise the cabin that the partial oxygen pressure is sufficient
(a) Passengers and cabin crews
(c) To allow or shut off the oxygen flow to the distribution manifold
(b) By a frangible disk
Could be either but as per diagram, the dish is the first line of protection on the actualy cylinder.
Pressure relief valve is more for system pressure
diagram pg 373 11.15
What are the percentages of oxygen and nitrogen in air?
21% Oxygen
78% Nitrogen
What is hypoxia?
It is the pressure of the atmosphere that forces oxygen into the bloodstream as it passes through the lungs.
As the pressure reduces with altitude, less pressure is exerted on the lungs and therefore the bloodstream absorbs less oxygen.
List the safety precautions for oxygen? (5)
- Keep oxygen away from fire
- Keep oil and grease away from oxygen hoses and fittings
- Wear clean overalls
- Use clean spark-proof tools
- Never mix oxygen with other gasses
What is the difference between aviation O2 and medical O2?
Medical Oxygen contains a high moisture content and other contaminants unlike aviation oxygen
What is LOX?
LOX = Liquid Oxygen Systrem
- Used by military
Oxygen kept in a ‘Dewar’ bottle at -107^C
Big disadvantage is handling this extremely low temperature.
What is the standard pressure, rupture pressure and regulated pressure of an O2 cylinder?
Standard pressure = 1800 psi
Rupture pressure (disk) = > 2600 psi
Regulated pressure = 80 psi (pressure regulating valve)
Differentiate between Diluted and 100% oxygen?
Diluted oxygen is a mixture of cabin air and oxygen. The ratio depends on cabin altitude.
Above 35000 ft cabin altitude or if selector is in 100% position, the mask delivers 100% pure oxygen.
At what altitude is a warning given and when do the masks drop?
At 14000 ft, the ‘‘SYS ON’’ warning light is illuminated and the masks deploy automatically.
From cabin pressure chapter, a warning + aural sound is given at 10000 ft cabin altitude.
What combines to make O2 in an O2 generator?
A chemical reaction of sodium chlorate and iron
What temp does an O2 generator get to and do the passengers feel this?
Surface temperature of the generator may get as high as 260^C
No, passengers do not feel this as a filter in the generator cools the oxygen and filters out any contaminants.
When oxygen is needed for a backup in a pressurised aircraft, the _________ system is used because of it’s simplicity, efficiency, and minimum maintenance required.
Chemical oxygen system (candle)
Aviator’s oxygen is different from hospital oxygen because of its low ________ content
moisture (water)
The type of contaminant most generally found in gaseous oxygen systems is ________
Water
The rate or release of the oxygen from a chemical oxygen generator system __________ (may or may not) be adjusted for the altitude flow.
may not
Supplemental oxygen is normally provided for passengers of a pressurised aircraft by the _______ (continuous-flow or demand) type system
Continuous flow
The cockpit crew of a pressurised aircraft normally have their supplemental oxygen supplied by a ________ (continuous flow or demand) type oxygen system
demand
A diluter-demand oxygen regulator dilutes the oxygen it meters at the lower altitudes with _______
cabin air
The demand valve on a diluter-demand oxygen regulator opens each time the wearer of the mask ______
inhales
The amount of oxygen in a gaseous bottle is indicated by it’s ________
pressure
Thread lubricants used with oxygen system components must contain no ________
petroleum (oil)
or grease
It is the ______ of the _____ that forces oxygen into the bloodstream as it passes through the lungs
It is the pressure of the atmosphere that forces oxygen into the bloodstream as it passes through the lungs
Use only aviation oxygen in aircraft systems as medical or welding oxygen gas is not suitable. This is due to the high _________ and other contaminants found in commercial or medical oxygen.
moisture content
Gaseous oxygen is usually stored in steel cylinders at a pressure of approximately _________
1800 psi
Liquid oxygen is stored at an extremely low temperature (-107^C) by storing it in a ______ bottle
Dewar
Crew Oxygen System Components
How is the LP supply valve operated and controlled?
The LP supply valve is elecrically operated and controlled from the CREW SUPPLY P/B
What electrical power is used to operate the crew oxygen system?
What are the 3 ways in which the oxygen masks from the PSU (Passenger Service Unit) may be released.
- Automatically by high cabin altitude 14000ft (low cabin pressure)
- Manually from the flight compartment
- Mechanically by a manual release tool
How long should oxygen to passengers be supplied for?
A minimum of 10 minutes
What type of mechanism holds the oxygen container door in place?
Latch mechanism
In a chemical oxygen generator, Oxygen is generated inside the generator by a chemical reaction of __________ and _____
Sodium chlorate and iron
How is the reaction started in a chemical oxygen generator?
The firing pin strikes the primer which starts the reaction in the generator.
How is oxygen cooled for use in a chemical oxygen generator?
A filter in the generator cools the oxygen and filters out and contaminants.
A heat sensitive tape on the generator turns _____ if the generator is used.
Black
