Oxygen and pressurization systems Flashcards
What are the 4 types of oxygen mask used with supplemental oxygen?
Cannula
Re-breather
Diluter-demand mask
Pressure-demand mask
What are the 4 types of oxygen supply?
Gaseous
Liquid
Solid
Mechanical extrication
How is gaseous oxygen supplied?
Stored in cylinders around 2000PSI
How is liquid oxygen (LOX) supplied?
Kept cool (-180 F0, expands 862:1
How is solid chemical oxygen supplied?
“Candle” of sodium chlorate, chemical reactions heat and breathable oxygen
How is Mechanical extraction oxygen supplied?
Uses molecular sieve to trap all gas molecules except oxygen from compressor bleed air
What is the molecular makeup of the atmosphere?
21% oxygen, 78% nitrogen, and 1% miscellaneous
What colors can oxygen cylinders be and what two markings must be on them?
Normally green (high pressure); yellow (low pressure)
Marked with hydro-static date and must be marked “aviators breathing oxygen
Explain the differences between the continuous flow and demand type oxygen systems.
Continuous flow: turned on by pilots or an altitude sensing anderoid w/pressure regulator. Oxygen flows continuously to the mask when turned on
Demand: Uses pressure regulators at each mask to allow gas to flow only when the user inhales
What is hypoxia?
A physiological condition caused by high altitude without sufficient oxygen
How does hypoxia affect people?
Impairs vision and judgment, gives a headache, increases breathing rate, eventually unconsciousness and death.
What tools can be used while servicing oxygen systems?
Clean tools. Dedicated clean tools clean of greases, fuel, and oil
What is a hydrostatic test and why is it important?
Oxygen bottle test
Bottles filled with water and pressurized 5/3 working pressure to test integrity of the bottle
Name 5 things to check for when servicing an oxygen bottle?
Hydrostatic date (stamped near neck)
Bottle pressure ( do not service if under 50PSI)
Inspect for damage
Filled with “aviators breathing oxygen”
Use a pressure-temperature chart and fill slowly
Service from the lowest bottle first
When would you need to purge an oxygen system?
If the system is low or they system is contaminated
Name advantages for aircraft pressurized and flying at high altitudes
Less drag
Less turbulence
Avoid bad weather
Reduced air traffic
Name disadvantages for aircraft being pressurized and flying at high altitudes
Cabin has to be pressurized=heavier
Costly and requires more maintenance and training
Pressurization failures
Shorter life cycle due to strain on aircraft
What is cabin differential pressure?
Difference between the cabin atmospheric pressure and the outside atmospheric pressure
What are 3 common sources that provide pressurized air to the reciprocating engines?
Superchargers
Turbochargers
Engine drive compressors
What is the advantage to the crew of using engine driven compressors over superchargers or turbo chargers?
Avoids contamination from either the fuel intake system or the exhaust system
What are three sources of pressurization for turboprops?
Piston type pump
Root blower
Jet pumps
What are 3 sources of pressurization for full jet aircraft?
Engine bleed air
Turbo-compressors
Jet pumps
Three modes of pressurization
Unpressurized
Isobaric
Constant differential
What is unpressurized mode?
Cabin pressure is the same as ambient air pressure (outflow valve fully open)
What is isobaric mode?
The pressure controller closes and opens the outflow valve to maintain a set cabin altitude
What is constant-differential mode?
The ratio between internal and external air pressure. The pressure controller will maintain a constant pressure differential as altitude changes
Three modes of operation?
Auto
Alternate
Manual
Explain auto
Normal mode providing automatic control
Explain alternate
Standby mode also providing automatic control but usually w/ different inputs and a standby controller and standby outflow valve operation
Explain Manual
In case auto and standby fail, allowing crew to directly position the outflow valve through pneumatic or electric control
What is the purpose of the outflow valve?
To let air out of the pressurized vessel, keeping the cabin pressure constant at the correct pressure
What is the difference between the negative pressure relief valve and the safety valve?
Negative pressure relief valve: makes sure that the inside cabin pressure is always equal to or greater than the outside air pressure. Valve will open if outside air pressure increases above cabin pressure to allow outside air into the cabin to balance the pressure
What mode of operation would an A&P mechanic use to perform a pressure check and why?
The manual mode would be used so that the outflow valve would close and pressurize on the ground
What is a standard day condition?
59F
14.69PSI
Explain partial pressure?
The percentage of the total pressure of a mixture of gases produced by each of the individual gases in the mixture
At what altitude do humans need supplemental oxygen?
10,000ft
What is humidity?
The measure of water vapor in the air
What is cabin pressure differential formula?
Cabin pressure-Ambient pressure=differential pressure
