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What oxygen systems are required to maintaining sufficient oxygen at altitudes above 10,000 feet?
- -pressurisation of the aircraft cabin,
- - using an oxygen system.
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What oxygen systems are in fighter/bomber operations?
- - Normally, oxygen systems are only used in an emergency
- -a combination of pressurisation and supplemental oxygen is used.
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What are the purpose of OXYGEN SYSTEMS?
- - maintain tissue oxygenation despite the reduction in the partial pressure of oxygen at altitude.
- - exclude toxic substances such as smoke and fumes.
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Describe the chemical characteristics of Oxygen?
- -colourless, odourless and tasteless gas
- - 21% of the atmosphere.
- - sustains animal life
- -and supports combustion
- - All elements (except inert gases) react with oxygen normally forming oxides.
- - Some elements, such as alkali metals (lithium, sodium and potassium), or alkali earth metals (calcium, strontium and barium) ignite spontaneously in the presence of oxygen.
- -Most elements however oxidise slowly at normal temperatures
- -some, (gold, silver and platinum) requiring very high temperatures.
- -Spontaneous ignition also occurs on contact with
- - oil or grease,
- -either mineral or animal based.
- -This includes most make?up, chap? sticks, suntan lotions/creams and some foods.
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Describe the OXYGEN requirements In aviation?
- - in aviation must be very pure and dry.
- - to prevent corrosion of oxygen equipment, which may cause fires, and to prevent icing at altitude.
- -Contaminants must be excluded as the gas must be harmless to the crew and odourless.
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To what altitude is 100% oxygen not required?
- - altitude of 33,700 feet.
- -uneconomical to use 100% O2 all he time
- -also irritates
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Describe problems with breathing 100% oxygen for extended periods?
- -irritation of the respiratory passages
- - respiratory difficulties
- -coughing
- - painful respiration and
- -chest discomfort (?False Chokes?)
- - increased risk of acceleration atelectasis (collapse of alveoli) during exposure to high G forces.
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What Problems breathing 100% O2?
After flight breathing 100% oxygen , there can be problems with ?oxygen ear?.
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What would be the Ideall oxygen system for aviation environment?
- -an air/oxygen mixture in a sliding scale up to a cabin altitude of 33,700 feet,
- -100% oxygen to 40,000 feet
- -and oxygen under pressure above 40,000 feet cabin altitude.
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Describe the OXYGEN EQUIPMENT REQUIREMENTS?
- -deliver oxygen at all operational altitudes?
- -safety margins for possible leaks in the mask seal.
- -Pressure breathing
- - a continuous flow or
- - greater concentration of oxygen.
- -The safety pressure also guards against toxic fumes entering the mask.
- -Protection from toxic fumes
- - minimal resistance to breathing.
- -indications of oxygen flow and contents.
- -Means of checking the integrity of the system must be available, for example an hypoxia warning valve
- to indicate disconnection from the supply.
- -An emergency system should be provided for ejection at high altitude.
- Additionally, in low cabin pressure differential aircraft, an emergency system should be available for use following failure of the main oxygen system
- or after ejection.
- -The system should provide an underwater breathing capability, in case of unconscious ejection into water.
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What are the SOURCES OF OXYGEN in Aviation Environment?
- - stored in a solid, liquid or gaseous form,
- - may be generated in flight.
- -Currently, the majority of aircraft use liquid or gaseous oxygen systems
- -lthough solid oxygen storage and On?Board Oxygen Generating Systems (O.B.O.G.S.) are seen in certain aircraft such as the BAe Hawk.
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OXYGEN SYSTEMS IN AVIATION?
- -High?pressure oxygen systems (1800-2200psi) are normally used f
- -number and size of the bottles depending on the size and role of the aircraft. G
- -are relatively simple,
- -do not suffer from oxygen loss
- - when not in use and the oxygen is ready for use immediately after re? charging.
- -disadvantage of gaseous systems is their weight and large size,
- -Gaseous oxygen is also stored inlow?pressure systems (400-450psi) for ?walk?around bottles?.
- -limited endurance (5-30min) depending on activity, altitude and regulator setting.
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Gaseous aviation oxygen standards?
- a) a minimum purity of 99.5%,
- b) not more than 0.005mg of water vapour per litre at 760mmHg at 20oC (to prevent freezing), and
- c) it must be odourless and free from contaminants.
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LIQUID OXYGEN (LOX)?
- -boiling point of liquid oxygen is ?182.95oC
- -PROVIDE MORE OXYGEN 1 litre of liquid oxygen provides between 840 to 860 litres of gaseous oxygen.
- -expansion ratio is almost 7 times that of gaseous oxygen stored at 1800psi.
- -cylinders are about half the weight and size of equivalent gaseous oxygen bottles.
- -Disadvantage oxygen lost by evaporation, Only 1/8 reache the aircraft converter.
- -LOX systems require frequent re?charging.
- -used when aircraft weight and the size of the system are of prime importance.
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SOLID CHEMICAL OXYGEN?
- -Sodium chlorate in combination with powdered iron produces oxygen when the mixture is ignited
- -purity of oxygen obtained is -about 99.9%.
- -Once initiated the reaction is difficult to stop.
- -best suited for situations where a continuous flow of oxygen is required for a specific time,
- -eg such as an emergency oxygen supply for passengers.
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ON-BOARD OXYGEN GENERATING SYSTEMS(OBOGS)?
- -use compressed air from aircraft engines
- -main disadvantage of this method is the oxygen is released at a low pressure.
- -molecular sieve absorbs nitrogen and increases the concentration of oxygen to between 50 and 90%.
- Supplementary oxygen would be required for cabin altitudes above 30,000 feet,
- for flight through contaminated air, or for protection from toxic fumes.
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OXYGEN SYSTEMS TYPICAL OXYGEN SYSTEM OXYGEN REGULATOR?
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OXYGEN SYSTEMS TYPICAL OXYGEN SYSTEM OXYGEN REGULATOR?
- -supplying oxygen or an oxygen/air mixture on demand
- -and 100% oxygen under pressure above 32,000 feet.
- - three control levers
- -an ON/OFF lever,
- -a diluter lever
- -an emergency lever
- -as well as a pressure/contents gauge
- -and a flow indicator. NORMAL setting,
- -at sea level, - the regulator delivers cabin air.
- - As altitude increases, the proportion of oxygen gradually increases, so that by about 32,000 feet 100% oxygen is being delivered
- - Because air leaks into the mask become more critical above 30,000 feet,
- -a small over?pressure (2-4mmHg) is automatically introduced between 28,000 ? 30,000 feet
- - By 40,000 feet, over-pressure is progressively increased for pressure breathing,
- -reaching and maintaining 28?30 mmHg at 45,000 feet.
- -100% oxygen may be selected at any altitude.
- -EMERGENCY selection provides between 5-7 mmHg over-pressure, and TEST MASK between 20-30 mmHg.
- CAUTION: with the SUPPLY lever OFF and the DILUTER lever NORMAL only cabin air will be breathed.
- So, the regulator is normally set to 100% and OFF when switching it off.
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OXYGEN SYSTEMS TYPICAL OXYGEN SYSTEM OXYGEN REGULATOR?
- - three control levers
- -an ON/OFF lever,
- -a diluter lever
- -an emergency lever
- -pressure/contents gauge
- -Flow indicator-NORMAL setting,
- -sea level-cabin air.
- -altitude increases-proportion of oxygen gradually increases, 100% AT 32,000
- -a small over-pressure (2-4mmHg) is automatically introduced between 28,000-30,000 feet
- -40,000 feet, over-pressure is progressively increased TO 28-30 mmHg at 45,000 feet.
- -100% oxygen may be selected at any altitude.
- -EMERGENCY selection provides between 5-7 mmHg over-pressure, and TEST MASK between 20-30 mmHg.
- CAUTION: with the SUPPLY lever OFF and the DILUTER lever NORMAL only cabin air will be breathed.
- So, the regulator is normally set to 100% and OFF when switching it off.
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Describe the PRICE Check procedure?
- The acronym ?PRICE? represents:
- P (Pressure). Check pressure is within specified limits for aircraft type.
- R (Regulator). A full check is completed before flight looking for signs of obvious damage including a functional
- test of the mask and associated equipment, and regulator switches are in the appropriate settings.
- I (Indicator). Check the flow indicator flicks in unison with breathing, this shows gas flow through the regulator.
- C (Connections). Check the condition of all hoses and connections (including the emergency oxygen connection
- where fitted) by pushing to ensure connections are not dislodged.
- E (Emergency Assembly). Check the contents of the emergency oxygen supply and security of the ?firing?
- handle. Portable oxygen bottles should also be checked as part of this check
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