1Aviation Medicine CHAPTER 06 OXYGEN SYSTEMS 75 2017.01.26 STUDY CARD 18022017

  1. What oxygen systems are required to maintaining sufficient oxygen at altitudes above 10,000 feet?
    • -pressurisation of the aircraft cabin,
    • - using an oxygen system.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. To what altitude is 100% oxygen not required?
    • - altitude of 33,700 feet.
    • -uneconomical to use 100% O2 all he time
    • -also irritates
  7. 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.
  8. What Problems breathing 100% O2?
    After flight breathing 100% oxygen , there can be problems with ?oxygen ear?.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
  14. 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.
  15. 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.
  16. 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.
  17. 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.
  18. 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.
  19. 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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1Aviation Medicine CHAPTER 06 OXYGEN SYSTEMS 75 2017.01.26 STUDY CARD 18022017
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1Aviation Medicine CHAPTER 06 OXYGEN SYSTEMS 75 2017.01.26 STUDY CARD 18022017
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