• Created by: stonesy71
  • Created on: 05-11-19 10:54

Define the phrase ‘Time of Useful Consciousness’

  • The onset of the symptoms of hypoxia is gradual and surreptious in nature, leave little time or no time to react to danger. The reaction time is known as ‘Time of useful consciousness’ and is dependent on altitude and fitness of the individual.

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2. How aircraft oxygen cylinders identified and

  • what are the maximum bottle pressures?

- Black cylinder with white neck. 1800 PSI maximum (Safe limit), 50 PSI Lox Charge (stops ingress of moisture).

  • Aircraft oxygen bottles (Trolley) max 4400 PSI minimum 50 PSI????

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Describe the function of the 5psi and 20psi

  • differential check valves during and following a heavy demand on the LOX system?


  • High demand operation - differential pressure across the 5psi valve will cause it to open allowing a flow of LOX into the supply line from the base of the main container. This will vaporise and change to a gas causing an increase in pressure, subsequently closing the valve and continuing high demand operation.

  • Reduction in high demand - this will cause gas pressure to rise opening the 20psi valve and allowing residual pressure to pass to the top of the main container. The pressure will cause the valve to reset to pressure attained stage.

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Why can you not use a LOX system immediately after

it has been replenished and how do fast jet get around this problem?

The pressure must be allowed to build up to a level that is sufficient to sustain a demand on the system. However at -183°c lox will not book at a sufficient rate to achieve this. The temperature of the lox must be increased to just below it's boiling point . Pressure must be stabilised. Stabilisation required for use.


Fast jets use pre charged LOX which has already had time to stabilise. 

-Self-contained within the vent system.

- modern aircraft have MSOCS


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