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Pilot's Handbook of Aeronautical Knowledge
Aircraft Systems
Oxygen Systems

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Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




Diluter-Demand Oxygen Systems
Diluter-demand oxygen systems supply oxygen only when
the user inhales through the mask. An automix lever allows
the regulators to automatically mix cabin air and oxygen or
supply 100 percent oxygen, depending on the altitude. The
demand mask provides a tight seal over the face to prevent
dilution with outside air and can be used safely up to 40,000
feet. A pilot who has a beard or mustache should be sure it is
trimmed in a manner that will not interfere with the sealing
of the oxygen mask. The .t of the mask around the beard
or mustache should be checked on the ground for proper

Pressure-Demand Oxygen Systems
Pressure-demand oxygen systems are similar to diluter
demand oxygen equipment, except that oxygen is supplied to
the mask under pressure at cabin altitudes above 34,000 feet.
Pressure-demand regulators create airtight and oxygen-tight
seals, but they also provide a positive pressure application of
oxygen to the mask face piece that allows the user's lungs
to be pressurized with oxygen. This feature makes pressure
demand regulators safe at altitudes above 40,000 feet. Some
systems may have a pressure demand mask with the regulator
attached directly to the mask, rather than mounted on the
instrument panel or other area within the flight deck. The
mask-mounted regulator eliminates the problem of a long
hose that must be purged of air before 100 percent oxygen
begins flowing into the mask.

Continuous-Flow Oxygen System
Continuous-flow oxygen systems are usually provided for
passengers. The passenger mask typically has a reservoir
bag, which collects oxygen from the continuous-flow oxygen
system during the time when the mask user is exhaling.
The oxygen collected in the reservoir bag allows a higher
aspiratory flow rate during the inhalation cycle, which
reduces the amount of air dilution. Ambient air is added to
the supplied oxygen during inhalation after the reservoir bag
oxygen supply is depleted. The exhaled air is released to the
cabin. [Figure 6-45]

Electrical Pulse-Demand Oxygen System
Portable electrical pulse-demand oxygen systems deliver
oxygen by detecting an individual's inhalation effort and
provide oxygen flow during the initial portion of inhalation.
Pulse demand systems do not waste oxygen during the
breathing cycle because oxygen is only delivered during
inhalation. Compared to continuous-flow systems, the pulsedemand
method of oxygen delivery can reduce the amount
of oxygen needed by 50–85 percent. Most pulse-demand
oxygen systems also incorporate an internal barometer
that automatically compensates for changes in altitude by
increasing the amount of oxygen delivered for each pulse as
altitude is increased. [Figure 6-46]

Continuous flow mask and rebreather bag.
Figure 6-45. Continuous flow mask and rebreather bag.

EDS-011 portable pulse-demand oxygen system.
Figure 6-46. EDS-011 portable pulse-demand oxygen system.