MD-11 Flight Crew Operations Manual
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Emergency Equipment Chapter Emer
Description and Operation Section 10
Emer.10.1
Emer.10 Emergency Equipment-Description and Operation
Crew Oxygen
General
The crew oxygen system is supplied by one high pressure cylinders which connect
directly to a high pressure regulator. Low pressure distribution lines deliver
regulated oxygen to mask mounted regulators. This system supplies oxygen to the
Captain, First Officer and up to two observers.
The oxygen supply cylinder has a usable capacity of about 115 cu. ft. and an
operating pressure of 1,850 psig at 21° C. The cylinder pressure increases and
decreases as the temperature of the oxygen increases and decreases.
The cylinder shutoff valve is threaded into the top of the crew oxygen cylinder.
The shutoff valve incorporates an overboard relief indicator that relieves an
overpressured condition. The indicator is a green plastic disk on the lower left side
of the aircraft nose. There is also a high pressure gauge for direct reading of the
cylinder pressure.
A high pressure regulator mounts directly to the cylinder shutoff valve. This
regulator reduces cylinder pressure to a constant system pressure.
The regulator has a relief port that dumps the oxygen overboard if the system
overpressured.
There is also a high pressure transducer port on the regulator to measure cylinder
pressure. This transducer sends an electrical signal to an indicator in the cockpit
near the First Officer oxygen mask. The indicator is lighted so the crew can
monitor cylinder pressure in a dark cockpit.
The mask assembly at each flight station consists of:
• Oronasal mask.
• Microphone with a quick disconnect fitting.
• Mask mounted diluter demand regulator.
• Inflatable pneumatic harness.
• Supply hose with a quick disconnect fitting.
The mask is equipped with a vent valve to purge the smoke from the goggles. The
regulator can function in normal diluter demand, 100 percent oxygen, or
emergency pressure breathing.
The regulator follows an automatic pressure breathing schedule. The regulator
incorporates a toggle valve and a rotating selector valve to permit selection of the
different modes of operation to supply oxygen to the mask.
October 02, 2006
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