Learjet 20 Series Pilot Training Manual page 342

OXYGEN CYLINDER
The system is supplied with oxygen from a
storage cylinder located in the right nose section
on 23 and 24 models and model 25 through SN
25-024.
Except as noted above, the oxygen cylinder
is located in the dorsal fin on all 25 models
(Figure 17-4).
Each oxygen cylinder has a storage capacity of
38 cubic feet at 1,800 psi. System pressure
should be between 1,800 and 1,850 psi. The
shutoff valve and pressure-regulator assembly is
attached to the storage cylinder and provides for
pressure regulation and servicing. Oxygen
pressure for the passenger and crew distribution
system is regulated at 60 to 80 psi. The cylinder,
along with its shutoff valve and regulator
assembly, can be reached through an access
door. Under normal conditions, this valve should
always be left in the on (open) position.
Figure 17-4. Oxygen Cylinder and Overboard Discharge Indicator
LEARJET 20 SERIES PILOT TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
The pilot should be aware that if the oxygen
cylinder shutoff valve is closed, oxygen pressure
will still be read on the OXY PRESS gage in the
cockpit. During the interior preflight inspection,
ensure that the shutoff valve is open by checking
for oxygen flow through both crew oxygen
masks, using the 100%, or EMER, position.
OVERBOARD DISCHARGE
INDICATOR
The overboard discharge indicator (green
blowout disc) (Figure 17-4) provides the pilot
with a visual indication that there has not been
an overpressure condition in the oxygen storage
cylinder. The disc blows out if the cylinder
pressure reaches 2,700 to 3,000 psi, releasing all
oxygen pressure. The green blowout disc is
located on the right side of the dorsal fin or the
lower right side of the nose section.
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17-5