King Air C90GTi, Pilot Training Manual

Page: 477 / 557

OXYGEN SYSTEM CONTROLS
A shutoff valve regulator in the cylinder is ac-
tuated by its a push-pull shutoff control lo-
cated overhead between the pilot and copilot
seats (see Figure 17-5). Pushing in the han-
d l e d e a c t iva t e s t h e ox y g e n s u p p ly, wh i l e
pulling out the handle actuates the oxygen
supply. The regulator is a constant-flow type
which supplies low-pressure oxygen through
aluminum plumbing to the outlets.
OXYGEN DURATION
A preflight requirement is to check the oxy-
gen available, considering the number of
crew and passengers, to assure that it is suf-
f icient for descent to 12,500 feet, or until
loss of pressure in the air plane can be cor-
rected and cabin altitude pressure restored.
Full oxygen system pressure is 1800 ±50 psi
at 70° F for the 22 cubic feet cylinder, and
1850 ±50 psi for the larger cylinders. First,
read the oxygen pressure gage and note the
p r e s s u r e . D e t e r m i n e f r o m t h e OX Y G E N
AVA I L A B L E W I T H PA RT I A L LY F U L L
B OT T L E g r a p h t h e p e r c e n t o f u s a bl e c a -
pacity. To obtain the duration in minutes of
the supply, obtain the duration for a full bot-
tle from the Oxygen Duration table, con-
s i d e r i n g t h e n u m b e r o f p e r s o n s a b o a r d .
Multiply the full bottle duration by the per-
c e n t o f f u l l b o t t l e ava i l a bl e t o o b t a i n t h e
available oxygen duration in minutes.
On the C90GTi and C90GTx air plane, oxy-
gen duration is for a Puritan-Zep oxygen
system which must use the red, color-coded,
plug-in mask, rated at 3.7 standard liters per
m i n u t e – n o r m a l t e m p e r a t u r e p r e s s u r e
(SLPM–NTPD) flow. Both aircraft are ap-
proved for altitudes up to 30,000 feet.
OXYGEN DURATION
COMPUTATION
In this sample computation, oxygen dura-
tion is computed for a Puritan-Zep oxygen
system which utilizes the red, color-coded,
plug-in mask rated at 3.7 standard liters per
minute (SLPM) flow and is approved for al-
titudes up to 30,000 feet. This table is also
used for the quick-donning, diluter-demand
crew oxygen masks. When selected to the
100% mode, the number of crew masks in
use should be doubled for computation. To
compute oxygen duration for four passen-
g e r s a n d t wo c r e w m e m b e r s u s i n g t h e i r
masks in 100% mode, consider eight peo-
ple using oxygen.
To compute the duration in minutes of avail-
able oxygen for eight people, assume the
pressure gage shows 1,500 pounds. Enter
the Percent of Usable Oxygen Capacity chart
( F i g u r e 1 7 - 8 ) a t 1 , 5 0 0 p o u n d s a n d r e a d
across to intersect the 32° F diagonal, then
d ow n t o r e a d 8 5 % o f u s a bl e c a p a c i t y. To
compute the duration available, enter the
Oxygen Duration char t (Table 17-1) at the
8-people-using column and read down to 55
minutes available for a 66 cubic-foot sup-
ply bottle. Now take 85% of 55 and f ind the
c u r r e n t ox y g e n d u r a t i o n ava i l a bl e o f a p -
proximately 46 minutes.
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
17-6
FOR TRAINING PURPOSES ONLY
17
OXYGEN
SY
STEM
Figure 17-8. Percent of Usable
Oxygen Capacity