King Air C90GTi, Pilot Training Manual

Page: 481 / 557

FILLING THE OXYGEN SYSTEM
When f illing the oxygen system, only use
aviator’s breathing oxygen (MIL-0-27210).
D O N OT U S E M E D I C A L OX Y -
GEN. It contains moisture which can
cause the oxygen valve to freeze.
Fill the oxygen system slowly by
adjusting the recharging rate with
the pressure regulating valve on the
servicing cart, because the oxygen,
under high pressure, will cause ex-
cessive heating of the f iller valve.
Fi l l t h e cy l i n d e r ( 2 2 - c u b i c - f o o t
cylinder installation) to a pressure
of 1,800 ±50 psi at a temperature
of 70°F. This pressure may be in-
creased an additional 3.5 psi for
each degree of increase in temper-
ature; similarly, for each degree of
d r o p i n t e m p e r a t u r e , r e d u c e t h e
pressure for the cylinder by 3.5 psi.
The oxygen system, after f illing,
will need to cool and stabilize for
a shor t period before an accurate
r e a d i n g o n t h e g a g e c a n b e o b -
tained. The 49- or 66-cubic-foot
cylinders may be charged to a pres-
sure of 1,850 ±50 psi at a temper-
ature of 70° F. When the system is
properly charged, disconnect the
f iller hose from the f iller valve and
replace the protective cap on the
f iller valve.
OXYGEN CAPACITY
O x y g e n f o r u n p r e s s u r i z e d, h i g h - a l t i t u d e
flight is supplied by a cylinder in the com-
par tment immediately aft of the pressure
bulkhead (see Figure 17-4). A 22-, 49-, or
66-cubic-foot cylinder may be installed.
OXYGEN CYLINDER
RETESTING
Oxygen cylinders used in the air plane are
of two types. Lightweight cylinders, stamped
“3HT” on the plate on the side, must be hy-
drostatically tested ever y three years and
the test date stamped on the cylinder. This
bottle has a ser vice life of 4,380 pressur-
izations or 15 years, whichever occurs f irst,
and then must be discarded. Regular weight
cylinders, stamped “3A,” or “3AA,” must be
hydrostatically tested ever y f ive years and
stamped with the retest date. Service life on
these cylinders is not limited.
WARNING
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
17-10
FOR TRAINING PURPOSES ONLY
17
OXYGEN
SY
STEM