Beechcraft C-12C Operator And Technical Reference Manual page 96

TM 1-1510-218-10
life raft, toilet etc. A placard inside the door reads
NOTE: CREW SYS MUST BE ON as a reminder that
the PULL ON SYS READY knob in the cockpit must
be pulled on before oxygen will be available at the first
aid mask.
Due to the possibility of the oxygen valve
control cable freezing, The crew oxygen
valve shall be kept open during flight.
b. Pilot and Copilot Masks.
copilot masks are diluter demand, quick donning,
masks equipped with a carbon microphone, and are
stowed on the partition aft and outboard of the pilot
and copilot. The masks are held in the armed position
by spring tension clips, and can be donned
immediately with one hand.
masks deliver oxygen only upon inhalation.
(1) C D1 There is no loss of oxygen when
the masks are plugged in and the PULL ON SYS
READY control knob is pulled on.
diluter demand 100% regulator masks, which provide
the proper dilution of oxygen with cabin air to conserve
oxygen at lower altitudes. Placing the small diluter
control lever on the mask regulator to the NORMAL
position permits the
schedule a proportional increase in oxygen as the
altitude increases. Each mask has a pressure
detector in the supply line. A red signal indicates low
pressure, a green signal indicates adequate pressure.
The masks will be plugged in and hung on the sidewall
at all times.
(2) D2 T Use of Pilot and Copilot Oxygen
Masks. To don the mask, grasp the red levers
protruding from the stowage compartment and pull the
mask down. Inflate the mask harness by pressing the
red lever on the left side of the regulator and then don
the mask and release the lever.
operation are available which are controlled by a
selector lever located on the bottom right side of the
regulator:
(a) NORMAL Mode. When the selector
lever is placed in the NORMAL position, oxygen is
automatically mixed with the proper amount of air at
the aircraft's altitude. The NORMAL mode may be
selected at the discretion of the user at any altitude.
(b) 100% Mode. When the selector lever
is placed in the 100% position, pure undiluted oxygen
is supplied to the mask. The 100% mode may be
selected at the discretion of the user at any altitude.
2-80
NOTE
The pilot and
The diluter demand
The masks are
regulator to automatically
Three modes of
(c) Emergency (EMERG) Mode. Turning
the EMERG knob, located on the bottom of the
regulator, places the mask in the emergency mode. In
the EMERG, mode the regulator will supply 100%
undiluted oxygen to the user under a positive pressure
to the facemask. The emergency mode should be
used if smoke or fumes are present in the aircraft. The
emergency mode may be selected at the discretion of
the user at any altitude.
c. Passenger Oxygen.
passenger oxygen system is of the constant-flow type.
When in use, the oxygen is delivered through the
masks at a rate of flow of approximately 3.7 LPM-
NTPD (Liters Per Minute
Pressure Dry). If the cabin altitude exceeds
approximately 12,500 feet, a barometric pressure
switch will energize a solenoid, which automatically
opens the passenger oxygen system shut-off valve.
The oxygen will charge the passenger oxygen system
supply line and extend a plunger against each of the
passenger mask dispenser doors, forcing the door
open. The oxygen masks will then drop down about
9 inches below the dispenser. A lanyard pin at the top
of each oxygen mask must be pulled for oxygen to
flow to the mask, and must be reinserted to stop
oxygen flow when the mask is no longer needed.
There are four auto-deployment mask dispensers in
the aircraft. Three of the dispensers contain three
masks each and the other contains a single unit. The
shut-off valve can also be opened by pulling the
PASSENGER MANUAL
adjacent to the PULL ON SYS READY knob. After
the passenger system has been opened, either
automatically or manually, a pressure sensitive switch
in the supply line will activate to illuminate the green
PASS OXY ON annunciator
caution/advisory panel.
will illuminate in the full bright mode, regardless of the
CABIN LIGHTS switch position.
oxygen may be shut off and the remaining oxygen
isolated to the pilot, copilot and first aid masks by
pulling the AUTO OXYGEN circuit breaker in the
ENVIRONMENTAL group on the overhead circuit
breaker panel (provided the PASSENGER MANUAL
O'RIDE knob is on the off position).
d. Oxygen Duration. Each passenger oxygen
position has its own regulating orifice. The Oxygen
Duration Table is based on a flow rate of 3.70 NLPM
(Normal Liters Per Minute). The only exception is the
diluter-demand pilot/copilot mask when used in the
100% mode.
e. Emergency Operation. A control is provided
on the masks for the pilot and copilot. The control may
be set to 100% OXY when required.
The auto-deployment
Normal Temperature
O'RIDE knob located
legend on
Additionally, all cabin lights
The passenger
the