is in use, a check of the supply pressure should be
made at intervals during flight, to note the quantity
available and to approximate the supply duration. The
outside temperature is reduced as an aircraft ascends to
higher altitudes. Oxygen cylinders thus cooled by
temperature change will show a pressure drop. This
type of drop in pressure will raise again upon return to a
lower or warmer altitude.
b. Oxygen masks. Oxygen masks for the pilot and
copilot are provided. To connect a mask into the
oxygen system, the individual connects the line attached
to the mask to the flexible hose which is attached to the
cockpit sidewall. The microphone in the oxygen mask is
provided with a cord for connecting with the microphone
jack. To test mask and hose integrity, the individual
places the supply control lever on the regulator control
panel to the ON position, puts on and adjusts his mask,
selects TEST MASK position, and checks for leaks.
Pure oxygen will support combustion.
Do not smoke while oxygen is in use.
If any symptoms occur suggestive of
the onset of hypoxia, immediately set
the emergency pressure control lever
to the EMERGENCY position and
descend below 10,000 feet. Whenever
carbon monoxide or other noxious gas
is present or suspected, set the dilutor
control lever to 100% OXYGEN and
continue breathing undiluted oxygen
until the danger is past.
maintained at all times to the regulator control panels if
the cylinder shut-off valves are open and if there is
pressure in the cylinders. Each individual places the
supply lever (green) on his regulator control panel to the
ON position, and the diluter lever (white) to the
NORMAL OXYGEN position.
operation, the affected crew member selects the
EMERGENCY position of the emergency pressure
control lever (red) on his regulator control panel. This
selection provides 100% oxygen at a positive pressure,
regardless of the position of the diluter control lever on
e. First Aid Operation. A first aid oxygen mask is
installed in the aft cabin area as a supplemental or
emergency source of oxygen. The mask is stowed
behind an overhead cover, placarded FIRST AID
OXYGEN PULL. Removing the cover allows the mask
to drop out of the container, exposing a manual control
valve, which releases oxygen to the mask when placed
in the ON position. After using the mask, the manual
valve in the container must be turned OFF before
stowing the mask and replacing the cover.
Oxygen Duration Example Problem.
Duration in minutes of oxygen at 100% capacity.
Two man crew plus one passenger, cabin pressure
altitude = 15,000 feet, crew masks, normal, 100%
Find "two man crew plus one pass" line, move right
then down to 15,000 - "normal" read 232.1 minutes.
Duration of oxygen for previous example data at
84% of capacity.
232.1 minutes duration at 100%, 84% capacity,
total aircraft flow = 13.9 LPM.
Multiply 232.1 X 0.84 = 194.9 minutes. or Multiply
3,226 X 0.84 = 2709.8, divide by 13.9 LPM = 194.9
Duration of oxygen for complement at other cabin
pressure altitude, at less than 100% capacity.
Cylinder at 84% capacity, 100% capacity = 3,226 L,
cabin pressure altitude = 21,000 feet.
1 crew mask = LPM (100%), 1 passenger mask =