APPLICATION OF EXTERNAL POWER.
Before connecting the power cables
from the external power source to the
aircraft, ensure that the GPU is not
touching the aircraft at any point Due
to the voltage drop in the cables, the
two ground systems will be of
different potentials. Should they
come in contact while the GPU is
operating, arcing could occur. Turn
connecting the power cable to, or
removing it from, the external power
supply receptacle. Be certain that
polarity of the external power source
is the same as that of the aircraft
before it is connected. Minimum
GPU requirements are as follows:
400-amperes, 28V continuous output
DC and 115V, 3 phase, 400 cycle, 3
KVA continuous output AC.
An external power source is often needed to supply
the electric current required to properly ground service
the aircraft electrical equipment and to facilitate starting
the aircraft's engines. An external DC power receptacle
is installed on the underside of the right wing, just
outboard of the engine nacelle. An external AC power
receptacle is installed on the underside of the left wing,
just outboard of the engine nacelle.
SERVICING OXYGEN SYSTEM.
The oxygen system furnishes breathing oxygen to
the pilot, copilot, and first aid position. The oxygen
cylinder location is shown in figure 2-26.
Oxygen System Safety Precautions.
Keep fire and heat away from oxygen
equipment. Do not smoke while
equipment, and take care not to
handled tools when working on the
Keep oxygen regulators, cylinders, gages,
valves, fittings, masks, and all other components of the
oxygen system free of oil, grease, gasoline, and all other
readily combustible substances. The utmost care shall
be exercised in servicing, handling, and inspecting the
Do not allow foreign matter to enter
Never allow electrical equipment to come
into contact with the oxygen cylinder.
Never use oxygen from a cylinder without
first reducing its pressure through a regulator.
Replenishing Oxygen System.
Remove oxygen access door on outside of
aircraft (fig. 2-26).
Remove protective cap on oxygen system
Attach oxygen hose from oxygen servicing
unit to filler valve.
If the oxygen system pressure is
below 200 PSI, do not attempt to
service system. Make an entry on DA
Ensure that supply cylinder shutoff valves on
aircraft are open.
Slowly adjust valve position so that pressure
increases at a rate not to exceed 200 PSIG
Close pressure regulating valve on oxygen
servicing unit when pressure gage on
oxygen system indicates pressure obtained
Pressure Chart (fig. 2-45).
To compensate for loss of aircraft
cylinder pressure as the oxygen
cools to ambient temperature after
recharging, the cylinder should be
charged initially to approximately
Experience will determine what initial
pressure loss upon cooling. A
The final stabilized cylinder pressure should be
adjusted for ambient temperature per figure 2-45.
servicing unit and filler valve.
Install protective cap on oxygen filler valve.
Install oxygen access door.
Ground handling covers all the essential information
concerning movement and handling of the aircraft while