2-102. 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 off all external power while 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 stub, just outboard of the engine nacelle. An external AC power receptacle
is installed on the underside of the left wing stub, just outboard of the engine nacelle.
2-103. SERVICING OXYGEN SYSTEM.
The oxygen system furnishes breathing oxygen to the pilot, copilot, and irst aid position. Oxygen cylinder location
Keep ire and heat away from oxygen equipment. Do not smoke while working with or near oxygen
equipment and take care not to generate sparks with carelessly handled tools when working on the
a. Oxygen System Safety Precautions.
(1) Keep oxygen regulators, cylinders, gauges, valves, ittings, 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 oxygen system.
Do not allow foreign matter to enter oxygen lines.
Never allow electrical equipment to come in contact with the oxygen cylinder.
Never use oxygen from a cylinder without irst reducing its pressure through a regulator.
b. Replenishing Oxygen System.
Remove oxygen access door on outside of aircraft (Fig. 2-31).
Remove protective cap on oxygen system iller valve.
Attach oxygen hose from oxygen servicing unit to iller valve.
If the oxygen system pressure is below 200 PSI, do not attempt to service system. Make an entry on
DA Form 2408-13.
Ensure that supply cylinder shutoff valves on the aircraft are open.
Slowly adjust the valve position so that pressure increases at a rate not to exceed 200 PSIG per