GROUND POWER
A ground power unit (GPU) can be connected
to the airplane through a power receptacle
(Figure 2-8) located on the left side of the air-
plane adjacent to the tailcone door. GPU capa-
bility should be limited to 28 VDC at a maximum
of 1,000 amperes. The external power overvolt-
age cutout circuit limits the maximum voltage
to 33 ±2 VDC. The 1,000-amp limit is to pre-
vent exceeding starter shaft torque limits.
Airplanes with a Single Battery
Switch
(SNs 24-230 through -263, excluding
-260, and 25-070 through -102,
excluding -090)
To charge both batteries using external power,
plug in the GPU and regulate the voltage out-
put to 28 VDC. Ground power unit output should
be limited to a maximum of 1,000 amperes.
Airplanes with Dual Battery
Switches
(SNs 24-260, -264, and Subsequent,
and 25-090, -103, and Subsequent)
To charge both batteries using external power,
turn on both battery switches. Plug in the GPU
and regulate the voltage to 28 VDC. Ground
power unit output should be limited to a max-
imum of 1,000 amperes.
2-7
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
Figure 2-6. Generator Switches
Figure 2-7. DC Ammeters
Figure 2-8. Ground Power Receptacle
