b. If the aircraft servicing input is providing the
2. Place the BUS SELECTOR switch (12, fig.
7-63) in the SPLIT position.
power for the load bank's control power
circuit, the indicated load is greater than
3. If load testing, the aircraft servicing input is not
selected (approximately 40 amps greater).
required while testing the power plant for jet
C h a n g e t h e s e t t i n g s o f t h e L OA D
starting performance. Skip to step 7.
SELECTORS DC AMPS toggle switches
4. P l a c e t h e D C C O M M O N B U S L O A D
(10 or 14, fig. 7-63), as required, and use the
PROGRAM SELECTOR switch (2, fig. 7-63)
VARIABLE 0-55 AMPS controls (1 and 4,
in the desired position.
fig. 7-62) if needed to obtain the desired load
a. I n t h e C O N T I N U O U S p o s i t i o n , a
indications.
continuous load of up to 1,500 amperes can
NOTE: The LOAD SELECTOR DC AMPS
be applied to the aircraft servicing input for
switches marked 0-55 must be in the ON position to
as long as the COMMON BUS SHOCK
permit operation of the VARIABLE 0-55 AMPS
LOAD switch (13) is in the ON position. b.
controls.
In the 5-MIN position, a load of up to 1,500
c. The amount of load may be adjusted at any
amperes can be applied when the
time by operating the LOAD SELECTORS
COMMON BUS SHOCK LOAD switch
DC AMPS toggle switches (10 or 14, fig.
(13) is in the ON position. The load is
7-63) or the VARIABLE 0-55 AMPS
automatically dropped after 5 minutes.
controls (1 or 11, fig. 7-62).
c. I n t h e 5 - S E C p o s i t i o n , t h e l o a d i s
NOTE: To ensure accurately timed programs, do
automatically dropped after 5 seconds.
not change the position of the DC COMMON BUS
5. S e l e c t t h e d e s i r e d l o a d b y p l a c i n g t h e
LOAD PROGRAM SELECTOR switch (2, fig. 7-63)
appropriate LOAD SELECTORS DC AMPS
unless the COMMON BUS SHOCK LOAD switch
toggle switches (14, fig. 7-63) in the ON
(13) is in the OFF position.
position.
5. To stop the test and drop the load, place the
COMMON BUS SHOCK LOAD switch (13) in
6. Place the COMMON BUS SHOCK LOAD
the OFF position. If the DC COMMON BUS
switch (13, fig. 7-63) in the ON position and
LOAD PROGRAM SELECTOR switch (2) is in
read the DC AMPS meter (3). Place the DC
the 5-MIN or the 5-SEC position, this action
AMMETER RANGE SELECTOR switch (4,
also resets the timers.
fig. 7-63) in the position closest to, but greater
than, the dc load applied.
Split Bus DC Operation
a. If the aircraft servicing input is providing the
If the power plant has split bus characteristics, 28
power for the load bank's control power
volts dc must be fed to the aircraft servicing input to
circuit, the indicated load is greater than
operate the load bank while the jet starting voltage is
selected (approximately 40 amps greater).
fed to the jet starting input of the load bank. If the jet
C h a n g e t h e s e t t i n g s o f t h e L OA D
s t a r t i n g p ow e r p l a n t d o e s n o t h ave s p l i t bu s
SELECTORS DC AMPS switches (14, fig.
characteristics, connect a source of 115/200 volts,
7-63), as required, and use the VARIABLE
three-phase, four-wire, 400-Hz power to the ac input of
0-55 AMPS control (1, fig. 7-62) if needed
the load bank and place the CONTROL CIRCUIT
to obtain the desired load indication.
s w i t c h ( 7 , fi g . 7 - 6 2 ) i n t h e a c p o s i t i o n . T h i s
NOTE: The LOAD SELECTORS DC AMPS
arrangement enables the 115/200-volt power source to
toggle switch marked 0-55 must be in the ON position
operate the control power circuit of the load bank while
to permit operation of the VARIABLE 0-55 AMPS
the jet starting power plant is being loaded and tested.
control.
To test power plants by using the jet starting input
b. The amount of load may be changed at any
of the load bank, proceed as follows:
time by operating the LOAD SELECTORS
DC AMPS toggle switches (14, fig. 7-63) or
1. Verify that the SPLIT BUS SHOCK LOAD
the VARIABLE 0-55 AMPS control (1, fig.
switch (11, fig. 7-63) is in the OFF position.
7-62).
7-62
