4-2 Change 3
(11) Radio altimeter switch. The radio altimeter
switch, placarded RADIO ALT - ON, OFF, controls opera-
tion of the radio altimeter system. This switch allows
turning off the radio altimeter system to reduce radio
emissions from the aircraft.
(12) TDOA (CHAALS) system switch. The time di-
rection of arrival (CHAALS) switch, placarded TDOA
SYSTEM ON - OFF, controls operation of the TDOA
(13) TDOA (CHAALS) test switch. The time direc-
tion of arrival (CHAALS) test switch, placarded TDOA
BIT ON, is used to initiate the TDOA built in test (BIT).
(14) Data link high voltage switch. The data link
high voltage switch, placarded DATA LINK HV, ON -
STBY - OFF, controls high voltage to the data link power
(a) ON. Applies high voltage power to the
data link power amplifier.
(b) STBY. The STBY (standby) position ap-
plies high voltage power to the data link power amplifier
for warm up before ON is selected, and for cooldown
before OFF is selected.
(c) OFF. Removes high voltage power from
the data link power amplifier.
(15) Data link antenna select switch. The data link
antenna select switch placarded DATA LINK ANT SEL -
NOSE - AUTO - TAIL, is used to manually select the nose
or tail data link antenna or to select automatic antenna
(16) Three-phase AC bus cross tie switch. The
three-phase AC bus cross tie switch, placarded 3Ø AC
CONTROL BUS CROSS TIE ON/AUTO - OFF, controls
the AC bus cross tie.
(a) Due to the additional AC loading in the
RC-12N aircraft, a single three-phase inverter can no
longer support all three-phase electrical loads. The au-
tomatic bus cross-tying feature should only be used if the
threat allows the mission to continue without use of the
ALQ-136 radar jammer and the ALQ-162 CW jammer.
If the threat dictates constant protection of the ALQ-136
and ALQ-162, the automatic bus cross tie feature for the
three-phase busses should not be used. Cross tying
should only be implemented after the GRCS mission
equipment is shut off.
(b) OFF. In the OFF position the AC busses
will not be connected (no cross-tie).
(17) Three-phase AC inverter control switches.
Two three-phase AC inverter control switches, placarded
3Ø AC CONTROL #1 and #2 INV RESET - ON - OFF,
control operation of the three-phase inverters.
(a) RESET. When an inverter is off-line due
either to a fault or to placing the inverter switch to the
OFF position, the affected unit cannot have its output
restored until the inverter switch is moved to the spring
loaded RESET position, then to the ON position.
(b) ON. ON position selects inverter opera-
(c) OFF. OFF position turns off inverter.
(18) Three-phase AC external power switch. The
three-phase AC external power switch, placarded 3ØAC
CONTROL EXT PWR - RESET - ON - OFF, controls
application of external three-phase AC power to the air-
(a) RESET. The AC external power switch
must be moved to the spring loaded RESET position,
then to the ON position to bring AC external power on
(b) ON. ON position applies AC external pow-
er to the three-phase busses through the AC external
power receptacle under the left wing.
(c) OFF. OFF position removes AC external
power from the three-phase busses.
(19) Three-phase AC meter switch. The three
phase meters switch, placarded METERS AØ - BØ - CØ
controls which phase of the three-phase inverters is be-
ing measured by the AC voltage, frequency, and loadme-
(20) ASE control switch. The ASE control switch,
placarded ASE SILENT - NORM - OFF, controls opera-
tion of the ASE.
(a) SILENT. When the SILENT position is se-
lected, the transmitting elements of the ASE are placed
in a passive mode.
(b) NORM. The NORM position allows nor-
mal ASE operation.
(c) OFF. The OFF position removes power
from ASE equipment. When the ASE control switch is
set back to NORM, the originally selected mode will
again become active.