Figure 2-26. Overhead Circuit Breaker Panel
on the warning annunciator panel, placarded INST
AC, will illuminate if all instrument AC busses
(3.) Inverter Control Switches.
switches, placarded INVERTER No.1 and No.2 on
the overhead control panel (fig. 2-12) give the pilot
control of the single-phase AC inverters.
(4.) Volt-Frequency Meters. Two volt-
frequency meters (fig. 2-12) are mounted in the
overhead control panel to provide monitoring capa-
bility for both 115 VAC buses. Normal display on
the meter is shown in frequency (Hz). To read volt-
age, press the button located in the lower left corner
of the meter. Normal output of the inverters will be
indicated by 115 VAC and 400 Hz on the meters.
Three Phase AC Power Supply. Three phase
AC electrical power for operation of the inertial nav-
igation system and mission avionics is supplied by
two DC powered 3000 volt-ampere solid state three
Three phase inverter control switches.
Two three position switches placarded #1 INV-OFF-
ON-RESET and NO. 2 INV-OFF-ON-RESET,
located on the mission control panel (fig. 4-1) con-
trols three phase inverter operation.
(2.) Three phase volt/frequency meters.
Two three phase volt/frequency meters, mounted on
the mission control panel (fig. 4-l), monitor and dis-
play the voltage and frequency outputs of the three
(3.) Three phase loadmeters. Two three
phase loadmeters, mounted on the mission control
panel (fig. 4-l), monitors inverter output level.
Three phase AC off annunciator light.
An indicator light placarded 3!zsl! AC OFF, located
on the misson annunciator panel (fig. 4-l), indicates
a problem with one of the three phase AC power
Three phase AC external power. Exter-
nal three phase AC power for operation of the iner-
tial navigation system or mission equipment, can be
applied to the aircraft through an external power
receptacle located on the underside of the left wing
leading edge just outboard of the engine nacelle (fig.
2-l). The receptacle is installed inside the wing
structure and is accessible through a hinged access
panel. The AC electrical system is automatically iso-
lated from the external power source if the external
power is over or under voltage, over or under fre-
quency, or has an improper phase sequence.