(3) Three phase load meters. Two, digital, three phase load meters mounted on the mission control panel
(4) Three phase AC OFF annunciator. The annunciator placarde 3ø AC OFF , located on the mission
annunciator panel (Fig. 4-1), indicates a problem with one of the three phase AC power busses.
(5) Three phase AC external power. See igure 4-1. External three-phase AC power for operation of the
inertial navigation system or mission equipment can be applied to the aircraft through an external power receptacle
located in the underside of the left wing stub just outboard of the engine nacelle. The receptacle is installed inside
the wing structure, accessible through a hinged access panel. The AC electrical system is automatically isolated
from the external power source if: the external power is over or under voltage, over or under frequency, or has an
improper phase sequence.
(a) External AC power Annunciator. The annunciator placarde EXT AC PWR ON, located on the mis-
sion annunciator panel (Fig. 4-1), and indicates that external AC power is connected to the 3 phase busses. The
EXTERNAL POWER annunciator on the advisory annunciator panel indicates that an AC GPU plug is mated to the
AC external power receptacle.
(b) External AC power control switch. The switch placarded EXT PWR - RESET - ON - OFF , located
on the mission control panel (Fig. 4-1), controls application of three-phase AC power to the aircraft.