of the two MASTER CAUTION annunciators and either
fault annunciator indicates that either the identified gener-
ator has failed or voltage is not sufficient to keep it
connected to the power distribution system.
The GPU shall be adjusted to regulate at 28
t+.2 volts. The GPU shall be capable of
producing 1000 amperes for 5 seconds, 500
amperes for 2 minutes, and 300 amperes
DC External Power Source. External DC power
can be applied to the aircraft through an external power
receptacle on the underside of the right wing, just
outboard of the engine nacelle (fig. 2-1). The receptacle
is installed inside of the wing structure and is accessible
through a hinged access panel. DC power is supplied
through the DC external power plug, through the external
power relay, directly to the battery bus. Turn off all
external power while connecting the power cable to or
removing it from the external power supply receptacle.
The holding coil circuit of the relay is energized by the
external power source when the BATTERY switch is in the
ON position. The GPU shall be adjusted to regulate at 28
volts maximum to prevent damage to the aircraft battery.
The EXTERNAL POWER annunciator indicates that the
DC external power plug is connected. The EXT DC PWR
connected to the aircraft DC bus.
Security Keylock Switch. The aircraft has a
security keylock switch (fig. 2-13) installed on the
overhead control panel, placarded OFF - ON. The switch
is connected to the battery relay circuit and must be ON
when energizing the BATTERY MASTER SWITCH. The
key cannot be removed from the lock when in the ON
Circuit Breakers. The overhead circuit breaker
panel (fig. 2-7) contains circuit breakers for most aircraft
systems. The circuit breakers on the panel are grouped
into areas which are placarded as to their general
function. A DC power distribution panel is mounted
beneath the aisleway, forward of the main spar. This
panel contains higher current rated circuit breakers and is
not accessible to the flight crew under normal conditions.
AC POWER SUPPLY.
Single Phase AC Power Supply. AC power for
the aircraft is supplied by inverter units, numbered #1 and
#2 (fig. 2-28), which obtain operational current from the
DC power system Both inverters are rated at 750 volt-
amperes and provide single phase output only. Each
inverter provides 115 volts, 26 volts, and 400 Hz AC
output The inverters are protected by circuit breakers
mounted on the DC power distribution panel mounted
beneath the floor. Controls and indicators of the AC
power system are located on the overhead control panel
and on the caution/advisory annunciator panel.
annunciators. Illumination of the two MASTER CAUTION
annunciators, and the illumination of the # 1 INVEIER
and/or #2 INVERTER caution annunciator indicates
(2) Instrument AC annunciator. A red INST AC
warning annunciator, will illuminate if all instrument AC
(3) Inverter control switches. Two switches,
placarded 10 INVERTER # 1 and # 2 on the overhead
control panel (fig. 2-13), control the single-phase AC
Volt-Frequency Meters. The two digital volt-
frequency meters (fig. 2-13) are mounted on the
overhead control panel to provide continuous monitoring
of voltage and frequency on each 115 VAC bus. Normal
bus conditions will be indicated by a reading of 115 VAC
and 400 Hz on each meter.
Three Phase AC Power Supply. Three phase AC
electrical power (fig. 2-29) for operation of the inertial
navigation system and mission avionics is supplied by two
DC-powered 3000 volt-ampere solid state three phase
(1) Three phase inverter control switches. Two
three-position switches, placarded #1 INV - RESET - ON -
OFF and #2 INV - RESET - ON - OFF, located on the
mission control panel (fig. 4-1), control three phase
(2) Three phase volt/frequency meters. Two
digital three-phase volt/frequency meters, mounted on the
mission control panel (fig. 4-1), monitor and display the
voltage and frequency outputs of the three phase
(3) Three phase loadmeters. Two digital three-
phase loadmeters, mounted on the mission control panel
(fig. 4-1), monitor inverter output level.
(4) Three phase AC off annunciator.
annunciator placarded 30 AC OFF, located on the mission
annunciator panel (fig. 4-1), indicates a problem with one