TM 1-1510-262-10
Figure 2-38. Mission AC/DC Power Cabinet
c. Master Switch. All electrical current may be shut off using the MASTER SWITCH (gangbar) (Fig. 2-13)
which extends above the battery and generator switches. The MASTER SWITCH (gangbar) is moved forward when
a battery or generator switch is turned on. When moved aft, the bar positions each switch to the OFF position.
d. DC Load and Voltmeters. Four digital meters, located on the overhead panel, display voltage readings and
show the rate of current usage from the left and right generating systems. The two load meters indicate output
amperage as a percent of rated capacity from the respective generator. Current consumption is indicated as a per-
centage of total output amperage capacity for the generating system being monitored. The two volt meters indicate
bus voltage for the respective generating system.
e. Battery Volt/Amp Meter. The mission control panel (Fig. 4-1), located on the fuselage sidewall adjacent
to the copilot s seat, incorporates a digital volt/amp meter that displays available battery voltage, and amperage.
Minimum battery voltage for engine starting is 22V DC.
f. Battery Charge Monitor. The aircraft has a charge-current sensor which will detect a charge current. The
charge current system senses battery current through a shunt in the negative lead of the battery. Any time the
battery charging current exceeds approximately 7-amperes for 6 seconds or longer, the amber BATTERY CHARGE
annunciator and the master fault caution annunciator will illuminate. Following a battery engine start, the caution
annunciator will illuminate approximately six seconds after the generator switch is placed in the ON position. The
annunciator will normally extinguish within two to ive minutes, indicating that the battery is approaching a full charge.
The time interval will increase if the battery has a low state of charge, the battery temperature is very low, or if the
battery has previously been discharged at a very low rate (i.e., battery operation of radios or lights for prolonged
periods). The caution annunciator may also illuminate for short intervals after landing gear and/or lap operation.
If the caution annunciator should illuminate during normal steady-state cruise, this indicates that conditions exist
that may cause a battery thermal runaway. If this occurs, the battery current should be monitored using the battery
ammeter. If battery current continues to increase, the battery is in thermal runaway and should be selected off until
the beginning of the approach.
2-77
