STUDENT GUIDE FOR T-1A AIRCRAFT SYSTEMS
indicates the standby battery is the only source powering the standby bus, and the ARM indicator
AHRS Battery Power
A 24 VDC lead-acid AHRS auxiliary battery
Two BATTERY test switches and an annunciator
The AHRS auxiliary battery (mounted in the avionics rack) provides power to either/or both
AHRS computers. If either the left load bus and/or right load bus power fails or if either load
bus power falls below a preset limit, it is capable of supplying 24 VDC input power to both the
AHRS computers for up to ten minutes.
DC Power Distribution
Primary Power Distribution
DC power is distributed from the left and right main buses to their respective load buses through
two identical sets of three feeder lines, which are Remote Controlled Circuit Breaker (RCCB)
protected. In each set, only two feeder lines are active, while the third is considered a standby
feeder. The third feeder becomes active and the L BUS FDR FAIL or R BUS FDR FAIL
annunciator illuminates if either or both of the active feeder RCCBs trip.
DC Standby Power Distribution
The DC standby power distribution subsystem connects the standby battery to the standby bus.
The emergency bus supplies a charge current to the standby battery.
Emergency Power Distribution
The emergency power subsystem supplies DC power to safety of flight subsystems under
emergency conditions. The emergency bus normally receives power from the aircraft generator
through the emergency bus power relay, which is connected to the emergency bus feeder RCCB.
DC Electrical Controls and Indicators
The ammeters placarded LH AMPS and RH AMPS are located on the overhead switch panel.
range is from 0 to 500 ampere.
ELECTRICAL POWER SYSTEMS